Temporal Patterns of Neural Activity and Their - CiteSeerX

BIOLOGY

OF

REPRODUCTION

51-72

24,

Temporal

(1981)

Patterns

of Neural

Relation

DREIFUSS,2

Pituitary

ELIANE

of

Hormones1

TRIBOLLET

and

M. MUHLETHALER

Department of Physiology, University of Geneva Medical Geneva,

system than controlling lobe

anterior nocellular

of

for its parvicellular the secretions

the

endocrine

amic

bursts

pituitary

gland.

The

of

hypothal-

paraventricular

which synthesize the two and vasopressin, are well logically and biochemically, trophysiological their spiking

techniques activity.

secretion mental available

can be stimuli, to assay

seconds

in the

Intermittent

living

Release

ejection during of a neuroendocrine Maternal oxytocin

concept apply each

and of in species day, such

et a!., detected

to record hormone

fact,

milk

is

and

the myogland to This

coupling

1974b). There is, however, of evidence which suggests

these

species

oxytocin

is released

discharge

each episode can be inspection (Fig. 1). In

interval

between

milk

on the nipples stimulates the gland, during

a that in

the

simple may

pups

immobile

reaction” probably

ejections, and suckle. contraction

a phase of vigorous which the pups shift

stretch

is associated accentuates

thereby

themselves

for a few with the

facilitates teat

when

has

tying off the pups

the nipple.) This complex recurs at regular intervals

the

anesthetized In lightly

discrete

cannulate the

‘Research from the authors’ laboratory mentioned in this review article was supported in part by grants from the Swiss National Science Foundation. 2Addrcss repnnt requests to: Dr. J. R. Dreifuss, DEpartement de Physiologic, 20 Rue de l’Ecole-deMdecine, 1211 Genve 4, Switzerland.

one

or

rise

in

ejection. contraction

An

pressure

recurring

served occurs

during nearly

taken from the pressure milk ejection 51

animal anesthetized more

(Fig.

suckling. The simultaneously several waves to

(It by

behavior of 4-15

of min

or more observed,

ducts

intramammary

every

milk.

occluded

succeseven in

6A). rats, it is possible

teat

intermittent characterized

of

been

20

and

“stretch

suck which difference

removal

is absent

growing even in

The

a large pressure

the

the

rigid

seconds.

as long as the young suckle; sive milk ejections are readily

which nurse for a short period as rabbit, cow, and man (Lin-

coln, body

the

that visual

lie quietly as oxytocin

which

remain

is theclassic (see Gaines, in response

stimulates mammary

stimulus-response

prolonged

weight from one foot to the other and perform pushing movements directed towards the gland. This “treading reaction” is followed by a phase

suckling reflex released

ejected.

during

of the mammary movements occurs

in

the young of the

1974), so by simple

the pups As soon

of Oxytocin

Milk example 1915).

contract

are used Moreover,

histodcc-

animal.

Suckling

by cells

oxytocin

characterized and vatious

in a steady,

has been shown to be associated with pulses of oxytocin released at regular intervals (Lincoln et a!., 1973). All pups in a litter display a synchronous behavioral reaction at milk ejection (Vorherr et al., 1967; Drewett

nuclei,

hormones

not

of milk identical

mag-

induced by natural or experiand biological methods are the released hormones within

During

to suckling epithelial

the

and

(see Cowie and Tindal, 1971). Other species such as rat, mouse, and hamster spend many hours every day with the pups attached to the nipples. In the rat, for example, reflex ejection

counthe

neurones

and

supraoptic

of

School,

Switzerland

Present knowledge of the electrophysiological correlates of neurosecretion is much more extensive for the hypothalamic magnocellular terparts

and Their

to the Secretion

Posterior

J. J.

Activity

to

pressure pattern by an few main

to

measure at

milk

of mammary abrupt rise minutes

is

in ob-

pressure wave in recordings

glands (Fig. 2); in addition, are similar in shape from one the next. A similar rise in

DREIFUSS

52

FIG.

1. Pup

behavior

A) before

intramammary

pressure

i.v.

of

injection

oxytocin. Interestingly, oxytocin response provided (1975)

during to an by the measured

can

0.5-1.0 the

and

be

B) during

induced

mU

of

intermittent

milk

by

the

release

the

negative

pressure

changes

produced by the pups sucking on the nipples. They observed that pups suckle in short bursts and that the overall suckling stimulus provided

For further

injection.

by

the

of

ous, milk

for 15-20

activation

suck However,

the

during

ejections

release sec

interval

3).

A

occurs at the this suck cannot of

after

responsible

the

(Fig.

oxytocin,

the for

period hormone

vigor-

time of be the since of

it

neural

secretion

below).

Several influence of

constant

milk

synchronous ejection.

trigger

(see

was

two

occurs

see text.

explanation,

litter

between

synthetic

suckling in the rat is a reflex essentially constant stimulus litter. Wakerley and Drewett

ET AL.

oxytocin

studies of litter

have attempted to size on the temporal

secretion.

Acute

changes

assess the pattern in

the

PATTERNS

TEMPORAL

IN NEUROHYPOPHYSIAL

SECRETION

53

r

r]

I

I

I

I

I

I

I

I

I

I

I

I

I

mm

FIG. 2. Intermittent nature of reflex milk ejections during suckling in the rat. The doe was anesthetized with urethane (1.3 g/kg, i.p.); intrainammary pressure was recorded from two teat ducts during suckling of the remaining nipples by nine pups. Four milk ejections occurred during the 12 mm of recording shown, each being characterized by a sudden, synchronous rise in intrainammary pressure. The i.v. injection of 0.5 mU synthetic oxytocin yielded a milk ejection response of similar magnitude (not shown).

number

of

suckling

little

influence tocin secreted (Wakerly et conscious only 1 suckling proportional

pups

were

found

to

have

on either the amount of oxyor the timing of milk ejections a!., 1978a). Russell (1980) used

rats

suckled

by

pup. Although stimulus was to

litter

litters

the found size,

the

of

intensity to be mean

10,

22,

or

of the directly frequency

of

milk

ejection

depended

little

(Table In litters

1). a study by Van der Schott of 5 or 10 pups were used.

milk

ejections

light

period

frequency during

occurred of

of the

dark

the milk

period

each day

for

hour both

ejections (Fig.

fell 4).

on

litter

et al. Four

size

(1978), to five

during groups. significantly

the The

DREIFUSS

54 A1

ET AL. TABLE

1.

litter

Frequency

from

Intensity Pups

A2

1 -1201

mm

2.35 4.86

±

o.25c.

±

099d

22

82

5.55

±

l.3l

Pups

=

observation

attached

b

=

-60

-40

-20

0

Seconds

FIG.

3. Suckling activity of pups during nursing in rat. A1, and A3) The upper trace illustrates negative pressure waves induced by a single pup sucking a cannulated nipple, the lower trace illustrates the pressure recorded simultaneously from another mammary gland during two consecutive reflex milk ejections induced by a litter of 10 sucklings. Note the intermittent and apparently random occurrence of short bursts of suckles and the large suck coincident with the rise in intramainmary pressure at milk ejection. B) Histogram showing the average number of pups in a litter displaying sucking movements before and during the rise in intramainmary pressure at milk ejection (ME). The period of spike activity, based on deethe

trophysiological

recordings

hypophysial neurones, (Adapted from Wakerley

Recordings indicate

in

by 15-25 1975.)

sec.

conscious

is released

does

in response

to

only when the electroencephalographic of the rat is synchronized (Fig. 5). Milk never occurred during arousal or during sleep

and

(Lincoln

Tramezzani,

We

have

stimulus

is

essentially

yet

learn

which

al.,

0.05;

d vs e, NS.

1980;

Volo

into

path

process of

the

and the number relay stations innervate

an

the

afferent

the

suckling

intermittent, of

limb

and localization of between the sensory mammary

the endocrine hypothalamus are unknown. A number of attempts made by lesioning experiments

gland

30

min

in six animals.

c vs d, NS (not

afferent

but

path

of

conflicting

significant);

the

results

(Voloschin and and Dottaviano,

Wakerly,

milk

ejec-

have

been

Tramezzani, 1976;

1973; and

Juss

1,980).

A

different,

pharmacological

transmitter-specific define

the

affect

various

the

oxytocin

during

cholinergic

the

that

suckling

in

receptor

one

antagonists,

induce nervous

the

reflex system.

ejecting effect; which

milk on the either

induction

of

(1980)

normally, other hand, failed to

propranolol in refractory eject milk or

many

to propose

be

localized

mic

cell

that

that

the

modulate

downstream bodies,

the

found

to

the

central rat was

had no animals, after the the

of

reflex

functioning, (Tribollet and

et

Richard

13-adrenergic, milk ejection the

from

possibly

drugs,

in which hours

antagonists restored it Recent studies led Moos

receptors

6), and Richard, Tribollet

of

action on a lactating

after

(Fig.

been

by an When

anethesia

subsided

13-receptor a!., 1978).

has

involves

1979;

class

at

the

of

rat and

1978,

Only

results

release

the

(Moos

1979;Clarkeetal., 1978).

The

the

adrenergic

components

al.,

to

which

reflex.

suggest

(nicotinic),

uses

antagonists

transmitters

of

far

dopaminergic

and

synaptic

functioning

so

1975,

approach

agonists

obtained

had

for

inhibimay

hypothalalevel

of

the

neurohypophysis.

hormone neural

the

obtained Voloschin

et

nipples

all

afternoon

superscript

reflex,

tory

where

transformed

The

of the reflex the synaptic

et

1979). to

all-or-none

secretion.

nerves

precedes ME and Drewett,

oxytocin

paradoxical schin

hypothalamo-neuro-

performed

that

suckling activity ejection

of

tion

in the

with

selectively -80

to

period.

Determined

-100

Milk ejections per hourb (mean ± SEM)

stimulus

4

Mean c vs e, P

I

varying

41

a1% ME

with

10

mm

B

of

suckling (%

(n)

milk ejections Russell, 1980.)

of

size. (Adapted

and

still largely have been to interrupt

Activity During

of Oxytocinergic Milk

all

Virtually

neurohypophysis located nuclei

in of

Neurones

Ejection the

axons

originate the

supraoptic

the

hypothalamus.

that

terminate

from and

in

cell

the

bodies

paraventricular This

fact

has

TEMPORAL

PATTERNS

IN NEUROHYPOPHYSIAL

EEG0

1.0

01

‘---PT,

C ,‘

Fur..-

UI in

C

SR

-

0 Ca.

55

SECRETION

2

I

3

4

0

a

I!#{149} : 05

i1j;liSl

-

i1IlU

#{149}

ii

ii,

.0

-*

i-N

i

I

-

U

-

-*I-

UI

I-

SR

SR

6

7

8

9

0

FIG. z

8

12

16

20

24

4

5. Simultaneous

record

of a suckling

8

ing short periods of awakening occurring EEG activity recorded from hippocampus frontal cortex (FC) was typical of slow

(Adapted

12

8

from

16

20

24

8

4

conducted

Voloshin

Day 12

+u

Day

13-

FIG. 4. Suckling behavior and incidence of reflex milk ejections during a 24 h period on Days 12-13 of lactation in rats. Intensity of the suckling stimulus and stretch reactions displayed by the pups was determined in 45 rats nursing a litter of 5 pups (s) and in 45 rats nursing a litter of 10 pups (0). A suckling intensity of 1.0 denotes uninterrupted suckling by more than 80% of the litter. Note 1) that both stimulus intensity and frequency of reflex milk ejections recorded during the dark period were reduced relative to the light period and 2) that the frequency of milk ejections in rats nursing 5 pups was not different from that in rats with 10 pups, although the suckling stimulus was double in the rats nursing the larger litter. (Modified from Van der Schott et al., 1978.)

neurohypophysial so that the cell body approximate

tract

the

of

electrophysiologicaf

identification

neurones.

be

of

By passing

electrode (or in the can

hormone-

current

through

positioned pituitary

initiated

tech-

the

axon

can

and

fibers,

the

be

range i.e.,

which

neuroaction

travel

up

estimated.

record physial

cell body. These antidromically-conspikes are detected by a recording elecwhich explores the supraoptic or paraven-

tricular tential

nucleus. at a fixed that

the

vasopressinergic (Fig. 7). In possible occurrence

to

The detection latency after

activity

of

an oxytocinergic

neurone spontaneously apply of

the

stimulus

a spontaneous,

of an action the stimulus

is

being active shortly

monitored cells, it after

the

latency

of for

velocity

It was for

found

small

anti-

to

bL in

unmyelinated physiological release

of

(Wakerley et al., 1973), it is expected oxytocinergic neurones should alter of firing in relation to each episode of secretion.

Fortunately the

of

milk

rat

ejection

(Lincoln (1973)

and

1975)

at

for

displays

the a

and been

therefore

in Fig.

cells. responsive

a

synchronous

burst

is

lasted \‘100 ejection.

of and

Wakerley able to

of hypothalamo-neurohypomilk ejection. Their

is summarized

dccnormal

at surgical levels 1973). Wakerley

Lincoln

have

the activity neurones finding

a!.,

et

neurosecretory ed that all

attained

the and

of the

9: each

of oxytocin is preceded by an explosive eration in the spike activity of about half

posugor

orthodromically

cipal

each other, reaches the

m/sec.

“.‘0.5

oxytocin that only their rate

Lincoln (1974,

the

the

suckling provides a which causes the preferential

anesthesia

in the stalk),

cancel never

conduction

characteristic

Since stimulus

spikes

hypothalamo-

From a knowledge between stimulation

electrodes

pattern

to the

ducted trode

gests

use

the

for

a stimulating hypophysis axon

the and

sleep.

two

the

and spike

antidromic

invasion,

oxytocin

potentials

SR5, (H)

wave 1979.)

The

along

(Fig. 8). distance

recording dromic the

potential.

somewhere

trophysiologist,

producing

at

and Tramezzani,

action

collide

niques

and

______________

0

permitted

pup

of the electroencephalogram of its mother. A suckling pup with electrodes implanted in the muscles of the neck displayed three stretch reactions (SR) during the ‘-‘10 min of continuous recording shown. Except dur-

0.0

prinpulse accelof the

Double recordings indicatneurones discharged of

action

potentials,

a

which

2-4 sec and involved the production of action potentials per cell at each milk The peak firing rate of 25-80 Hz was within

‘\‘l

sec;

thereafter

the

firing

DREIFUSS

56 A

saline

ET AL.

I

0-3m1

i

(0-9Z)

I

I

H

A

phentolamin. 1mg/kg

phenoxybenzamine 4mg/kg I

0

1

Hours

I

I

2

3

B 15 pMntolanHn. Milk Ejection Ratio xynne

8

B 0-5

1-0

20

Dose

3-0 mg/kg

FIG. 6. Effects of o-adrenergic antagonists on the ejection reflex of the rat. A) The results of three animals are shown in dixgraxnmatic form, with each milk ejection expressed as a vertical bar. Suckling was commenced at time 0. In two animals, phentolamine and phenoxybenzamine, injected about 80 miss later, inhibited the reflex. With phentolamine, the frequency of the milk ejections returned to normal at once after the inhibition had worn off. With phenoxybenzamine, the second milk ejection interval was still increased. B) Quantification of the inhibition induced by the antagonists. The length of the milk ejection interval which followed the application of a drug was expressed as a ratio of the mean for the six preceding milk ejection intervals. (From Tribollet et a!., 1978.) milk

rate

decayed

returned 10).

At

the

typed

high

(Fig.

9).

gland.

rate

ejection,

short of

the

discharge two

cells”

not

stereo-

occurred

again bursts

of

activity

of

consisted

did

(Fig.

same

electrical

which

pause

firing

successive

background

ejection

of

of

differ

a slow,

from

firing

hypothalamo-neurohypophysial in

nonlactating

rise

gave

pressure hormone

milk

firing

observed

This

next

a

resting

frequency

“milk

patterns

firing

low

the

irregular

following

the

Between

activity,

these

and

to

after latency

to

to

an

increase

a latent is due circulate

to

Each

The sudden acceleration cannot be explained

effect

exerted

burst

of

in intramammary

period the and

ejection

hypothalamus precede the

cells rats.

of

time act

it on

by

12-20 takes the

C

sec. for

the

mammary

in firing at milk some feedback

by circulating oxytocin on the since 1) the bursting discharges action of the hormone on its target,

FIG. 7. Some criteria of antidromic identification. Double stimuli 0.7 msec in duration were applied through a stimulation electrode located on the pituitary stalk in an anesthetized rat. The tracings show the stimulation artifacts (first voltage transient in each trace) and the extracellularly recorded action potentials from a neurone located in the hypothalamic supraoptic nucleus. Time base, 1 msec. Note 1) the occurrence of antidromically conducted action potentials 7.5 msec after the stimulus artifact; 2) the ability of the cell to follow stimuli applied at intervals of 10 macc (A), 7 msec (B), and 5 msec (C); 3) the accentuation of the inflection on the rising phase of the action potential (arrows) at short stimulation intervals which is due to the slowing of the passage of the spike from the axon hillock to the partially refractory cell body.

TEMPORAL

PATTERNS

IN NEUROHYPOPHYSIAL

57

SECRETION

A

B

D

H F 100 N

Ut 8

C 0

=

470

80

I-

C

60

in-

0 I-

40

.0

E

20

z 0 0

2

6

6

Antidromic

8

10

latency

12

14

16

18

20

(msec)

FIG. 8. Electrophysiological identification of supraoptico-neurohypophysial neurones. A-E) Tracings from the oscilloscope screen. In each panel, the upper trace records cell firing, and the lower shows 1 macc time marks. Single, 0.5 macc electrical stimuli were applied every 2 sec to the exposed $tuitary stalk; the largest voltage transient, occurring 15 macc after the onset of each oscilloscope sweep, is the stimulation artifact. Two antidromically conducted action potentials occur at latencies of 5 macc (“small” spike) and 10 macc (“large” spike), respectively (A,D,E). In B, a “small” spike occurred spontaneously 2.5 macc before stimulation; collision took place along the hypothalamo-neurohypophysial tract and only the “large” spike reached the site of recording. In C, stimulation was applied 1.5 macc after a “large” action potential had reached the site of stimulation; because of refractoriness, only the “small” spike was conducted antidromically. F) Histogram of the latency for antidromic invasion of supraoptic neurones. Note that most cell bodies are invaded 5-15 macc after stimulation of the pituitary stalk.

DREIFUSS

58

Unit !(

activity

(

ET AL.

RME 13

((If (i

( (f

Mammary

tI (11 11 ‘i:r:if(; I fI(iI(I1I(I

pressure

-

n

-

RME 14

I 1(1(IIIIti(I(ft I (II

((11 (((111ff

#{163} _

.-.‘

__._.

--

RME 15

(11(1 1(11(1(1 (II ((((((1

(1 111 111 11 ft1(1(1 11 1.10mm

J

Hg

f40 ‘10 Exogenous

sec

oxytocin

III((ff(1 I11(I11 if (g 11(1 tIffft 111(11111111(11 (11 I (((1Itt1(1(((11(1 O5mU

.--

I

-

FIG. 9. Record of a supraoptic neurosecretory cell to show the accelerated spike activity which precipitates release of oxytocin during suclding in the rat. Reflex milk ejections (RME) are numbered from the onset of suckling. Note: 1) the uniformity of the acceleration in activity, 2) the 12-13 sec latency from the acceleration in spike activity to the rise in intramammary pressure, and 3) the failure of oxytocin injected iv. and the induced milk ejection to influence the spike activity of the neurone. (From Lincoln, 1974a.) the

and i.v.

2) no injection

alteration

in

of

oxytocin

unit

Lincoln, 1974c; Wakerley Immunocytochemical entially adsorbed antisera both

supraoptic

contain distinct and oxytocinergic Dierickx

these

section.

They

saw

the also 1975). differthat

paraventricular

nuclei

of vasopressinergic Vandesande

succeeded neurones

the

and Deverson, studies using have indicated

populations neurones.

(1975)

staining supporting

and

firing follows (Fig. 9) (see

in the

no

double-stained

“one

neurone-one

in same

and

differentially histological cells, hormone”

thus

hypothesis.

Cell

al.

showed

(1975)

oxytocinergic

equal optic cell

bodies;

performed that

by

and antibody.

were only

in nearly The “6500

supralarge

vasopressinergic, 16% Of the

forming the magnocellular ventricular nuclei, 51% were vasopressin and 40% oxytocin. One possible interpretation

et and

distributed

in both nuclei. found to contain

53%

Swaab

vasopressinergic

are

neurones

proportions nuclei were

oxytocinergic, with either

counts

failed 2100’

31% to stain neurones

part of the parafound to contain of

the

fact

that

TEMPORAL

PATTERNS

IN NEUROHYPOPHYSIAL

40

Though

0 0

30

ea

rate

Rote

between

at

e;ection

IIk

neural

additional

of

15

C a

a spurt

caused

by

slow

the

high

0

20

40 F,r:ng

FIG.

10.

cinergic ing the

of

between

burst

milk

preceding

from

60

rate

Distribution

cells

(Adapted

firing ejection

a reflex

Cross,

50

(spIkes

100

Brimble

et

rates of 47 oxytoresponses and durof

oxytocin.

Phasic

Activity

and

Neuro

nes

1974.)

Early

the

intermittent

suckling of action neurohypophysial

onal cells.

takes no

responsive to

react

at

if

ejection,

cell

it

was

ejections

the

ejection ejection

cells cells; of

neur-

Wakerley,

was

obtained

of

a

other

milk

one

1975). that

F2a

or milk

no

effect

on

precise

distention more

in

have

seen

that

during cue

from

provides

easily

graded

the

timing

of the

release

Jennings, et al., relative

was

when

by

drinking rats,

all were

in

water,

normal

teristic

of

which

et al.,

can

1976b).

to

is

release

now

et

phases

only

the

activity

of the supraoptic

in the normally was increased was the

the

Thus,

one-tenth in

hydratup to

chronically

monkeys

from

In

1975).

to

after

compared (Fig.

cause

hormones.

a!.,

1978; firing

which

located

widely spike

dog

(Hay-

phasically

secretion

conditions

an

It

later

and

al.,

hypothalamo-neurohypophysial not excited prior

discharged

was

cat,

of

preventing

(Arnauld

which

Initially

firing

stimuli

monkey

hormone

stimulated

of

stimulus

by

nucleus fired phasically ed animal; this proportion 50%

often

12).

sheep,

cells

pattern

(Dreifuss

phasic

lactating cells ejection

milk

deprivation

with

only

of

12%

under

13). accepted in

that the

rat

a

phasic

is a charac-

vasopressinergic

neurones

stimulated

their

Evidence

supporting

hormone.

a of

which

1973;Jenningset 1979).

conscious

and

which

(Fig.

proportion

neurosecretory

poten-

Dreifuss

activity

of neurohypophysial

in the

action

neurones

influenced

secretion

intermit-

of activity

activity

second

rat,

indi-

firing cells, consisting

hypothalamo-neurohypophysial

suckling is not governed by the suckling pups. Vaginal acute

of

spike

of

monkey,

an

1971;

no

per

the in

drinking

oxytocin

or

spikes

in

bursts

phasically 1-2 mm

periods

had

hypothalamo-

devoid

Lincoln,

these every

low

15

The

them. In obtained

In

with

noticed

cells

possessing distinct afferent connections of angiotensin II cells, and electrical

exerting

of

“milk cells”

of prostaglandin prostaglandin excited

while

al.,

fire

by

periods

and

periods

alternate

ward and Yamashita

subsequent

“non-milk-ejection

by

1972). recurs

described

the

septum inhibited effects were

latter,

al.,

et

of

characterized

Kelly, pattern

on

and inhibited most non-milkmorphine reduced the rate of

the

et

Wakerley

studies

proportion

(Wakerley

milk ejection, at the previ-

all

ejection

Poulain

Vasopressinergic

neurones

pattern,

exceed

former. We

be

before

milk

electrophysiological that

interrupted

if a cell

before

and

separate entities characteristics or 2). Administration both classes of

injection The

firing

excited

and

following morphine.

one

ejection;

evidence

of the differential

this

observed:

of

excited

stimulation contrast,

that

to respond

was

cells”

represent receptor (Table excited

time

(Lincoln

Additional ejection

is

been

milk

a

oxytocin

place in all oxytocinergic progressive recruitment

failed

following

hand,

of

has

regularly

or

milk

tials

neurones

also

ous

by a high frequency burst in half of the hypothalamoneurones

response Indeed,

failed

during

tent

secretion

is preceded potentials

of “milk continuous never reached

during

1978;

see

release

stimulation

and

1977; al.,

neurohypophysial

a

osmotic

fast however,

Dyball,

shall

1978b).

Isec)

release

1977;

a

we

As

recruitment

observed

and

cated

of

relationship

hormone

and

progressive

levels

(Brimble

0

of

hypothalamothe secretion

11).

persisting

cells” into rates of firing,

amount

causal

(Fig.

and

hemorrhage a

ejection activity;

5

the

a

in firing of neurones and

10

induced

it

the

smaller than those the results provided

for

increase

of hormone

the

and

were suckling,

evidence

below,

59

response

released during

between the neurohypophysial

ejectIons

mIlk

S

z

the

hormone observed

35

0

SECRETION

DREIFUSS

ET AL.

administration

of drugs

60 2. Effects

TABLE

of intracerebroventricular

M ilk eje ction cellsb

F20

Morphine Angiotensin Septal

ng)

f

11(10

displayed

in firing

5

0

0

5

15

Akaishi

7

0

0

0

12

Clarke

7

0

0

5

0

0

Akaishi

et al. (1980)

0

0

13

0

0

9

Poulain

et al. (1980)

rate;

a brief,

to be oxytocinergic. to be vasopressinergic

Reference

0

ng)

t, Increase

cells

bThese

cells’ ‘V

25

ng)

stimulation

aSymimls:

assumed

(500

(2-10

cells.a

Non-milkejection

I\

Prostaglandin

on hypothalamo-neurohypophysial

,

high

in firing

decrease frequency

burst

since

neurones,

their

rate; of

Negoro

(1979)

no effect.

“.,

action

activity

and

et al. (1980)

potentials

failed

at milk

to correlate

1

ejection

with

milk

are therefore

ejection.

10

Firing

frequency

(spikes

]v5

and

/sec)

Intramammary pressure (mrnHg)

I

I

I

I

Firing frequency

(spikes/sec)

Intramommory pressure (mmHg)

15

20-30

11.

sec

Effects

after

the

of

onset

vaginal

distention

sec

on the rate of firing of two supraoptic neumnes. The latencies for antidromic invasion were 10.5 msec for cell A and 12.0 msec for cell B. Both neurones were excited by an increase in intravaginal pressure to 260-300 mm Hg for the duration indicated by the length of the black bars; in cell B, this period of accelerated spike activity was followed by a pause in firing. Intramainmary pressure started to rise FIG.

of distention.

TEMPORAL

PATTERNS

IN NEUROHYPOPHYSIAL

SECRETION

61

ANH

1

20

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FIG. 12. Phasic pattern of firing of a neurone from the supraoptic nucleus projecting to the neurophyophysis (antidromic latency, 9 macc). A) 3.5-mm ratemeter record of the spontaneous activity. The faster time scale applies to B and C, where the onset of 20 successive bursts (B) and their average rate of firing prior to and at the beginning of the bursts (C) are shown.

this

contention

the

effects

of

cells

which

had

cells”

derives

and

been

which

pressin

and

by

1978b)

or by

water

cells,”

of

a faster pattern

types

same time to a detectable Vaginal distention for

way,

both randomly

et

carotid

14).

saline

secretion

displayed

increased;

in a

into

cells

low the

which of

those

and typical

the

were phases

which

irregular pattern

a

fired rate, charac-

the

which

of

vasopressin to

(Dreifuss triggered

an

Approximately

one

circulation

intramammary

pressure

rose.

increase

of

vasopressin,

mammary

in

pressure

that

al.,

exerts

cells

Occlusion burst

of

(Fig.

15).

time In

this from

an

is about

1975)

firing

period

resulted

which gland

et

additional

latent

by

a preferential

1976a).

short

the

a

(Fig.

is provided

phasically al.,

both

neurones

(Harris et

releases

excited

causes

excite

vasopressin.

which

stimulus

found

after

of

firing

convenient

selectively

activity

adopted

In

was

consistently

latter

duration

and

fashion.

never

phasically

occlusion,

irregular

but

the

evolved

slow,

The

response.

at

different

release

hormones,

and

A more

13).

secretion can also and lead at the

example,

neurohypophysial

et al., of the al.,

(Fig.

of hormone firing neurones

The

activity.

of

neurones

vaso-

(Poulain pressure

a

phasic

both

discharge,

phasically, activity

in from

of

spontaneously activity

ejection

of hypertonic

but

of

Acute stimuli excite phasically

cells.”

(Wakerley

injection

changed

firing

“milk

teristic

on

sustained

withdrawal the osmotic

i.p.

former to

a

which

and Dyball, 1977). All stimuli excited “milk ejection cells” and the “non-

The

two

in

deprivation

milk-ejection

phasic

as

in tested

released

oxytocin

plasma

firing

were

probably

blood in raising

and

(Brimble both the

studies

classified

in

1977)

from stimuli

“non-milk-ejection

stimuli,

consisted

various

effect

one-sixth

later, instance,

an

action on

the

that

oxytocin. More

than

90%

of

all

phasically

firing

of

DREIFUSS

62 Normal

ET AL.

Rat cell

Dehydrated

-J

A

Rat

111111 1(1(111111111111(111

I

I Utli ( (1llhII[

ti ii 1 1 1

C

C

I 1(ItII (1I 1 iiiiriiiiiiiiiit

#{163} IU I I

(I

I I(1I#{149}

It((( III(IIIII(

I

1I I 1(1 1III!I IIIIV( I1 1111 (UII

IHI

E

I

HI

I I

F

s.e.c FIG. 13. Firing patterns of presumed oxytocinergic and vasopressinergic cells in a normally hydrated rat and in a rat deprived of drinking water for 18 h. Middle panel shows the approximate sites of recording of 12 antidromically identified neurones in the supraoptic nucleus (SON), lateral to the optic tract (OT). On the right and left are shown for each neurone a pen recording of a few minutes of electrical activity. Each cell was recorded during suckling, and the period of activity shown encompasses a single reflex milk ejection, signaled by an abrupt rise in intramammary pressure (not shown). The arrows beneath the traces indicate the expected time of oxytocin release associated with milk ejection. In the normal rat, cells B, C, and F showed a characteristic burst of firing at this time, and the cells were deemed to be oxytocinergic (blackened arrows); for cells A, D, aiid E (open arrows), no excitation occurred at milk ejection and hence these cells were classified as presumptive vasopressinergic neurones. In the rat dehydrated for 18 h, cells A, C, and F were classified as oxytocmn-producing neurones, and cells B, D, and E as vasopressinergic. Note the striking phasic activity of the three vasopressinergic neurones during water deprivation and the distinct periodicity of each. (Modified from Wakerley et aL, 1978b.)

neurones

were

carotid

activated

occlusion

Neurones

firing

either

at

inhibited

animals,

It should

conditions, timing of one

from

in

low

unaffected noted

phasically

firing

simultaneously

microelectrode,

two

or must vitro

to the neurones

cells,

ing occlusion (Fig. 16). To determine whether hypoth alamo-neurohypophysial

in

the

through

both

origin

neurone phasic

not synchronized prior synchronous bursts of

using

the

under

were

which

were

by

a synaptic

be

in

relative

studied

techniques.

Results

pattern

slices, have

next. single

where

and

this

pattern

contrast, electrodes,

to

that

the

the

hypothalamic inputs of

of

cells

them

still

with

a

that observed in the intact Wakerley, 1980). Some cells following

use

can

impaled

and

within

proportion

explant

supraoptic

neurones

in

many

retained tion.

living

so

a

identical (Haller

studies

generates

resides

extrahypothalamic

severed, phasically,

of

that

activity Thus,

most

been

In

drive,

mechanism of

pattern animal

area

isolation obtained

the

nuclei.

discharge

usually

phasic activity of neurones is of

is imposed

that

phasic

same

to occlusion, discharged action potentials followthe

suggest

same

were a

far the

magnocellular

there is a great variability in the the phases of activity and quiescence

recorded

cells

rates in

that

by

1976a).

al.,

irregular

be

when

the

manner

et

or

However,

local

this

(Dreifuss

synaptic cultures

nucleus be

visualized

with

stained

17) after several weeks and Dreifuss, 1979a,b). taneous activity revelaed discharge patterns: slow

of

isolafrom

neonatal under

intracellular

for

further

the rats, phase

micro-

analysis

(Fig.

of culturing (G#{227}hwiler Analysis of the spononce more two basic irregular activity or a

TEMPORAL

PATTERNS

IN NEUROHYPOPHYSIAL

SECRETION

63

Unit

jijA

lntro-vo,oI

pressure

n.J

I

A

-

-

IIP

A

..

-

15

j14

1

JMIIIJIU 300

i-iI

0’

1 mm FIG. 14. Effects of vaginal The record is continuous for trace, burst etal.,

time (in mm). of firing whose 1976b.)

phasic

whether

with

by

quiescent

the of

cultures

were

block

synaptic

these

the

these

cells

synaptic to

the

activity

was majority

an

in origin, known

In was

tested. of

Judging cells

exhibited

of vaginal the intensity

a minority

criteria the to

for

pacemaker in

ed

by

on

membrane

Phasic

brain

is not

that

they

their

they still

were

solutions and

an additional (From Dreifuss

of follower cells (Fig. of neurones fulfilled

cells:

active

latency, 7 macc). pressure; lower

each induced distention.

establishing

transmission on

distention; of vaginal

typical

However,

addition,

dependent

periods upon

features

determine

endogenous

solutions

transmission. phasic

bursts

To

was

or

to five depended

frequency

activity

exposed

potential criteria,

high periods.

phasic

property

whether membrane

The animal was subjected latency and magnitude

pattern

separated

on a phasically firing supraoptic neurone (antidromic min. Upper trace, firing rate; middle trace, intravaginal

distention about 16.5

were

18).

the true

phasically

that

blocked

synaptic

phase

parameters

depend-

potential.

neural

restricted

activity

in

to

the

presumptive

mammalian

vasopres-

DREIFUSS

64

ET

AL.

A intro

mammary

-

pressure

f”

unit I

I

I

B_,#{231}_

JI I

I

I

I

I

I

lx5

C

Jo

i4iJ

r

S

I

I

:i i

I

I

1nn FIG. 15. Responses of a phasically firing supraoptic neurone to bilateral carotid occlusion (B) and to exogenous vasopressin (C). Each panelu upper trace, intramammary pressure; middle trace, firing rate; iower trace, time (in min). This neurone, electrophysiologically identified as projecting to the neurohypophysis (antidromic latency, 9 macc) fired spontaneously with bursts of activity separated by quiescent intervals (A). Bilateral occlusion of the common carotid arteries applied for 15 sec (black bar) triggered a supplementary burst of activity from the neurone, whose peak firing rate exceeded that of the spontaneously occurring bursts. A rise of intramammary pressure occurred about 16 sec after the peak firing rate of the supplementary burst was attained (B). The i.v. injection of 0.25 mU vasopressin (black triangle) caused a similar milk ejection response after a comparable latency, but failed to affect the periodicity of the neurone (C).

sinergic

neurones;

cells

hypothalamus gions Thus,

and

were

probably

included

cells

from the

usually

synaptic

was

most

the

and

activity. firing

ventromedial 1975).

upon neurones

Potentials

in Other

Recent

evidence

indicates

that

action

potentials

and

nuclei Phasic

related to their secretory

this

of type

can

generate at first

surprising

little attention.

those

midseventies, Petersen most gland cells appeared

optic nucleus exist in the thalamus remains to be seen.

mediobasal

supra-

hypo-

ability

to

intermittent by be

activity.

all-or-none

of their connectivity (Geller and Hoffer, 1977). Whether true pacemaker neurones similar to of the

the

That classical endocrine cells, which lack the axon and dendrites characteristic of neurones, appears

a consequence

in cultures

Cells

is a property also shared endocrine cells and may

trains of spikes some non-neural

received

demonstrated

Endocrine

generate

which

elimination that

Action

re-

neuroendocrine

suggesting in

of

cultures

(Geller,

vanished

transmission,

activity

in

parvicellular

arcuate

areas

patterns of of phasically

detected

hypothalamus

firing of

the

other

extrahypothalamic

display comparable a significant number

neurones

of

in

in

review

of

excitable.

the

Two

literature

action until

recently

From

an

extensive

published

(1976) not

exceptions

potentials

and

until

the

concluded that to be electrically

were

noted,

the

j3

TEMPORAL

Unit

IN NEUROHYPOPI-IYSIAL

PATTERNS

SECRETION

65

1

Jn1 -

Unit 2

I

I

I

r

JLn#

M&rwv’

I

U U)

a, U)

a, -‘

(1)

---I-

mm Responses to bilateral carotid occlusion of two phasically firing supraoptic neurones recorded simultaneously through a single recording micropipette. Continuous ratemeter record for about 8 mm shows that their bursts, which were out of phase prior to occlusion, were briefly synchronized by occlusion applied during time indicated by heavy black bar. (From Dreifuss et al., 1976a.) FIG.

16.

cells of Matthews,

the endocrine pancreas 1970) and cells of the

exposed

to

(Matthews recorded

and from

variable

amplitude

Moreover, cells pituitary action

of

ACTH

cells

and

of

failed

medulla to disclose Consequently,

long from

duration. chromaffin

from the the

and

impact

on

anterior

rine

have

be

seen

that

al.,

1976;

of

(Tischler

findings

of

kevich

however,

been

et

and

cells

in

Biales

al.,

1976),

Douglas,

little

immediate

community.

shown

The main are summarized

et

existence

had

scientific

years,

cells

potentials. authors

coworkers

the

In recent

The spikes of low and

and

Matthews

media

1973). were

recordings

adrenal

potentials.

potassium-free

Saffran, these cells

early the

in

(Dean and adrenal cortex

many to

more

generate

endocaction

findings from a number of in Table 3, where it can the et

adrenal al., the 1977,

medulla 1976), the anterior

1978;

lobe Osawa

(Brandt thyroid (Tarasand

DREIFUSS

66

ET AL.

V

I.

T.

%;

I

#{149}-1 ,b5’1

-

.

FIG. 17. Upper) was taken from the stained with Bodian’s and Dreifuss, 1979b.)

Sand,

1978),

pituitary

and

category.

some

potentials the

phasic

secretory

of

these

occur

in

has

been

this

glands,

of

especially high

firing

is

of stimulated of

low

quiescent;

a period

the

‘interphase’ potential. burst

phasic

continuous period.

cells of

pancreatic

glucose a

rise

pattern cells.

concentrations, in

external

of continuous

of

glucose

firing,

first

but

this

These

reduction

al.,

Except

(which were

and

the

glucose

for

were less

spontaneous

the

derived

thoroughly action

phasic

each

length

of

a new

phase

and develop are related

and

1978) of

the

may effects

(Meissner

a

during

their resting membrane addition of glucose, the

decreases,

firing

into

repolarize

increases,

periods

et

cells

towards Upon further

secretion

In the j3 cells

the

duration

quiescent

rates

common

-

develops

in which

neuro-

in

average

-.

subsequently

pattern

comparable

hypothalamic

activity

man

presence induces

to

endocrine clusters

noticed

the

1976;

belong

occurrence

relatively

discharge are

of

of

Hadley,

1978)

-

of living neurones after 25 days of culture; the initial explant supraoptic nucleus in a neonatal rat. Lower) Two large neurones culture of the hypothalamic supraoptic region. (From Gahwiler

lobe

and

The

displayed

firing. Phasic

intermediate

pattern

cells.

activity which

the (Davis

Taraskevich,

In

action to

and gland

Douglas

Phase contrast photograph area of the hypothalamic silver stain in a 21-day-old

,-.

I,

for

a to

the of

short insulin

Schmelz,

1974;

Gager-

rapidly

reversed

upon

are

concentration.

thyroid

from studied), potentials

parafollicular

cells

a tumor the

line

frequency in

all

the

and of

cell

TEMPORAL

IN NEUROHYPOPHYSIAL

PATTERNS

SECRETION

67

A

U

_

_

_

_

_hj80

U) U.’

_

_

_

U.’

(I)

_jj30

_

20

sec

B

2 sec FIG. 18. Phasically firing neurones in cultures of the hypothalamic supraoptic ares. A) Ratemeter records of two simultaneously recorded neurones in a 31-day-old culture. Bursts (similar to those seen in the living rat, Fig. 11) are seen to occur synchronously in both cells, unlike what is usually seen in situ (Fig. 15). (From G#{225}hwiler et al., 1978.) B) Intracellular records of the spontaneous activity of a supraoptic neurone kept 44 days in vitro. Upper trace shows phasic firing when the cell was moderately hyperpolarized (-0.2 nA). Lower trace illustrates that stronger hyperpolarization (-0.6 nA) reveals the prominent excitatory postsynaptic potentials which trigger the bursts of activity, but affects neither the periodicity nor the duration of the bursts. (From G#{228}hwiler and Dreifuss, 1979a.)

types known

tabulated was or suspected

shown to be secretagogues

by substances which example is provided chromaffin cells to choline.

The

increased

firing

in

which

cells

was

is

of

on

increased

a

(Douglas

rate

et

1975;

of of

pars

intermedia

and

Taraskevich,

of

the

firing of

to

secretion of the

1978).

cells

by

prolactin

Douglas, presumed

of

1978). be a MSH,

dissociated

pituitary

types

cell.

causes with

gland

listed

This

the the

quently coalesced

rise

are

Gorman

and

critical

the extracellular depolarizing believed

to

the

and

within

calcium granules subse-

space. Action cell-limiting

induce

located external

Thomas,

site

free

forms at the site of the leaving the hormone free

on this calcium

the

opening

membrane. flows into

secretion. A bursting shown to be particu-

in causing an calcium (Eckert

In neurosecretory

their

which concentra-

the secretory membrane,

interior to activate of firing has been

larly effective cellular free

3 liberate process in the

some

of

an opening membranes, into by

a rise

in cytoplasmic

apposition cell-limiting

of calcium-channels As a consequence, the cell pattern

in Table

by exocytosis, by a transient free calcium at

membrane,

Taras-

reduced

cell

to diffuse potentials,

frequency

and

also

by

Comprolactin

discharge

and

effect not

1976).

All secretion triggered tion of the

cells an

but al.,

inhibitor

inhibitor the

the

atropine,

1977)

known

acetyl-

chromaffin

(Kidokoro,

(Taraskevich which is

physiological from

TRH

adrenal

of

manner,

their

Douglas,

dopamine,

of

adenohypophysial that

by

and

decreased

response

cultured

by

shown

A good

application

(Brandt studies

secretion Dopamine,

the

the

blocked

have

kevich

by

secretion.

a dose-dependent

hexamethonium parable

diminish

increased by and reduced

increase et

in al.,

1978). cells

such

as hypothalamo-

intra1977;

is

DREIFUSS

68 TABLE

3. Action

Approximate duration

potentials

in nonneuronal

spike

endocrine

ET AL.

cells.a

Pancreas (ft-cells)

Adrenal medulla

Thyroid (C-cells)

Anterior lobe

Intermediate lobe

100

2

3

5

4

(+)

+

(+)

+

(macc)

Na component

Ca component Spontaneous firing rate (spikes/sec) Bursting activity Effects of secretagogues and release-inhibitors

asymbols: acetylcholine;

separated

at

from

than

the

occur

as

vertebrate

membrane

hormone

hor-

vitro

cell

body,

known axons

to and

In hand,

argued

in

that

so

they

in

non-neural

can

be

endocrine of

et

parallel

with

al.,

1971).

To

cause

to Electrical

The

studies

hypophysial that

release in

of

on

potentials, of

obtained

in

has

stimulated

trical or eters

stimuli in

situ of

studies

have to

establish

stimulation

suggest,

patterns

Further

of

the

the to

10

Hz.

short tion cies

cellular

either

in

vitro

nerve

paramamounts

10

of

periods action

at

interpreted of

terminal

These hypophysis

and

Hz,

are

calcium when

necessity

studies showed an individual

on

a

at

some

impulse al.,

that action

is

facilita-

synapses,

chemical

et

which

temporal

depend

(Dreifuss

for

The

frequency,

next

of

effective

conducfrequen-

remaining the

hormone

because at high

axons. of

to

about

frequency

frequencies

to

have of

“-‘50

a critical process

of

stimuli

with

many

hormone

amplitude

frequency

unmyelinated

observed

vary

in

the

only, probably potentials fails above of the

site

in

potential),

steeply

po-

to (Dreifuss

increase

Between

action

output

a critical

secre-

found

was

increases

in small

fraction elec-

temporal

of

compound

decrease

Higher

been

been

of

the

above

to stimulate reminiscent

Trains

applied how

applied

tion

deterhas

neurohypophysis

electrically.

relate

that

patterning, secretion

where

been

and

evidence

their

hormone

be

a

the depolarization

hormone

action

stimulation.

the

and

oxytocinergic

and

rate

little

modulate

temporal

cells.

the

been

the

compound

output

leave

oxytocin

between

vasopressinergic action

above

potentials and

that differ

hypothalamo-neuro-

outlined

action

addition,

mine

the

vasopressin

activity

in

Stimulation

system

doubt

Release

the

a

a detectable (and

stimulaconducted

depolarize

amplitude

and

studies.

electrical

axonal

as

whose

in

epiphenomenon

vitro

release

generates

This

recorded

tential

in

bodies,

hormone

by

which

endings.

been

cell

for

stimulus

para-

have

viable

increased

potentials

tory

can

hypothesis

remain

the from

and they

neurohypophysis,

be

each

is of

supraoptic when

preparation

isolated

secretion

Response

ACh,

majority originating

hypothalamic

axons

the

action

do

their

a useful

tion;

the

Even

from

secretory

In

1976).

the

the

in

-nuclei.

secretion

far,

(Petersen,

Hormone

rate;

neurohypophysis

the great endings

located

separated

coalescence.

Neurohypophysial

in firing

The

contain axon

ventricular

provide

exocytosis.

studied

an

4, decrease

studies.

neurones

that

and of

out

only

rate;

secreted.

In

a consequence

rules

potentials

firing

in

widely

place in the cell-limiting

secretion

potentials this

represent

of

of cells which shed their by exocytosis, in particular

action

action

cells

be

cells

increase

are

other

take of the

consequence

opinion,

t,

generated. the

are

of

4

4

sites

are

exocrine

generate

that

cause

t

4

occasions;

the

on

it can

t

hormone.

of

potentials

a

ACh

on

the

secretion areas

a majority product

our

Serotonin Dopamine

endings

cells

action

However, secretory

In

(+)

TRH t Dopamine

axon

Therefore, cells

not

(+)

region

and adjacent

membrane.

all