A procedure for intravenous injection using external jugular vein in Mongolian gerbil (Meriones unguiculatus) D Kakol Palm1 and P Holla¨nder2 1
Department of Integrative Pharmacology; 2Department of DMPK and Bioanalytical Chemistry, AstraZeneca R&D Mo¨lndal, Sweden
Summary The Mongolian gerbil is commonly used in medical research. Intravenous administration of compounds in gerbils is difficult as tail vein injection sites are not visible. The present study describes a method for intravenous administration into the jugular vein in Mongolian gerbil by using an ‘over-the-needle’ catheter under anaesthesia. The catheter penetrates the pectoral muscle and is easily inserted into the vein. The method is simple and avoids extensive surgery in the animals.
Keywords Gerbil; anaesthesia; intravenous administration; jugular vein
The Mongolian gerbil has been used as an experimental animal for many years. Some of the earliest studies were performed over 40 years ago (Schwentker 1960, Rich 1968). Other reports include behavioural studies, both for exploratory and avoidance behaviour measurements (Walters et al. 1963). The usage of gerbils in experiments often requires injection of compounds. Intraperitoneal or oral administration of compounds is relatively easy to perform in gerbils. However, intravenous administration of compounds is more difficult as, in contrast to rats and mice, tail vein injection sites are not visible in gerbils. The jugular and femoral veins are alternative routes for compound administration in rodents. Many investigators use catheters for intravenous administration. To avoid bleeding by puncturing with a needle during surgery, it is necessary to ligate the vein (Popovic & Popovic 1960). This procedure affects the blood circulation in general,
increases surgery time and results in the need for postoperative care. To prevent this in gerbils, some investigators have used a minimally invasive procedure for intravenous administration, for instance via a femoral vein (Pe´rez-Garcı´a et al. 2003). Under anaesthesia, the thigh was shaved and a 0.5 cm incision parallel to the vein was made. The connective tissue was withdrawn and the femoral vein was exposed. A syringe with a 30 G needle was used for the injection (Pe´rez-Garcı´a et al. 2003). However, under some conditions, the jugular vein is preferred as an injection site as larger volumes can be administered. Therefore, the aim of the present study was to develop a method for compound administration into the jugular vein in gerbils without ligating the vein and without causing any bleeding.
Correspondence: D Kakol Palm, Department of Integrative Pharmacology, AstraZeneca R&D Mo¨lndal, S-431 83 Mo¨lndal, Sweden. Email:
[email protected]
Fifty male Mongolian gerbils, weighing 62–130 g (Charles River, Sulzfeld, Germany)
Accepted 8 December 2006
Materials and methods Animals
r Laboratory Animals Ltd. Laboratory Animals (2007) 41, 403–405
D Kakol Palm & P Holla¨nder
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were used. The animals were between eight weeks and 11 months old. Before and after surgery, the animals were kept five by five or 10 by 10 in environmentally enriched cages (80 cm 60 cm, height 40 cm), in conditions adjusted for gerbils (plastic tubes, sand, hay, nesting material) with 12 h light/dark cycle. Food and water were available ad libitum. All experiments were approved by the local animal ethics review committee in Go¨teborg, Sweden.
Jugular vein Pectoral muscle
Figure 1 Exposed jugular vein and pectoral muscle
Experimental procedure
The current technique was developed in order to study the pharmacokinetic profile of compounds administered intravenously in gerbils. The animals were moved one by one from their home cages to the laboratory and anaesthetized with isoflurane (Forenes, Abbott Scandinavia AB, Solna, Sweden). The throat was shaved, disinfected and a 1–1.5 cm incision was made just over one of the external jugular veins. The adjacent connective tissue was carefully stretched apart, exposing the external jugular vein and a part of the pectoral muscle (Figure 1). An ‘over-the-needle’ catheter for intravenous injection (BD Neoflons, Becton Dickinson Infusion Therapy AB, Helsingborg, Sweden) was used. The catheter (24GA, 0.7 19 mm) consists of a needle inside a plastic tube. The end of the catheter was inserted into the vein after penetrating through the pectoral muscle (Figure 2). The needle was removed and the catheter was moved deeper into the vein. The catheter was immediately used for administration or for blood sampling (Figure 3). To avoid potential bleeding during removal of the plastic tube, tweezers were clamped around the plastic tube and the tube was removed slowly. The skin was then sutured. The whole procedure took less than 5 min. There was no bleeding detected in any case, neither immediately after the administration nor subsequently. After recovery from anaesthesia, the animals were observed individually and moved to their home cages. The procedure did not cause any disturbance in the home cage environment (e.g. hierarchy). Analgesics were not administered following the procedure. Laboratory Animals (2007) 41
Figure 2 Use of the cannula
Figure 3 Plastic tube from the cannula inside a jugular vein
The incision was small and no visual signs of discomfort or pain were detected in any case. Besides, we wanted to avoid any risk
Procedure for intravenous injection in gerbils
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of pharmacokinetic interactions that might occur between analgesics and the administered compounds.
is simple and avoids extensive surgery in the animals, which recover very quickly afterwards.
Discussion
Acknowledgements We thank Ann-Christin Nordstro¨m from the Department of Integrative Pharmacology/Laboratory Animal Resources for the excellent contribution with photographs and Dr Erik Lindstro¨m from the Department of Integrative Pharmacology for his help with the manuscript.
Mongolian gerbils (Meriones unguiculatus) are nowadays commonly used in laboratories. Intravenous drug administration in gerbil is difficult to perform mostly because the external injection sites, for example tail veins, are not visible. The method using the femoral vein described by Pe´rez-Garcı´a et al. (2003) is quick as the vessel is easily visualized, but the maximum inserted volume is limited to 0.1–0.2 mL. The current study describes a method for intravenous administration in the jugular vein. This injection procedure allows the administration of a larger volume (up to 0.5 mL) and ensures that the intended dose and volume enter the circulatory system without the risk of perivascular administration. The other advantage of the current method is a possibility of blood sampling from the jugular vein. The method
References Pe´rez-Garcı´a CC, Pen˜a-Penabad M, Cano-Ra´bano MJ, et al. (2003) A simple procedure to perform intravenous injection in the Mongolian gerbil (Meriones unguiculatus). Laboratory Animals 37, 68–71 Popovic V, Popovic P (1960) Permanent cannulation of aorta and vena cava in rats and ground squirrels. Journal of Applied Physiology 15, 727–8 Rich ST (1968) The Mongolian gerbil (Meriones unguiculatus) in research. Laboratory Animal Care 18, 235–43 Schwentker V (1960) The gerbil, a new laboratory animal. Illinois Veterinarian 6, 5–9 Walters GC, Pearl J, Rogers JV (1963) The gerbil as a subject in behavioral research. Psychological Reports 12, 315–18
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