Repeated acquisition of blood samples from small laboratory animals, such as rodents, guinea pigs, and rabbits, is an important aspect for pharmaceutical lead optimization and also for reducing the number of animals used in research1,2. The pipeline for developing new diagnostic tools and drug formulation (e.g., vaccine) requires access to different volumes of blood in order to evaluate their robustness and performance in vivo, such as pharmacokinetics (PK), toxicity, and sensitivity3,4,5.
The laboratory approach to blood sample collection is broadly classified into two types, surgical and nonsurgical6. The nonsurgical approach is relatively easy to grasp for the researcher, which includes common techniques, such as cardiac puncture, orbital sinus puncture, and bleeding of the saphenous and tail vein. Multiple blood sampling is possible by some non-surgical methods, but the sample volume is small and can cause physical wound and psychological stress to the animals1. On the other hand, the surgical approach is a favorite alternative to repeated venipuncture, and it involves placement of a temporary or permanent cannula in the blood vessels of animals7,8,9. The large blood volume could be repeatedly withdrawn through the cannula in conscious rats while avoiding the stress and pain due to the handling technique, restrain, and anesthesia7,8,10,11. However, the cannula implantation requires an experienced researcher with adequate training in order to successfully collect the blood.
Blood collection through jugular vein cannulation (JVC) in rats is the most widely used method to study the drug PK6,10,12,13. Yet, establishment of the JVC rat model needs careful practice of microsurgical skills and knowledge of postsurgical care and maintenance. Especially, after the surgery, the rat requires administration of analgesics and sufficient recovery time to reach stable physiological condition for further experiments13,14,15. Although the body weight gain (i.e., >10 g) is a valid and commonly applied indicator for the rat's recovery, it is not uncommon that the rats have unexpected death postoperatively due to dehydration, infection, and inflammation, which could be subtle to notice at the early onset14,15. In addition, catheter obstruction in the JVC model remains to be an issue during the blood collection.
The present protocol has demonstrated in detail the microsurgical procedures for JVC in an anesthetized rat with specific focus on the identification, isolation, and cannulation of the jugular vein. The importance of physiological and hematological monitoring of the rats during the recovery phase is highlighted. Finally, serial blood samples were collected through the venous catheter to study the PK of the orally administered natural phenol ellagic acid with poor bioavailability (i.e., low systemic concentration) to verify the JVC rat model.