Abstract
Teaching practicals for receptor physiology/pharmacology in medical and veterinary schools have involved the use of in vitro experiments using tissues from laboratory animals, which have been killed for isolated vascular strip or ring preparations. However, the use of scavenged tissues has been advocated to reduce animal use. Utilising discarded tissues from routine surgical procedures, such as canine neutering, has not previously been investigated. Canine testicular and uterine tissues (discarded tissues) were obtained from routine neutering procedures performed by the veterinary team at a local animal neutering clinic for stray dogs. Rings of uterine and testicular artery were dissected and mounted on a Mulvany-Halpern wire myograph in order to characterize the adrenergic and serotonergic receptors mediating vasoconstriction. Cumulative contractile concentration-response curves were constructed for the alpha adrenoceptor agonists epinephrine (α1 and α2 receptors), phenylephrine (α1 selective) and UK14304 (α2 selective). Pre-treatment with the α1-selective antagonist, prazosin, was also investigated. The response to serotonin (5-HT) receptor agonists were also investigated, including 5-HT (acting at both 5-HT1 and 5-HT2 receptors), 5-carboxamidotryptamine (5-CT; 5-HT1 selective) and α-methyl 5-HT (5-HT2 selective). A contractile response was observed in both canine uterine and testicular arteries to epinephrine and phenylephrine, and prazosin caused a dose-dependent parallel rightward shift in the phenylephrine dose-response curve (pA2 values of 7.97 and 8.39, respectively). UK14304 caused a contractile response in canine testicular arteries but very little appreciable contractile response in uterine arteries. The maximum responses produced by the uterine arteries to 5-HT was significantly lower than those of the testicular arteries. In the testicular artery, the 5-HT2 receptor selective agonist, α-methyl 5-HT, produced a similar contractile response to 5-HT but the administration of 5-CT failed to produce a response in either the testicular or uterine artery segments. These results validate the use of discarded tissue from routine canine neutering procedures as a useful source of vascular tissue for pharmacological teaching, for characterizing alpha and 5-HT receptor contractile responses.
Highlights
Domestic animal species such as dogs are still widely used for drug design and development, toxicity testing, research and education [1]
This study investigated the post-junctional α-adrenergic and 5-HT receptors mediating vasoconstriction in canine uterine and testicular arteries, in order to characterise the receptor populations to see how these blood vessels might be useful for teaching purposes
Adrenoceptors and 5-HT receptors in canine uterine and testicular arteries arteries, with further characterisation conducted to determine the subtypes. It demonstrated that the use of discarded tissues from routine neutering procedures is a valid and useful source of experimental tissue
Summary
Domestic animal species such as dogs are still widely used for drug design and development, toxicity testing, research and education [1] Their use has provided a great deal of knowledge about animal physiology and disease, the pharmaco-kinetics and pharmacodynamics of pharmaceutical compounds, and the development and application of many procedures and devices [2]. The principles of ‘the 3Rs’ (Replacement, Reduction and Refinement) were developed over 50 years ago providing a framework for performing more humane animal research [3] Since they have been embedded in national and international legislation and regulations on the use of animals in scientific procedures, as well as in the policies of organisations that fund or conduct animal research. The area of teaching and education is one where all three principles can, and should, be applied
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