Pain, Pathophysiological Mechanisms, and New Therapeutic Options for Alternative Analgesic Agents in Sheep: A Review and Investigation

Abstract

Relief from suffering is the guiding principle of medical and veterinary ethics. Medical care for animals should be carried out to meet all welfare conditions. The need for pain management is demonstrated by recent monographs devoting attention to this urgent ethical need. Little data, however, are available on the prevention and attenuation of pain in sheep. After administration of narcotic analgesics used for severe visceral pain, sheep react with a state of excitement. Therefore, it was decided to experimentally investigate the usefulness of potential non-narcotic drugs to relieve pain in sheep with intestinal colic caused by 10 min of mechanical distension of their duodenal and/or descending colonic wall. The results indicate the potential usefulness of VGCCIs (diltiazem, nifedipine, verapamil), cholecystokinin receptor antagonists (PD, proglumide), and metabotropic glutaminergic receptor antagonists (mGluRAs), such as L-AP3, DL-AP3. As a premedication, these substances prevented the occurrence of symptoms of acute intestinal pain including atony of reticulo-rumen, tachycardia, hyperventilation, moaning, gnashing of teeth, hypercortisolemia, and catecholaminemia; hence, these substances are considered potential agents in the treatment of sheep visceral pain.