Naloxone-induced abdominal distress in the horse.
Endogenous opioid peptides have been implicated in the regulation of pain perception, behaviour, gastrointestinal activity and other physiological responses. However, the functional role of these peptides in the horse has yet to be elucidated. The opioid antagonist, naloxone, is often administered to infer endogenous opioid effects. In the present study, naloxone (0.75 mg/kg bodyweight) was administered to eight Thoroughbred racehorses and a number of behavioural and autonomic responses were measured. Naloxone produced rapid onset diarrhoea, restlessness, abdominal checking, tachycardia, tachypnoea, paradoxical yawning and diaphoresis. These responses described an acute abdominal distress syndrome similar to spasmodic colic. Results from this study suggest that, in the horse, endogenous opioids: 1) influence behaviour, 2) modify intestinal activity and sensation, and 3) if perturbed, may be involved in pathophysiology of colic.
Department of Veterinary Physiology, Pharmacology and Toxicology, School of Veterinary Medicine, Baton Rouge, Louisiana 70803-8422.
S G
SG
Kamerling
J G
JG
Hamra
C A
CA
Bagwell
D015746:Abdominal Pain / Q000139:chemically induced / Q000662:veterinary; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003085:Colic / Q000139:chemically induced / Q000662:veterinary*; D003672:Defecation / Q000187:drug effects; D003967:Diarrhea / Q000139:chemically induced / Q000662:veterinary; D005767:Gastrointestinal Diseases / Q000139:chemically induced / Q000662:veterinary*; D006339:Heart Rate / Q000187:drug effects; D006734:Horse Diseases / Q000139:chemically induced*; D006736:Horses; D009270:Naloxone / Q000009:adverse effects*; D012119:Respiration / Q000187:drug effects; D013577:Syndrome; D015000:Yawning / Q000187:drug effects
D009270:Naloxone