Effects of ovine corticotropin-releasing factor and vasopressin on plasma beta-endorphin, cortisol and behavior after minor surgery in sheep.
The evidence for an analgesic effect arising from increased peripheral concentrations of beta-endorphin (beta-EP) in various animal species is controversial, and has not been fully evaluated in the sheep. To stimulate beta-EP release, ovine corticotropin-releasing factor (oCRF) and arginine vasopressin (AVP) were injected intravenously (iv) into a group of 12 out of 24 sheep, 15 min prior to minor surgery on all sheep. This brought about significant increases (P less than 0.01) in plasma beta-endorphin (beta-EP) and cortisol concentrations, relative to the non-injected control sheep, 15-30 min after injection. Ultrafiltration indicated that less than 30% of the released beta-EP immunoreactivity was present as higher molecular weight forms (mol. wt greater than 10,000) and that the majority (about 75%) of the beta-EP was probably bound to plasma proteins. By 75 min after injection there was no significant difference in plasma beta-EP or cortisol concentrations between the two groups of sheep. Consistent with previous observations the sheep showed a characteristic aversive behavior to the human handler following surgery, lasting several days. This behavior appeared to be unaffected by a pre-operative increase in peripheral plasma beta-EP, and may indicate that this increase in beta-EP was not sufficiently analgesic to block the cognitive response to the operation, or long-lasting enough to prevent the perception of post-operative soreness.
Shutt
D A
DA
NSW Agriculture & Fisheries, Hawkesbury Agricultural Research Unit, Richmond, Australia.
Connell
R
R
Fell
L R
LR
D000818:Animals; D001127:Arginine Vasopressin / Q000008:administration & dosage / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects*; D003346:Corticotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006234:Handling, Psychological; D006854:Hydrocortisone / Q000097:blood*; D007275:Injections, Intravenous; D011863:Radioimmunoassay; D012016:Reference Values; D012756:Sheep; D001615:beta-Endorphin / Q000097:blood*
D001127:Arginine Vasopressin; D001615:beta-Endorphin; D003346:Corticotropin-Releasing Hormone; D006854:Hydrocortisone