Anti-analgesia and reduced antinociception from supraspinally administered beta-endorphin in stressed rats: dependence on spinal cholecystokinin via cholecystokinin B receptors.
Rats exposed to the stress of repeated exposure to a noxious heat source (52.5 degrees C, hot plate) exhibit stress-induced analgesia, but reduced antinociception (detected using the tail-flick test) to the administration of beta-endorphin into the periaqueductal gray region of the brain. This is accompanied by an anti-analgesic response (reduction in the stress-induced increase of tail flick latency) to doses of beta-endorphin (0.03 nmol) lower than those usually associated with antinociception. These alterations are prevented and antinociceptive potency is maintained when rats are treated with cholecystokinin (CCK) antagonists intrathecally. The potency of L-365,260 and L-364,718, selective CCK(B) and CCK(A) receptor antagonists, respectively, correlated with their apparent affinities for CCK(B) receptors, suggesting that the altered sensitivity to beta-endorphin is mediated via CCK(B) receptors.
Department of Pharmacology and Toxicology, Robert C. Byrd Health Sciences Center of West Virginia University, Morgantown 26506, USA.
A A
AA
Hawranko
M
M
Serafini
D J
DJ
Smith
D000698:Analgesia / Q000379:methods*; D000818:Animals; D001570:Benzodiazepinones / Q000494:pharmacology; D002766:Cholecystokinin / Q000502:physiology*; D020109:Devazepide / Q000494:pharmacology; D018882:Heat Stress Disorders / Q000503:physiopathology*; D006727:Hormone Antagonists / Q000494:pharmacology; D006930:Hyperalgesia / Q000139:chemically induced; D007278:Injections, Spinal; D008297:Male; D009619:Nociceptors / Q000187:drug effects* / Q000502:physiology; D010671:Phenylurea Compounds / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin / Q000037:antagonists & inhibitors / Q000502:physiology*; D013237:Stereoisomerism; D001615:beta-Endorphin / Q000008:administration & dosage*
D001570:Benzodiazepinones; D006727:Hormone Antagonists; D010671:Phenylurea Compounds; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin; C058121:L 365260; D001615:beta-Endorphin; D002766:Cholecystokinin; D020109:Devazepide