title: Spinal beta-endorphin analgesia involves an interaction with local monoaminergic systems.
abstract: beta-Endorphin administered intrathecally (i.t.) in rats produced a dose-dependent elevation in tail-flick latency. Naltrexone administered i.t. as a pretreatment reversed the spinal antinociceptive action of beta-endorphin, suggesting that the opioid interacts directly with spinal opiate receptors. Spinal administration of the alpha 1-adrenoceptor antagonist WB-4101 failed to alter the analgesic effects of the opioid, whereas the alpha 2-adrenoceptor antagonist yohimbine completely blocked beta-endorphin-induced elevations in tail-flick latency. Thus, there is an apparent specificity for the alpha 2-adrenoceptor to mediate the spinal action of beta-endorphin. The 5-HT1 and 5-HT3 receptor antagonists (spiroxatrine and ICS 205-930, respectively) also reversed the analgesic effects of the opioid, while the 5-HT2 receptor antagonist ritanserin only partially blocked beta-endorphin-induced elevations in tail-flick latency. The present results suggest that beta-endorphin produces analgesia at the spinal level via an opiate receptor-mediated interaction with spinal monoaminergic nerve terminals.
authors.affiliation: Department of Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown 44272.
authors.forename: T
authors.initials: T
authors.lastname: Crisp
authors.forename: J L
authors.initials: JL
authors.lastname: Stafinsky
authors.forename: J E
authors.initials: JE
authors.lastname: Hess
authors.forename: M
authors.initials: M
authors.lastname: Uram
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000700:Analgesics / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D015306:Biogenic Monoamines / Q000502:physiology*; D007278:Injections, Spinal; D008297:Male; D009271:Naltrexone / Q000494:pharmacology; D009638:Norepinephrine / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000502:physiology; D012702:Serotonin Antagonists / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects*; D001615:beta-Endorphin / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*
chemical_list: D000317:Adrenergic alpha-Antagonists; D000700:Analgesics; D015306:Biogenic Monoamines; D012702:Serotonin Antagonists; D012701:Serotonin; D009271:Naltrexone; D001615:beta-Endorphin; D009638:Norepinephrine