title: Systemic administration of beta-endorphin: potent hypotensive effect involving a serotonergic pathway.
abstract: In normal adult rats anesthetized with urethane, intravenous injections of beta-endorphin (30--150 micrograms kg-1) induced a transient fall of blood pressure followed by a small hypertension and a prolonged hypotension. Prior administration of naloxone completely blocked these effects, whereas naloxone, given 1 hr after beta-endorphin, did not reverse the prolonged depressor phase of the opioid peptide. The effects of beta-endorphin on the arterial blood pressure were greatly reduced in animals pretreated with p-chlorophenylalanine, a specific depletor of serotonin. Moreover, in rats pretreated with potent serotonin antagonists such as cyproheptadine, mianserin, and metergoline, beta-endorphin did not produce a significant hypotension. Furthermore, the depressor effect of beta-endorphin was potentiated by fluoxetine, a specific serotonin uptake inhibitor. These observations suggest the participation of a serotonergic pathway in the action of beta-endorphin on the arterial blood pressure.
mesh_terms: D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004723:Endorphins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010134:Fenclonine / Q000494:pharmacology; D005473:Fluoxetine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009434:Neural Pathways / Q000187:drug effects; D011985:Receptors, Serotonin / Q000187:drug effects; D012701:Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists
chemical_list: D004723:Endorphins; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D005473:Fluoxetine; D012701:Serotonin; D009270:Naloxone; D010134:Fenclonine