Systemic administration of beta-endorphin: potent hypotensive effect involving a serotonergic pathway.
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.[1]References
- Systemic administration of beta-endorphin: potent hypotensive effect involving a serotonergic pathway. Lemaire, I., Tseng, R., Lemaire, S. Proc. Natl. Acad. Sci. U.S.A. (1978) [Pubmed]
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