Inhibition of the response to pain by the action of serotonin and carbachol topically applied to the area postrema of conscius guinea pigs

• Published in: Brazilian journal of medical and biological research Vol. 18; no. 1; pp. 79 - 86
• Main Authors: Menescal-De-Oliveira, L, Lico, M C
• Format: Journal Article
• Language: English
• Published: 01.01.1985
• ISSN: 0100-879X

The amplitude of vocalization and the motor defense response evoked by painful electrical simulation were recorded in unanesthetized guinea pigs submitted to topical application of 1.0 mu g/ mu l carbachol to the area postrema. Carbachol was found to have an analgesic effect. A similar application of 3.0 mu g/ mu l 5-hydroxytryptamine (5-HT) also had an analgesic effect, whose duration, however, was only half that of carbachol and whose intensity was lower. The results, taken together with those obtained with noradrenalin in a previous study, suggest that the rich endowment of neurotransmitters in the area postrema many indicate a polyvalent analgesic mechanism able to provide a finer regulation of analgesia.