Inhibition of suckling in weaning-age rats: A possible serotonergic mechanism.

Four experiments studied the nature, development, and specificity of serotonergic involvement in the control of suckling behavior in Sprague-Dawley rat pups from 10 to 35 days of age. During development, suckling normally declines after 10 days and is abandoned after 30 days. It was found that (a) methysergide, a serotonin (5-hydroxytryptamine, 5-HT) receptor blocker, reinstated suckling behavior in pups 15 days of age and older; (b) quipazine, a 5-HT receptor agonist, inhibited suckling of pups 10 days of age and older; (c) methysergide pretreatment blocked the quipazine inhibition of suckling; and (d) metergoline, another 5-HT blocker, also stimulated suckling, and fenfluramine, a 5-HT releaser, blocked suckling in deprived pups. Data support the hypothesis that a serotonergic inhibitory mechanism modulates the suckling of weaning-age rats. These pharmacological manipulations of 5-HT appear to alter specific components of suckling behavior involved in its initiation and maintenance but do not appear to alter a general hunger system. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)