Pharmacological manipulation of milk-induced behaviors in three-day-old rat pups.

The effects of a variety of pharmacological agents on the ingestive and behavioral activating responses to intraoral milk infusion were investigated in three-day-old Sprague-Dawley rat pups. Results indicated that the ingestive component--typified by a mouthing response--was primarily influenced by serotonergic agents. Mouthing behavior was increased following administration of the serotonergic agonist, quipazine, and decreased following the serotonergic antagonists, methysergide and methiothepin. In contrast, the behavioral activating component was not found to be clearly influenced by drugs affecting any one neurotransmitter system, suggesting the tentative hypothesis that this activating response to milk infusion may in part be modulated by interactions between several neurotransmitter systems.