Is there a "serotonergic syndrome" in neonatal rat pups?

Neonatal rat pups given the serotonergic agonist quipazine exhibited alterations in the frequency of several behaviors including an increase in mouthing, forward locomotion, forelimb paddling, unusual position of limbs (UPL), and a decrease in twitching and lying still. The serotonergic antagonist metergoline potently blocked quipazine-induced mouthing and UPL, and partially attenuated the increase in forward locomoting and decrease in lying still induced by quipazine. Pretreatment with the alpha-noradrenergic antagonist phentolamine partially attenuated the quipazine-induced increase in mouthing, with both phentolamine and the dopaminergic antagonist haloperidol exhibiting some tendency to suppress the forward locomotion induced by quipazine. Thus, serotonin appears to be most important for the expression of quipazine-induced behaviors in the neonate, although there appears to be some catecholaminergic involvement as well. While quipazine may induce in neonates some components of the adult "serotonergic syndrome" [8], there are some clear age differences in the response patterns. Serotonergically-influenced behaviors seen only early in ontogeny may subserve adaptive functions for the young organism.