Suckling behavior of the infant rat: modulation by a developing neurotransmitter system

Drugs which alter serotonin receptor activity modified the suckling behavior of 20-day-old rat pups. Suckling could be reinstated in nondeprived pups, which normally do not suckle, by blockade of serotonin receptors with methysergide. Stimulation of serotonin receptors with quipazine inhibited suckling in deprived pups, and this effect was prevented by methysergide pretreatment. This evidence suggests that suckling in weaning age pups is controlled by a serotonergic inhibitory mechanism.