The effect of oxytocin on feeding, drinking, and male copulatory behavior was studied in rats neonatally injected with monosodium glutamate (MSG), a treatment that destroys neuronal perikarya of the arcuate nucleus and depletes the brain of proopiomelanocortin-derived peptides (melanocortins, endorphins). Both oxytocin-induced inhibition of feeding (1 and 10 micrograms/rat ICV and 150 micrograms/rat IP) and drinking (75 and 150 micrograms/rat IP) and oxytocin-induced improvement of male copulatory behavior (200 ng/rat IP) were either unaffected or in fact increased by neonatal MSG treatment. These data suggest that oxytocin neither inhibits feeding and drinking nor improves male sexual behavior through the release of melanocortin peptide(s) in the brain.