Central oxytocin and reproductive behaviours.

Oxytocin is a neurohypophyseal hormone that has long been associated with uterine contraction during parturition and milk ejection during nursing. Recent studies have suggested that oxytocin is also a neurotransmitter that has central effects important for reproduction, including the initiation of parental and sexual behaviours. This review describes oxytocin pathways in the brain and examines their regulation by gonadal steroids. Brain oxytocin receptors are remarkable for their plasticity and for striking species differences in their distribution. The molecular characterization of this receptor has provided several clues to the regulation of its expression. Comparative and transgenic studies suggest that central oxytocin release may influence reproductive behaviours, but the importance of these central effects depends on the pattern of expression of the receptor--a pattern that is species-specific.