Central functions of oxytocin.

Oxytocin, the peptide well-known for its hormonal role in parturition and lactation, is present in several extrahypothalamic brain areas besides the neurohypophyseal system. The peptide is found in neurons which send their projections to brain areas containing specific oxytocin-binding sites. Oxytocin is also released from its synapses in a calcium-dependent fashion and may be the precursor of potent behaviorally active neuropeptides. These findings suggest that this ancient neuropeptide acts as a neurotransmitter in the central nervous system. We have attempted to review the most recent behavioral, morphological, electrophysiological and neurochemical studies providing evidence that oxytocin plays an important role in the expression of central functions, such as maternal behavior, sexual behavior (penile erection, lordosis and copulatory behavior), yawning, memory and learning, tolerance and dependence mechanisms, feeding, grooming, cardiovascular regulation and thermoregulation.