Table 1.

Oxytocin systems

Oxytocin systems	Origin	Projections	Function
Magnocellular (axonal)	SON/PVN	Posterior pituitary	Parturition, uterine contractions, milk ejection reflex
Magnocellular (dendritic)	SON/PVN	SON/PVN, extrahypothalamic regions	Autoregulation, endocannabinoid stimulation
Parvocellular	PVN	Ventral tegmental area, hippocampus, brainstem, spinal cord	Penile erection, ejaculation, gastric reflexes, respiration

Central oxytocin pathways. Within the CNS, two major oxytocin pathways exist; (1) the magnocellular oxytocin system originating in the SON and PVN can be further subdivided by its release characteristics in to axonal release (into the posterior pituitary) which regulates reproductive behavior and dendritic release (within the SON and PVN and may diffuse to other distant sites) to mediate oxytocin autoregulation (2) the parvocellular oxytocin system originates in the parvocellular PVN and projects to numerous CNS sites to regulate autonomic functions such as respiration and gastric reflexes.