Neural pathways controlling central and peripheral oxytocin release during stress.

Oxytocin is released from the pituitary gland in response to a variety of stressful stimuli, including noxious stimuli, conditioned fear and exposure to novel environments. These responses are believed to be mediated, at least in part, by noradrenergic projections from the medulla oblongata, and some of these noradrenergic neurones also contain prolactin-releasing peptide (PrRP). Central administration of either PrRP or noradrenaline stimulates oxytocin secretion into the circulation. Stressful stimuli activate PrRP-containing noradrenergic neurones in the medulla oblongata, and it is thus possible that PrRP/noradrenergic projections to the hypothalamus mediate oxytocin responses to stressful stimuli. Here, the roles of brainstem PrRP/noradrenergic projections to the hypothalamus in oxytocin responses to different kinds of stressful stimuli are reviewed, with a particular emphasis on conditioned fear. Roles of dendritic oxytocin release during stress and metabolic factors affecting stress pathways are also discussed.