Inhibitory effect of oxytocin on corticotrope function in humans: are vasopressin and oxytocin ying–yang neurohormones?

Oxytocin (OT) and vasopressin (VP) are very similar neurohypophyseal peptides. While VP is known as an ACTH stimulating factor synergistic to CRF since two decades, the inhibiting activity of OT, first demonstrated in the human, is now confirmed in various species including mouse and rat!It is likely that endogenous oxytocinergic system which can be activated by physiological and/or pharmacological manipulation can "buffer" the stress activated vasopressin-ACTH-cortisol action. Since VP and OT share also opposite action on cognitive function, those two "sister" neuropeptides might be considered as "ago-antagonist" or "ying-yang" neurohormones!