Central inhibition of oxytocin release in the rabbit: role of the midbrain.

Transection of the ventral central grey and surrounding midbrain tegmentum in anaesthetized lactating rabbits caused repeated milk ejections which, on comparison with the effects of i.v. infusions of synthetic oxytocin, synthetic arginine-vasopressin or a mixture of the two, were attributed to continuous release of 1.25-2.5 mu. oxytocin/min, although it is not known whether lesser amounts of vasopressin might also have been released. It is suggested that the ascending midbrain reticular formation, which is known to project rostrally through this region, controls the central inhibition of oxytocin release via the previously described septo-hippocampo-subicular route to the hypothalamus.