Oxytocin release from neurohypophysis evoked by preganglionic stimulation of the rat superior cervical ganglion.

Abstract

1. In male rats under urethane/chloralose anaesthesia the pituitary gland was exposed by transpharyngeal approach. The following methods were applied: (a) posterior pituitary lobe incubation in situ with the anterior lobe removed and the posterior lobe elevated so that only the vessels between the lobe and the meninges are broken, and continuous exchange of the incubation fluid; (b) removal of the entire pituitary and continuous exchange of the fluid washing the cut proximal end of the pituitary stalk. 2. 20 to 30-min samples of incubation or washing fluid were collected for 3-5 hrs and oxytocin was assayed according to Van Dongen and Hays (1966). 3. Preganglionic stimulation of the superior cervical ganglion caused significant increase (ca. 25 times) of oxytocin release from the posterior pituitary lobe. 4. Preganglionic stimulation of the superior cervical ganglion did not alter oxytocin content in the fluid washing the cut proximal end of the pituitary stalk. 5. The sympathetic neurons of the superior cervical ganglia could evoked oxytocin release from the neurohypophysis but did not change its outflow from the hypothalamus to the neurohypophysis.