Vasopressin release into the 3rd cerebral ventricle and into the blood after sciatic and trigeminal nerve stimulation

The aim of the experiments was an assessment of vasopressinergic (AVP-ergic) neurons response to somatic afferent impulsation in the spinal and in the cranial nerves. Experiments were carried out on male rats in urethane anaesthesia with the perfusion cannula introduced into the 3rd cerebral ventricle and with the catheter in the internal maxillary vein, in the vicinity of the cavernous sinus. Four samples of perfusing fluid, each of about 1.5 ml/30 min., and four samples of blood, 0.8 ml each, were collected. Vasopressin (AVP) was determined by radioimmunoassay in samples of perfusing fluid from the 3rd cerebral ventricle and in blood plasma. The central end of the left sciatic, supraorbital or infraorbital nerves was electrically stimulated with an intensity which increased the respiratory rate by 10-15% during collection of the IIIrd samples. The AVP concentration in the fluid perfusing the 3rd ventricle did not change during stimulation of the nerves. On the contrary, sciatic and supraorbital nerve stimulation caused a significant increase of AVP concentration in the blood. It can be concluded that sciatic and supraorbital nerve afferentation induced AVP release from the posterior pituitary lobe and did not affect AVP-ergic neurons projecting to the ventricular ependyma and responsible for AVP release into the cerebrospinal fluid.