DISCHARGE PATTERNS OF SUPRAOPTIC AND PARAVENTRICULAR NEURONES IN RATS GIVEN A 2% NaCl SOLUTION INSTEAD OF DRINKING WATER

Abstract

SUMMARY The firing rates of antidromically identified neurones in the supraoptic and paraventricular nuclei were monitored in control animals, animals which had received a 2% Nacl solution instead of drinking water for 3 days and animals (recovery group) which after treatment were again allowed to drink tap water for 2 days. Treatment with NaCl depleted the pituitary stores of vasopressin and oxytocin and significantly increased the firing rate of antidromically activated neurones but not that of other hypothalamic neurones. In the recovery group the neurohypophysial stores of vasopressin and oxytocin had increased but were still significantly below control levels and the firing rates of the antidromically identified neurones were similar to those in control animals. Since the firing rates were increased by NaCl treatment and returned to control values when the treatment ceased it may be concluded that the excitation was due to stimulation of the neurosecretory neurones by the NaCl treatment.