EFFECTS OF HEMORRHAGE AND RE-TRANSFUSION ON THE UNIT ACTIVITIES OF SUPRAOPTIC NUCLEUS (SON) UNDER DENERVATION OF THE VAGUS AND/OR THE CAROTID SINUS NERVES

Abstract

Present experiment is concerned with the effects of hemorrhage and re-transfusion of shed blood on the unit activities of antidromically identified neurohypophysial neurosecretory neurons in SON of 36 adult male Wistar rats under denervation of the vagus and/or the carotid sinus nerves.
The firing rates in 5 of 12 units were increased, in 6 were not changed and in 1 unit were decreased in intact rats by hemorrhage which reduced the arterial systolic pressure to 50 % of prehemorrhagic pressure. Re-transfusion reversed the changes of firing rates due to hemorrhage, i. e. increased 5 units by hemrrhage except one showed decrease of firing rates and unchanged 6 units remained unchanged by re-transfusion.
Under bilateral vagotomy, firing rates of all examined 7 units were not changed by hemorrhage and re-transfusion.
Under denervation of carotid sinus nerves, hemorrhage did not cause any detectable changes in firing rates in 6 of 7 units and increased firing rates in 1 unit. 4 of unchanged 6 units during hemorrhage remained unchanged during re-transfusion.
Under both bilateral vagotomy and denervation of carotid sinus nerves, firing rates of all examined 4 units did not change by both hemorrhage and re-transfusion.
Those results implied that two types, one is responsible for hemorrhage and the other is not responsible for it, existed in neurosecretory neurons of SON, and that neural information in both vagus and carotid sinus nerves played an important role for neurohypophysial secretory mechanism in SON.