Reactions of neurons in or near the supraoptic nuclei

Abstract

The reactions of neurons within or near the supraoptic nuclei of the hypothalamus to a variety of "stimuli" were studied. A few neurons were found to be excited by stimulation of muscle afferents. Other neurons were inhibited by stimulation of gastrocnemius and tibialis nerve fibers. Stimulation of the vagus nerve activated some neurons and inhibited a few but, as in the case of muscle nerve stimulation, the vast majority of neurons were unaffected. Stimulation of midbrain and pontine reticular formation inhibited some neurons and activated others. Intracarotid injections of isotonic saline had no effect on neuron discharge but low concentrations of glucose augmented neuron firing as did hypertonic NaCl. Distilled water reduced neuron activity. Epinephrine, norepinephrine, and acetylcholine accelerated neuron firing; atropine was without effect in concentrations employed. Responses to injected materials developed more slowly and lasted longer than did effects of nerve stimulations. Some neurons were affected by several of the stimuli employed but the majority of neurons were unresponsive during the periods of recording which could be maintained.