Vago-Neurohypophysial Pressor Reflex

Abstract

Conclusions and Summary

Stimulation of the central end of the vago-sympa-thetic trunk in a dog with diabetes insipidus gives a pressor response. This pressor response is due to stimulation of the sympathetics of the head, since the response is abolished by sympathetic ganglionectomy. In the absence of the supraopticohypophysial connection the vagus-postpituitary reflex is not obtainable even under the best conditions, as when the basal blood pressure level is high.

3. In a number of acute experiments the infundibulum was stimulated directly with weak faradic current. Fine bipolar electrodes were used and introduced manually through a buccal opening. The spinal cords were completely crushed in each of these dogs. Striking elevations in blood pressure were obtained. These experiments supplement those of Clark and Wang 12 in which hypothalamic stimulation produced pressor effects in spinal cats, and offer further indication that the results of these workers were due to activation of the neurohypophysis.

1. In dogs with only vascular connections between head and body, stimulation of the central end of the severed vagus causes blood pressure elevations in the body. Acute hypophysectomy abolishes this reflex. 2. This reflex cannot be obtained in preparations with chronic diabetes insipidus caused by interruption of the supraopticohypophysial tract. This rules out possible error due to shock, trauma, etc., consequent to acute hypophysectomy. 3. These results add to the evidence found elsewhere that the neurohypophysis is subject to nervous control mediated by the supraopticohypophysial tract.