Baroreceptor influences on oxytocin and vasopressin secretion.

Abstract

The objective of these studies was to investigate the role of arterial baroreceptors in the control of neurohypophyseal secretion. The effect of sinoaortic denervation on basal and osmoticinduced release of oxytocin and vasopressin and on blood pressure was determined. Hypertonic or isotonic saline was infused intravenously into sham-operated or denervated rats 3 days after surgery. Plasma oxytocin and vasopressin were measured at 5 and 15 minutes after the infusion. The control levels of oxytocin were increased in the denervated rats, but vasopressin levels were not significantly altered. The vasopressin and oxytocin responses to hypertonic saline were greater after baroreceptor denervation. Plasma oxytocin was increased from 4.7±0.9 to 72.2±8.7 pg/ml in the denervated rats and from 1.8±0.3 to 39.9±6.7 pg/ml in the shamoperated control group at 5 minutes after the infusion (/?<0.01). The plasma vasopressin response to hypertonic saline was 7.1 ±0.6 pg/ml in the sham-operated versus 11.1±1.6 pg/ml in the denervated rats (p<0.05). There was no difference between sham-operated and denervated rats hi the effect of hypertonic saline on plasma sodium and hematocrit. Mean arterial blood pressure was increased after sinoaortic denervation (116.3±4.2 mm Hg in the sham-operated vs. 138.2±8.3 mm Hg in the denervated rats, p<0.05); however, there was no difference in the pressor response to hypertonic saline. These results show that the baroreceptor system influences the secretion of both oxytocin and vasopressin, with effects on basal secretion as well as the response to an osmotic stimulus. These changes may be important in the regulation of cardiovascular and fluid balance under conditions of baroreceptor deficiency. {Hypertension 1989; 13:110-114) I nformation on the status of the cardiovascular system is conveyed to the central nervous system by afferent fibers in the glossopharyngeal and vagus nerves. These primary afferents terminate mainly in the nucleus tractus solitarii with secondary pathways projecting to higher brain structures. Although these pathways are not completely known, brainstem noradrenergic centers are known to receive visceral afferent information and to send projections to the paraventricular and the supraoptic hypothalamic neurohypophyseal nuclei. 1Information on the role of baroreceptor input is provided by studies of the effects caused by surgical interruption of the arterial baroreceptor nerves.From the Department of Physiology and Pharmacology, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina and the Department of Medicine, University of Southern California School of Medicine, Los Angeles, California.Supported by grants HL-19251 (to N.A.) Results show that sinoaortic denervation (SAD) has widespread effects on both the cardiovascular and endocrine systems; there are increases in blood pressure, sympathetic nerve activity, and vasopressin secretion, while plasma prolactin and atrial natriuretic peptide concentrations are reduced. 2 -7 The objective o...

Afferent signaling drives oxytocinergic preautonomic neurons and mediates training-induced plasticity

“…Indeed, a previous study demonstrated that SAD did not change OT and VP mRNA expression within the SON and did not change the plasma levels of these hormones in rats maintained under tap water drinking (36), a condition similar to that of the present study. Sinoaortic denervation also did not prevent neurohypophyseal secretion but maintained its ability to cause modest or strong OT and VP release after isotonic or osmotic and hypovolemic stimuli, respectively (31,36,41,42). The differential effects of SAD on OT content within PVN neurons (i.e., a marked reduction) and SON neurons (i.e., no change) indicated the specificity of baroreceptors and chemoreceptors in driving the PVN OTergic neurons that modulate autonomic control and not the regulation of fluid balance by the SON OTergic pathway.…”

Effect of the interaction between food state and the action of estrogen on oxytocinergic system activity

“…8 pg/ml. The RIA was performed, as previously described (Morris & Alexander 1989), using a specific antiserum, which was a generous gift from Dr Mariana Morris from Wright State University (OH, USA), a standard from Bachem-Peninsula Labs (San Carlos, CA, USA) and a secondary antibody produced by Dr Franci's Laboratory (School of Medicine of Ribeirão Preto, University of São Paulo, Brazil). The results were reported as meansGS.E.M.…”

Transgenic mouse models of vasopressin expression.

“…With a marked decrease in blood volume or blood pressure, the baroreceptor mechanism can cause secretion of large quantities of vasopressin from the posterior pituitary. 5 - 8 Other less potent stimuli of magnocellular vasopressin secretion include fever and emesis. 6 High levels of plasma vasopressin cause arteriolar vasoconstriction, although vasopressin may also cause local vasodilation in the arteries of the forearm.…”