Hepatic denervation does not affect plasma vasopressin response to intragastric hypertonic saline in conscious rats

Peripheral osmoreceptors monitor dietary NaCl and modify central nervous sy stem and renal sympathetic nervous system activity accordingly. Experimenta l evidence suggests that these responses are dependent on the hepatic nerve s. Peripheral osmoreceptors also modify arginine vasopressin (AVP) secretio n. However, although hepatic denervation reportedly blunts activation of bo th supraoptic and paraventricular hypothalamic neurons after intraportal Na Cl infusion, the role of the hepatic nerves in the AVP release has not been directly examined. The present study tests the hypothesis that the hepatic nerves modify AVP release in response to intragastric NaCl infusion. Wista r-Kyoto rats (WKY) received either hepatic denervation or a sham operation. Intragastric NaCl infusion significantly elevated plasma AVP in both sham- operated WKY and hepatic-denervated WKY, and the responses were not differe nt between these groups. Second, previous studies suggest that both AVP sec retion and baroreflexes are blunted in spontaneously hypertensive rats (SHR ), deficits that contribute to the observed hypertension in SHR. We hypothe sized that SHR also have a blunted peripheral osmoreceptor reflex and that this contributes to NaCl-sensitive hypertension. In contrast to our predict ion, in SHR intragastric NaCl infusion induced an increase in plasma AVP th at was similar to that in the WKY groups. Thus, although hepatic osmorecept ors are important for chronic regulation of arterial pressure, renal sympat hetic nervous system activity, and the activity of hypothalamic neurons, th ey do not appear to influence plasma AVP concentration in response to intra gastric NaCl.