Responses of vasopressin, atrial natriuretic peptide, and blood pressure to central osmotic stimulation.

To assess whether intracerebroventricular osmoreceptors are involved in vasopressin (AVP) and atrial natriuretic peptide (ANP) release and in the pressor response to centrally administered hypertonic NaCl, artificial cerebrospinal fluid (ACSF) or ACSF made hypertonic by adding 0.2 M NaCl, 0.4 M mannitol, and 0.4 M glucose in isotonic ACSF or 0.4 M urea was infused into the 3rd ventricle of conscious rats. In addition, intravenous infusion of [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid),2-(O-methyl)tyrosine]AVP (TMeAVP), a V1-AVP antagonist, was given in rats receiving intracerebroventricular infusion of 0.2 M NaCl in isotonic ACSF. Intracerebroventricular 0.2 M NaCl, 0.4 M mannitol, and 0.4 M glucose in isotonic ACSF increased plasma AVP and mean arterial pressure (MAP) without changing heart rate (HR) or plasma ANP. Urea at 0.4 M decreased plasma AVP and ANP with a slight rise in MAP but no change in HR. ACSF alone did not affect plasma AVP, ANP, MAP, or HR. Intravenous TMeAVP attenuated the pressor response to infusion of 0.2 M NaCl in isotonic ACSF, decreased plasma ANP, but did not affect HR. These results indicate that central osmoreceptors are involved in the release of AVP and in the pressor response to centrally administered hypertonic NaCl.