Reduced V₁ vasopressin binding in the rat nucleus solitarii after nodose ganglionectomy

1. Anaesthetized male Sprague‐Dawley rats underwent unilateral nodose ganglionectomy or sham operation. 2. One week later hindbrain V₁ vasopressin binding site density was assessed by in vitro autoradiography with the selective V₁ antagonist radiolgand [¹²⁵I] [d(CH₂)₅, Sar⁷]AVP. 3. Specific binding was observed in the nodose ganglion, nucleus tractus solitarius (NTS), area postrema, and inferior olive. Only binding in the medial subnucleus of the NTS was reduced by ipsilateral nodose ganglionectomy. 4. These findings are consistent with V₁ vasopressin receptors occurring pre‐synaptically on vagal primary viscerosensory afferent fibres. 5. Such receptors may be involved in the effect of AVP on blood pressure and/or the baroreflex.