Evidence for vasopressin V1 receptors of rostrodiencephalic neurons: iontophoretic studies in the in vivo rat. Responses to oxytocin and to angiotensin.

Extracellular recordings were obtained in anaesthetized rats from single neurons located in various structures around the rostral end of the third ventricle, known to harbour integrative neurons sensing deficiencies in and originating corrective responses for water-electrolyte balance. Once arginine vasopressin (AVP) responsive neurons were located, a selective antidiuretic agonist (binding to V2 receptors) and either V1 (pressor response related) or V2 (antidiuretic) antagonists were iontophoretically applied. Neurons in this region did not respond to the V2 agonist and only the V1 antagonist was able to block the response to AVP. It is assessed that the investigated region has neurons equipped only with receptors of the V1 type. Interestingly, a number of these neurons also responded to angiotensin II (AII), oxytocin and to blood pressure changes. The integrative neuronal population of parasagittal rostrodiencephalic neurons seem therefore to sense indices of haemodynamic changes including their neuro-hormonal signals within the brain such as AII and AVP which bind to V1 (pressor response related) receptors.