Rapid accumulation of inositol phosphates in isolated rat superior cervical sympathetic ganglia exposed to V₁-vasopressin and muscarinic cholinergic stimuli

1. An accumulation of ³H-labelled inositol phosphates is observed when prelabelled rat superior cervical sympathetic ganglia are exposed to [8-arginine]vasopressin or to muscarinic cholinergic stimuli. The response to vasopression is much greater than the response to cholinergic stimuli. 2. The response to vasopressin is blocked by a V₁-vasopressin antagonist, and oxytocin is a much less potent agonist than vasopression. Vasopressin causes no increase in the cyclic AMP content of ganglia. These ganglia therefore appear to have functional V₁-vasopressin receptors that are capable of activating inositol lipid breakdown, but no V₂-receptors coupled to adenylate cyclase. 3. The first [³H]inositol-labelled products to accumulate in stimulated ganglia are inositol trisphosphate and inositol bisphosphate, suggesting that the initiating reaction in stimulated inositol lipid metabolism is a phosphodiesterase-catalysed hydrolysis of phosphatidylinositol 4,5-bisphosphate (and possibly also phosphatidylinositol 4-phosphate) 4. This response to exogenous vasopressin occurs in ganglia incubated in media of reduced Ca²⁺ concentration. 5. The physiological functions of the V₁-vasopressin receptors of these ganglia remain unknown.