RECEPTOR-MEDIATED INHIBITION OF OCTOPAMINE-STIMULATED ADENYLATE-CYCLASE IN THE OPTIC LOBE OF OCTOPUS-VULGARIS

. Inhibition of octopamine-stimulated adenylate cyclase was studied in the optic lobe of Octopus vulgaris. 2. The octopamine antagonist, mianserin, and the dopamine D2 agonists, PPHT and metergoline, induced dose-dependent inhibition of octopamine-stimulated adenylate cyclase activity. 3. The binding of the tritiated benzazepine neuroleptic YM-09151-2 to octopus membranes and the displacement of [3H]YM-09151-2 by PPHT, metergoline and spiperone were consistent with the presence of a D2-like dopamine receptor in the octopus optic lobe. 4. The conclusion is drawn that octopamine-stimulated adenylate cyclase in the octopus is negatively regulated by a dopamine D2-like receptor.