Pharmacological properties and localization of dopamine-sensitive adenylate cyclase in the carp retina

There is a specific dopamine (DA)-sensitive adenylate cyclase (EC 4.6.1.1) in the carp retina that can be stimulated by DA, DA agonists, and potassium. Experiments with the presynaptic blocker cobalt and the neurotoxin 6-hydroxydopamine strongly indicate that this adenylate cyclase is located postsynaptically. By separating retinal neurons with velocity sedimentation at unit gravity it was determined that horizontal cells possessed a DA-sensitive adenylate cyclase. The sensitivity of these cells to DA antagonists was found to be in the nanomolar range, but could be changed to the micromolar range by altering calcium concentrations within the cell. These results are discussed with respect to the multiple DA receptor theory.