Catecholamine-Sensitive Adenylate Cyclase in the White Perch (Roccus americanus) Retina: Evidence for ?-Adrenergic and Dopamine Receptors Linked to Adenylate Cyclase

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Abstract
We have examined the catecholamine-sensitive adenylate cyclase in the retina of the white perch (Roccus americanus). Both dopamine and the .beta.-adrenergic agonist isoproterenol stimulate cyclic AMP accumulation in this retina, but serotonin, an indoleamine, and phenylephrine, an .alpha.-adrenergic agonist, had no effect. The stimulation of adenylate cyclase by isoproterenol is more potent and effective than that of dopamine. The effects of dopamine and isoproterenol are mediated via independent dopamine and .beta.-adrenergic receptors. Haloperidol, a dopamine antagonist blocks the stimulatory effect of dopamine but not of isoproterenol. Conversely, propranolol, a .beta.-adrenergic antagonist, blocks the stimulatory effect of isoproterenol but not of dopamine. The effects of dopamine and isoproterenol are not additive. In fractions of purified horizontal cells we found evidence for dopamine receptors linked to adenylate cyclase but did not find evidence for the presence of cyclase coupled .beta.-adrenergic receptors. The cellular location of the .beta.-adrenergic receptors is unknown. Our findings demonstrate the existence of both .beta.-adrenergic and dopamine receptors coupled to adenylate cyclase in the white perch retina. However, we did not find either epinephrine or norepinephrine, endogenous ligands of the .beta.-receptor, to be present in retinal extracts subjected to HPLC.