PT - JOURNAL ARTICLE AU - HERBERT SHEPPARD AU - CHARLES R. BURGHARDT TI - The Effect of <em>Alpha, Beta</em>, and Dopamine Receptor-Blocking Agents on the Stimulation of Rat Erythrocyte Adenyl Cyclase by Dihydroxyphenethylamines and Their β-Hydroxylated Derivatives DP - 1971 Jan 01 TA - Molecular Pharmacology PG - 1--7 VI - 7 IP - 1 4099 - http://molpharm.aspetjournals.org/content/7/1/1.short 4100 - http://molpharm.aspetjournals.org/content/7/1/1.full SO - Mol Pharmacol1971 Jan 01; 7 AB - A study was made of the activation of rat erythrocyte adenyl cyclase by dopamine, D(-)-norepinephrine, and their N-methyl and N-isopropyl derivatives. The concentrations required for 50% maximal stimulation (ED50) for norepinephrine, epinephrine, and isoproterenol were 5, 0.69, and 0.24 µM, respectively. For dopamine, N-isopropyldopamine, and N-methyldopamine the ED50 values were 84, 8, and 6.8 µM. While the maximum stimulation achieved with norepinephrine and its N-alkylated derivatives was the same, that for dopamine and its derivatives varied with potency. It was postulated that the D(-)-configuration of the β-hydroxylated series, in contrast to the deoxy analogues, induced a more activating conformational change in the cyclase. This was supported by the finding that L(+)-isoproterenol was equipotent with N-isopropyldopamine. Propranolol, chlorpromazine, haloperidol, phentolamine, serotonin, and phenoxybenzamine inhibited to the same extent the stimulation of adenyl cyclase produced by N-methyldopamine and norepinephrine. At low concentrations of inhibitor the stimulation by norepinephrine, but not by dopamine, could be reduced. These observations, along with the inactivity of apomorphine as a stimulator of adenyl cyclase, negate the existence of a specific dopamine receptor associated with the rat erythrocyte adenyl cyclase.