Adenosine 3′,5′-Monophosphate Content in Rat Caudate Nucleus: Demonstration of Dopaminergic and Adrenergic Receptors

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Abstract
Dopamine, apomorphine, isoproterenol, and norepinephrine each increased the concentration of adenosine 3′,5′-monophosphate in slices of rat caudate nucleus. The concentrations of dopamine, apomorphine, isoproterenol, and norepinephrine causing half-maximal increases were 60, 150, 0.03, and 30 micromoles per liter, respectively. The effect of dopamine was blocked by fluphenazine, a dopamine receptor antagonist, but not by propranolol, a β-adrenergic receptor antagonist. Conversely, the effect of isoproterenol was blocked by propranolol but not by fluphenazine. The results suggest that in rat caudate nucleus there are two distinct catecholamine receptors capable of causing increased concentrations of adenosine 3′,5′-monophosphate, one having the characteristics of a dopamine receptor, and the other having the characteristics of a β-adrenergic receptor.