Specific Inhibition of Dopamine D‐1‐Mediated Cyclic AMP Formation by Dopamine D‐2, Muscarinic Cholinergic, and Opiate Receptor Stimulation in Rat Striatal Slices

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Abstract
The ability of different receptors to mediate inhibition of cyclic AMP accumulation due to a variety of agonists was examined in rat striatal slices. In the presence of 1 mM 3-isobutyl-1-metbylxanthine, dopamine D-2, muscarinic cholinergic, and opiate receptor stimulation by RU 24926, carbachol, and morphine (all at 10−-8-−1(10−-5M), respectively, inhibited the increase in cyclic AMP accumulation in slices of rat striatum due to dopamine D-1 receptor stimulation by 1 μM SKF 38393. In contrast, these inhibitory agents were unable to reduce the ability of a number of other agonists, including isoprenaline, prostaglandin E1, 2-chloroadenosine, vasoactive intestinal polypeptide, and cholera toxin, to increase cyclic AMP levels in striatal slices. These results suggest that in rat striatum either (a) dopamine D-2, muscarinic cholinergic, and opiate receptors are only functionally linked to dopamine D-l receptors or that (b) the D-1 and D-2 receptors linked to adenylate cyclase lie on the cells, distinct from other receptors capable of elevating striatal cyclic AMP levels.