Differential location of adenosine A1 and A2 receptors in striatum.

Stimulation of either adenosine A1 or A2 receptors results in a decrease or an increase in the adenylate cyclase activity, respectively. With various concentrations of the adenosine agonist N6-phenylisopropyladenosine, both responses on cyclase are observed in a crude membrane preparation from rat striatum. The A2 receptors appeared to be associated primarily with intrinsic striatal neurons, as a kainic acid injection into the striatum resulted in about a 70% loss of receptor responsiveness to cyclase. The A1 receptors were more diffuse, being associated with intrinsic neurons and with cortical-striatal nerve terminals. From studies with 6-hydroxydopamine, we were unable to associate either receptor with dopaminergic nerve terminals within the striatum.