Autoradiographic analysis of dopamine receptor-stimulated [S]GTPγS binding in rat striatum

Autoradiographic analysis of [³⁵S]GTPγS binding was used to investigate functional activation of dopamine receptors in rat striatum. Dopamine-stimulated [³⁵S]GTPγS binding was observed with a maximal increase of 38% over basal activity. A similar stimulatory response was obtained with the D₂ agonist quinpirole, but not SKF-238393, a D₁ agonist. The effect of dopamine was blocked by the D₂ antagonist raclopride, but was unaffected by SCH-23990, a D₁ antagonist. There appeared to be a differential distribution of dopamine-stimulated [³⁵S]GTPγS binding, with the lowest activity obtained in the medial portion of the caudal striatum. These results demonstrate, using an autoradiographic approach, (i) that dopamine stimulated [³⁵S]GTPγS binding in the rat striatum occurs through activation of D₂ receptors, and (ii) that the effects of dopamine activation vary in different areas of the rat striatum.