Motor depressant effects mediated by dopamine D2 and adenosine A2A receptors in the nucleus accumbens and the caudate-putamen.

We compared hypolocomotion and catalepsy mediated by striatal dopamine D2 and adenosine A2A receptors using microinfusions of the adenosine A2A receptor agonist 2-p-(2-carboxyethyl) phenethylamino-5'-N-ethylcarboxamidoadenosine hydrochloride (CGS21680) and the dopamine D2 receptor antagonist raclopride into the nucleus accumbens and the caudate-putamen. The effective doses (ED25/50) of CGS21680 and raclopride which produced equivalent reductions of spontaneous locomotion after microinfusion into the nucleus accumbens were found to induce similar degrees of catalepsy after microinfusion into the caudate-putamen. This comparable, little separation of the effective doses of a dopamine D2 receptor antagonist and an adenosine A2A receptor agonist to produce locomotor inhibition and catalepsy support the idea that adenosine A2A receptor agonists as potential antipsychotic agents may have a similar therapeutic profile as dopamine D2 receptor antagonists.