STIMULATION OF BOTH D1-DOPAMINE AND D2-DOPAMINE RECEPTORS INCREASES BEHAVIORAL ACTIVATION AND ASCORBATE RELEASE IN THE NEOSTRIATUM OF FREELY MOVING RATS

Electrochemically modified carbon-fiber electrodes were used to assess the effects of indirect (amphetamine and GBR-1209) as well as direct D1 (SKF-38393) and D2 (quinpirole) dopamine agonists on extracellular ascorbate in the neostriatum of awake, behaving rats. Relative to controls, 2.5 mg/kg d-amphetamine and 20.0 mg/kg GBR-12909 produced marked behavioral activation concomitant with a significant increase in ascorbate. Comparable effects were observed following the combined administration of 10.0 mg/kg SKF-38393 and 1.0 mg/kg quinpirole, but not after either of these drugs alone. Thus, behavioral activation and release of neostriatal ascorbate were closely related to the concurrent stimulation of both D1 and D2 dopamine receptors.