INTRANIGRAL INJECTIONS OF SCH-23390 INHIBIT SKF-82958-INDUCED ROTATIONAL BEHAVIOR

The selective Dl receptor antagonist, SCH 23390, was injected into the pars reticulata region of the lesioned substantia nigra at various concentrations (3.0, 1.5, 1.0, 0.6 or 0.3 mM) just before a s.c. injection of either the selective D1 agonist, SKF 82958; the selective D2 agonist, quinpirole; or the mixed D1-D2 receptor agonist, apomorphine. SCH 23390 pretreatment (1) had no significant effect on quinpirole rotational behavior, (2) attenuated apomorphine rotational behavior and (3) dose-dependently inhibited SKF 82958 rotational behavior with the highest SCH 23390 doses completely blocking SKF 82958 rotational behavior in some animals. These data provide further evidence that dopamine release in the midbrain may act as a neuromodulator of motor behavior, and that Dl receptors play a functional role in this process.