ROLE OF NEOSTRIATUM AND NUCLEUS-ACCUMBENS IN STEPPING INDUCED BY APOMORPHINE AND DEXAMPHETAMINE

Systemic administration of apomorphine and dexamphetamine are known to produce circling in rats by changing the functioning of hindlimb stepping and forelimb stepping, respectively. In the present study intracranial injections of the dopamine antagonist sulpiride were used to study the involvement of the neostriatum and nucleus accumbens in these effects. It was found that injections of sulpiride into the neostriatum, but not the nucleus accumbens, dose-dependently (1-20 ng) reduced the number of apomorphine-induced hindlimb doublets without affecting the dexamphetamine-induced forelimb crossing steps. On the other hand, it was found that injections into the nucleus accumbens, but not the neostriatum, reduced the number of dexamphetamine-induced forelimb crossing steps without affecting the apomorphine-induced hindlimb doublets. This effect was not dose-dependent. The data suggest that the neostriatum, but not the nucleus accumbens, is primarily involved in the apomorphine-induced changes in hindlimb stepping, and that the nucleus accumbens, but not the neostriatum, is primarily involved in the dexamphetamine-induced changes in forelimb stepping.