Anodal polarization in the substantia nigra increases rotational behavior in the rat.

Rotational behavior was examined in rats after unilateral application of an anodal direct current (3 microA, 30 min) to the substantia nigra pars compacta (SNC). The current application increased contralateral rotation in two stages. One was during the period immediately after the current application, in which the increase in rotation declined within 30 min. The other period was long lasting, in which rotation increased 2 hr after the application and persisted for 24 hr or more. These results suggest that anodal direct currents induce transient and long-lasting activation of the SNC neurons, resulting in increases in rotational behavior.