Autogenous oscillatory potentials in neurons of the guinea pig substantia nigra pars compacta in vitro.

In spontaneously firing neurons of the guinea pig substantia nigra pars compacta (SNC) maintained in slices, blockade of the fast spikes by tetrodotoxin (TTX) revealed a slow oscillatory potential change, which was depressed by Cd2+, a Ca2+-channel blocker. The spontaneous firing was suppressed by the application of Ca2+-free saline, Cd2+ or Co2+, but not by nifedipine. These findings lend support to the view that the spontaneous firing of SNC neurons is produced by an intrinsic, Ca2+-dependent pacemaking process affected by Cd2+ but not by nifedipine.