A, Population PSTHs compare MC-induced responses of six GPe neurons in 6-OHDA rats recorded before and after intra-Str injection of muscimol. Neurons responding with an early excitation, a short inhibition, and a late excitation to MC stimulation were selected for the experiment. A, D, The bin width of the PSTHs is 4 ms and the green PSTH shows the delta of the before and after PSTHs. B, C, Behavioral effects of intra-Str injection of methyl l-DOPA. Methyl l-DOPA altered the preferred turning direction from left to right and increased the total distance of ambulation of two 6-OHDA rats (a and b are before and a+ and b+ are after the injection.) D, Population PSTHs of six GPe neurons that responded with an early excitation, a short inhibition, and a late excitation to MC stimulation in 6-OHDA rats recorded before and after intra-Str injection of methyl l-DOPA.