Short-Term Depression of Synaptic Transmission during Stimulation in the Globus Pallidus of 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine-Treated Primates

Firing rate changes during stimulation. A, Mean firing rate changes of GPe and GPi neurons during stimulation compared with the prestimulation period (±SEM, **p < 0.001, paired t test). S, Stimulation site; R, recording site. B, C, Examples of (B) a GPe neuron with increased firing rate and (C) a GPi neuron with decreased firing rate at the beginning of GPi stimulation. For B and C, thick horizontal line marks the stimulation period, dashed vertical lines mark stimulation beginning and end, and dotted horizontal lines mark confidence limits (p < 0.01). Firing rate is calculated using 1 s bins, smoothed by a Gaussian window, SD = 0.8 s. D, Firing rate change during the first 20 s of stimulation compared with prestimulation baseline (mean ± SEM). Inset, Firing rate change during the whole stimulation period. Data from two monkeys are shown to the left of the vertical dashed line, data from monkey N only are shown to the right of the dashed line (longer stimulation time). E, F, Same as D, but for cells that had time-locked response to stimulation (E) and cells that were not time-locked to stimulation (F) during the early period. In color coding: S, stimulation site; R, recording site.