A constant current isolated stimulator (Digitimer, Welwyn Garden City, Hertfordshire, UK) delivered continuous electrical pulses to the STN electrodes at an intensity below the threshold for induced movement (50–250 μA). The motor performance of the hemi-Parkinsonian rat before (5 min), during (2 min), and after (5 min) STN-DBS were compared with the spontaneous exploratory movement (5 min) of intact rats (ANY-maze 4.70 software; Stoelting,Wood Dale, IL). The dependence of the efficacies of DBS-STN on stimulation frequencies (0.2, 1, 5, 10, 50, 125, 200, and 250 Hz) and pulse width (10, 20, 40, 60,

80, and 100 μs) were studied systematically. While the animals were performing in the open field test, both extracellular Sirolimus order spike trains and the local field potentials (LFPs) in MI were recorded simultaneously using a 32-channel electrophysiological data acquisition system (OmniPlex system, Plexon, Dallas, TX). In the behavioral assessment, muscle contractions in the contralateral face and limb could be induced when the stimulation site was located at the lateral STN border (confirmed

postmortem) or the stimulation amplitude used was high (>1 mA). Thus, contralateral muscle contraction at low threshold stimulation was indicative of the possibility that the electrode was very near or inserted NLG919 into the internal capsule and considered unacceptable. For all other cases, the stimulation value was set below the threshold of visible muscular contraction, but at which it could bring behavioral improvement. The t tests were performed to compare the motor performance from different groups. Paired t tests were performed on the data

from hemi-Parkinsonian isothipendyl rats only, comparing the STN-DBS period to both the “pre” and “post” periods. To study the dependence of behavioral improvement on stimulation frequency and pulse width in hemi-Parkinsonian rats, an additional ANOVA repeated-measures analysis (stimulus frequency and pulse width as repeated-measures, respectively) followed by a LSD post hoc test was also performed. All these behavioral test results are shown as mean ± SEM. The stimulus artifact removal and single-unit spike-sorting process were performed in the Off-line Spike Sorter V3 workspace (Plexon, Dallas, TX), using a combination of automatic and manual sorting techniques. Burst discharge was quantified by the Legendy surprise method. Cross-correlation analysis was applied to study the synchronization level among CxFn. The oscillatory rhythm in MI was measured as the spectrum of LFP using fast Fourier transform at 0.2 Hz resolution. When investigating the coherence phase between the spikes of each CxFn and the simultaneously recorded LFP, the polar histogram was built by filtering the LFP into beta band (11–30 Hz). Coronal sections were cut at the STN (20 μm), MI (20 μm), SNc (20 μm), and striatum (200 μm) by freezing microtome.