Table 3.

Effect of valproate on the regularity of SNr firing

ISIH parameters	Predrug	After VPA	p
Kurtosis	21.2 ± 2.9	11.1 ± 2.2*	0.0156
Skewness	3.8 ± 0.3	2.7 ± 0.3*	0.0156
Coefficient of variation	1.2 ± 0.1	1.1 ± 0.8	0.3750

The regularity of firing of SNr neurons before and after systemic application of VPA was analyzed based on the ISIH parameters coefficient of variation, kurtosis, and skewness. Kurtosis and skewness were significantly changed (marked by asterisk) after injection of VPA compared to predrug values indicating a change towards a more regular neuronal discharge pattern caused by VPA. The coefficient of variation was not significantly altered by VPA (mean ± SEM; Wilcoxon's signed rank test; n = 7).