In a rat model of Parkinsonism: Upregulation of SK2 channel expression in the subthalamic nucleus. Decrease of SK3 channel expression level in the substantia nigra pars compacta. Behavioral performance in a reaction time task of 6-OHDA-lesioned rat. Impairment by SK channel blockade with apamin in the subthalamic nucleus. Improvement by SK channel blockade with apamin in the substantia nigra pars compacta.