This study tested the effect of intravenous injections of CyPPA [the activator of small conductance calcium-activated potassium channels of types 2 and 3 (SK2/SK3)] on the firing frequency of cerebellar Purkinje cells of laboratory male mice at the age of 6 months via the method of extracellular in vivo recordings from Purkinje cells. This method revealed that 1 mM CyPPA tail vein injections lead to progressive reduction of Purkinje cells firing frequency. Thus, simple spike’s firing frequency decreases by 16% in one hour after injection, by 49% in two hours after injection, and by 61% in three hours. The obtained results confirmed the hypothesis about the important role of SK channels in the maintenance of Purkinje cells spontaneous activity in vivo. Since deterioration of biophysical and physiological functions is observed in many cerebellar ataxias, SK channels can serve as a potential target for the treatment of such disorders.