Effects of intravenous cocaine administration on cerebellar Purkinje cell activity.

The goal of the present study was to investigate the effects of intravenous cocaine administration on cerebellar Purkinje cell firing. Extracellular neuron activity was recorded and cells were locally excited with spaced microiontophoretic pulses of glutamate. Glutamate-evoked and spontaneous discharges were compared before and immediately following cocaine administration. Cocaine injections (1. 0 and 0.25 mg/kg, i.v.) induced a reversible suppression of both spontaneous activity and glutamate-evoked excitation. Procaine was ineffective in producing similar actions. Cocaine only inhibited glutamate-induced excitation in animals pre-treated with reserpine (5 mg/kg, i.p.). Propranolol injections (10 mg/kg, i.p.) were ineffective in blocking cocaine-induced inhibitions. Yohimbine (5 mg/kg, i.p.) pre-treatment abolished cocaine-induced suppressions of either spontaneous or glutamate-evoked excitation. Therefore, cocaine administration decreases Purkinje cell spontaneous and glutamate-evoked discharges by a mechanism involving alpha(2)-adrenoceptor activation. It is suggested that by changing the normal function of the cerebellum cocaine can produce drug-related alterations in overt behavior and cognition.