Lack of stimulation by high amphetamine doses following a low dose of spiperone

The locomotor stimulant and stereotypic effects of amphetamine were investigated in rats pretreated with the specific dopaminergic blocker spiperone (0.25 mg/kg). Amphetamine doses from 8.0 to 64.0 mg/kg failed to stimulate behavior significantly and consistently after spiperone treatment. These results suggest the possibility of non-competitive antagonism by spiperone at dopaminergic synapses.