Effects of amphetamine on intracellular responses of caudate neurons in the cat.

The effects of acute administration of amphetamine on membrane potentials and evoked postsynaptic potentials of caudate neurons in cats were assessed using intracellular recording. High doses of amphetamine (0.5 mg/kg, i.v.) produced a reversible depolarization of the cell membrane in 78% of cells tested. Low doses (0.1 mg/kg) had no effect on the resting membrane potential. Long-lasting increases in amplitude of both excitatory and inhibitory components of evoked postsynaptic potential sequences were observed after both high and low doses of amphetamine. These changes were more evident to cortical than to substantia nigra or to intralaminar thalamic stimulation. These results were shown to be independent of the peripheral autonomic actions of amphetamine. These effects appear to be mediated by the ability of amphetamine to alter catecholaminergic mechanisms in the caudate nucleus and suggest that increased dopamine release may have a facilitatory effect on both excitatory and inhibitory synaptic transmission.