Comparative effect of amphetamine and caffeine on spontaneous activity of sensomotor cortical units and their responses to stimulation of the caudate nucleus.

In acute experiments on anesthetized cats activity of sensomotor cortical units was recorded during low-frequency stimulation of the head of the caudate nucleus. Amphetamine (1 mg/kg), although not significantly affecting the spontaneous firing rate, increased the number of spontaneously active cortical units. Meanwhile inhibition of these units during stimulation of the caudate nucleus was weakened. Amphetamine had a stronger suppressive action on the inhibition arising from the ventro-lateral portion than from the dorso-medial portion of the head. In the case of caffeine the location of the stimulating electrodes was unimportant.