Rotational behavior induced by unilateral electrical stimulations of nigro-striatal dopamine neurons: modification by low doses of apomorphine.

Unilateral electrical stimulation of nigro-striatal dopamine axons produced marked turning contralateral to the stimulated side. Iterative stimulation led to a progressive increase of this response, followed by a definitive decrease associated with lesions of dopamine neurons. A low dose of apomorphine (25 micrograms/kg) slightly modified the time course and intensity of this response. On the contrary, in rats with a lesioned contralateral nigro-striatal system, low doses of apomorphine (6.25-50 micrograms/kg) markedly depressed contralateral turning whereas a higher dose (150 micrograms/kg) no longer depressed it. These results are discussed with regard to the dopamine autoreceptors.