Electrophysiological and clinical desensitization to apomorphine administration in parkinsonian patients undergoing stereotaxic neurosurgery

A decreased motor response after repeated doses of apomorphine is observed in severely affected Parkinson's disease patients. We simultaneously studie d clinical symptoms and internal pallidus single unit activity in three par kinsonian patients underlying stereotaxic neurosurgery for deep brain stimu lation. In each patient, two closely spaced doses of intraoperatory apomorp hine were administered, while recording the same extracellular unit. The re duced clinical effect of the second administration was correlated to a less ened inhibition of the pallidal single unit recorded throughout the double administration. Our data support the proposition that fast postsynaptic des ensitization to dopamine agonists may take place in the basal ganglia nucle i and play a role in the physiopathology of levodopa long-term treatment sy ndrome. (C) 1999 Academic Press.