EFFECTS OF INCREASING DOSES OF APOMORPHINE DURING STEREOTAXIC NEUROSURGERY IN PARKINSONS-DISEASE - CLINICAL SCORE AND INTERNAL GLOBUS-PALLIDUS ACTIVITY

We analysed the firing activity of internal globus pallidus cells in t wo Parkinson's disease patients undergoing stereotaxic surgery. Both p atients showed an advanced rigid-akinetic syndrome with disabling levo dopa induced dyskinesias. Apomorphine, intraoperatively administered a t doses (1-2mg) inducing a short but clear: clinical improvement witho ut involuntary movements, reduced the pallidal discharge rate by >50% in both patients. An higher apomorphine dose (2.5mg), tested in one he misphere, blocked the firing activity with a time course independent f rom the occurrence of dyskinesias. These finding suggest that the redu ction of internal pallidus excitability is one of the mechanisms under lying the efficacy of dopaminergic therapy, but also that changes in o ther basal ganglia stations are likely to be involved in dyskinesias.