Acute effects of levodopa plus carbidopa on evoked potentials in Parkinson's disease

Visual evoked potentials by flash (VEP-f) and pattern reversal (VEP-p) stimulation and BAEPs were performed in parkinsonian patients before and after 1 and 4 hours levodopa + Carbidopa administration in two separate experiments. In the first experiment (9 patients and 9 controls) an increase of latencies of peaks III and IV of VEP-f was observed in parkinsonian patients but not in controls. In the second experiment (6 patients) an increase of latencies of peaks N70 and P100 of VEP-p and an increase of latency of peak III and of III-V interval of BAEPs was observed. The results confirm the influence of dopaminergic systems on visual pathways and suggest that the effects of acute 1-DOPA administration may differ from those of chronic treatment. Moreover some evidence exists that dopaminergic systems are involved also in acoustic pathways.