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292

33.P2

Readiness Potential in Parkinson’s Disease: Effects ofL-Dopa Therapy and Brain Transplants

D.N. Vel8zquez Martnez, F. Ostrosky-Solis, Y. Rodrguez, C. Garcade la Cadena, R. Chayo, M.A. Guevara, M. LOpez Cabrera and I. Madrazo

Depto. Psicofisiolog fa, Facultad de Psicolog fa; Depto. Farmacolog fa, Facultad de Medicine,Universidad NacionalAutOnoma de Mcicoy Centro Medico Siglo XXI, Mexico

A fundamental question in the study of trans-plants to the central nervous system is theidentification of the brain mechanisms that arerelated to the clinical improvement observedafter intracerebral grafts of catecholamineproducing tissue to the nigro-striatal system insome of the patients affected by Parkinson’sdisease (PD). The use of reliable event-relatedpotentials may provide complementary clinicaland basic information related to the grafttherapeutic effects. The Vertex ReadinessPotential (RP) or Bereitschaftspotential pre-ceding self-paced voluntary movements and theMotor Potential (MP) have been reported to bemodulated by noradrenergic and dopaminergicmechanisms in the brain; they were used tostudy pre- and postoperative changes afterautoadrenal surgery.

The RP and MP preceding self-paced volun-tary movements were recorded in 10 normalsubjects, 15 PD patients who were candidates forsurgery and 5 PD patients who had submitted toautoadrenal transplant. Brain electrical activitywas recorded using Ag/AgC1 electrodes placedat F3, F4, Fz, C3, C4, Cz and Pz, all referencedto linked mastoids. Eye movements were moni-tored by electrooculogram placing electrodesabove and below the left lid. Brain electricalactivity was amplified (bandpass 0.3-70 Hz) anddigitalised by a computer. Subjects were in-structed to press a telegraphic key with the indexfinger approximately every 4 sec. Electro-myographic activity (EMG) was derived fromsurface electrodes placed over the forearmmuscle group that contracted when the key waspressed. A reverse computation program trig-gered from the EMG registered 1500 ms beforeto 500 msec after the movement onset. Individ-ual trials with excessive muscular activity or eye

blinks were excluded. After an average of 80trials, the RP and MP were identified by thecriteria of Shibasaki, Shima and Kuroiwa (JNeurol 1978; 219: 15-25). Evoked potentialswere recorded in normals 45 minutes after theadministration of placebo or the dopaminergicagonist L-DOPA (250 mg) with 25 mg carbidopa(Sinemet 275). The PD patients were studiedwith L-DOPA and after 36 hours without L-DOPA both preoperatively and postoperatively(3 months after surgery). For each neuroelectricrecording repeated measures ANOVAs wereperformed in which changes in group (Normalvs. PD), and treatment (Placebo vs. L-DOPA)were analyzed.

Without medication, differences betweennormal subjects and PD patients were observedin the amplitude of the RP and MP; the PDpatients had lower amplitude than the normalsat Cz, C3 and C4. Before surgery L-DOPA pro-duced a significant (p<0.01) increase in theamplitude of the RP and MP of PD patients, butonly marginal changes in normal subjects. In fivepatients who were registered three months aftersurgery we observed, without medication, a sig-nificant increase in the amplitude of the RP andMP at Cz and C3 and minor changes in the samedirection at C4 and Fz. The changes in theseelectrophysiological measures seem to be re-lated to dopaminergic activity and could behelpful in evaluating some of the biochemicaland electrophysiological changes after braingrafting.

(C) FREUND PUBLISHING HOUSE LTD., LONDON. JOURNAL OFNEURALTRANSPLANTATION & PLASTICITY,Vol. 3, No. 4, 1992

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