Presynaptic inhibition and disynaptic reciprocal 1a inhibition in parkinson's disease,the effect of the dopaminergic treatment [Parkinson hastali{dotless}ǧi{dotless}'nda presinaptik i̇nhibisyon ve disinaptik resiprokal 1a i̇nhibisyonu,dopaminerjik tedavinin etkisi]

Objective: in recent years,increasing number of studies about the spinal cord pathology in parkinson's disease had been conducted. h reflex investigation is an important choice in the studies dealing with neurophysiological and interneuronal alterations of the spinal cord. the effect of the dopaminergic treatment on the spinal interneuronal reflex pathways is a relatively less investigated issue. this study has been adressed to assess the presynaptic and disynaptic inhibition levels in parkinson's disease,and the effect of dopaminergic treatment. methods: presynaptic inhibition and dysynaptic reciprocal 1a inhibition is investigated by double stimulation of the tibial nerve at the popliteal fossa and peroneal nerve at the fibular head in patients with parkinson's disease and also in control subjects for the 1-100 ms conditioning test intervals. the amplitude changes of the test and the conditioned h reflex responses were calculated and compared in the affected and less affected sides in both before and under dopaminergic treatment. results: disynaptic and presynaptic inhibitions existed in all subjects. disynaptic reciprocal 1a inhibition was shortened only at 2 ms conditioning interval. the conditioned and test h reflex ratio (hc/ht) for the 20 ms conditioning test interval (presynaptic inhibition) was significantly smaller in the affected side than the controls (p: 0.046). the percentages of the inhibitions for the 20-10-5-3-2 ms conditioning intervals significantly increased in the affected side under treatment when compared with the ones obtained in the pretreatment period (p: 0.031,0.027,0.014,0.026,0.037). conclusion: presynaptic inhibition was decreased and disynaptic inhibition duration was shortened in the affected side of the patients with parkinson's disease,dopaminergic treatment caused significant increases in both periods of inhibition. these findings indicate an abnormal supraspinal influence on the spinal cord in parkinson's disease,and also the role of some dopa responsive neural mechanisms.