[The effect of L-threo-DOPS on P-300 in parkinsonism]

The P-300 has been recently utilized as an objective electrophysiological index of cognitive function in some neurological disease. Hansch et al first described prolonged latency for the P-300 component in Parkinson disease patients and suggested these measures reflects a common, disrupted aspect of cognitive function in this disease. This cognitive disorder may be caused not only from the dysfunction of dopaminergic system but from non-dopaminergic lesions such as norepinephrine ones. On the other hand, L-threo-DOPS, a non-physiological precursor of norepinephrine, has been used for the treatment of some neurological illness such as the freezing phenomenon in Parkinsonism. In the present study we investigate the effect of L-threo-DOPS on cognitive function in Parkinsonism by measuring P-300 component succeedingly. Twenty-four patients, i.e. 19 cases of Parkinson disease (PD), 3 Juvenile Parkinsonism (JP) and 2 cerebrovascular Parkinsonism, are studied. The latencies of P-300 are significantly shortened after treatment of DOPS compared with those of the previous treatment and placebo administration respectively (p less than 0.05, p less than 0.01). The main factors which have influence upon these shortened latencies are analyzed multivariate analysis. The factor analysis and principal component analysis suggest three main factors such as DOPS, age (onset of age), and duration of illness. The patients' groups are divided into three by cluster analysis. The most effective group mainly consists of JP. The least effective one mainly consists of older, long-duration Parkinson disease patients. And there is another group which consists of younger, short-duration PD cases with moderate effect of DOPS. This tendency seems to suggest the different pathological findings between JP and PD. It is postulated that L-threo-DOPS would raise the level of attention and arousal mediated by norepinephrine neuronal system which may improve the cognitive disorder in Parkinsonism.