Changes in electroretinogram and serum potassium during l-DOPA treatment in parkinsonism

Abstract

The relationship of L-DOPA plasma level, parameters of ERG and severity of extrapyramidal symptoms after a single dose of L-DOPA was investigated in 11 patients suffering from parkinsonism of idiopathic or arteriosclerotic origin. After a drug-free night, each patient received his/her usual morning dose of L-DOPA. In the subsequent 3 h, the ERG recordings, blood levels and clinical ratings of extrapyramidal symptoms significantly dropped after a delay of 60 min in relation to the occurrence of the peak plasma L DOPA level. The initial "b" wave amplitudes as well as initial serum potassium values were abnormally high. There was a statistically significant correlation between the decrease of "b" wave amplitude (delta "b") and the potassium "normalization index" (i.e. the ratio between the observed decrease of serum potassium and the pretreatment difference from the middle normal potassium value). A definite interpretation of the data cannot be provided until more knowledge about the origin of "b" wave of ERG is available. It can be concluded tentatively that dopaminergic processes influence electrophysiological reactivity of the retina.

L-dopa improves colour vision in Parkinson's disease

“…, 1978;Bodis-Wollner et al, 1987;Gawel et al, 1981;Hutton et al, 1991;Mestre et al, 1990;Regan and Maxner, 1987). These alterations could be partially restored by a dopaminergic medication (Bodis-Wollner and Tagliati, 1993;Sollazzo, 1985;Terziivanov et al, 1982). Additionally circadian fluctuations of contrast sensitivity and the dependance on "on"-and "off"-phases in patients with motoric fluctuations support the hypothesis of visual disorders in PD due to dopamine-deficiency (Bodis-Wollner and Tagliati, 1993;Struck et al, 1990).…”

“…In Parkinsonian retinas reduced dopamine content could be shown as compared to age-matched controls (Harnois and Di Paolo, 1990). The amplitude of the B-wave in the ERG of Parkinsonian patients decreased after L-Dopa ingestion (Terziivanov et al, 1982). The Bwave originates in the bipolar cell layer of the retina were maximum dopaminergic activity is present.…”

Topical Mydriatics Affect Light-Evoked Retinal Responses in Anesthetized Mice

“…Paracrine mechanisms in the retina that produce an augmentation of the ERG waveforms have been reported for amacrine cells that release dopamine, a global modulator of retinal activity that is known to produce a change in all the major ERG waves (for review, 35). Parkinsons disease patients, reported to have low retinal dopamine levels 36, manifest abnormally high amplitude ERG waveforms when un-treated, but the amplitudes rapidly revert to normal levels with L-DOPA treatment 37. Although it is not obvious how muscarinic antagonists and alpha-adrenergic agonists in the presence of K+X anesthesia could affect the dopaminergic amacrine cells in the murine retina, the receptor types on which they act are known to be closely related to dopaminergic amacrine cell activity in different species (for example, guinea-pig: 38; tiger salamander and chicks 39, 40; rats: 41).…”

Low-Level Human Equivalent Gestational Lead Exposure Produces Supernormal Scotopic Electroretinograms, Increased Retinal Neurogenesis, and Decreased Retinal Dopamine Utilization in Rats

“…Scotopic ERG supernormality is a rare clinical finding; the only other reported occurrence is in drug-free patients with early Parkinson disease (Terziivanov et al 1983). In advanced stages of Parkinson disease, the ERG is subnormal (Gottlob et al 1987; Ikeda et al 1994).…”