The effects of levodopa and haloperidol on flash and pattern ERGs and VEPs in normal humans

Abstract

We investigated the effects of single doses of the dopamine agonist levodopa and the dopamine antagonist haloperidol on pattern and flash electroretinograms (ERGs) and visual evoked potentials (VEPs) in normal subjects. A placebo and two treatment regimens were administered in a randomized double-masked design. No significant intertreatment differences in the pattern ERGs and VEPs were noted. Although not statistically significant, a clearly discernible tendency was found for increased flash ERG b-wave amplitudes after levodopa administration compared with placebo. In comparison with placebo and levodopa, haloperidol was associated with significantly prolonged flash ERG b-wave implicit times, including each oscillatory potential, which also showed increased duration, particularly in the O1-O3 interpeak implicit time. The failure of pattern ERGs and VEPs to show changes after haloperidol may have been related to the timing of the recordings, which took place during the presumed phase of rising blood levels and before the flash ERG and VEP recordings. Our findings further demonstrated the reliability of the flash ERG in revealing changes in dopaminergic status in the visual system and suggest that steady-state (flicker) ERGs, cone ERGs, and oscillatory potentials have particular use in this regard.

Effects of Two Anticholinergic Drugs on Electroretinograms and Visual Evoked Potentials in Healthy Human Subjects

“…Applying essentially the same battery of ERGs and VEPs which we have previously shown to be sensitive to antidopaminergic drugs [10,14], the present study has failed to provide convincing evidence of anticholinergic effects. It was anticipated and supported by findings that biperiden would have greater central effects (sedation) than atropine, but biperiden failed to cause any signifi cant ERG effects.…”

Pharmacological modifications in dopaminergic neurotransmission affect the quinpirole-evoked suppression of serotonin N-acetyltransferase activity in chick retina: an impact on dopamine D4-like receptors

“…Several electrophysiological studies have reported a visual dysfunction in Parkinson's disease, and strongly suggested that the visual impairment can be related to dopaminergic deficiency in the visual pathway, presumably in the retina (Bodis-Wollner and Yahr, 1978;Stanzione et al, 1989;Bodis-Wollner, 1990). It has been shown that the blockade of D2-family DA receptors by neuroleptic drugs affects the visual electrophysiological performances with the same trend as that observed in Parkinsonic subjects (Bartel et al, 1990;Stanzione et al, 1991Stanzione et al, , 1992Rudolf and Wioland, 1993). Based on these data it appears likely that alterations in sensitivity of retinal DA receptors, including the D4-subtype, may affect several aspects of retinal physiology, particularly those which are dependent on or modulated by DA and melatonin.…”

The effect of physical effort on retinal activity in the human eye: rod and cone flicker electroretinogram studies

“…During cycloergometer exercise, significant changes in heart rate were observed compared to rest, both in the first experiment (scotopic conditions) (F (2,27) =62.12, p<0.001) and second experiment (photopic conditions) (F (2,27) = 68.24, p<0.001). Effort-induced changes in heart rate were the same for both experiments (F (2,27) =0.04, p>0.05).…”

“…The results of several studies demonstrated that higher levels of neurotransmitters enhanced neuroretinal activity. For instance, it has been shown that levodopa administration increased ERG bwave amplitudes in normal human subjects [27]. In contrast, short-term oral administration of dopaminergic receptor blockers (chlorpromazine and fluphenazine) significantly reduced ERG b-wave amplitudes and also selectively reduced the amplitude of the OP1 [28].…”