The effect of L-dopa on pupillary diameter in mice.
Injection of L-dopa in mice produces dose-dependent mydriasis. Pre-treatment with peripheral dopa-decarboxylase inhibitors (carbidopa and benserazide) or with an alpha-adrenergic blocking agent (phentolamine) abolishes the pupillary dilation caused by L-dopa. Pretreatment with fusaric acid, an inhibitor of dopamine-beta-hydroxylase, also antagonizes the mydriatic effect of L-dopa. Thus, our results suggest that the mydriasis produced in mice following the injection of L-dopa is caused by its peripheral conversion to noradrenaline, which stimulates alpha-adrenergic receptors in the dilator iridis. There was no evidence that stimulation of specific dopaminergic receptors was involved.
D000818:Animals; D001545:Benserazide / Q000494:pharmacology; D002230:Carbidopa / Q000494:pharmacology; D005669:Fusaric Acid / Q000494:pharmacology; D007980:Levodopa / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D010646:Phentolamine / Q000494:pharmacology; D011680:Pupil / Q000187:drug effects / Q000502:physiology*
D007980:Levodopa; D001545:Benserazide; D005669:Fusaric Acid; D002230:Carbidopa; D010646:Phentolamine