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Abstract #6658 Published in IGR 4-1
New insight into the functional role of acetylcholine in developing embryonic rat retinal neurons
Yasuyoshi H; Kashii S; Kikuchi M; Zhang S; Honda Y; Akaike AInvestigative Ophthalmology and Visual Science 2002; 43: 446-451
PURPOSE: To examine the effects of acetylcholine (ACh) on glutamate-induced neurotoxicity in embryonic rat retinal neurons. METHODS: Primary cultures were obtained from rat retinas at embryonic days 17-19. Cultured cells were exposed to glutamate for ten minutes, followed by incubation in glutamate-free medium for one hour. Drugs were added to the incubation medium for one to 24 hours until immediately before glutamate exposure, and were removed from culture medium during glutamate exposure and the postincubation period. The neurotoxic effects on retinal cultures were quantitatively assessed by the trypan blue exclusion method. RESULTS: Cell viability was markedly reduced by a ten-minute exposure to 500 μm glutamate followed by a one-hour incubation in glutamate-free medium. Incubating the cultures with 1 μm ACh for 12 hours before glutamate exposure reduced glutamate neurotoxicity. A similar effect was induced by application of carbachol (1 μm). The protective effect of ACh against glutamate neurotoxicity was inhibited by a nicotinic acetylcholine receptor (nAChR) antagonist, mecamylamine (0.5 μm), whereas a muscarinic acetylcholine receptor (mAChR) antagonist, atropine (0.5 μm) did not affect ACh-induced protection. In addition, a similar protection was induced by application of nicotine (1 μm), but not by muscarine (1 μm). Pretreatment with nicotine induced a protective effect in a time-dependent manner, ranging from one to 12 hours. Pretreatment with nicotine at concentrations ranging from 0.001-1 μm induced dose-dependent protection against glutamate neurotoxicity. Furthermore, the protective action of nicotine was inhibited by simultaneous application of dopamine D1 receptor antagonist, SCH23390 (1 μm), with nicotine, whereas a dopamine D2 receptor antagonist, domperidone (1 μm), did not affect nicotine-induced protection. CONCLUSIONS: These results suggest that pretreatment of cultured rat retinal neurons with ACh or the nAChR agonists, nicotine and carbachol, has a protective action against glutamate neurotoxicity through nAChRs and that the dopamine release induced by nicotinic stimulation subsequently protects the retinal neurons by way of dopamine D1 receptors
Classification:
2.15 Optic nerve (Part of: 2 Anatomical structures in glaucoma)
3 Laboratory methods
5 Experimental glaucoma; animal models
