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G Coude, F Huppe-Gourgues, C Casanova; Retinal Dopamine Depletion Alters Contrast Sensitivity Function of Lateral Geniculate Cells in Cats . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1804.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Retinal dopamine (DA) is involved in several aspects of visual function. For instance, it has been suggested that a lack of retinal DA may be responsible for the altered contrast sensitivity function (CSF) of Parkinson's disease patients. We examined the response properties of lateral geniculate nucleus (LGN) neurons after the intraocular administration of the catecholaminergic neurotoxin 6-hydroxydopamine (6-OHDA). Methods: Experiments were conducted on adult anesthetized cats. Animals were monocularly treated with two injections of 6-OHDA (150µg in 100µl) one day apart. Controlateral eyes of each animal received the identical amount of vehicle (saline). Two to four weeks after the first injection, extracellular activity of neurons in LGN was recorded. Receptive fields of LGN units were characterized by counterphased and drifting sinewave gratings and their CSF was measured. Results: Immunocytochemical procedures revealed that the DA amacrine network was altered by the neurotoxin. HPLC assays of retinal tissue showed a 48 to 84% reduction of DA in 6-OHDA-treated retinas. To date, comparing the CSF of LGN neurons innervated by the normal and treated eyes indicated a change in the CSF. For cells connected to the DA-deprived eye, the CSF tended to be displaced towards lower spatial frequencies. Conclusion: These preliminary findings suggest that retinal DA may be necessary to fully establish the normal CSF of cells in the LGN.
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