Morphological impairments in retinal neurons of the scotopic visual pathway in a monkey model of Parkinson's disease

Authors

  • Nicolás Cuenca,

    Corresponding author
    1. Departamento de Biotecnología, Facultad de Ciencias, Universidad de Alicante, Campus San Vicente del Raspeig, E-03080 Alicante, Spain
    • Departamento de Biotecnología, Universidad de Alicante, Apartado 99, E-03080 Alicante, Spain
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  • María-Trinidad Herrero,

    1. Departamento de Anatomía Humana y Psicobiología, Facultad de Medicina, Universidad de Murcia, Campus Espinardo, E-30071 Murcia, Spain
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  • Antonia Angulo,

    1. Departamento Interuniversitario de Óptica, Escuela Universitaria de Óptica y Optometría, Universidad de Alicante, Campus San Vicente del Raspeig, E-03080 Alicante, Spain
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  • Emilio de Juan,

    1. Departamento de Fisiología, Genética y Microbiología, Facultad de Ciencias, Universidad de Alicante, Campus San Vicente del Raspeig, E-03080 Alicante, Spain
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  • Gema C. Martínez-Navarrete,

    1. Departamento de Biotecnología, Facultad de Ciencias, Universidad de Alicante, Campus San Vicente del Raspeig, E-03080 Alicante, Spain
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  • Salvador López,

    1. Departamento de Biotecnología, Facultad de Ciencias, Universidad de Alicante, Campus San Vicente del Raspeig, E-03080 Alicante, Spain
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  • Carlos Barcia,

    1. Departamento de Anatomía Humana y Psicobiología, Facultad de Medicina, Universidad de Murcia, Campus Espinardo, E-30071 Murcia, Spain
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  • José Martín-Nieto

    1. Departamento de Fisiología, Genética y Microbiología, Facultad de Ciencias, Universidad de Alicante, Campus San Vicente del Raspeig, E-03080 Alicante, Spain
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Abstract

Physiological abnormalities resulting from death of dopaminergic neurons of the central nervous system in Parkinson's disease also extend to the retina, resulting in impaired visual functions. In both parkinsonian patients and animal models, low levels of dopamine and loss of dopaminergic cells in the retina have been reported. However, the morphology and connectivity of their postsynaptic neurons, the amacrine cells, have not been analyzed. Here we report, with macaques chronically treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as a model of Parkinson's disease, that morphological impairments in dopaminergic retinal neurons and their plexus in the inner retina are accompanied by an immunoreactivity decrease in γ-aminobutyric acidergic and glycinergic amacrine cells. Especially deteriorated were AII amacrine cells, the main neuronal subtype postsynaptic to dopaminergic cells, which exhibited a marked loss of lobular appendages and dendritic processes. Concomitantly, electrical synapses among AII cells, as well as chemical synapses between these and rod bipolar cells, were highly deteriorated in parkinsonian monkeys. These results highlight that the scotopic visual pathway is severely impaired in the parkinsonian condition and provide a morphological basis for a number of abnormalities found in electrophysiological and psychophysical trials in Parkinson's disease patients and animal models. J. Comp. Neurol. 493:261–273, 2005. © 2005 Wiley-Liss, Inc.

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