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Ignacio Alcalde, Jose M. Garcia-Fernandez, Cruz Morenilla-Palao, Carlos Belmonte, Jesus Merayo-Lloves; Morphological Characterization of an Amacrine Cell Subpopulation Expressing TRPM8 Ion Channels. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4555.
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© ARVO (1962-2015); The Authors (2016-present)
To establish the cytoarchitecture and cytochemical pattern of a subset of amacrine cells expressing the TRPM8 cold-transducing channel.
Retinas from adult transgenic TRPM8-EYFP mice, in which a fluorescent protein was attached to the cold-transducing channel TRPM8 were used. A total of ten animals were employed. Immunohistochemical staining for calcium binding proteins (Calretinin, Calbindin, Parvalbumin), and for markers to Tyrosine hyroxylase, Choline acetyltransferase, GABA and Glycine, was performed in whole mounted retinas and in transversal cryostat sections of TRPM8-EYFP eye globes. To define the cytoarchitecture of isolated TRPM8-positive cells and their dendritic arborization and synaptic connections within the internal plexiform layer, iontophoretic injections of Neurobiotin were performed. Animals were handled and cared following the guidelines of ARVO and the European Commission (86/609/EC).
A population of TRPM8-positive cells homogeneously distributed in the central and periferal retina and located at the level of the inner border of the inner nuclear layer (INL) was observed. They were identified morphologically as amacrine cells, and were never grouped in clusters. Their dendritic processes were located in a densely packed layer at the outer border of the inner plexiform layer (IPL). Fluorescent cells were also seen in the ganglion cell layer (GCL), being classified as displaced amacrine cells of the GCL. These were CR+ and form a well defined sublayer at the IPL.
A subtype of amacrine cells expressing TRPM8 channels was identified. It appears unlikely that TRPM8 channels expressed by these neurons is involved in cold detection. Electrophysiological experiments have been initiated to determine the functional properties and role of this subpopulation of amacrine cells.
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