Adult human retinal neurons in culture: Physiology of horizontal cells

PURPOSE. Adult postmortem human retinal neurons in long-term monolayer cult ures were recorded to characterize the voltage- and transmitter-gated curre nts in putative human horizontal cells (HCs). METHODS. Enzymatically and mechanically dissociated human retinal cells wer e seeded on polylysine and laminin-coated coverslips. Cells were identified by immunocytochemistry with cell type-specific antibodies anti recorded wi th the patch-clamp technique. RESULTS. Immunostaining and responses to voltage steps confirmed the surviv al of various retinal cell types. Horizontal cells were identified by their specific glutamate-modulated anomalous rectifier K+ current conductance. T his identification was further confirmed by subsequent immunolabeling of dy e-labeled recorded cells with an anti-parvalbumin antibody that selectively stained HCs in frozen human retinal sections. Horizontal cells generated v oltage-gated currents classically observed in HCs from fish to mammals. a t ransient outward K+ current, a sustained outward K+ current, and an L-type Ca2+ current. Na+ currents were observed in only a few HCs. As in other spe cies, glutamate, gamma-aminobutyric acid (GABA), and glycine generated resp onses mediated by the activation of kainate/(RS)-alpha-amino-3-hydroxy-5-me thyl-4-isoxazolepropionic acid (AMPA), GABA(A), and glycine receptors, resp ectively. CONCLUSIONS. Various human retinal cell populations survive in vitro as ind icated by immunolabeling with specific cell markers and by the diversity of responses to voltage steps. Human HCs exhibited extensive physiological si milarities to HCs from other vertebrate species and a maintained expression of parvalbumin. These results constitute a comprehensive analysis of volta ge- and transmitter-gated currents in a primate retinal neuron and validate the use of long-term monolayer cult-Lire of adult human neurons as a novel in vitro model for the study of human vision.