title: Differential expression of three T-type calcium channels in retinal bipolar cells in rats.
abstract: Retinal bipolar cells convey visual information from photoreceptors to retinal third-order neurons, amacrine and ganglion cells, with graded potentials through diversified cell types. To understand the possible role of voltage-dependent T-type Ca2+ currents in retinal bipolar cells, we investigated the pharmacological and biophysical properties of T-type Ca2+ currents in acutely dissociated retinal cone bipolar cells from rats using whole-cell patch-clamp recordings. We observed a broad group of cone bipolar cells with prominent T-type Ca2+ currents (T-rich) and another group with prominent L-type Ca2+ currents (L-rich). Based on the pharmacological and biophysical properties of the T-type Ca2+ currents, T-rich cone bipolar cells could be divided into three subgroups. Each subgroup appeared to express a single dominant T-type Ca2+ channel subunit. The T-type calcium currents could generate low-threshold regenerative potentials or spikes. Our results suggest that T-type Ca2+ channels may play an active and distinct signaling role in second-order neurons of the visual system, in contrast to the common signaling by L-rich bipolar cells.
authors.affiliation: Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
authors.forename: Caiping
authors.initials: C
authors.lastname: Hu
authors.forename: Anding
authors.initials: A
authors.lastname: Bi
authors.forename: Zhuo-Hua
authors.initials: ZH
authors.lastname: Pan
mesh_terms: D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020747:Calcium Channels, T-Type / Q000737:chemistry / Q000378:metabolism*; D018929:Cell Culture Techniques; D002460:Cell Line; D004229:Dithiothreitol / Q000494:pharmacology; D006801:Humans; D017136:Ion Transport; D008564:Membrane Potentials / Q000187:drug effects; D009532:Nickel / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D051245:Retinal Bipolar Cells / Q000187:drug effects / Q000502:physiology*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014131:Trace Elements / Q000494:pharmacology
chemical_list: D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D021122:Protein Subunits; D026941:Sodium Channel Blockers; D014131:Trace Elements; D013779:Tetrodotoxin; D009532:Nickel; D004229:Dithiothreitol