Inward rectifying currents stabilize the membrane potential indendrites of mouse amacrine cells: Patch-clamp recordings andsingle-cell RT-PCR

[摘要] Purpose: To explore the possible existence of inward rectifyingcurrents in the distal dendrites of amacrine cells.Methods: Patch-clamp recordings were made from amacrine cells in anew horizontal slice preparation of mouse retina. Single-cell RT-PCRstudies were performed after the patch-clamp recordings.Results: In contrast to results from vertical slices or dissociatedcells, all amacrine cells tested demonstrated inward rectifyingcurrents, IIR. Within the limits of our sample, this current didnot depend on the morphological and physiological type of the amacrinecell. Amacrine cells from which the dendrites had been removed did notpossess detectable amounts of IIR. Pharmacological experimentswith ZD7288 (100 μM) and single-cell RT-PCR from recorded cellsrevealed that IIR includes an h-current (I(H)) carried byhyperpolarization-activated cyclic nucleotide gated channels (HCN), HCN1and/or HCN2 subtypes. In the presence of extracellular Cs+ (5 mM),which greatly suppressed IIR, the resting membrane conductance wasreduced. IIR suppressed the generation of oscillatory potentials.Intracellular cAMP (8-cpt-cAMP, 1 mM) activated IIR.Conclusions: IIR appears to occur within dendrites of manyamacrine cells, where it tends to stabilize the resting membranepotential. HCN1 and/or HCN2 channels contribute to IIR in amacrinecells. Dendritic IIR would be expected to contribute to functionalindependence of the distal dendrites of amacrine cells that express it.

[学科分类] 生物化学/生物物理