Electrical coupling of retinal horizontal cells mediated by distinct voltage-independent junctions.

Lu C, Zhang DQ, McMahon DG
Vis Neurosci. 1999 16 (5): 811-8

PMID: 10580717 · DOI:10.1017/s0952523899165015

Electrical coupling between H2 horizontal cell pairs isolated from the hybrid bass retina was studied using dual whole-cell, voltage-clamp technique. Voltage-dependent inactivation of junctional currents in response to steps in transjunctional voltage (Vj) over a range of +/-100 mV was characterized for 89 cell pairs. Approximately one-quarter of the pairs exhibited strongly voltage-dependent junctions (>50% reduction in junctional current at +/-100 mV), another quarter of the pairs exhibited voltage-independent junctional current (<5% reduction at +/-100 mV), and the remainder of the pairs exhibited intermediate values for voltage inactivation. We focused on further characterizing the Vj-independent junctions of horizontal cells, which have not been described previously in detail. When Lucifer Yellow dye was included in one recording pipette, pairs exhibiting Vj-independent coupling showed no (9/12), or limited (3/12), passage of dye. Vj-independent coupling was markedly less sensitive to the modulators SNP (100-300 microM, -9% reduction in coupling) and dopamine (100-300 microM, -6%) than were Vj-dependent junctions (-45% and -44%). However, simultaneous application of both SNP and dopamine significantly reduced Vj-independent coupling (-56%). Both Vj-independent and Vj-dependent junctions were blocked by DMSO (1-2%), but Vj-independent junctions were not blocked by heptanol. Single-channel junctional conductances of Vj-independent junctions range from 112-180 pS, versus 50-60 pS for Vj-dependent junctions. The results reveal that Vj-independent coupling in a subpopulation of horizontal cells from the hybrid bass retina is mediated by cellular junctions with physiological and pharmacological characteristics distinct from those previously described in fish horizontal cells.

MeSH Terms (11)

Animals Bass Cells, Cultured Dimethyl Sulfoxide Dopamine Gap Junctions Heptanol Nitroprusside Patch-Clamp Techniques Retina Synaptic Transmission

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