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Visual System

開催日 2014/9/13
時間 11:00 - 12:00
会場 Poster / Exhibition(Event Hall B)

Histamine Affects the Voltage-Gated Currents in the Mouse Amacrine Cell

  • P3-115
  • 堀尾 佳世 / Kayo Horio:1 大熊 真人 / Mahito Ohkuma:1 宮地 栄一 / Ei-ichi Miyachi:1 
  • 1:藤田保健衛生大・医・生理II / Dept of Physiol, Sch of Med, Fujita Health Univ, Aichi, Japan 

Mammalian retinae express histamine receptors. In the macaque retinal bipolar cell, histamine has been reported to enhance the potassium current via histamine receptors. Recent immunohistochemical studies showed that histamine H1 receptor (HR1) was expressed in the mammalian amacrine cells. Here we investigated the effect of histamine on mouse amacrine cells, using the whole-cell version of the patch-clamp technique. Mouse retinae were sliced at 200 µm in thickness. The slice patch-clamp recording was performed at the inner nuclear layer of the retina. The amacrine cells were identified by the locations of the soma in the retinal layer and by the shapes of the fluorescence with injected Lucifer yellow. First, we confirmed the effect of histamine in the amacrine cells (n = 19). Under voltage-clamp conditions, the amplitude of the voltage-gated outward currents was enhanced by the application of 100 µM histamine in eleven amacrine cells (37.9 ± 7.3%; mean ± SEM). Although histamine decreased the outward currents in other three cells (-30.6 ± 6.1%), did not affect these currents in five cells. Some amacrine cells exhibited obvious voltage-gated inward currents (n = 7). Histamine also augmented the peak amplitude of the inward currents in three amacrine cells. These results suggest that histamine contributes to the modulation of the membrane potential in some amacrine cells. Next, we identified the type of histamine receptors in the amacrine cells. Triprolidine, the specific HR1 antagonist, was applied to the amacrine cells, whose outward currents were increased by histamine (n = 6). In five amacrine cells, triprolidine reduced the effects of histamine. This result indicates that histamine affected these currents via the HR1. Since several types of amacrine cells exist in the mouse retina, we expect that the difference of histaminergic responses may depend on the types of amacrine cells. Our findings suggest that histamine contributes to the modulation of the membrane potential in the particular types of amacrine cell. The amacrine cells participate in the lateral modulation in the retina. Therefore, histamine may be one of the important neuromodulators in the visual processing.

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