EFFECTS OF CA2+ CHANNEL BLOCKERS ON DIRECTIONAL SELECTIVITY OF RABBIT RETINAL GANGLION-CELLS
EFFECTS OF CA2+ CHANNEL BLOCKERS ON DIRECTIONAL SELECTIVITY OF RABBIT RETINAL GANGLION-CELLS
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DOI：
10.1152/jn.1995.74.1.12
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发表时间：
1995-07-01
影响因子：
2.5
通讯作者：
JENSEN, RJ
中科院分区：
文献类型：
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作者：
JENSEN, RJ
(1)对灌流的兔视网膜中的ON-OFF定向选择性神经节细胞进行细胞外记录，以检查电压激活的Ca2+通道阻滞剂对这些神经节细胞对移动光条的反应的影响。2． Cd2+ (67-110 μM) 的浴应用消除了神经节细胞的方向选择性。也就是说，细胞对沿首选方向和零方向移动的光条的前缘和后缘给出几乎相同的响应。 Cd2+的这种效应是可快速逆转的。3．神经节细胞的方向选择性不受 Ni2+ (120-440 μM)、Co2+ (180-690 μM) 或 L 型 Ca2+ 通道阻滞剂尼卡地平 (7-29 μM) 和甲氧基维拉帕米 (18-60 μM) 的影响，然而，这些阻滞剂确实降低了神经节细胞对沿首选移动的光条的反应。 方向.4. omega-芋螺毒素 MVIIC (130 nM-1.9 mu M) 可有效阻断 N 型和 Q 型 Ca2+ 通道，消除神经节细胞的方向选择性。 omega-芋螺毒素 MVIIC 不仅对零方向上的光条移动产生较大的前缘和后缘响应，而且还增加了对首选方向上的光条移动的前缘和后缘响应。 omega-芋螺毒素MVIIC的作用是缓慢可逆的。5． N型Ca2+通道阻滞剂omega-芋螺毒素GVIA (1.4-6.3 μM)不会消除神经节细胞的方向选择性。然而，该阻挡器确实对沿零方向移动的光条的前缘产生了一些响应。 omega-芋螺毒素 GVIA 的这种作用似乎是不可逆的。6． omega-Agatoxin IVA 是 P 型 Ca2+ 通道的有效阻断剂，当以低浓度 (66-83 nM) 进行沐浴时，会增加对首选方向上的光条移动的响应，但对零方向上的光条移动仅产生很小的响应。据报道，在高浓度 (250-280 nM) 下，omega-雷蛇毒素 IVA 可以阻断 Q 型 Ca2+ 通道大于或等于 50%，几乎消除了方向选择性。 omega-agatoxin TVA 的这种作用是缓慢可逆的。7．这些结果表明，omega-芋螺毒素 MVIIC- 和 omega-agatoxin IVA 敏感的 Ca2+ 通道（可能是 Q 型通道）在兔视网膜神经节细胞的方向选择性的产生中发挥重要作用。
(1) Extracellular recordings were made from ON-OFF directionally selective ganglion cells in superfused rabbit retinas in order to examine the effects of voltage-activated Ca2+ channel blockers on the response of these ganglion cells to a moving bar of Light.2. Bath application of Cd2+ (67-110 mu M) abolished directional selectivity in the ganglion cells. That is, the cells gave nearly equal responses to the leading and trailing edges of a bar of light moved in the preferred and null directions. This effect of Cd2+ was rapidly reversible.3. Directional selectivity in the ganglion cells was not affected by Ni2+ (120-440 mu M), Co2+ (180-690 mu M), or the L-type Ca2+ channel blockers nicardipine (7-29 mu M) and methoxyverapamil (18-60 mu M) These blockers did, however, reduce the responses of the ganglion cells to a bar of light moved in the preferred direction.4. omega-Conotoxin MVIIC (130 nM-1.9 mu M), which potently blocks N-type and Q-type Ca2+ channels, abolished directional selectivity in the ganglion cells. omega-Conotoxin MVIIC not only brought out large leading and trailing edge responses to movement of a bar of light in the null direction, but it also increased the leading and trailing edge responses to movement of the bar of light in the preferred direction. The effect of omega-conotoxin MVIIC was slowly reversible.5. The N-type Ca2+ channel blocker omega-conotoxin GVIA (1.4-6.3 mu M) did not abolish directional selectivity in the ganglion cells. This blocker did, however, bring out some response to the leading edge of a bar of a light moved in the null direction. This effect of omega-conotoxin GVIA appeared to be irreversible.6. omega-Agatoxin IVA, a potent blocker of P-type Ca2+ channels, when bath applied at low concentrations (66-83 nM), increased the responses to movement of a bar of light in the preferred direction but brought out only small responses to movement of the bar of light in the null direction. At high concentrations (250-280 nM) that reportedly block Q-type Ca2+ channels by greater than or equal to 50%, omega-agatoxin IVA nearly abolished directional selectivity. This effect of omega-agatoxin TVA was slowly reversible.7. These results indicate that omega-conotoxin MVIIC- and omega-agatoxin IVA-sensitive Ca2+ channels (possibly Q-type channels) play an important role in the generation of directional selectivity in rabbit retinal ganglion cells.