Somatostatin modulates voltage-gated K+ and Ca2+ currents in rod and cone photoreceptors of the salamander retina
Somatostatin modulates voltage-gated K+ and Ca2+ currents in rod and cone photoreceptors of the salamander retina
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DOI：
10.1523/jneurosci.20-03-00929.2000
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发表时间：
2000-02-01
影响因子：
5.3
通讯作者：
Witkovsky, P
中科院分区：
文献类型：
--
作者：
Akopian, A;Johnson, J;Witkovsky, P
我们研究了生长抑素[或生长激素释放抑制因子（SRIF）]受体之一sst（2A）在蝾螈视网膜中的细胞定位，并研究了SRIF对视杆细胞和视锥细胞光感受器中电压门控K+和Ca 2+电流的调节作用。SRIF免疫组化染色见于分布广泛的无长突细胞，其胞体位于内核层和内网层的交界处。sst 2A免疫染色见于视杆细胞和视锥细胞的内节和终末。其他sst（2A）免疫反应性由假定的双极和无长突细胞表达。SRIF在100-500 nM的浓度下增强了视杆细胞和视锥细胞中的延迟外向整流K+电流（I-K）。在用百日咳毒素（PTX）预处理的细胞中，SRIF作用被阻断，并且被细胞内GDP（β）S显著降低。SRIF对视杆细胞和视锥细胞的电压门控L型钙电流有不同的调节作用。SRIF减少了33%的杆中的钙电流，但增加了40%，平均在锥。这两种作用都是通过G蛋白激活介导的，并被PTX阻断。Ca 2+成像实验支持了这些结果，表明500 nM SRIF减少了K+诱导的视杆细胞感光末梢细胞内Ca 2+的增加，但增加了视锥细胞内Ca 2+的增加。我们的研究结果表明，SRIF可能通过调节电压门控K+和Ca 2+电流在调节谷氨酸递质从光感受器释放中发挥作用。
We investigated the cellular localization in the salamander retina of one of the somatostatin [or somatotropin release-inhibiting factor (SRIF)] receptors, sst(2A), and studied the modulatory action of SRIF on voltage-gated K+ and Ca2+ currents in rod and cone photoreceptors. SRIF immunostaining was observed in widely spaced amacrine cells, whose perikarya are at the border of the inner nuclear layer and inner plexiform layer. sst2A immunostaining was seen in the inner segments and terminals of rod and cone photoreceptors. Additional sst(2A) immunoreactivity was expressed by presumed bipolar and amacrine cells. SRIF, at concentrations of 100-500 nM, enhanced a delayed outwardly rectifying K+ current (I-K) in both rod and cone photoreceptors. SRIF action was blocked in cells pretreated with pertussis toxin (PTX) and was substantially reduced by intracellular GDP(beta)S. Voltage-gated L-type Ca2+ currents in rods and cones were differently modulated by SRIF. SRIF reduced Ca2+ current in rods by 33% but increased it in cones by 40%, on average. Both effects were mediated via G-protein activation and blocked by PTX. Ca2+-imaging experiments supported these results by showing that 500 nM SRIF reduced a K+-induced increase in intracellular Ca2+ in rod photoreceptor terminals but increased it in those of cones. Our results suggest that SRIF may play a role in the regulation of glutamate transmitter release from photoreceptors via modulation of voltage-gated K+ and Ca2+ currents.