Nitric oxide directly activates GABAA receptor function through a cGMP/protein kinase-independent pathway in frog pituitary melanotrophs

被引:20
作者
Castel, H [1 ]
Vaudry, H [1 ]
机构
[1] Univ Rouen, European Inst Peptide Res IFRMP 23, Lab Cellular & Mol Neuroendocrinol, UA CNRS,INSERM,U413, F-76821 Mont St Aignan, France
关键词
nitric oxide donor; gamma-aminobutyric acid type A receptor; redox site; S-nitrosylation; sulfhydryl-modifying agent; patch-clamp; inside-out;
D O I
10.1046/j.1365-2826.2001.00683.x
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
The direct effects of nitric oxide (NO) donors and sulfhydryl-modifying agents on the GABA(A) receptor function were examined by perforated patch, whole-cell and single channel recordings in cultured frog melanotrophs. In amphotericin B-perforated cells incubated with the soluble guanylyl cyclase inhibitors LY 83583 and ODQ (10(-4) M each), the NO donor sodium nitroprusside (SNP) (10(-3) M) reversibly increased the current evoked by GABA (5 x 10(-6) M). In the whole-cell configuration, internal application of the oxidizing agent H2O2 (0.05%) potentiated the GABA-evoked current while the reducing agent 2-mercaptoethanol (5 x 10(-3) M) slightly decreased the current amplitude. In inside-out patches, GABA (2 x 10(-7) M) triggered single channel bursts of openings. Incubation with the NO donors SNP or DEA/NO (10(-4) M each) enhanced the open probability of the GABA(A) receptor channel but did not modify the chloride reversal potential and did not affect the conductance states. The oxidizing agents H2O2 (0.05%) or DTNB (10(-4) M) mimicked the stimulatory effect of the NO donors on the open probability while the reducing Compounds 2-mercaptoethanol (5 x 10(-3) M) or DTT (10(-4) M) markedly attenuated the channel activity. Potentiation of the GABA-induced single channel activity by SNP or H2O2 was blocked by 2-mercaptoethanol. Similarly, the potentiating effect produced by DEA/NO or DTNB on the open probability was reversed by DTT. In outside-out patches, incubation with SNP also significantly enhanced the open probability of single channels activated by GABA (10(-6) M). These data indicate that, in frog pituitary melanotrophs, NO potentiates the GABA-evoked current independently of the cGMP/protein kinase pathway. The effect of NO can be accounted for by S-nitrosylation/oxidation of thiol groups either directly on the GABA(A) receptor subunits or on a regulatory protein tightly associated with the GABA(A) receptor.
引用
收藏
页码:695 / 705
页数:11
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