Mechanism of GABAB receptor‐mediated inhibition of spontaneous GABA release onto cerebellar Purkinje cells
Mechanism of GABAB receptor‐mediated inhibition of spontaneous GABA release onto cerebellar Purkinje cells
复制标题
GABAB 受体介导的抑制小脑浦肯野细胞自发 GABA 释放的机制
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
G. Stephens
中科院分区：
文献类型：
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作者：
V. L. Harvey;G. Stephens
本实验研究了γ-氨基丁酸B受体对3~5周龄小鼠小脑片自发释放氨基丁酸的调节作用。GABA受体激动剂巴氯芬和CGp 44533分别降低微小抑制性突触后电流(MIPSC)的频率，但对mIPSC的幅度没有显著影响；两者共同作用，与突触前的作用部位一致。GABA受体拮抗剂CGp 55845可阻断巴氯芬的抑制作用。巯基烷基化试剂N-乙基马来酰亚胺阻断了巴氯芬的作用，暗示Gi/o亚基介导了GABAB G蛋白偶联受体途径。在K+通道阻断剂Ba2+和钙通道介导的GABA释放阻断剂CD2+的存在下，巴氯芬对GABA的抑制作用持续存在。应用名义上无钙的胞外液可降低mIPSC的频率和幅度；然而，巴氯芬对mIPSC的频率有明显的抑制作用，进一步表明这一途径不依赖于钙内流。腺苷环化酶激活剂Forsklin和佛波酯12，13-二丁酸酯增加了GABA的自发释放。然而，巴氯芬诱导的抑制在这两种情况下都没有显著改变。腺苷环化酶抑制剂SQ 22536或蛋白激酶C抑制剂氯化白屈菜红碱也不影响巴氯芬的作用。在多价阳离子钌红的存在下，巴氯芬仍然降低了mIPSC的频率；然而，巴氯芬诱导的抑制作用显著降低。此外，巴氯芬在强大的促分泌剂α-拉曲霉毒素诱导的高频mIPSCs爆发过程中没有明显的抑制作用。综上所述，这些结果表明，GABAB的抑制发生在钙离子内流的下游，可能部分是通过抑制囊泡释放机制来实现的。
γ‐Aminobutyric acid (GABA)B receptor‐mediated modulation of spontaneous GABA release onto Purkinje cells was investigated in cerebellar slices from 3‐ to 5‐week‐old mice. The GABAB receptor agonists baclofen and CGP 44533 each reduced the frequency of miniature inhibitory postsynaptic currents (mIPSCs), with no significant effect on mIPSC amplitude; together, consistent with a presynaptic site of action. The GABAB receptor antagonist CGP 55845 blocked baclofen‐induced inhibition. The sulphydryl alkylating agent N‐ethylmaleimide occluded baclofen effects, implicating Gi/o subunits in mediating a GABAB G protein‐coupled receptor pathway. Baclofen‐induced inhibition persisted in the presence of Ba2+, a blocker of K+ channels, and Cd2+, a blocker of Ca2+ channel‐mediated GABA release. Application of nominally Ca2+‐free extracellular solutions reduced mIPSC frequency and amplitude; however, baclofen produced a significant inhibition in mIPSC frequency, further suggesting that this pathway was independent of Ca2+ influx. Spontaneous GABA release was increased by the adenylate cyclase activator, forskolin, and the phorbol ester, phorbol 12,13‐dibutyrate. However, baclofen‐induced inhibition was not significantly changed in either condition. Baclofen action was also not affected by the adenylate cyclase inhibitor SQ 22536 or the protein kinase C inhibitor chelerythrine chloride. Baclofen still reduced mIPSC frequency in the presence of the polyvalent cation ruthenium red, which acts as a secretagogue here; however, baclofen‐induced inhibition was reduced significantly. Furthermore, baclofen produced no clear inhibition during high‐frequency mIPSCs bursts induced by the potent secretagogue α‐Latrotoxin. Together, these results suggest that GABAB inhibition occurs downstream of Ca2+ influx and may be mediated, in part, by an inhibition of the vesicular release mechanism.
影响因子：
2.5
作者：
DOZE, VA;COHEN, GA;MADISON, DV
通讯作者：
MADISON, DV