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突触前含α7和β2的烟碱型乙酰胆碱受体通过不同的细胞机制调节大鼠前额叶皮质神经末梢兴奋性氨基酸的释放。

Presynaptic alpha 7- and beta 2-containing nicotinic acetylcholine receptors modulate excitatory amino acid release from rat prefrontal cortex nerve terminals via distinct cellular mechanisms.

作者信息

Dickinson Jane A, Kew James N C, Wonnacott Susan

机构信息

Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom.

出版信息

Mol Pharmacol. 2008 Aug;74(2):348-59. doi: 10.1124/mol.108.046623. Epub 2008 Apr 29.

Abstract

Nicotine can enhance working memory and attention. Activation of both alpha7 and beta2() nicotinic acetylcholine receptors (nAChRs) in the prefrontal cortex (PFC) has been implicated in these processes. The ability of presynaptic nAChRs to modulate neurotransmitter release, notably glutamate release, is postulated to contribute to nicotine's effects. We have examined the cellular mechanisms underlying alpha7 and beta2() nAChR-mediated [(3)H]d-aspartate release from the PFC in vitro. Using the alpha7 and beta2() nAChR-selective agonists (R)-N-(1-azabicyclo[2.2.2]-oct-3-yl)(5-(2-pyridyl)thiophene-2-carboxamide) (compound A) and 5-iodo-3-(2(S)-azetidinylmethoxy)pyridine (5-iodo-A-85380), respectively, in conjunction with inhibitors of voltage-operated Ca(2+) channels (VOCCs) and intracellular Ca(2+) stores, we show that [(3)H]d-aspartate release evoked by activation of beta2() nAChRs occurs via VOCCs. In contrast, alpha7 nAChR-evoked release was unaffected by VOCC blockers but was abolished by modulators of Ca(2+) stores, including ryanodine. The alpha7 nAChR ligand alpha-bungarotoxin and ryanodine receptors were colocalized to a subpopulation of PFC synaptosomes. Compound A-evoked [(3)H]d-aspartate release was also blocked by mitogen-activated protein kinase kinase 1 inhibitors, implicating extracellular signal-regulated kinase (ERK)1/2 in alpha7 nAChR-evoked exocytosis. Western blotting confirmed that compound A, but not 5-iodo-A-85380, application increased ERK2 phosphorylation in PFC synaptosomes, and this was dependent on ryanodine-sensitive stores. Compound A also promoted synapsin-1 phosphorylation at ERK1/2-dependent sites, in a ryanodine-sensitive manner. Thus, beta2(*) and alpha7 nAChR subtypes in the PFC mediate [(3)H]d-aspartate release via distinct mechanisms as a result of their differential coupling to VOCCs and Ca(2+)-induced Ca(2+) release (CICR), respectively. The ability of alpha7 nAChRs to promote the phosphorylation of presynaptic ERK2 and synapsin-1, downstream of CICR, provides a potential mechanism for presynaptic facilitation in the PFC.

摘要

尼古丁可增强工作记忆和注意力。前额叶皮质(PFC)中α7和β2烟碱型乙酰胆碱受体(nAChRs)的激活与这些过程有关。据推测,突触前nAChRs调节神经递质释放(尤其是谷氨酸释放)的能力有助于尼古丁发挥作用。我们研究了体外α7和β2 nAChR介导的PFC中[³H]d-天冬氨酸释放的细胞机制。分别使用α7和β2* nAChR选择性激动剂(R)-N-(1-氮杂双环[2.2.2]辛-3-基)(5-(2-吡啶基)噻吩-2-甲酰胺)(化合物A)和5-碘-3-(2(S)-氮杂环丁烷甲氧基)吡啶(5-碘-A-85380),结合电压门控钙通道(VOCCs)抑制剂和细胞内钙库,我们发现β2* nAChRs激活诱发的[³H]d-天冬氨酸释放通过VOCCs发生。相比之下,α7 nAChR诱发的释放不受VOCC阻滞剂影响,但被包括ryanodine在内的钙库调节剂所阻断。α7 nAChR配体α-银环蛇毒素和ryanodine受体共定位于PFC突触体的一个亚群。化合物A诱发的[³H]d-天冬氨酸释放也被丝裂原活化蛋白激酶激酶1抑制剂所阻断,这表明细胞外信号调节激酶(ERK)1/2参与α7 nAChR诱发的胞吐作用。蛋白质免疫印迹法证实,应用化合物A而非5-碘-A-85380可增加PFC突触体中ERK2的磷酸化,且这依赖于ryanodine敏感的钙库。化合物A还以ryanodine敏感的方式促进突触结合蛋白-1在ERK1/2依赖位点的磷酸化。因此,PFC中的β2*和α7 nAChR亚型分别通过与VOCCs和钙诱导钙释放(CICR)的不同偶联,以不同机制介导[³H]d-天冬氨酸释放。α7 nAChRs促进CICR下游突触前ERK2和突触结合蛋白-1磷酸化的能力,为PFC中的突触前易化提供了一种潜在机制。

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