Department of Neurobiology and Behavior, State University of New York at Stony Brook, Stony Brook, New York, United States of America ; Center for Nervous System Disorder, State University of New York at Stony Brook, Stony Brook, New York, United States of America.
Center for Nervous System Disorder, State University of New York at Stony Brook, Stony Brook, New York, United States of America ; Department of Pharmacological Science, State University of New York at Stony Brook, Stony Brook, New York, United States of America.
PLoS One. 2013 Dec 5;8(12):e82719. doi: 10.1371/journal.pone.0082719. eCollection 2013.
Presynaptic nicotinic acetylcholine receptors (nAChRs) have long been implicated in the modulation of CNS circuits. We previously reported that brief exposure to low concentrations of nicotine induced sustained potentiation of glutamatergic transmission at ventral hippocampal (vHipp)-striatal synapses. Here, we exploited nAChR subtype-selective antagonists and agonists and α7nAChR knockout mutant mice (α7-/-) to elucidate the signaling mechanisms underlying nAChR-mediated modulation of synaptic transmission. Using a combination of micro-slices culture from WT and α7-/-mice, calcium imaging, and immuno-histochemical techniques, we found that nicotine elicits localized and oscillatory increases in intracellular Ca(2+) along vHipp axons that persists for up to 30 minutes. The sustained phase of the nicotine-induced Ca(2+) response was blocked by α-BgTx but not by DHβE and was mimicked by α7nAChR agonists but not by non-α7nAChR agonists. In vHipp slices from α7-/- mice, nicotine elicited only transient increases of axonal Ca(2+) signals and did not activate CaMKII. The sustained phase of the nicotine-induced Ca(2+) response required localized activation of CaMKII, phospholipase C, and IP3 receptor mediated Ca(2+)-induced Ca(2+) release (CICR). In conclusion, activation of presynaptic nAChRs by nicotine elicits Ca(2+) influx into the presynaptic axons, the sustained phase of the nicotine-induced Ca(2+) response requires that axonal α7nAChR activate a downstream signaling network in the vHipp axons.
突触前烟碱型乙酰胆碱受体 (nAChRs) 长期以来一直被认为参与了中枢神经系统 (CNS) 回路的调节。我们之前的研究报告表明，短暂暴露于低浓度尼古丁会导致腹侧海马 (vHipp)-纹状体突触的谷氨酸能传递持续增强。在这里，我们利用 nAChR 亚型选择性拮抗剂和激动剂以及 α7nAChR 敲除突变体小鼠 (α7-/-) 来阐明 nAChR 介导的突触传递调节的信号转导机制。通过使用 WT 和 α7-/-小鼠的微切片培养、钙成像和免疫组织化学技术的组合，我们发现尼古丁会引起 vHipp 轴突中局部和振荡性的细胞内 Ca(2+) 增加，持续时间长达 30 分钟。α-BgTx 可阻断尼古丁诱导的 Ca(2+) 反应的持续相，但 DHβE 不能阻断，α7nAChR 激动剂可模拟该反应，但非-α7nAChR 激动剂不能模拟该反应。在 α7-/-小鼠的 vHipp 切片中，尼古丁仅引起轴突 Ca(2+) 信号的短暂增加，而不会激活 CaMKII。尼古丁诱导的 Ca(2+) 反应的持续相需要局部激活 CaMKII、PLC 和 IP3 受体介导的 Ca(2+)-诱导的 Ca(2+) 释放 (CICR)。总之，尼古丁激活突触前 nAChRs 会引起 Ca(2+) 流入突触前轴突，尼古丁诱导的 Ca(2+) 反应的持续相需要轴突 α7nAChR 激活 vHipp 轴突中的下游信号转导网络。
