Salamone Alessia, Zappettini Stefania, Grilli Massimo, Olivero Guendalina, Agostinho Paula, Tomé Angelo R, Chen Jiayang, Pittaluga Anna, Cunha Rodrigo A, Marchi Mario
Department of Pharmacy, University of Genoa, Italy.
CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Portugal; Faculty of Medicine, University of Coimbra, Portugal.
Neuropharmacology. 2014 Apr;79:488-97. doi: 10.1016/j.neuropharm.2013.12.014. Epub 2013 Dec 25.
The presynaptic control of dopamine release in the nucleus accumbens (NAc) by glutamate and acetylcholine has a profound impact on reward signaling. Here we provide immunocytochemical and neurochemical evidence supporting the co-localization and functional interaction between nicotinic acetylcholine receptors (nAChRs) and N-methyl-D-aspartic acid (NMDA) receptors in dopaminergic terminals of the NAc. Most NAc dopaminergic terminals possessed the nAChR α4 subunit and the pre-exposure of synaptosomes to nicotine (30 μM) or to the α4β2-containing nAChR agonist 5IA85380 (10 nM) selectively inhibited the NMDA (100 μM)-evoked, but not the 4-aminopyridine (10 μM)-evoked, [(3)H] dopamine outflow; this inhibition was blunted by mecamylamine (10 μM). Nicotine and 5IA85380 pretreatment also inhibited the NMDA (100 μM)-evoked increase of calcium levels in single nerve terminals, an effect prevented by dihydro-β-erythroidine (1 μM). This supports a functional interaction between α4β2-containing nAChR and NMDA receptors within the same terminal, as supported by the immunocytochemical co-localization of α4 and GluN1 subunits in individual NAc dopaminergic terminals. The NMDA-evoked [(3)H]dopamine outflow was blocked by MK801 (1 μM) and inhibited by the selective GluN2B-selective antagonists ifenprodil (1 μM) and RO 25-6981 (1 μM), but not by the GluN2A-preferring antagonists CPP-19755 (1 μM) and ZnCl2 (1 nM). Notably, nicotine pretreatment significantly decreased the density of biotin-tagged GluN2B proteins in NAc synaptosomes. These results show that nAChRs dynamically and negatively regulate NMDA receptors in NAc dopaminergic terminals through the internalization of GluN2B receptors.
谷氨酸和乙酰胆碱对伏隔核（NAc）中多巴胺释放的突触前控制对奖赏信号传导有深远影响。在此，我们提供免疫细胞化学和神经化学证据，支持烟碱型乙酰胆碱受体（nAChRs）与N-甲基-D-天冬氨酸（NMDA）受体在NAc多巴胺能终末的共定位和功能相互作用。大多数NAc多巴胺能终末具有nAChR α4亚基，突触体预先暴露于尼古丁（30 μM）或含α4β2的nAChR激动剂5IA85380（10 nM）可选择性抑制NMDA（100 μM）诱发的，但不抑制4-氨基吡啶（10 μM）诱发的[³H]多巴胺外流；这种抑制作用可被美加明（10 μM）减弱。尼古丁和5IA85380预处理也抑制了NMDA（100 μM）诱发的单个神经终末钙水平升高，二氢-β-刺桐碱（1 μM）可阻止该效应。这支持了同一终末内含α4β2的nAChR与NMDA受体之间的功能相互作用，单个NAc多巴胺能终末中α4和GluN1亚基的免疫细胞化学共定位也支持这一点。NMDA诱发的[³H]多巴胺外流被MK801（1 μM）阻断，并被选择性GluN2B拮抗剂ifenprodil（1 μM）和RO 25-6981（1 μM）抑制，但不被优先选择GluN2A的拮抗剂CPP-19755（1 μM）和ZnCl₂（1 nM）抑制。值得注意的是，尼古丁预处理显著降低了NAc突触体中生物素标记的GluN2B蛋白密度。这些结果表明，nAChRs通过GluN2B受体的内化动态且负向调节NAc多巴胺能终末中的NMDA受体。
