The acute and chronic effects of alcohol on the brain and behavior are linked to alterations in inhibitory synaptic transmission. Alcohol's most consistent effect at the synaptic level is probably a facilitation of γ-aminobutyric acid (GABA) release, as seen from several rodent studies. The impact of alcohol on GABAergic neurotransmission in human neurons is unknown, due to a lack of a suitable experimental model. Human neurons can also be used to model effects of genetic variants linked with alcohol use disorders (AUDs). The A118G single nucleotide polymorphism (SNP rs1799971) of the OPRM1 gene encoding the N40D (D40 minor allele) mu-opioid receptor (MOR) variant has been linked with individuals who have an AUD. However, while N40D is clearly associated with other drugs of abuse, involvement with AUDs is controversial. In this study, we employed Ascl1-and Dlx2-induced inhibitory neuronal cells (AD-iNs) generated from human iPS cell lines carrying N40D variants, and investigated the impact of ethanol acutely and chronically on GABAergic synaptic transmission. We found that N40 AD-iNs display a stronger facilitation (versus D40) of spontaneous and miniature inhibitory postsynaptic current frequency in response to acute ethanol application. Quantitative immunocytochemistry of Synapsin 1⁺ synaptic puncta revealed a similar synapse number between N40 and D40 iNs, suggesting an ethanol modulation of presynaptic GABA release without affecting synapse density. Interestingly, D40 iNs exposed to chronic intermittent ethanol application caused a significant increase in mIPSC frequency, with only a modest enhancement observed in N40 iNs. These data suggest that the MOR genotype may confer differential sensitivity to synaptic output, which depends on ethanol exposure time and concentration for AD-iNs and may help explain alcohol dependence in individuals who carry the MOR D40 SNPs. Furthermore, this study supports the use of human neuronal cells carrying risk-associated genetic variants linked to disease, as in vitro models to assay the synaptic actions of alcohol on human neuronal cells.

酒精对大脑和行为的急性和慢性影响与抑制性突触传递的改变有关。从几项啮齿动物研究中可以看出，酒精在突触水平上最一致的作用可能是促进 γ-氨基丁酸 (GABA) 的释放。由于缺乏合适的实验模型，酒精对人类神经元中 GABA 能神经传递的影响尚不清楚。人类神经元还可用于模拟与酒精使用障碍 (AUDs) 相关的遗传变异的影响。所述A118G单核苷酸多态性（SNP rs1799971）的的OPRM1编码 N40D（D40 次要等位基因）μ-阿片受体 (MOR) 变体的基因与患有 AUD 的个体有关。然而，虽然 N40D 显然与其他滥用药物有关，但与 AUDs 的关系是有争议的。在这项研究中，我们采用了由携带 N40D 变体的人类 iPS 细胞系产生的Ascl 1 和Dlx 2 诱导的抑制性神经元细胞 (AD-iN)，并研究了乙醇对 GABA 能突触传递的急性和慢性影响。我们发现 N40 AD-iNs 对急性乙醇应用的自发和微型抑制性突触后电流频率显示出更强的促进作用（与 D40 相比）。Synapsin 1 ^{+ 的}定量免疫细胞化学突触点显示 N40 和 D40 iNs 之间的突触数量相似，表明乙醇调节突触前 GABA 释放而不影响突触密度。有趣的是，暴露于慢性间歇性乙醇应用的 D40 iNs 导致 mIPSC 频率显着增加，仅在 N40 iNs 中观察到适度增强。这些数据表明，MOR 基因型可能赋予突触输出不同的敏感性，这取决于 AD-iN 的乙醇暴露时间和浓度，并且可能有助于解释携带 MOR D40 SNP 的个体的酒精依赖。此外，这项研究支持使用携带与疾病相关的风险相关遗传变异的人类神经元细胞作为体外模型来测定酒精对人类神经元细胞的突触作用。