Bajo Michal, Madamba Samuel G, Roberto Marisa, Blednov Yuri A, Sagi Vasudeva N, Roberts Edward, Rice Kenner C, Harris R Adron, Siggins George R
Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines, La Jolla, CA 92037, USA.
Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines, La Jolla, CA 92037, USA.
Brain Behav Immun. 2014 Aug;40:191-202. doi: 10.1016/j.bbi.2014.03.007. Epub 2014 Mar 24.
Excessive ethanol drinking in rodent models may involve activation of the innate immune system, especially toll-like receptor 4 (TLR4) signaling pathways. We used intracellular recording of evoked GABAergic inhibitory postsynaptic potentials (eIPSPs) in central amygdala (CeA) neurons to examine the role of TLR4 activation by lipopolysaccharide (LPS) and deletion of its adapter protein CD14 in acute ethanol effects on the GABAergic system. Ethanol (44, 66 or 100mM) and LPS (25 and 50μg/ml) both augmented eIPSPs in CeA of wild type (WT) mice. Ethanol (44mM) decreased paired-pulse facilitation (PPF), suggesting a presynaptic mechanism of action. Acute LPS (25μg/ml) had no effect on PPF and significantly increased the mean miniature IPSC amplitude, indicating a postsynaptic mechanism of action. Acute LPS pre-treatment potentiated ethanol (44mM) effects on eIPSPs in WT mice and restored ethanol's augmenting effects on the eIPSP amplitude in CD14 knockout (CD14 KO) mice. Both the LPS and ethanol (44-66mM) augmentation of eIPSPs was diminished significantly in most CeA neurons of CD14 KO mice; however, ethanol at the highest concentration tested (100mM) still increased eIPSP amplitudes. By contrast, ethanol pre-treatment occluded LPS augmentation of eIPSPs in WT mice and had no significant effect in CD14 KO mice. Furthermore, (+)-naloxone, a TLR4-MD-2 complex inhibitor, blocked LPS effects on eIPSPs in WT mice and delayed the ethanol-induced potentiation of GABAergic transmission. In CeA neurons of CD14 KO mice, (+)-naloxone alone diminished eIPSPs, and subsequent co-application of 100mM ethanol restored the eIPSPs to baseline levels. In summary, our results indicate that TLR4 and CD14 signaling play an important role in the acute ethanol effects on GABAergic transmission in the CeA and support the idea that CD14 and TLR4 may be therapeutic targets for treatment of alcohol abuse.
在啮齿动物模型中，过量饮酒可能涉及先天性免疫系统的激活，尤其是Toll样受体4（TLR4）信号通路。我们采用细胞内记录中央杏仁核（CeA）神经元中诱发的GABA能抑制性突触后电位（eIPSPs），以研究脂多糖（LPS）激活TLR4及其衔接蛋白CD14缺失在急性乙醇对GABA能系统影响中的作用。乙醇（44、66或100mM）和LPS（25和50μg/ml）均增强了野生型（WT）小鼠CeA中的eIPSPs。乙醇（44mM）降低了双脉冲易化（PPF），提示其作用机制为突触前机制。急性LPS（25μg/ml）对PPF无影响，但显著增加了平均微小抑制性突触后电流（mIPSC）幅度，表明其作用机制为突触后机制。急性LPS预处理增强了乙醇（44mM）对WT小鼠eIPSPs的作用，并恢复了乙醇对CD14基因敲除（CD14 KO）小鼠eIPSP幅度的增强作用。在CD14 KO小鼠的大多数CeA神经元中，LPS和乙醇（44 - 66mM）对eIPSPs的增强作用均显著减弱；然而，测试的最高浓度乙醇（100mM）仍增加了eIPSP幅度。相比之下，乙醇预处理阻断了WT小鼠中LPS对eIPSPs的增强作用，而对CD14 KO小鼠无显著影响。此外，TLR4 - MD - 2复合物抑制剂（+）-纳洛酮阻断了LPS对WT小鼠eIPSPs的作用，并延迟了乙醇诱导的GABA能传递增强。在CD14 KO小鼠的CeA神经元中，单独使用（+）-纳洛酮可减弱eIPSPs，随后联合应用100mM乙醇可将eIPSPs恢复至基线水平。总之，我们的结果表明，TLR4和CD14信号在急性乙醇对CeA中GABA能传递的影响中起重要作用，并支持CD14和TLR4可能是治疗酒精滥用的治疗靶点这一观点。
