San Martin Loreto S, Armijo-Weingart Lorena, Araya Anibal, Yévenes Gonzalo E, Harvey Robert J, Aguayo Luis G
Department of Physiology, Programa de Neurociencia, Psiquiatria y Salud Mental, Universidad de Concepción, Concepción, Chile.
School of Health and Behavioural Sciences, University of the Sunshine Coast, Sunshine Coast, QLD, Australia.
Front Mol Neurosci. 2021 Oct 22;14:756607. doi: 10.3389/fnmol.2021.756607. eCollection 2021.
The glycine receptor (GlyR), a ligand-gated ion channel, is critical for inhibitory neurotransmission in brainstem, spinal cord, and in supraspinal regions. Recent data from several laboratories have shown that GlyRs are expressed in the brain reward circuitry and that α1 and α2 are the principal subunits expressed in the nucleus accumbens (nAc). In the present study, we studied the sensitivity to ethanol of homomeric and heteromeric α3 GlyR subunits in HEK293 cells and dissociated neurons from the nAc. Finally, we explored ethanol-related behaviors in a knockout mouse ( ). Studies in HEK293 cells showed that while homomeric α3 GlyR subunits were insensitive to ethanol, heteromeric α3β GlyR subunits showed higher sensitivity to ethanol. Additionally, using electrophysiological recordings in dissociated accumbal neurons, we found that the glycine current density increased in mice and the GlyRs were less affected by ethanol and picrotoxin. We also examined the effect of ethanol on sedation and drinking behavior in mice and found that the duration in the loss of righting reflex (LORR) was unchanged compared to wild-type (WT) mice. On the other hand, using the drinking in the dark (DID) paradigm, we found that mice have a larger ethanol consumption compared to WT mice, and that this was already high during the first days of exposure to ethanol. Our results support the conclusion that heteromeric α3β, but not homomeric α3, GlyRs are potentiated by ethanol. Also, the increase in GlyR and GABA R mediated current densities in accumbal neurons in the KO mice support the presence of compensatory changes to α3 knock out. The increase in ethanol drinking in the mice might be associated to the reduction in β and compensatory changes in other subunits in the receptor arrangement.
甘氨酸受体（GlyR）是一种配体门控离子通道，对脑干、脊髓和脊髓上区域的抑制性神经传递至关重要。多个实验室的最新数据表明，GlyRs在大脑奖赏回路中表达，并且α1和α2是伏隔核（nAc）中表达的主要亚基。在本研究中，我们研究了HEK293细胞中同聚体和异聚体α3 GlyR亚基对乙醇的敏感性，以及来自nAc的解离神经元的敏感性。最后，我们在基因敲除小鼠中探究了与乙醇相关的行为。在HEK293细胞中的研究表明，虽然同聚体α3 GlyR亚基对乙醇不敏感，但异聚体α3β GlyR亚基对乙醇表现出更高的敏感性。此外，通过在解离的伏隔核神经元中进行电生理记录，我们发现甘氨酸电流密度在基因敲除小鼠中增加，并且GlyRs受乙醇和印防己毒素的影响较小。我们还研究了乙醇对基因敲除小鼠镇静和饮水行为的影响，发现与野生型（WT）小鼠相比，翻正反射消失（LORR）的持续时间没有变化。另一方面，使用黑暗中饮水（DID）范式，我们发现基因敲除小鼠比WT小鼠的乙醇消耗量更大，并且在接触乙醇的第一天就已经很高。我们的结果支持以下结论：异聚体α3β而非同聚体α3 GlyRs被乙醇增强。此外，基因敲除小鼠伏隔核神经元中GlyR和GABAR介导的电流密度增加，支持了对α3敲除存在代偿性变化的观点。基因敲除小鼠中乙醇饮用量的增加可能与β亚基的减少以及受体排列中其他亚基的代偿性变化有关。
