GABA Receptors and Kv7 Channels as Targets for GABAergic Regulation of Acetylcholine Release in Frog Neuromuscular Junction

IF 3.7 3区医学 Q2 BIOCHEMISTRY & MOLECULAR BIOLOGY

Neurochemical Research Pub Date : 2024-11-20 DOI:10.1007/s11064-024-04274-x

Andrei N. Tsentsevitsky, Guzel V. Sibgatullina, Alexey M. Petrov, Artem I. Malomouzh, Irina V. Kovyazina

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Abstract

Effects of gamma-aminobutyric acid (GABA) and some selective GABAergic ligands on the quantal acetylcholine (ACh) release in the frog neuromuscular contacts were investigated using combination of microelectrode technique with fluorescent and immunohistochemical assays. Significant attenuation of ACh release was observed in the presence of GABA as well as selective GABA_A and GABA_B receptor agonists. Neither GABA_A nor GABA_B antagonists abolished to full extent this effect of GABA. Fluorescent assay allowed to detect the GABA-induced opening of K⁺ channels, which was inhibited by XE-991, a selective antagonist of K_v7 type. Electrophysiological recordings of endplate potentials in the presence of XE-991 confirmed the contribution of K_v7 type potassium channels to the effects of GABA on ACh release that was not associated with GABA_A and GABA_B receptors activation. Note that XE-991 effectively precluded the action of retigabine, neuronal K_v7 channel opener, on ACh release. Immunohistochemical assay revealed that frog mature skeletal muscle fibers contain a significant amount of GABA, and substantial amount of GABA can be released in the extracellular space at the muscle contractions induced by prolonged high-frequency nerve stimulation. Besides, some binding sites for exogenous GABA were detected on the plasma membranes. It is concluded that GABA, in addition to affecting GABA_A and GABA_B receptors, can directly activate K_v7 channels, thereby negatively modulating the evoked ACh release. Endogenous GABA may serve as a retrograde regulator of neurotransmitter exocytosis.

Graphical abstract

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GABA 受体和 Kv7 通道是 GABA 能调节蛙神经肌肉接头处乙酰胆碱释放的靶点

研究人员采用微电极技术结合荧光和免疫组织化学方法，研究了γ-氨基丁酸（GABA）和一些选择性GABA能配体对蛙神经肌肉接触点乙酰胆碱（ACh）量释放的影响。在 GABA 以及选择性 GABAA 和 GABAB 受体激动剂存在的情况下，观察到 ACh 释放明显减弱。GABAA 和 GABAB 拮抗剂都不能完全消除 GABA 的这种作用。荧光测定可检测 GABA 诱导的 K+ 通道开放，Kv7 型选择性拮抗剂 XE-991 可抑制这种开放。在有 XE-991 存在的情况下对终板电位的电生理记录证实，Kv7 型钾通道对 GABA 对 ACh 释放的影响做出了贡献，而这种影响与 GABAA 和 GABAB 受体的激活无关。需要注意的是，XE-991 有效地阻止了神经元 Kv7 通道开启剂瑞替加宾对 ACh 释放的作用。免疫组化检测发现，蛙成熟骨骼肌纤维中含有大量的GABA，在长时间高频神经刺激诱发肌肉收缩时，细胞外空间可释放出大量的GABA。此外，在质膜上还检测到一些外源 GABA 的结合位点。结论是 GABA 除影响 GABAA 和 GABAB 受体外，还能直接激活 Kv7 通道，从而对诱发的 ACh 释放产生负向调节作用。内源性 GABA 可能是神经递质外渗的逆行调节因子。

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来源期刊

Neurochemical Research 医学-神经科学

CiteScore

7.70

自引率

2.30%

发文量

320

审稿时长

6 months

期刊介绍： Neurochemical Research is devoted to the rapid publication of studies that use neurochemical methodology in research on nervous system structure and function. The journal publishes original reports of experimental and clinical research results, perceptive reviews of significant problem areas in the neurosciences, brief comments of a methodological or interpretive nature, and research summaries conducted by leading scientists whose works are not readily available in English.