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

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

doi:10.1007/s11064-024-04274-x

GABA Receptors and K_v7 Channels as Targets for GABAergic Regulation of Acetylcholine Release in Frog Neuromuscular Junction

Neurochem Res. 2024 Nov 20;50(1):25. doi: 10.1007/s11064-024-04274-x.

Authors

Andrei N Tsentsevitsky¹, Guzel V Sibgatullina¹, Alexey M Petrov^{1

2

3}, Artem I Malomouzh^{1

4}, Irina V Kovyazina^{5

6}

Affiliations

¹ Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, 2/31 Lobachevsky St, Kazan, 420111, Russia.
² Kazan State Medical University, 49 Butlerova St, Kazan, 420012, Russia.
³ Kazan Federal University, 18 Kremlyovskaya St, Kazan, 420008, Russia.
⁴ Kazan National Research Technical University, 10 K. Marx St, Kazan, 420111, Russia.
⁵ Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, 2/31 Lobachevsky St, Kazan, 420111, Russia. i.kovyazina@kazangmu.ru.
⁶ Kazan State Medical University, 49 Butlerova St, Kazan, 420012, Russia. i.kovyazina@kazangmu.ru.

PMID: 39562376
DOI: 10.1007/s11064-024-04274-x

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.

Keywords: Acetylcholine release; Exocytosis; GABA; GABA receptor; GIRK channel; Kv7 potassium channel; Neuromuscular junction.

MeSH terms

Acetylcholine* / metabolism
Animals
Anthracenes
KCNQ Potassium Channels* / metabolism
Neuromuscular Junction* / drug effects
Neuromuscular Junction* / metabolism
Receptors, GABA / drug effects
Receptors, GABA / metabolism
Receptors, GABA-B / drug effects
Receptors, GABA-B / metabolism
gamma-Aminobutyric Acid* / metabolism

Substances

Acetylcholine
gamma-Aminobutyric Acid
KCNQ Potassium Channels
Receptors, GABA
10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone
Receptors, GABA-B
Anthracenes

Grants and funding

23-75-10022/Russian Science Foundation