Noncanonical Potentiation of Evoked Quantal Release of Acetylcholine by Cannabinoids Anandamide and 2-Arachidonoylglycerol in Mouse Motor Synapses.

Autor: Tarasova, E. O., Khotkina, N. A., Bogacheva, P. O., Chernyshev, K. A., Gaydukov, A. E., Balezina, O. P.
Zdroj: Biochemistry (Biokhimiya). Supplemental Series A, Membrane & Cell Biology; Oct2021, Vol. 15 Issue 4, p395-405, 11p
Abstrakt: We studied the effects of the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) on the evoked activity of neuromuscular junctions (NMJs) of mouse diaphragm and m. extensordigitorum longus (m. EDL). Using the microelectrode technique, spontaneous miniature endplate potentials (MEPPs) and multiquantal endplate potentials (EPPs) evoked by short rhythmic nerve stimulation trains (50 Hz, 1 s) were recorded. AEA (30 µM) caused an increase in the MEPP frequency but not in the MEPP amplitude, which lead to an increase in amplitude and quantal content (QC) of each EPP in a train. Quantal analysis showed that AEA causes an enlargement of the size of the readily releasable pool (RRP) of vesicles in motor terminals. The AEA-induced increase in EPP amplitude and QC was prevented by L-type Ca2+-channel blocker nitrendipine (1 µM), which suggests that this channel type is upregulated upon the AEA application. 2-AG (1 µM) caused an increase in MEPP amplitude but not in their frequency in mouse diaphragm NMJs. This was accompanied by an increase in the EPP amplitude, whereas their QC remained at the control level. The same effect was reproduced in synapses of m. EDL. The rise of the EPP amplitude caused by 2-AG was prevented by PKA inhibition by H-89 (1 µM). These data, together with previous evidence that blocking vesicular transport of acetylcholine (ACh) abolishes the 2-AG-induced increase in MEPP amplitude, allows us to suggest that 2-AG stimulates ACh pumping into vesicles in a PKA-dependent way, thus causing an increase in the size of a single ACh quanta. This work is the first to show a fast noncanonical facilitating action of AEA and 2-AG on the evoked activity of mouse NMJ. AEA and 2-AG cause similar presynaptic and CB1-receptor-dependent changes of neuromuscular transmission, but they exert their effects through two different ways, leading to facilitation of different parameters of ACh secretion. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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