• Andrei N Tsentsevitsky, Irina V Kovyazina, and Ellya A Bukharaeva.
• Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC "Kazan Scientific Center of RAS", Post Box 30, 420111 Kazan, Russia.
• Neuroscience. 2019 Dec 15; 423: 162-171.

AbstractDespite the long history of investigations of adrenergic compounds and their biological effects, specific mechanisms of their action in distinct compartments of the motor unit remain obscure. Recent results have suggested that not only skeletal muscles but also the neuromuscular junctions represent important targets for the action of catecholamines. In this paper, we describe the effects of adrenaline and noradrenaline on the frequency of miniature endplate potentials, the quantal content of the evoked endplate potentials and the kinetics of acetylcholine quantal release in the motor nerve endings of the mouse diaphragm. Noradrenaline and adrenaline decreased the frequency of the spontaneous release of acetylcholine quanta. The effect of noradrenaline was prevented by the β adrenoreceptor blocker propranolol, whereas the action of adrenaline was abolished by the α adrenoreceptor antagonist phentolamine. Noradrenaline did not alter the quantal content of endplate potentials, while adrenaline suppressed the evoked release of acetylcholine. Blocking the α adrenoreceptors prevented the decrease in quantal secretion caused by adrenaline. Quantal release became more asynchronous under noradrenaline, as evidenced by a greater dispersion of real synaptic delays; in contrast, adrenaline synchronized the release process. Our data suggest an involvement of α and β adrenoreceptors in the diverse modulation of the frequency of miniature endplate potentials, the quantal content of the evoked endplate potentials and the kinetics of acetylcholine quantal secretion in the mouse neuromuscular junction. Moreover, the adrenoblockers affected both the evoked and spontaneous quantal release of acetylcholine, suggesting the presence of endogenous catecholamines in the vicinity of cholinergic synapses.Copyright © 2019 IBRO. Published by Elsevier Ltd. All rights reserved.

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