Effect of Noradrenaline on the Kinetics of Evoked Acetylcholine Secretion in Mouse Neuromuscular Junction
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In contrast to frog neuromuscular synapses, where noradrenaline (norepinephrine) and its analogues caused synchronization of the acetylcholine release process, in mouse diaphragm endplates noradrenaline increased the degree of asynchrony of neurosecretion. The effect of noradrenaline on release timing persisted at different levels of external calcium ions (0.25–2.0 mM) and was abolished in presence of both α- and β‑adrenoblockers phentolamine and propranolol. The computer reconstruction of multiquantal endplate currents accounting for experimentally observed modification of release kinetics under noradrenaline showed that the rise time of postsynaptic response changes to a greater extent than the amplitude and falling phase of the multiquantal responses. We conclude that there exists a principal difference in the action of noradrenaline in the cholinergic neuromuscular synapses of warm-blooded and cold-blooded animals that can be accounted for by the differences in the type of adrenoreceptors involved in the modulation of synaptic transmission and/or in the involvement of distinct intracellular pathways triggered by receptor activation.
Keywords:neuromuscular junction endplate current noradrenaline acetylcholine release timing
The authors thank Dr. Victor Ilyin for critical reading and helpful comments on the manuscript. The work was supported by the Russian Science Foundation (project no. 18-15-00046).
COMPLIANCE WITH ETHICAL STANDARDS
Conflict of interests. The authors declare that they have no conflict of interest.
Statement on the welfare of animals. All procedures were performed in accordance with the European Communities Council Directive (November 24, 1986; 86/609/EEC) and the Declaration on humane treatment of animals. The Protocol of experiments was approved by the Commission on Bioethics of Kazan State Medical University.
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