Participation of the enzyme glycogen synthase kinase-3 and voltage-dependent <sup>Сa2+</sup> channels in the vesicular cycle of transmitter secretion in cholinergic motor nerve endings of the somatic muscles of the earthwo

The effects of specific blockers (ω-conotoxin GVIA, ω-agatoxin IVA, nitrendipine, SNX-482, mibefradil) of N, P/Q, L, R, and T-type potential-dependent Ca2+ channels were studied by fluorescence confocal microscopy, as well as the glycogen synthase kinase-3 enzyme inhibitor GSK3 (1-azakenpaullone) on exo-endovesicular cycle processes in cholinergic neuromuscular synapses of somatic muscle of the earthworm Lumbricus terrestris. The mechanisms of the vesicular cycle involve Ca2+ ions entering the terminals through all types of potential-dependent Ca2+ channels of the presynaptic membrane. At the same time, N-, P/Q-, and L-type Ca2+ channels contribute most to endocytosis processes, whereas only N- and P/Q-type channels contribute to exocytosis. Dynamin-dependent endocytosis plays an essential role in recycling processes, and the recovery of vesicular pools in such synapses is predominantly facilitated by clathrin-dependent endocytosis. It can be considered that the basic mechanisms of vesicular cycle regulation in motor neuromuscular synapses are common to the entire phylogenetic tree of vertebrates and invertebrates, beginning with annelids. At the same time, the importance of individual regulatory elements of the vesicular secretion machinery in annelids has its own distinct specificity.