Participation of Ca<sup>2+</sup>-acceptor proteins in the mechanisms of the exo-endocytic cycle of synaptic vesicles in the motor nerve endings of the somatic musculature of the earthworm <i>Lumbricus terrestris</i>

Using fluorescence microscopy, we studied the participation of Ca2+-acceptor proteins in the processes of the exo-endocytotic cycle of neurotransmitter quantal secretion in the neuromuscular junction of the somatic muscle of the earthworm Lumbricus terrestris. Inhibition of calcineurin, calmodulin and Ca2+/calmodulin dependent protein kinases led to an increase in the process of endocytosis. Blocking the phosphorylation of synaptic proteins enhances the process of endocytosis, causes an increase in the size of the total vesicular pool and accelerates the turnover of synaptic vesicles. It can be concluded that calcium modulation of vesicle exo-endocytosis at the synapses of the evolutionarily primary somatic muscles of annelids occurs with the participation of calcineurin, calmodulin and Ca2+/calmodulin-dependent protein kinases.