De-Miguel, F.F. The Thermodynamically Expensive Contribution of Three Calcium Sources to Somatic Release of Serotonin. Int. J. Mol. Sci.2022, 23, 1495.
De-Miguel, F.F. The Thermodynamically Expensive Contribution of Three Calcium Sources to Somatic Release of Serotonin. Int. J. Mol. Sci. 2022, 23, 1495.
De-Miguel, F.F. The Thermodynamically Expensive Contribution of Three Calcium Sources to Somatic Release of Serotonin. Int. J. Mol. Sci.2022, 23, 1495.
De-Miguel, F.F. The Thermodynamically Expensive Contribution of Three Calcium Sources to Somatic Release of Serotonin. Int. J. Mol. Sci. 2022, 23, 1495.
Abstract
The soma, dendrites and axon of neurons may display calcium-dependent release of transmitters and peptides. Such release is named extrasynaptic for occurring in the absence of synaptic structures. This review describes cooperative actions of three calcium sources on somatic exocytosis. Emphasis is given to the release of serotonin by the classical serotonergic leech Retzius neuron, which has allowed detailed studies of each step between excitation and exoctytosis. Trains of action potentials induce transmembrane calcium entry through L-type channels. If the frequency of action potentials is above 5 Hz, summation of calcium transients upon individual action potentials increases the intracellular calcium concentration to activate calcium–induced calcium release. The amplified calcium wave activates motochondrial ATP synthesis that fuels the transport of vesicles to the plasma membrane. Serotonin that is released activates autoreceptors coupled to phospholipase C. Production of IP3 produces release of calcium that sustains the large-scale exocytosis. The swiss-clock workings of the release machinery for somatic exocytosis has a striking disadvantage. The essential calcium-releasing endoplasmic reticulum that lays between resting vesicles and the plasma membrane becomes an obstacle for the vesicle transport. Such architecture reduces drastically the thermodynamic efficiency of the vesicle transport and elevates its energy cost..
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