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Publisher Summary This chapter considers the aspects of the localization of 5-HT in peripheral and central neurons particularly in relationship to nerve endings and synaptic vesicles. This information is important in deciding if 5-HT plays a role as a true neurotransmitter. An analysis of neuronal compartmentation of 5-HT implies an integrated and dynamic study of the metabolism, localization, and function of 5-HT in the nervous tissue. Different models are formulated to interpret the information available on uptake, synthesis, storage, release, reactive sites, and inactivation of monoamines, either by enzymic degradation or by adsorption to “sites of loss” or “silent receptors” of the neuron. The largest amount of the amine is in a storage entity called granule, separated from monoamine oxidase (MAO) by an intracellular membrane, whose content is in equilibrium with other more labile pools inside or outside the granule. The function of the granule is not confined to storage but is also essential for the quanta transmission of the nerve impulse. Several methods are used to obtain a physical counterpart of those metabolic pools at the cellular, subcellular, and molecular levels. |
