Exocytosis serotonin release

There is considerable evidence that the release of 5-HT occurs by exocytosis, i.e. by the discharge from the cell of the entire content of individual storage vesicles. First, 5-HT is sufficiently ionized at physiological pH so that it does not cross plasma membranes by simple diffusion. Second, most intraneuronal 5-HT is contained in storage vesicles and other contents of the vesicle including SPB are released together with serotonin. By contrast, cytosolic proteins do not accompany electrical stimulation-elicited release of 5-HT. Third, the depolarization-induced release of 5-HT occurs by a calcium-dependent process indeed, it appears that the influx of extracellular calcium ions with or without membrane depolarization can increase the release of 5-HT. Calcium stimulates the fusion of vesicular membranes with the plasma membrane (see Chs 9,10). 

Serotonin is stored in synaptic vesicles and blood platelets in the form of an ATP complex in the ratio of 2 1. Very little is known about its release, but exocytosis is the assumed mechanism. The released neurotransmitter is deactivated primarily by reuptake, but a significant amount is metabolized by MAO to the corresponding indoleacetic acid. 

Monoaminergic neurotransmitters (dopamine, noradrenaline, adrenaline, histamine, and serotonin) are released by exocytosis of small dense-core vesicles from... 

Our knowledge of presynaptic dopamine and serotonin receptors dates back to the 1970s (Famebo and Hamberger 1971). Presynaptic histamine receptors were discovered in 1983 (Arrang et al. 1983). Presynaptic dopamine receptors occur as autoreceptors, i.e., on dopaminergic axon terminals, and as heteroreceptors on nondopaminergic axon terminals. By analogy the same holds true for presynaptic histamine and serotonin receptors. The early days of the dopamine autoreceptors were stormy, but the controversies were finally solved (see Starke et al. 1989). The main function that presynaptic receptors affect is transmitter release, which in this article means Ca2+-dependent exocytosis. However, some receptors discussed in... 

The catecholamines and serotonin share similar pathways of biosynthesis and metabolism, including in some steps, the same enzymes. Catecholamines and serotonin are sequestered and stored in vesicular granules from where they are released mto the extracellular environment by calcium-dependent exocytosis. Termination of the physiological effects of both the catecholamines and serotonin is dependent on active uptake processes, facilitated by specific... 

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