Maturation serotonin action

It has been reported that serotonin can produce opposite and complementary action on neuronal functioning, maturation, proliferation and apoptosis, depending on the kind and the density of receptors synthesized by the cells [1]. There are at least fourteen different receptor subtypes described for 5-HT, 13 different heptahelical G-protein-coupled receptors and one ligand-gated ion channel (Table 3). The 5-HT receptor family has been, and is at present, subjected to intense research. Excellent and complete reviews of functional, molecular and pharmacological aspects of 5-HT receptors have been published [5-7]. 

For a growing number of neurotransmitters, direct neurotrophic actions have been reported (for a review see Schwartz, 1992 Schwartz and Tani-waki, 1994). These transmitters are serotonin, acetylcholine, norepinephrine, glutamate and endogenous opioid peptides. Some of these neurotrophic transmitters may also be produced by astrocytes. The family of neurotransmitters synthesized by astrocytes comprises y-aminobutyric acid, glutamate, proenkephalin, neuropeptide Y, somatostatin and others. Martin (1992) has coined the term gliotransmitter for such substances. The role of gliotransmission in development and function of the mature nervous system has not been firmly established yet. It can be anticipated, however, that neurotrophic activity of astroglia-derived transmit-... 

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