Regulación de la liberación de serotonina en distintos compartimientos neuronales

SUMMARY Serotonin is fundamental for the modulation of social behavior, emotions and a wide variety of physiological functions. The functions of serotonergic systems have been highly conserved along the evolutionary scale and in general small numbers of neurons innervate virtually all the nervous system, and exert multiple effects depending on the site of release. Synaptic pools produce fast and local effects, while extrasynaptic pools in the soma, dendrites, axons and the periphery of synapses produce diffuse effects, characteristic of mood modulation. Serotonin release from synaptic terminals is produced by exocytosis of small clear vesicles and is activated by single or low-frequency impulses, while increases in the stimulation frequency produce synaptic facilitation and depression. In contrast, release from the soma is produced by exocytosis of dense-cored vesicles and requires stimulation at high frequencies, the activation of L-type calcium channels and calcium-induced calcium release from intracellular stores. Serotonin released from the presynaptic terminals immediately activates autoreceptors in the same terminals, locally decreasing the subsequent excitability, firing frequency and release. Differential regulation of serotonin release in different cell compartments allows the same neuron to produce different types of effects depending on the firing rate.