Physiology and Pathophysiology of the Serotonergic System and its Implications on Mental and Physical Performance. Part I

Abstract

Serotonin (5-HT), one of the evolutionary oldest central neurotransmitters, regulates the most extensive modulatory behavioral system in the brain of vertebrates. 5-HT projections are influenced by extrinsic and intrinsic impulses from different cortical brain areas, which reach Raphe nuclei over feedback loops, containing external and internal body information about planning, evaluation, motivation or excitation. Serotonergic neurotransmission adjusts neuromodulation with consecutive adequate stimulation of the neuronal network. This depends on appropriate equilibration of presynaptic 5-HT storage and release but also on 5-HT reuptake from synaptic cleft by 5-HT transporters. The associated pre and postsynaptic 5-HT receptor cooperation, postsynaptic second messenger response and phosphoinositide signaling mediated by postsynaptic 5-HT(2) receptor subpopulation alter signal transduction in which myristolated alanine rich C kinase substrate is prominently involved in regulation of further central 5-HT areas in the brain and corresponding functional neuronal changes. Even though the central function of 5-HT neurotransmission is dominating in the multifold behavioral regulation, peripheral concentration of tryptophan (TRP) adjusted by hepatic and non-hepatic TRP pyrrolase, TRP liberation from albumin especially by adrenergic stimulation of free fatty acids, TRP passage across the blood-brain barrier and TRP hydroxylase activity are also important for appropriate 5-HT neurotransmission as they affect central 5-HT synthesis. The high adaptability of 5-HT neurotransmission is able to compensate neuromodular dysfunctions in the brain by mechanisms which mediate 5-HT biosynthesis, release, reuptake, pre and postsynaptic receptor stimulation with the respective second messenger response and signal transduction to various areas of the brain which are involved in regulation of behavior, mood, memory, learning and attenuation of obsession, depending on the different vigilance states of the subject. Adequate 5-HT system function supports regulation of intercommunicative neuronal transmission in the brain, which optimizes behavioral neuromodulation during and after transient disturbances of neuromodular behavior caused by stress-induced exertions, but also in permanent disorder such as major depression. Serotonergic neurotransmission improves the clinical course due to compensatory 5-HT impulse correction. This hypothetical interpretation of the serotonergic central neuromodular regulation and interaction with the neuronal network is supported by findings both in functional disturbances and persistent impairments in mental disorders. A comparison of the symptomatology in permanent and transient disturbance of brain neuromodulation enhances our basic knowledge on the regulative factors e. g. in endogenous depression and depressive behavioral changes after exhaustive exercise. This consideration exhibits that the interaction between altered central neuromodulation and peripheral metabolic and hormonal dysfunctions is able to di...

Effects of type of physical exercise and leisure activities on the depression scores of obese Brazilian adolescent girls

“…In agreement with this hypothesis, Struder and Weicker (32,33) suggest a relationship between reduced body mass and lower fat percentages and lower plasma serotonin (5-HT) concentrations. These changes may be related to the biochemical alterations mentioned by Costil et al (34), whereby higher plasma concentrations of free fatty acids are observed after prolonged exercise due to lipolysis.…”

Implicações do sistema serotoninérgico no exercício físico

“…Os AGL competem pelo transporte com o triptofano, sendo que esta competição pelos locais de ligação da albumina faz com que ocorra maior disponibilidade de triptofano livre (25). A albumina humana possui apenas um local de ligação para o triptofano, já a bovina possuí dois (26). O sinergismo entre deslocamento da parcela livre, mediada por AGL, e menor competição, mediada pela redução plasmática dos ACR, tem como conseqüência maior produção de serotonina cerebral e desencadeamento de fadiga central precoce (figuras 1a e 1b).…”

O baixo consumo de oxigênio tem reflexos nos escores de depressão em idosos

“…[25][26][27][28] Neste sentido, é possível que a hipótese de aumento da monoamina cerebral serotonina possa contribuir para compreender os resultados, 29,30 sendo que a lipólise observada em exercícios físicos realizados na intensidade do LV-1 possa alterar a distribuição do triptofano (TRP), aminoácido precursor do neurotransmissor serotonina (relacionado com depressão). 25,31 A cronicidade do treinamento também pode ter contribuir nesse sentido.…”