Physiology and pathophysiology of the serotonergic system and its implications on mental and physical performance. Part II.

As shown in the first part of this review, well equilibrated neurotransmission in which 5-HT plays a dominant role is important for proper neuromodulation and adjustment of neuronal network elements. Adequate 5-HT system function supports regulation of intercommunicative neuronal transmission in the brain, which optimizes behavioral neuromodulation during and after different forms of exertions, thereby preventing transient dysregulation. Impairment of neuromodulation and neuronal network in the brain with transient dysfunctions or permanent substantial deficits at manifestation of various types of depression results from prevalent impairment of 5-HT neurotransmission and its central interaction with other neurotransmitter systems.

Physiology and pathophysiology of the serotonergic system and its implications on mental and physical performance. Part I.

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.

Influence of exercise on serotonergic neuromodulation in the brain.

Implications of exercise on serotonergic neuromodulation in the brain have been investigated in two studies. Acute paroxetine (selective serotonin (5-HT) reuptake inhibitor) administration to endurance athletes, who performed a cycle ergometer test to exhaustion at moderate intensity, reduced time to exhaustion and post exercise cognitive performance in comparison to trials with placebo or BCAA administration. Furthermore, during a 3-week moderate endurance training of sedentary males basaline values of Bmax of 5-HT transporters (5-HTT) and 5-HT2A receptors (5-HT(2A)R) on isolated platelet membranes increased while plasma prolactin (PRL) concentrations decreased as well as mood and physical efficiency improved.

Neuroendocrine system and mental function in sedentary and endurance-trained elderly males.

Hypothalamic-pituitary-adrenal (HPAA) and -gonadal (HPGA) axis modification and cognitive impairments have been reported in elderly subjects and related to physical training status. The aim of this study was to investigate if HPAA and HPGA regulation are altered in elderly distance runners (RUN; n = 8; age: 68.9+/-4.

Blood oxygen partial pressure affects plasma prolactin concentration in humans.

Responses of plasma prolactin (PRL) concentration to acute and repeated changes in blood oxygen partial pressure (PO2a) at rest were investigated in two studies (A; B), with special reference to possible effects mediated via serotonin (5-HT) synthesis. In A, nine male subjects inhaled for 105 min gas containing different oxygen fractions for 6 days. Gas concentrations consisted of 14% (A14), 21 % (A21), 40% (A40), 60% (A60) and 80% (A80) O2 mixed with N2 as well as 100% O2 (A100).