Optimal physical performance in athletes: key roles of dopamine in a specific neurotransmitter/hormonal mechanism.

It is proposed that exercise training leads to resetting of the central autonomic nervous system (ANS) status, modifies neuroendocrine function and consistently results in upgraded efficiency of physiological/metabolic regulations. The initiating neurotransmitter mechanism is widely held to be due, essentially, to activation of certain brain cholinergic neurons (amygdala n.), stimulation of the hypothalamic-pituitary-adrenocortical pathway, and to cortisol as the dominant peripheral effector of overall improved efficiency. This thesis raises certain questions. The present analysis, based on studies of sedentary and exercise trained humans, proposes the following: that (1) the ANS profile in exercise consists in enhanced dopaminergic (DA) relative to noradrenergic (NA) activity and increased vagal tone; (2) DA is the principal catecholamine neuromodulator/neurotransmitter of the brain, directly involved in motor control in the striatum and is key to the mechanism underlying increased and maintained efficiency of exercise trained humans; (3) DA is a major participant in many aspects of motor function which include the regulation of cardiovascular and renal function (heart rate, blood pressure, and other), muscle tone, visual processing, calcium homeostasis, protein synthesis and conceivably the optimal utilization of food intake; (4) the peripheral actions of DA reflect and are functionally interrelated to the observed global activation of brain DA systems in exercising animals, and probably man; (5) that a different enzyme profile evolves in exercise training which may potentiate DA synthesis and preserve the structural and functional integrity of central DA neurons; (6) that a shift to enhanced DA vs. NA activity occurs in exercise trained Whites which resembles the norm for sedentary Africans and confers distinct physiological advantages; (7) there is unequivocal evidence for the physiological efficiency of a DA dominated ANS profile which can be correlated to the low incidence of DA related diseases in aging Africans; (8) data suggests that the superiority of top-class African athletes in distance running and their endurance capacity are related to an inherent neurophysiological advantage, to efficient DA and protein synthesis, a decreased rate of DA decline during aging and to improved calcium homeostasis, inter alia. Throughout this study, the term sedentary refers to subjects not undergoing specific exercise training of defined intensity and duration.