| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4353592 | Progress in Neurobiology | 2011 | 21 Pages |
This review focuses on the possibility that autonomic activity influences cerebral blood flow (CBF) and metabolism during exercise in humans. Apart from cerebral autoregulation, the arterial carbon dioxide tension, and neuronal activation, it may be that the autonomic nervous system influences CBF as evidenced by pharmacological manipulation of adrenergic and cholinergic receptors. Cholinergic blockade by glycopyrrolate blocks the exercise-induced increase in the transcranial Doppler determined mean flow velocity (MCA Vmean). Conversely, alpha-adrenergic activation increases that expression of cerebral perfusion and reduces the near-infrared determined cerebral oxygenation at rest, but not during exercise associated with an increased cerebral metabolic rate for oxygen (CMRO2), suggesting competition between CMRO2 and sympathetic control of CBF. CMRO2 does not change during even intense handgrip, but increases during cycling exercise. The increase in CMRO2 is unaffected by beta-adrenergic blockade even though CBF is reduced suggesting that cerebral oxygenation becomes critical and a limited cerebral mitochondrial oxygen tension may induce fatigue. Also, sympathetic activity may drive cerebral non-oxidative carbohydrate uptake during exercise. Adrenaline appears to accelerate cerebral glycolysis through a beta2-adrenergic receptor mechanism since noradrenaline is without such an effect. In addition, the exercise-induced cerebral non-oxidative carbohydrate uptake is blocked by combined beta 1/2-adrenergic blockade, but not by beta1-adrenergic blockade. Furthermore, endurance training appears to lower the cerebral non-oxidative carbohydrate uptake and preserve cerebral oxygenation during submaximal exercise. This is possibly related to an attenuated catecholamine response. Finally, exercise promotes brain health as evidenced by increased release of brain-derived neurotrophic factor (BDNF) from the brain.
► Sympathetic influence on brain blood flow (CBF) and metabolism in humans is examined. ► Adrenergic and cholinergic receptors control cerebral perfusion during exercise. ► Competition exists between the brain's demand for O2 and sympathetic control of CBF. ► A beta2-adrenergic receptor controls brain carbohydrate uptake during exercise. ► Training lowers brain carbohydrate uptake and promotes brain health.
