Sympathetic nervous system and metabolism

At the outset it is important to define the elements of the sympathetic nervous system (SNS) that are involved in the response to critical illness; for example, endocrine responses to adrenaline (A) compared to local neurotransmitter release, i.e. noradrenaline (NA) in pancreas, skeletal muscle, liver, etc. It must also be remembered that activation of the SNS input to individual organs may produce metabolic effects without changes in either the plasma concentration of catecholamines, or even in whole body noradrenaline kinetics. For example, isolated activation of the sympathetic innervation of the pancreas would have significant metabolic effects (reduction in insulin and increase in glucagon levels in the plasma) but might not be reflected as increases in plasma adrenaline, noradrenaline or even whole body noradrenaline kinetics. Organ-specific changes in SNS activation in endotoxic shock have already been demonstrated in animal models [1].