The physiological and metabolic consequences of muscle denervation.

Fundamental metabolic changes occur in muscle following damage of the nerve supply. These changes include alterations in the enzyme activities associated with oxidative phosphorylation and glycolysis, and alteration in the metabolism of cAMP, changes in the sensitivity to insulin and other alterations of the handling of glucose and probably also an alteration in the metabolism of Ca2+ possibly resulting in a metabolic myopathy. There are also changes in the turnover of acetylcholine receptors and possibly cytoskeletal proteins such as dystrophin-related protein. The biochemical changes are paralleled by similar alterations in physiological parameters such as electromyographic measurements and structural changes such as those that occur at the endplate. Similar genes to those which are active during muscle cell development may be "switched-on" following a nerve injury. The return of these parameters to normal after reinnervation is variable and may be incomplete.