THE RÔLE OF THE NERVOUS SYSTEM IN THE REGULATION OF THE GLYCOGEN METABOLISM OF SKELETAL MUSCLE

Abstract

The denervated gastrocnemius muscle of the rat had a normal glycogen content, and capacity to store ingested glucose as glycogen 24 hrs. after nerve section, the muscle of the opposite limb serving as control. A marked fall in the glycogen concn. (GC) occurred during the 3d day following denervation, with gradual small decreases thereafter. Ingested glucose failed to increase muscle GC when given 2 or more days after denervation; when the GC had been lowered by insulin or adrenalin (control and denervated muscle ca. equally), glucose ingestion was accompanied by glycogen deposition up to but not above the characteristic level for denervated muscles. Thyroxin in amts. insufficient to reduce the GC of normal muscle lowered the GC in denervated muscle. Fasting reduced the glycogen stores of denervated muscle, this effect sometimes being masked in the early postoperative periods by the concomitant decrease caused by the denervation itself. The normal GC and storage capacity found in muscle for 24 hrs. after denervation argues against the existence of important reflexes concerned directly with glycogen metabolism. The time after denervation at which muscle suffers a marked decrease in its GC and ability to store ingested sugar as glycogen above a certain characteristic level coincides with the loss of viability of the cut nerve and the appearance of altered physiologic properties of the muscle peculiar to denervation atrophy.