Short Term Effects of Reserpine on Noradrenaline Levels in Skeletal Muscle¹

In the skeletal muscle from the hindlimb of cat noradrenaline disappeared almost completely within 5 to 10 hours after reserpine (5 mg/kg i.v.). When the sympathetic nerve supply to the muscles was cut at a preganglionic level before reserpine was given, about 15% of the noradrenaline was still present after 5 hours. This remaining amount then disappeared more slowly during 24 to 48 hours, and its rate of disappearance was not influenced by a second dose of reserpine. When the preganglionic section of the sympathetic supply was performed 3 hours after reserpine administration it prevented the rapid disappearance of the remaining noradrenaline only to a small extent. It is known from previous investigations that the noradrenaline in skeletal muscle is stored almost exclusively in the adrenergic nerves. The effects of preganglionic section of the sympathetic nerve supply are presumably due to an interruption of the normal impulse discharge in these nerves. The data from the present investigation seem to indicate that noradrenaline in the adrenergic nerves of skeletal muscle is stored in two different compartments. One larger fraction disappears within a relatively short time after reserpine. Another smaller fraction disappears more slowly but this fraction is rapidly released during impulse activity.