Substrate supply and energy metabolism of skeletal muscle of mice treated with methamphetamine and propranolol

Abstract

In order to examine, whether the inhibition by propranolol of methamphetamine-induced motor excitation has to be ascribed to lack of substrate supply and inadequate energy production in skeletal muscle, the influence of 3 μg/g methamphetamine subcutaneously (s.c.) alone or in combination with 5 μg/g propranolol intraperitonially (i.p.) on liver glycogen, blood glucose, non-esterified fatty acids in the blood and the glycogen, pyruvate, lactate, ATP and phosphocreatine contents of skeletal muscle has been investigated in mice. The following results have been obtained: (1) Methamphetamine stimulates lipolysis in adipose tissue and glycogenolysis in liver and muscle and thus provides the substrate required for an adequate energy production in skeletal muscle. (2) Propranolol inhibits methamphetamine-stimulated lipolysis and at the same time enhances the mobilization of hepatic glycogen and the utilization of carbohydrates in skeletal muscle. In this way enough substrate can be supplied to skeletal muscle to maintain constant ATP and phosphocreatine levels. It is concluded from the results, that the inhibition by propranolol of methamphetamine-induced excitation is not due to an inhibition of energy metabolism of skeletal muscle.