Effect of pentobarbital on contractility of mouse skeletal muscle

Pentobarbital is a hypnotic drug commonly used as anesthesia for in vivo studies in various animals. A direct effect of pentobarbital on the central nervous system and skeletal neuromuscular junction has been known for at least 30 years. A recent study using single fiber preparations from amphibian muscles indicated a significant acute and direct effect on muscle contractility at drug concentrations within the anesthetic range. The present study using whole muscles from mice demonstrated a similar augmentation of twitch tension and rate of tension development whereas tetanic tension was reduced by this drug at similar concentrations. In addition, most time parameters of contraction were prolonged. It is of interest that the slow (oxidative) muscles were considerably more sensitive to pentobarbital than the fast (primarily anaerobic) muscles. We suggest that pentobarbital should not be used as the anesthetic agent for in vivo studies of other interventions when conclusions are based on changes in muscle contractility.