A PERIPHERAL COMPONENT OF CENTRALLY ACTING MUSCLE RELAXANTS: CHLORMEZANONE AND MEPHENESIN

¹ Sterling-Winthrop Research Institute, Rensselaer, New York

Blockade of the polysynaptic reflex arc has been used as an assay for the actions of " central muscle relaxants" and other noncurariform relaxants. A modification of Eccles stimulus interval contraction curve has been utilized to elucidate the peripheral actions of two such compounds, mephenesin and chlormezanone. Paired stimuli, with varying interpulse delays, were applied directly and indirectly to the anterior tibialis and soleus muscles of anesthetized cat. Chlormezanone inhibited the twitch contraction- enhancing effect of paired stimuli without affecting contractility to single shocks and without affecting nerve conduction or observed nerve or muscle refractory periods. Analysis of the data revealed that chlormezanone extended the refractory period of the neuromuscular junction. Mephenesin had similar characteristics. Phenobarbital was a general depressant without a specific action at the nerve-muscle junction.