Muscle relaxant activity of chlordiazepoxide and diazepam.

The effect of chlordiazepoxide and diazepam was studied upon the reflex and non-reflex contractions of the tibialis anterior muscle of the cat (anesthetized with chloralose). Results were obtained which indicate that, under these conditions, the primary muscle relaxant activity is central rather than peripheral. Evidence is presented which suggests that these agents more readily inhibit the contractions due to rapid (60 per minute) rather than slow (12 per minute) rates of reflex stimulation. Experiments on the isolated rat phrenic nerve – diaphragm preparation indicate that these compounds are capable of producing a dose-related inhibition of both directly and indirectly elicited contractions. With this preparation, no rate dependence was observed. An interesting feature was that diazepam was about five times as active as chlordiazepoxide, which is identical with the ratio of activity reported for muscle relaxant activity as tested by the inclined-screen test and anti-strychnine activity in mice, and gro...