An investigation, in cats, into the activity of diazepam at the neuromuscular junction.

Diazepam, in doses of 0.2-5 mg/kg i.v., was without effect on the maximal twitch response of the flexor hallucis longus or soleus muscles of the cat. When injected 5 minutes prior to or at the time of greatest depth of block produced by gallamine oi tubocurarine, diazepam was without effect on the depth or the time course of the paralysis. The commercial solvent for diazepam (Valium, Roche), in volumes thai contained doses of 1-5 mg/kg of the drug, itself slightly enhanced the rate of recovery from block produced by tubocurarine or gallamine. Twitch augmentation following highfrequency tetanic stimulation of the soleus nerve is known to be prejunctional in origin, and provides a sensitive test for detecting drug activity on intramuscular nerve endings. It was unaltered by diazepam, indicating absence of prejunctional blocking activity. The unimpressive peripheral activity of diazepam in cats emphasizes the importance of spinal or supraspinal sites in its ability to produce muscle relaxation in man and animals