[The inhibition of synaptic acetylcholinesterase by postsynaptic muscle relaxants]

In experiments on narcotized cats records of contractions of the anterior tibial muscle in response to indirect stimulation showed that the mean dose of acetylcholine (Ach) blocking neuromuscular conduction and that of carbachole (Cch) for their injection into the corresponding femoral artery was 18.9 and 0.16 mumole/kg, respectively. In the period of partial blockade induced by depolarizing myorelaxants, the blocking dose of Ach reduced to a greater measure than that of Cch. Most nondepolarizing myorelaxants used in the experiment increased the blocking Ach dose less than the Cch dose. Benzoquinone possessing the highest antiacetylcholinesterase activity in vitro even reduced the blocking dose of Ach. This difference is apparently due to inhibition of the activity of synaptic acetylcholinesterase by the muscle relaxants.