Effect of preceding physostigmine administration on neuromuscular transmission disturbances in rats caused by dichlorphos and phospholine.

The reported experiments were carried out on male Wistar rats. Under general anaesthesia with chloral hydrate in situ physiological preparations were made consisting of sciatic nerve and anterior tibialis muscle. Physostigmine was injected subcutaneously and was followed after from 15 to 60 minutes by intravenous injection of DDVP or phospholine. Physostigmine effect on the blockade of tetanic muscular contractions was studied after administration of these organophosphate inhibitors of acetylcholinesterase. At the same time, the effect of these substances on acetylcholinesterase was determined in the skeletal muscle. It was found that physostigmine in a dose of 125 microgram/kg protected the tibialis muscle against the development of blockade of tetanic response. The protective effect was greatest when the time between physostogmine injection and the subsequent administration of these organophosphate inhibitors was 30--40 minutes. In the same observation period the activity of AChE in the tibialis muscle of rats was found to be highest after physostigmine injection before administration of DDVP or phospholine.