The effect of anticholinesterase drugs on postjunctional potentials of skeletal muscle

Abstract

1. 1. Quantitative detailed investigation of the effects of seven anticholinesterase (anti-ChE) drugs—organophosphorus inhibitors (OPI) (armin, GD-42, GD-7), carbamates (proserine or neostigmine, eserine), quaternary ammonium salts (ambenonium, edrophonium)—on postjunctional potentials in skeletal muscle was carried out with a reduced quantum content of end plate potentials (EPP). 2. 2. It was established by the method of elimination of other possible causes that the amplitude of miniature end plate potentials (MEPP) and the duration of EPP were increased by inhibitors as a result of their anti-ChE action only. 3. 3. Curare-like action of the inhibitors was analysed. It was found to be related neither to their effect on membrane potential or passive electrical properties of the muscle fibres nor to inhibition of cholinesterases (ChE). 4. 4. It was found that inhibitors, excepting OPI, failed to affect the EPP quantum content and MEPP frequency. OPI affected these parameters in experiments on the frog sartorius muscle but not on the rat diaphragm muscle and only at concentrations of 2 × 10 −5 M and higher. Under these conditions armin decreased the EPP quantum content and the MEPP frequency. GD-42 and GD-7 decreased the EPP quantum content as well but increased MEPP frequency. These variations of parameters were not related to inhibition of ChE activity and were reversible by washout.