TIME COURSE OF NEOSTIGMINE ACTION ON THE END-PLATE RESPONSE

Miniature endplate currents (MEPCs) were focally recorded in frog sartorius muscle. In the presence of 3 μM neostigmine, the amplitude of MEPCs increased, but later, after 45-60 min of treatment, a decrease of the amplitude towards the initial levels appeared. The pronounced lengthening of the falling phase of MEPCs, which accompanied the increased amplitude, suggests that at the beginning the effect is mainly ascribed to cholinesterase inhibition. The final decreased amplitude of MEPC showed a shortening of the time course instead. This suggests that also a direct effect on endplate receptors is involved. © 1990.