Glucocorticoid effects on the edrophonium responsiveness of normal and degenerating mammalian motor nerve terminals.

An intensive short-term triamcinolone regimen in cats preserves the prejunctional actions of edrophonium in degenerating motor nerves. These edrophonium actions include the induction of a stimulus-dependent afterdischarge and the initiation of fasciculations. The relationship between fasciculations and stimulus-dependent afterdischarge is discussed. The glucocorticoid preservation of these edrophonium effects is like that previously reported for the preservation of posttetanic facilitation in motor nerves equally compromised. The results therefore show that glucocorticoid and facilitatory drug actions synergize to increase facilitation in degenerating but still functional motor nerves. This drug synergy is comparable to that which occurs in normal motor nerves. This interaction may provide a basis for effectively combining glucocorticoid and facilitatory drugs in the treatment of myasthenia gravis.