Effect of corticosteroids on the phrenic nerve-diaphragm of preparation treated with hemicholinium. A possible model of myasthenia gravis.

A marked protective action of the corticosteroids prednisolone, hydrocortisone, and dexamethasone has been shown on a hypothetical model of myasthenia gravis, using the rat phrenic nerve-diaphragm preparation treated with hemicholinium-3. Dexamethasone is much more effective than prednisolone, and hydrocortisone is the least effective. Prednisolone has no effect on a neuromuscular block caused by choline, decamethonium, physostigmine, d-tubocurarine, and a high or low calcium ion concentration. The possible implications of the present study for myasthenic disease are discussed. It is tentatively concluded that the site of action of corticosteroids in myasthenia gravis is located presynaptically.