Effects of chronic prednisolone treatment on post junctional membrane responses to agonist

Using frogs treated 1 month with prednisolone, we studied responses of the muscle postjunctional membrane to acetylcholine and carbamylcholine. In control muscles following a bath application of 3 μ M neostigmine or 30 μ M pyridostigmine, there was an increased depolarization response to iontophoretically applied acetylcholine or carbamylcholine. Results with prednisolone‐treated frog muscle were essentially identical. In some fibers of prednisolone‐treated muscle there was a decrementing response to repetitive iontophoretic application of carbamylcholine. Prolonged administration of prednisolone may accelerate desensitization of acetylcholine receptors during repetitive application of agonist.