MECHANISM OF BUFALIN-INDUCED BLOCKADE OF NEUROMUSCULAR TRANSMISSION IN ISOLATED RAT DIAPHRAGM

摘要

References(14) Cited-By(3) The mechanism of blockade by bufahn at the neuromuscular junction was examined by using the isolated diaphragm of the rat. Bufalin appears to reduce acetylcholine sensitivity at the motor end-plate by causing prolonged depolarization. According to the results of the studies of the post-tetanic potentiation, bufalin appears to have both stimulant and depressant phases of action on the motor nerve terminals, i.e., in smaller doses, it acts as a stimulant and in larger doses (corresponding to the doses of blockade), as a depressant. The amount of acetylcholine release was considerably increased immediately after washing out of bufalin treatment (incubated for 30 min with 10-4 g/ml), whereas in the presence of the same concentration of bufalin, obviously decreased. With regard to blocking effect, bufalin added to the bathing fluid was more potent than infused i.v. which indicates that the pre-junctional effect of this agent is essential for its blockade at the neuromuscular junction.