M₂ receptor mediates a decrease in ACh release at the frog neuromuscular junction

Abstract

Muscarinic receptors have been implicated in modulating ACh release at vertebrate neuromuscular junctions (NMJ). We characterized the roles of M₂ and M₃ receptors at the frog NMJ by pharmacologically isolating each receptor and measuring ACh release in terms of EPP amplitude. We observed an M₂ mediated inhibition of ACh release and no apparent involvement of M₃ receptors. We conclude that muscarinic responses in the frog are unlike those observed in the lizard or the rat.