Acetylchoine receptors (AchRs) at the neuromuscular junctions of the cat posterior cricoar ytenoid muscle (PCA muscle) were demonstrated by using erabutoxin b (Eb) which has a curare- like action. Eb is one of the short-chain neurotoxins which is obtained from Laticauda semifas- ciata. At the light microscopic level, the localization of the neuromuscular junctions was detected on the muscle fiber by rhodamine-labeled Eb (TMR-Eb) under a fluorescein microscopy. For the electron microscopy horeseradish peroxidase-labeled Eb (HRP-Eb) was used. After incubation with HRP-Eb conjugate the tissue was fixed in a mixture of parafolmaldehyde and glutaraldehyde, then embedded in Epon. The reaction products were largely restricted to the postsynaptic membrane at the neuromuscular junction.
Acetylcholinesterase (AchE) activity was also demonstrated electron microscopically by Karnovsky's and Lewis' methods respectively. The reaction products were localized at the subneural apparatus of the neuromuscular junction. Both these results were compared.