Cholinesterase localization at sites of nerve contact on embryonic amphibian muscle cells in culture.

Cholinesterase (ChE), detected histochemically, was found to be localized at many sites of nerve-muscle contact in cultures of spinal cord and muscle cells derived from Xenopus laevis embryos. Such contacts were often characterized by a corresponding localization of acetylcholine receptors and by synaptic ultrastructure, including aggregates of clear vesicles in the nerve fibre and an 80-100 nm wide intercellular cleft. The ChE reaction product was localized in the cleft. When cultures were grown in the presence of curare many of the nerve-contacted muscle cells still exhibited ChE at the sites of contact. It is concluded that ChE accumulates at synaptic contacts in these cultures even in the absence of muscle action potentials and contraction.