Appearance of new α-bungarotoxin-acetylcholine receptors in cultured sympathetic ganglia of chick embryos

α-Bungarotoxin (α-BuTX) has been used as a marker for studying the production of α-bungarotoxin-acetylcholine receptors (α-BuTX-AChRs) in explants of chick embryo sympathetic ganglia cultured in vitro. New α-BuTX-AChRs appear rapidly in the explants after blocking of the pre-existant ones with the toxin (40% of the total receptors at 3 h). There is a portion of α-BuTX-AChRs in the explants which for a short time is not accessible to the toxin. This portion constitutes the precursor pool of receptors and represents 18% of the total. The precursor pool of receptors supplies the neurons with new receptors for 1–2 h in the absence of protein synthesis. The appearance of new receptors from the precursor pool is an energy-dependent process.