Development of acetylcholine sensitivity of embryonic chick atria in culture.

Atria were isolated from chick embryos of 4--12 days incubation and maintained up to 9 days in culture to examine change in their sensitivity to acetylcholine (ACh). Beating of atria from 4-day embryos was not affected by ACh at the start but was inhibited after a few days of culture. Atria from old embryos which had been sensitive to ACh remained so in culture. Desensitization to ACh was marked in short-term culture of 4-day embryonic atria. Sera and embryo extracts facilitated the appearance of ACh sensitivity. Binding of quinuclidinyl benzilate was observed in ACh-insensitive atria. Cycloheximide, puromycin and actinomycin D prevented the appearance and maintenance of ACh sensitivity in culture, leaving the heartbeat unaffected.