Increase in acetylcholine release from chick embryo retina during development.

The release of [3H]acetylcholine (ACh) from 6-, 8-, 10-, 12-, 14- and 16-day chick embryo neural retina layers was determined using a perfusion system to collect the released neurotransmitter. After labeling the tissue with [3H]choline, samples of [3H]ACh released before and after stimulation by 80 mM KCl or 5 mM glutamate were collected and analyzed. The results showed a developmental increase in both basal and stimulated release. The increase was not caused by changes in [3H]choline uptake or total [3H]ACh synthesized which did not increase with developmental age. The developmental increase is correlated with the time of formation and maturation of retinal cholinergic synapses in ovo, but is not correlated with the developmental decrease in cholinergic synapses formed by retina neurons with striated muscles in vitro.