REGULATION OF NEURONAL DIFFERENTIATION BY RETINOIC ACID ALONE AND IN COOPERATION WITH THYROID-HORMONE OR HYDROCORTISONE

Cultures highly enriched in neurons obtained from embryonic mouse cere bra were used to demonstrate that: (1) at the optimum concentration of 10(-8) M retinoic acid stimulated the neurons to produce axon- and de ntrite-like structures as determined by phase contrast and fluorescent microscopy; (2) the same concentration of retinoic acid stimulated ac etyl cholinesterase and choline acetyltransferase activities; (3) trea tment of neurons of either prenatal or neonatal equivalent age with re tinoic. acid produced a sustained stimulation of neuronal differentiat ion, and (4) retinoic acid cooperatively stimulated neuronal different iation with either thyroid hormone or hydrocortisone.