Abstract
We have previously shown that retinoic acid-treated cultures of the P19 line of embryonal carcinoma cells differentiate into neurons, glia, and fibroblast-like cells (Jones-Villeneuve et al., 1982). We report here that the monoclonal antibody HNK-1 reacts with the neurons at a very early stage of their differentiation and is, therefore, an early marker of the neuronal lineage. Cells in differentiated P 19 cultures synthesized acetylcholine but not catecholamines, suggesting that at least some of the neurons are cholinergic. The neurons also carry high-affinity uptake sites for GABA but not for serotonin. In long-term cultures, neuronal processes differentiated into axons and dendrites, which formed synapses. This biological system should prove valuable for examining the development and maturation of cholinergic neurons, since their differentiation occurs in cell culture.