Choline acetyltransferase induction in cultured neurons: dissociated spinal cord cells are dependent on muscle cells, organotypic explants are not.

The dependence of the induction of choline acetyltransferase (CAT) on the type of tissue culture, monolayer or piece explants, of spinal cord (SC) and muscle (M) was studied. CAT activities of dissociated SC cells were low but were increased by M monolayers. In piece explants of SC, high CAT activities were achieved independently of muscle cells (chick, mouse). It is therefore likely that in tntact SC tissue factors other than the trophic influence of muscle are able to induce cholinergic maturation. M piece explants on SC monolayers did not induce CAT in, and their outgrowth was inhibited by, SC monolayers.