ACCELERATION OF NEURONAL MATURATION OF P19 CELLS BY INCREASING CULTURE DENSITY

P19 embryonal carcinoma cells differentiate into neurons, astrocytes, and fibroblast-like cells following induction with retinoic acid. The mature neurons are capable of neurotransmitter release, and form funct ional synapses. We have previously shown that high culture density sup presses the cholinergic phenotype of P19 neurons. Here we demonstrate that increasing culture density accelerates the maturation of P19 neur ons in a continuous manner. This is manifested by several criteria: in creased efficiency of evoked [H-3]aspartate release; decreased level o f basal release; up-regulation of synaptic vesicle proteins; increased neurite outgrowth rate; and earlier segregation of axons and dendrite s. While glutamate release is enhanced in dense cultures, the efficien cy of [H-3]GABA release is hardly affected, suggesting that P19 GABAer gic neurons are not affected by culture density. The acceleration of n euronal maturation in dense cultures is also exhibited by the ability of dense, but not sparse cultures to release [3H]aspartate at an earli er day of differentiation. Furthermore, density effects are monitored already a few hours after plating the cultures, when neurite length in dense cultures is several fold higher than in sparse cultures. This i ndicates that commitment to a faster and coordinated maturation proces s occurs already very early during P19 neuronal differentiation. (C) 1 997 Elsevier Science B.V.