HEAD-ACTIVATOR AND THE NEUROECTODERMAL DIFFERENTIATION OF P19 MOUSE EMBRYONAL CARCINOMA-CELLS

P19 embryonal carcinoma cells differentiate into neuroectodermal deriv ates upon aggregation and treatment with retinoic acid (RA). Such RA-i nduced P19 cells, concomitant with neuronal differentiation, produce t he neuropeptide head activator (HA) and release HA into the culture me dium. The amount of HA produced by such differentiating P19 cells is m ore than 100-fold higher than that of uninduced P19 cells. RA-induced P19 cells respond to HA treatment with a two-fold increase in total nu mber of neuronally differentiating P19 progeny. As early response to H A, an increase in intracellular calcium concentration is observed.