Chromaffin-adrenocortical cell interactions: effects of chromaffin cell activation in adrenal cell cocultures

Although the adrenal cortex and medulla are both involved in the maintenanc e of homeostasis and stress response, the functional importance of intra-ad renal interactions remains unclear. When primary cocultures of frog (Rana p ipiens) adrenocortical and chromaffin cells were used, selective chromaffin cell activation dramatically affected both chromaffin and adrenocortical c ells. Depolarization with 50 mum veratridine enhanced chromaffin cell neuro nal phenotype, contacts with adrenocortical cells, and secretion of norepin ephrine, epinephrine, and serotonin. Time-lapse video microscopy recorded t he rapid establishment of growth cones on the activated chromaffin cell neu rites, neurite branching, and outgrowth toward adrenocortical cells. Simult aneously, adrenocortical cells migrated toward chromaffin cells. Following chromaffin cell activation, adrenocortical cell Fos protein expression and corticosteroid secretion were increased, indicating that chromaffin cell mo dulation of adrenocortical cells is at the transcriptional level. These res ults provide evidence that intra-adrenal interactions affect cellular diffe rentiation and modulate steroidogenesis. Furthermore, this suggests that th e activity-related plasticity of chromaffin and adrenocortical cells is dev elopmentally and physiologically important.