Induction of c-fos-like protein in the rat adrenal cortex by acute stress--immunocytochemical evidence.

The effect of immobilization stress on the expression of c-fos protein in the adrenal cortex of adult rats was investigated immunocytochemically. After immobilization stress lasting for longer than 30 min, an enhanced c-fos-like immunoreactivity was observed in the cortical cells of the zona fasciculata and zona reticulata. Compared to unstressed controls, an about 5-fold increase in the density of the immunoreactive cells in a unit of the cortical area was seen following a 1-h immobilization. The enhanced immunoreactivity lasted for at least 3 h after 1-h immobilization and it began to diminish 5 h after the stress. Furthermore, administration of dexamethasone 2 h prior to 1-h immobilization attenuated the stress-enhanced immunostaining for the c-fos-like protein. These results suggest that an acute stress may cause a dramatic and long-persisting induction of c-fos-like protein in the cortical cells of rat adrenals. The characteristic zonal distribution of the c-fos induction in rat adrenals as well as the effect of dexamethasone suggest involvement of the pituitary adrenocorticotropic hormone (ACTH) in the induction.