Stress-triggered Changes in the Adrenal Medullary Cells Structure and Function in the Rat

Objective: previous authors provided electrophysiological evidence for selective activation of epinephrine or norepinephrine-secreting adrenal chromaffin cells. however, the corresponding histological changes in the adrenal chromaffin cells were not described.to provide histological and biochemical evidence that different sympathetic preganglionic neurons regulate epinephrine and norepinephrine secretion.methods: male wistar albino rats weighing 220-250g were subjected to stress inducing experiments including insulin-induced hypoglycemia, acute exposure to cold and acute hemorrhagic hypotension.the fine structure of adrenomedullary cells was examined; their catecholamine contents and volume fractions were measured.results: insulin injection was followed by gradual and progressive depletion of epinephrine storing granules with no effect on norepinephrine granules, acute exposure to cold produced a response consistent with activation of norepinephrine secreting chromaffin cells, while acute hemorrhagic hypotension produced activation of both epinephrine and norepinephrine cells, all these morphological changes were accompanied by corresponding changes in the catecholamine content of the adrenal gland as well as in the volume fractions of epinephrine and norepinephrine cells.conclusions: in the presence of similar nerve endings on the epinephrine and norepinephrine chromaffin cells, the above results suggest the presence of different adrenal sympathetic preganglionic neurons that regulate epinephrine and norepinephrine secretion.