Histamine-immunoreactive endocrine cells in the adrenal medulla of the rat

Histamine is widely distributed in various mammalian tissues and it has been shown that histamine is located in mast cells as well as in other structures. Biochemical evidence has been presented that histamine acts as a neurotransmitter in the central nervous system. Immunohistochemical studies have demonstrated the location of histamine-immunoreactive neuronal cells in both the central and peripheral nervous system. Biochemical studies have shown that histamine is present in the adrenal gland, while the location of histamine in the adrenal medulla is not known. There is pharmacological and biochemical evidence that exogenous histamine affects the catecholamine secretion of the adrenal medulla. The present study was undertaken to examine the location of histamine in the rat adrenal medulla by an indirect immunofluorescence method using a specific histamine antiserum. We now report the presence of histamine-immunoreactive endocrine cells in the adrenal medulla of the rat and suggest that histamine is located in the noradrenaline-secreting cells.