Regional distribution of mast cells containing histamine, dopamine, or 5-hydroxytryptamine in the mammalian brain.

Brain mast cells were studied in mice, rats, rabbits, hamsters, guinea pigs, cats, cows, monkeys, and humans with use of a variety of techniques. They were localized by staining with Astrablau or by toluidine blue-induced metachromasia and characterized by their ultrastructural appearance and by the presence of histochemically demonstrable histamine (o-phthaldiadehyde fluorescence method). The identity of the fluorophore was secured by microspectrofluorometry. Mast cells in brain usually had a perivascular localization but were also found scattered in the parenchyma. The regional variations in the number of mast cells agreed with the histamine concentration as measured fluorometrically. The variation was in the order leptomeninges greater than hypothalamus greater than cerebral cortex = mesencephalon greater than cerebellum = brain stem. In addition to histamine, murine mast cells stored serotonin, whereas bovine mast cells contained dopamine, visualized histochemically by the formaldehyde technique.