Effect of α-Fluoromethylhistidine on the Histamine Content of the Brain ofW/WvMice Devoid of Mast Cells: Turnover of Brain Histamine

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Abstract
In the brains of W/Wv mutant mice that have no mast cells, the histidine decarboxylase (HDC) level is as high as in the brain of congenic normal mice (+/+), but the histamine content is 53% of that of +/+ mice. The effects of a-fluoromethylhistidine (α-FMH) on the HDC activity and histamine content of the brain of W/Wr and +/+ mice were examined. In both strains, 30 min after i.p. injection of α-FMH the HDC activity of the brain had decreased to 10% of that in untreated mice. The histamine content decreased more gradually, and after 6 h about half of the control level remained in +/+ mice, whereas histamine had disappeared almost completely in W/Wv mice. It is concluded that the portion of the histamine content that was depleted by HDC inhibitor in a short time is derived from non-mast cells, probably neural cells. The half-life of histamine in the brain of W/Wv mice was estimated from the time-dependent decrease in the histamine content of the brain after administration of a-FMH: 48 min in the forebrain, 103 min in the midbrain, and 66 min in the hindbrain.