Effect of in vivo glucocorticoid administration on histamine metabolism in rat brain synaptosomes.

The effect of in vivo administration of acetonide triamcinolone (AT) on histamine (HA) metabolism in synaptosomes, highly purified from rat brain by discontinuous Ficoll-sucrose gradient centrifugation, was investigated. AT decreases ability of synaptosomes to actively accumulate HA precursor, L-[U-14C]histidine, measured after rapid centrifugation of synaptosomes through silicone oil, as well as lowers activity of HA catabolizing enzyme histamine N-methyltransferase (by 57%). In contrast, no changes in the level of HA, assayed by the single isotope enzymatic method, and the activity of HA synthesizing enzyme, histidine decarboxylase, were found. The results indicate that under applied conditions glucocorticoid administration may decrease turnover of neuronal pool of HA without significant effect on HA level.