INCREASE OF HISTIDINE-DECARBOXYLASE ACTIVITY IN MICE HYPOTHALAMUS AFTER INTRACEREBROVENTRICULAR ADMINISTRATION OF LIPOPOLYSACCHARIDE

The effect of intracerebroventricular (icv) administration of lipopoly saccharide on histidine decarboxylase activity and histamine content i n the hypothalamus were investigated in male mice of ddY strain in viv o. Two-fold increase in histidine decarboxylase activity (HDC) was obs erved 4 h after administration of 50 mcg lipopolysaccharide, and HDC a ctivity returned to the basal level within 12 h after injection. Furth ermore, histamine contents showed a slight decrease at 1 and 2 h and a mild increase al 12 h after administration. However, changes in hista mine content were not statistically significant. These results suggest that the increase of HDC activity in the hypothalamus by lipopolysacc haride may be involved in the central neuroimmune responses.