KAINIC ACID AND DECORTICATING LESIONS STIMULATE THE SYNTHESIS OF C1Q PROTEIN IN ADULT-RAT BRAIN

The first component of the classic complement cascade, C1q, was increa sed in whole rat brain after lesioning by intraperitoneally injected k ainic acid (KA) (20-fold, 3 days after KA) and in the striatum ipsilat eral to unilateral decortication (fivefold, 10 days after decorticatio n). C1q was measured after purification by chromatography and electrop horesis. De novo biosynthesis of C1q 3 days after KA was increased >10 -fold, as measured by the incorporation of [35S]methionine into C1q af ter incubation of brain slices from KA-treated rats for 2 h. In parall el with these responses, KA induced fivefold increase of C1q bioactivi ty, as evaluated with C1q-dependent hemolysis. The contribution of C1q from entrapped cerebrovascular blood was evaluated by the effects of perfusion and was minor relative to the increases of C1q in response t o KA lesioning. These findings support the hypothesis that the C1q pro tein detected by immunocytochemistry in senile plaques of Alzheimer br ains and in the hippocampus after deafferenting lesions is synthesized by resident brain cells.