LATERALITY IN THE HISTOLOGICAL EFFECTS OF INJECTIONS OF AMYLOID-BETA-25-35 INTO THE AMYGDALA OF YOUNG FISCHER RATS

We have observed that single amyloid-beta 25-35 (A beta) injection (5. 0 nmol) into the right amygdala of rats produce progressive cytoskelet al and astrogliotic reactions not only within the amygdala, but also i n distal brain regions that project to the amygdala. To determine if t hese effects are potentiated by bilateral injections, we injected A be ta (5.0 nmol) into the left and right amygdala of young male Fischer r ats. Animals were sacrificed 32 days postoperatively. Bilateral infusi ons of A beta induced significant neuronal shrinkage, tau-2 neuronal s taining, and reactive astrocytosis within the right amygdala and/or hi ppocampus, compared with vehicle-treated rats. Surprisingly, the same brain regions within the left hemisphere were significantly less affec ted even though no differences were observed between the left and righ t amygdala in the size of Congo-red-positive A beta deposits. Unilater al injections of A beta into the left amygdala led to significant hist ological changes in the right amygdala and hippocampus, but not in the same brain regions within the left hemisphere. These results suggest a laterality in the histopathological effects of A beta in male Fische r rats. Identification of the cause for the lateralized effect of A be ta may prove valuable for understanding the etiology of Alzheimer dise ase and provide possible therapeutic strategies designed to slow the p rogression of the disease.