Amyloid-beta injection in rat amygdala alters tau protein but not mRNA expression

Previously we demonstrated local and distant changes in tau protein imnnuno reactivity reminiscent of those seen in Alzheimer's disease (AD) following a unilateral injection of amyloid-beta (A beta)(25-35) into the rat amygdal a. To explore the relevance of these findings to AD, we compared the effect s of A beta(1-42) to those of A beta(25-35). Injections of both A beta(1-42 ) and A beta(25-35) into rat amygdala resulted in increased tau-2 immunolab eling in neurons. To determine whether these alterations were due to change s in the expression of tau, we measured tau protein expression by Western b lotting and tau mRNA isoform expression by the reverse transcription-polyme rase chain reaction in the amygdala, hippocampus, and cerebellum following a unilateral injection of A beta(25-35)-treated (59-69 kDa) compared to the vehicle-treated (67-72 kDa) animals 8 days following treatment. There were no changes in tau mRNA expression in any brain region examined. In this mo del, just as in AD, there is an increase in tau protein levels without a ch ange in tau mRNA expression, suggesting that A beta peptides may influence tau protein stability in both the rat and the human brain. (C) 2000 Academi c Press.