Abstract: The present invention relates to identification of agents that pay a role in regulating brain amyloid-? (A?) levels in vivo. The invention provides compounds and methods of using such compounds to treat amyloidogenic conditions. It also provides a useful animal model for screening for and evaluating candidate amyloid inhibiting or therapeutic compounds. In particular, ovariectomy (ovx) and estrogen replacement were found to affect brain A?, levels in guinea pigs. Long-term ovx of guinea pigs resulted in increased levels of total brain A?, as compared to intact animals, and the A?42/A?40 ratio was also elevated. Treatment of ovx guinea pigs with ?17-estradiol for ten days partially reversed the ovx-associated increase in brain A? levels.