Olfactory dysfunction is among the first signs of Alzheimer's disease (AD).
Since estrogen therapy may mitigate the cognitive symptoms of AD, we deter
mined whether 17 beta-estradiol (E-2) alters the olfactory discrimination p
erformance of female rats exposed to the olfactotoxicant 3-methylindole (3-
MI). Twelve ovariectomized rats received daily injections of E-2 (1 mg/kg i
.p.) in corn oil and 10 received daily injections of corn oil alone. Sensor
y testing occurred on a near-daily basis throughout a 10-week test period,
midway in which a single injection of 3-MI was administered (300 mg/kg i.p.
). On each pre- and post-3-MI test day, the rats were required to perform a
series of successively more difficult odor discrimination tasks until one
was reached where < 80% performance was attained. The tasks were between th
e odor of a 10(-4) v/v concentration of ethyl acetate (EA) and the odor of
each of six different concentrations of butanol added to the EA (10(-4), 10
(-4.5), 10(-5.0), 10(-5.5), 10(-6.0), 10(-6.5) v/v). Following 3-MI treatme
nt, the performance of the E-2-treated rats was found to be superior to tha
t of the oil-treated mts and to return more quickly to the pre-3 MI baselin
e, suggesting that high doses of E-2 mitigate 3-MI-induced smell loss in ra
ts. Additional work is needed to determine the physiologic basis of this ph
enomenon (C) 1999 Published by Elsevier Science B.V. All rights reserved.