We demonstrated previously that hippocampal dentate gyrus neurons were
sensitive to angiotensin II(AII) and recently discovered that AII app
lied directly to the dentate gyrus inhibited granule cell long-term po
tentiation induction and that the inhibition is mediated by the AT(1)
receptor and can be blocked by losartan, a specific AT(1) antagonist.
The purpose of the present study was to examine the effects of AII adm
inistered directly to the dentate gyrus, 1, 5, 50, 150, and 300 ng, on
the retention of an inhibitory shock avoidance response and to determ
ine if the resultant impairment of retention can be blocked by losarta
n. A total of 12 groups of rats in three experiments were studied. Thr
ee independent repetitions of 5 ng AII administered bilaterally to the
dentate gyrus demonstrate a clear impairment of retention under these
experimental conditions and that the impairment can be effectively pr
evented by pretreatment with 20 mg/kg of losartan IP.