Preliminary study of ovariectomy and chronic losartan-induced alterations in brain AT(1) receptors

Women who undergo oophorectomy prior to the age of natural menopause have a higher risk of neurological and psychological impairment. Treatment with the angiotensin receptor blocker (ARB) losartan for 10 weeks following ovariectomy of Long-Evans rats at 3 months of age reduced the ovariectomy-induced cognitive decrements. Following completion of the behavioral experiments, (Campos et al., 2019), the brains were harvested for preliminary receptor autoradiographic studies of AT(1) receptor (AT(1)R) binding in selected brain regions using quantitative densitometric analysis of autoradiograms of I-125-sarcosine(1), isoleucine(8) angiotensin II binding. Four of the brain regions (amygdala, ventral subiculum, piriform cortex, and cingulate cortex) are associated with cognitive and emotional behavior while one (lateral hypothalamus) is associated with homeostasis. The density of AT(1)R varied by region: ventral subiculum > amygdala and cingulate cortex, and piriform cortex > cingulate cortex. Losartan treatment decreased AT(1)R binding in the ventral subiculum of sham and ovariectomized rats by 41.6%, and 46% in the piriform cortex of the sham rats, but tended to increase AT(1)R binding in the piriform cortex and cingulate cortex 77% and 107%, respectively, in the ovariectomized rats. AT(1)R binding did not differ significantly between intact male and sham-vehicle female rats among surveyed brain regions. These results suggest that losartan-induced changes in brain AT(1)R expression may contribute to the reduced anxiety-like behavior and memory impairments seen in ovariectomized rats, but replication of these observations will be needed to determine the extent to which brain AT(1)R changes mediate the adverse behavioral effects of ovariectomy.