LOSARTAN, ANGIOTENSIN II TYPE 1 RECEPTOR BLOCKER, REDUCED AORTIC STIFFNESS AND IMPROVED COGNITIVE FUNCTION IN DAHL SALT SENSITIVE RAT MODEL OF AGE-ASSOCIATED VASCULAR DEMENTIA

Abstract

Objective: Cardiovascular diseases are the major contributors to the pathogenesis of vascular dementia. The Dahl salt sensitive (Dahl-S) rat model is characterized by the development of central arterial stiffness (CAS), hypertension and cognitive decline with age on a normal salt diet. We hypothesized that treatment with losartan (LOS), angiotensin II type 1 receptor (AT1R) blocker, via reduction of blood pressure (BP) and CAS, will improve cognitive function in aged Dahl-S rats. Design and method: Male Dahl-S rats (n = 30) were kept on a normal salt diet (0.5% NaCl) for the duration of the study. Baseline measurements were taken at 3- and/or 6-mo of age following by the treatment with LOS in drinking water (30 mg/kg/day, n = 14) or control treatment (n = 16) for 6-mo. Measurements were taken every 3 months and included systolic and diastolic BP (SBP, DBP), pulse wave velocity (PWV), a measure of CAS, left ventricular posterior wall thickness in diastole (LVPWd), fractional shortening (FS) and LV mass (by echocardiography). At 12-mo of age the rats were tested in operant chambers using a simple reaction task to assess attention and impulsivity, and in elevated plus maze (EPM) to assess anxiety-like behavior. Statistical analyses were performed using 2-way ANOVA and t-test. Data are presented as mean ± SEM. Results: Prior to the treatment, LOS and control groups did not display differences in any parameter analyzed. Following the treatment, LOS rats had lower SBP, DBP, PWV, thinner LVPWd, higher FS and smaller LV mass at 9- and 12-mo of age vs. control group (Fig.1A-F). In the reaction task, LOS rats demonstrated more correct responses and fewer premature responses. The LOS rats exhibited lower anxiety level, because they spent more time in the open arm of EPM vs. control rats (Fig.1G,H). Conclusions: Beneficial effect of LOS on cognitive function in aged male Dahl-S rats was associated with the improvement of cardiovascular function and remodeling. The CAS stabilizing and BP reduction by LOS treatment was associated with improved attentional performance, lower impulsivity and lower anxiety. The mechanistic basis of these effects of LOS on cognition via cerebrovascular and brain changes will be further investigated.