Intrahippocampal administration of losartan improves learning and memory in rats with model of depression

The brain renin-angiotensin system is involved in learning and memory, but the role of angiotensin II and its receptors in these processes is not well established. The effects of losartan (angiotensin type 1 receptor antagonist) and angiotensin II, microinjected bilaterally into CA1 hippocampal area on learning and memory in rats with a model of depression (bilateral olfactory bulbectomy), using two avoidance paradigms: active avoidance (shuttle box) and passive avoidance (step through) were investigated. After stereotaxic implantation of guide cannulas into the CA1 area of dorsal hippocampus angiotensin II (0.5 mu g) and losartan (100 mu g) were microinjected separately, 5 minutes before each training session. It was found that intra-CA1 losartan reverses memory deficits induced by bulbectomy unlike angiotensin II which did not show any effect. The data suggest an involvement of angiotensin type 1 receptors in modulating memory processes in rats with model of depression.