Hippocampal asymmetry in angiotensin II modulatory effects on learning and memory in rats.

Learning and memory effects of angiotensin II (Ang II) microinjected unilaterally (left or right) and bilaterally into hippocampal CA1 area on the background of the inhibited hippocampal angiotensin 1 receptors type (AT1) of male Wistar rats were studied. It was found that the combination (losartan 100 micrograms + Ang II 0.5 micrograms) microinjected bilaterally or into the left CA1 area improved learning and memory in shuttle-box and step through behavioral tests as compared to the respective controls. The effects were more pronounced after injection into the left CA1 area as compared to the right-side. These findings suggest that Ang II infused on the background of the inhibited CA1 hippocampal AT1 receptors ameliorated the cognitive processes. The data show also an asymmetric effect of Ang II on learning and memory processes in the hippocampus. The stronger modulating effect after microinjection of the combination (losartan + Ang II) into the left CA1 hippocampal area suggests a leftward bias in the rat. The results point to a differential distribution of angiotensin II receptors modulating the learning and memory processes in the left and right hippocampal CA1 area.