Correlations between angiotensinase activity asymmetries in the brain and paw preference in rats

The function of angiotensin peptides is dependent upon the action of several aminopeptidases (APs) termed angiotensinases. Soluble (SOL) and membrane (MEM)-bound alanyl-AP (AlaAP) and cystinyl-AP (CysAP) are involved in the metabolism of angiotensins and related to the modulation of behavior and memory. To study the interactions between angiotensinase activity in the hippocampus and behavioral lateralization, Wistar rats were selected on the basis of their performance in the paw preference test (left-handed, ambidextrous and right-handed) and the activities of SOL-AlaAP/CysAP and MEM-AlaAP/CysAP were measured in the both hippocampuses. We observed that: (1) the left hippocampus had higher activities of SOL-AlaAP/CysAP and MEM-AlaAP/CysAP than the right hippocampus; (2) rats showed significant differences in the activities of SOL-AlaAP/CysAP and MEM-AlaAP/CysAP in the hippocampus depending on the behavioral lateralization detecting by paw preference; (3) in three groups of rats, hemispheric dominance – %R/T [%R/T=right hemisphere/(right hemisphere+left hemisphere)×100] activities of MEM-AlaAP, SOL-CysAP and MEM-CysAP was significantly different whereby %RT was lower in left-handed, higher in ambidextrous and intermediate in right-handed rats; (4) individual %R/T activities of SOL-CysAP and MEM-CysAP in the hippocampus were positively correlated with paw preference scores. Finally, we used the passive avoidance behavior test to demonstrate the differences of long-term memory among the three groups. These results suggested that the asymmetric activity of angiotensinase in the rat hippocampus may be associated with both the direction and the intensity of behavioral lateralization as expressed by paw preference.