Lateralized learning and memory effects of vasoactive intestinal peptide infused into the rat hippocampal CA1 area

The effects of VIP microinjected unilaterally (left or right) and bilaterally (left and right) at a dose of 50 ng into hippocampal CA1 area of male Wistar rats on learning and memory (shuttle-box) were studied. Bilateral VIP microinjections impaired learning and memory, i.e., decreased the number of avoidances during the second training day and memory tests, compared to the respective controls. When infused into the left CA1 area, VIP exerted a marked inhibitory effect. Right-side VIP microinjections did not change the number of avoidances during the learning and memory tests. Compared to the right-side, left-side VIP infusions provoked a threefold decrease of the number of avoidances on the second training day and on the memory tests (24 h after the 2nd training day and on 7th day). These findings reveal lateralized inhibitory effects of VIP on cognitive processes in hippocampus.