RESUMO
Asymmetrical distribution of the vasoactive intestinal polypeptide (VIP)-immunoreactive neurons in the hippocam-pal formation of rat nd iv/iv mouse was detected by the immunocytochemical method. The animals were divided into 3 groups and group I was subdivided into 4 groups according to sex and handedness determined by the paw-preference test : group I (male right-handedness (MR), male left-handedness (ML), female right-handedness (FR), female left-handedness (FL)), group II (female rats ovariectomized in neonatal period), group III (iv/iv mouse, situs solitus & inversus). The number of VIP-immunoreactive neurons were counted under the light microscope and the following results were obtained. 1. In MR of group I, the area containing the higher density of VIP neurons in the left hippocampal formation than the right were the CA1, CA3, dentate gyrus and subiculum. In ML, the area containing the higher density of VIP neurons in the left cortex were the level 2 of dentate gyrus, and the area exhibiting higher density in the right cortex were level 1, 3 of dentate gyrus. 2. The asymmetrical distributional pattern of VIP in ovariectomized rat (group II) was similar to male subgroups in group I. 3. In group III, there was no asymmetrical distribution of VIP-immunoreactive neurons. Above results show that asymmetrical distribution of VIP neurons are prominent in the right handedness or male groups, and the sexually dimorphic pattern of VIP is related directly or indirectly to gonadal steroids, but there seems to be no relationship between iv gene and asymmetrical distribution of VIP neurons in cerebral cortex.