Immunohistochemical study on the effect of soft diet and omega 3-fortified soft diet on neurogenesis in the rat dentate gyrus and the subventricular zone

Background: Adult brain neurogenesis persists in the subventricular zone (SVZ) and in the subgranular zone (SGZ) of the dentate gyrus. Modulation of neurogenesis by diet is a mechanism by which nutrition affects memory, learning, and mood.Aim of the study: To study the effect of the soft diet with or without omega 3 fatty acids on neurogenesis.Materials and methods: Thirty weaned male albino rats (3 weeks) were divided into three groups. Group 1 (control group) were fed on hard diets, group 2 were fed on soft diets, and group 3 were fed on soft diets plus omega 3 fatty acids for 3 months. Nerve cell proliferation in the SVZ and the SGZ was detected immunohistochemically using thymidine analog bromodeoxyuridine (BrdU). The results were statistically analyzed.Results: In the dentate gyrus, there was a significant increase in the number of BrdU-positive cells in groups 1 and 3 compared with group 2. Meanwhile in the SVZ, there was a significant increase in the number of BrdU-positive cells in group 3 compared with group 1. In group 1, the newly formed cells in the SGZ reached the granular cell layer of the dentate gyrus. The newly formed cells in the SVZ reached the olfactory bulb (OB) after 2 weeks but failed to survive for 4 weeks in the OB. In group 2, few newly formed cells reached the granular cell layer of the dentate gyrus, but they failed to reach the OB. In group 3, the newly formed cells reached their destination in the granular cell layer of the dentate gyrus and the OB. In the OB, the cells succeeded to survive for 4 weeks and were incorporated among the granular cells of OB.Conclusion: Hard diet and omega 3-fortified soft diet had a stimulatory effect on the process of neurogenesis in the dentate gyrus. Meanwhile in the SVZ, fortified soft diet had more stimulatory effect on proliferation and improvement of the survival rate of the newly formed cells than the hard diet