Abstract
Background Ocimum basilicum(O. basilicum) was described to have antidepressant and anxiolytic activities. Although the relationship between the main olfactory bulb (MOB) and depression was recently reported, the chronic stress-induced dysfunction of the MOB is not clearly described. Objectives This study aimed to assess the efficacy of inhalation ofO. basilicumessential oils in improving chronic unpredictable mild stress (CUMS)-induced changes in MOB of mice and understand the mechanism underlying such effect. Materials and Methods Adult male mice (n=40) were assigned into four groups included the control, CUMS-exposed, CUMS + fluoxetine (FLU), CUMS +O. basilicum. Behavioral changes, serum corticosterone level, and gene expression of GFAP, Ki 67, and caspase-3 were assessed using real-time PCR (RT-PCR). Histopathological and immunochemical examination of the MOB was performed. Results FLU andO. basilicumsignificantly down-regulated (p = 0.002, p<0.001) caspase-3 gene expression indicating reduced apoptosis and up-regulated (p = 0.002, p < 0.001) Ki67 gene expression indicating enhanced neurogenesis in MOB, respectively. FLU andO. basilicum-treated mice markedly improved MOB mitral cell layer distortion and shrinkage induced by CUMS. Conclusion O. basilicumrelieved both biochemically and histopathological chronic stress-induced changes in the main olfactory bulb possibly through up-regulation of gene expression of GFAP and Ki67 and down-regulation of caspase-3 in the MOB.