Histological And Immunohistochemical Study of Annual Nothobranchius Rachovii Digestive Tract

The peptide hormone cholecystokinin (CCK) is known to play a key role in regulating food intake and satiety in higher vertebrates. In humans, increased concentration of CCK in older people was described as the basis of anorexia associated with aging [1, 2]. In rats as well, CCK induced strong anorexia in young adults and old subjects [3]. However, the role of increased plasma CCK concentrations in mediating the age-related decrease in appetite remains to be established. African annual fishes from the genus Nothobranchius are small teleosts that inhabit temporary water. They are emerging as a prominent model organism in biomedical research, evolution studies, and developmental biology due to their short captive lifespan, amenability to captive breeding, embryonic diapause, short generation time, and huge eggs, susceptible to microinjection therefore to genetic manipulations [4]. They are considered convenient experimental models for life-long investigations on the effects of dietary and environmental manipulations [4]. The present study aimed to investigate, for the first time, the morphology of the gastrointestinal tract and the expression of the CCK of the short lifespan Nothobranchius rachiovii. For this reason, we have investigated the histological features of Nothobranchius rachovii gastrointestinal tract using Masson's trichrome stain and alcian blue–PAS. The CCK expression pattern was studied through immunohistochemical labelling and quantitative RT-PCR. Indeed, CCK expression was detected in scattered intraepithelial cells, and the variation of the pattern of expression was recorded between the different segments of adult’s digestive tract. Our study introduces Nothobranchius rachovii as a potential model for anorexia of aging, giving the first bases on the gastrointestinal tract morphology and cck expression pattern. Future studies on young and elderly Notobranchius can divulge the contribution of cck in the mechanisms of anorexia associated with aging.