Effect of intraperitoneal injection of curcumin on food intake in a goldfish model

Although spice compounds have several pharmacological and biochemical actions such as antioxidant activity, their physiological effects on neuropeptides related to feeding regulation are not well known. The aim of the present study was to identify the pharmacological activities of spice compounds on appetite regulation using a goldfish (Carassius auratus) model with emphasis on the role of neuropeptides. The spice compounds used in this study were curcumin, piperine, and ursolic acid. Goldfish were injected intraperitoneally with test solutions containing each spice or vehicle (including 10% dimethyl sulfoxide in saline), and the changes in food intake were measured every 15 min for 60 min. Among the tested spice compounds, curcumin was found to reduce cumulative food intake and was thus selected for further experiments. Pretreatment with capsaicin, a neurotoxin of afferent nerves, abolished the curcumin-induced decrease of food intake. Curcumin-induced anorexigenic action was also attenuated by intracerebroventricular injection of the corticotropin-releasing hormone (CRH) receptor antagonist α-helical CRH((9-41)). We also examined the expression levels of mRNA for CRH, which is a potent anorexigenic neuropeptide in goldfish, in the diencephalon at 1 h after treatment with curcumin, and found that they were increased. Therefore, the reduction of appetite induced by curcumin treatment in goldfish was suggested to be mediated by the vagal afferent and subsequently through the CRH/CRH receptor pathway.