AIM: To determine whether serum leptin level and the leptinreceptor (OB-R) expression in the basolateral amygdala (BLA)change following conditioned taste aversion (CTA) formation.METHODS: The serum leptin concentration was measuredby rat leptin RIA kit, long and short forms of leptin receptor(OB-Rb and OB-Ra) mRNA in the brain sections wereexamined by in situ hybridization (ISH) and the expressionof OB-R was assessed by immunohistochemistry ABC methodwith a highly specific goat anti-OB-R antibody.RESULTS: The level of serum leptin didn't show significantdifference between CTA and control group. Comparing withthe control group, the CTA group had an increase on countof OB-R immunohistochemistry positive-stained cells in theBLA (127