Abstract
Endocannabinoid is known to enhance food intake by binding to cannabinoid receptor 1 (CB1R). It was reported that expression of CB1R was suppressed by injection of cholecystokinin (CCK). The underlying mechanism, however, has not been clarified until the present time. To investigate whether inhibitory effect of CCK on food intake is mediated by CB1R, mRNA expression of CB1R, CB2R (cannabinoid receptor 2), leptin receptor short type (Ob-Ra) and long type (Ob-Rb) in hypothalamus were measured by RT-PCR method before and after 24 hr-fasting. These mRNA expressions were compared between CCKA receptor deficient male Otsuka Long-Evans Tokushima Fatty (OLETF) rats and its normal counterpart of male Long-Evans Tokushima Otsuka (LETO) rats. The amount of daily food intake was measured before and after 24 hr-fasting. The expression of CB1R mRNA, but not CB2R mRNA, was significantly decreased after 24 hr-fasting in OLETF rats. The expression of CB2R mRNA in OLETF rats after 24 hr-fasting was significantly increased as compared with that in LETO rats. There were no significant differences of Ob-Ra and Ob-Rb mRNA expression between OLETF and LETO rats both before and after 24 hr-fasting. Amount of food intake at nighttime and daytime before fasting and at nighttime after fasting in OLETF rats were significantly increased as compared with those of LETO rats. These data suggest that CCK may influence the expression of CB1R mRNA in hypothalamus after 24 hr-fasting, thereby enhancing food intake. [J Physiol Sci. 2008;58 Suppl:S106]
