Endogenous
cannabinoid signaling, mediated predominately by
CB1 receptor activation, is involved in food intake control and
body weight regulation. Despite advances in determining the role of the
CB1 receptor in
obesity, its involvement in the driven nature of eating pathologies has received little attention. The present study examined
CB1 receptor alterations as a consequence of dietary-induced
binge eating in female Sprague Dawley rats. Four control groups were used to control for calorie restriction and highly palatable food variables characterizing this behavioral model. All groups were kept on their respective feeding schedules for 6-weeks and were given a uniform 33% calorie restriction (~22 h food deprivation) prior to sacrifice. Our findings indicate that regional CB1
mRNA and density were influenced by dietary conditions, but were not specific to the dietary-induced
binge eating paradigm used. An increase of approximately 50% (compared with naive controls) in
CB1 receptor mRNA levels in the nucleus of the solitary tract as measured by in situ hybridization was found in animals receiving continuous access to a highly palatable food (i.e., vegetable shortening with 10%
sucrose). This group also had a significant increase in
body weight and adiposity. An approximate 20% reduction in CB1
mRNA was observed in the cingulate cortex (areas 1 and 2) in animals exposed to an intermittent schedule of feeding, compared with groups that had ad libitum feeding schedules (i.e., continuous access and naive controls). Receptor density as measured by [(3)H]
CP55,940 autoradiography, was reduced by approximately 30% in the nucleus accumbens shell region in groups receiving repeated access to the highly palatable food. Taken together, these findings indicate that dietary conditions can differentially influence CB1 receptors in forebrain and hindbrain regions.