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  • Addiction, Drugs
  • Information from Lay-Language Summaries is Embargoed Until the Conclusion of the Scientific Presentation

    819—Cannabinoids: Neural Mechanisms, Addiction, Reinforcement, Seeking, Reinstatement, and Development

    Wednesday, November 13, 2013, 1:00 pm - 5:00 pm

    819.08: Low expression of CB1 receptor in the nucleus accumbens and prefrontal cortex compels adolescent rats to consume palatable food

    Location: Halls B-H

    *O. AMANCIO BELMONT, M. M…NDEZ-DÕAZ, A. ROMANO-L”PEZ, O. PROSP…RO-GARCÕA;
    Fisiologia, UNAM, Mexico, DF, Mexico

    Abstract Body: We have previously observed that both receptors (CB1 and CB2) to endocannabinoids exhibit a different expression in nucleus accumbens (NAcc) and prefrontal cortex (PFC) in adolescent (PND 28-42), adult (PND > 90) and aged (PND > 365) rats. Likewise, these groups of rats exhibit reward and decision-making behaviors differently.
    The present study investigated the motivational behavior to consume palatable food (Dustless Precision pellets ®, 45 mg Rodent Purified Diet chocolate flavor), using the self-administration paradigm in adolescent, adult and aged rats. In these subjects we evaluated the expression of CB1R and CB2R as well as the enzymes involved in synthesis (NAPE-PLD and DAGL) and degradation (FAAH and MAGL) of anandamide and 2- Arachidonylglycerol in PFC and NAcc.
    Results indicate that adolescent rats are much more motivated to consume palatable food compare to adult and aged rats and have a lower expression of CB1 in NAcc and PFC. The measurement of the other molecules have not shown changes.
    Results suggest that a low expression of the CB1R in adolescent rats plays a crucial role in generating their highly motivated consumption of palatable food.

    Lay Language Summary: Our research indicates that cannabinoid receptors 1 (CB1) expression in structures involved in regulation of motivated behaviors like the nucleus accumbens (reward system) and prefrontal cortex is different depending on the age of rats. Adolescent compared to adult and old rats showed a lower expression of CB1 receptor besides we observed that adolescent rats show much more motivation to consume palatable food compare to adult and old rats. These results are suggesting that the low expression of CB1 receptors in adolescent rats plays a crucial role in generating their highly motivated consumption of palatable food.
    The prevalence of overweight and obesity worldwide is growing at an alarming rate, especially in children and adolescents, pointing them as a vulnerable population. In most cases, the accumulation of body fat is attributed to a permissive environment, characterized by sedentarism and excessive consumption of palatable food, rich in salt, sugar and fat. However, the evidence suggests that adolescents lack a system that allows them to make correct decisions about the amount of palatable food they should consume.
    Brain generates several substances that modulate food intake. Some of them also regulate the level of alertness. Emotions in general influence our decision-making. Hence, when the reward system is active our decisions are strongly influenced by this emotion. As part of maturity, our prefrontal cortex is able of regulating the reward system hence reduces the impulsivity in our decision making.
    Previously, we have demonstrated that adolescent, compared to adult and old rats, exhibit an erroneous decision-making behavior for food when forced to choose between regular and palatable food which has been devalued with a delayed delivery. We found that adolescent rats had an unselective seeking behavior suggesting a limited decision-making ability. In this context, it has been described that CB1 and its endogenous ligands seem to play a role in deciding food type and amount of food to be consumed.
    This study investigated the motivated behavior to consume palatable food using the self-administration paradigm of chocolate flavored pellets in adolescent, adult and old rats. We found that adolescent rats consumed more chocolate flavored pellets, regardless the amount of work they have to do to get it. They show more motivation compared to adults and old rats. In addition we observed that CB1 and CB2 receptors are less expressed in the prefrontal cortex and nucleus accumbens of adolescent compared to adult and old rats. While the enzyme responsible for the synthesis (NAPE-PLD) of the endocannabinoid anandamide, exhibit a similar expression in the three groups of rats. Our interpretation of this finding is that adolescents have a greater motivation to consume palatable food than adult and old rats potentially due a CB1 and CB2 receptors lower expression in the prefrontal cortex and the nucleus accumbens compared to adult and old rats.
    These results support the role of endocannabinoids in the ingestion of food and rewarding behaviors, and suggest the importance of the endocannabinoid system in the prefrontal cortex and nucleus accumbens to regulate food intake and food motivation behavior.