title: Early exposure to environmental enrichment alters the expression of genes of the endocannabinoid system.
abstract: Early environmental enrichment (EE) produces several changes in gene expression in the brain and confers protection against the behavioral, neurochemical and molecular effects of repeated administration of drugs of abuse. Because the endogenous cannabinoid system (ECS) is known to play an important role in the rewarding effects of drugs, we investigated whether the positive effects of early exposure to EE are associated with changes in the expression of genes encoding for proteins that belong to the ECS in C57 mice. Using in situ hybridization, we compared the expression of the cannabinoid receptor CB1, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL) enzymes in brain regions involved in drug addiction in mice reared in either EE or standard environments (SE) from weaning until adulthood. We found that EE increases CB1 mRNA levels in the hypothalamus and in the basolateral amygdala but decreased them in the basomedial amygdala. Similarly, we found that FAAH mRNA levels are higher in the hypothalamus and the basolateral amygdala of EE mice compared to SE mice, with no change in the basomedial amygdala. In contrast, MGL mRNA levels were not affected by EE in any of the areas analyzed. The regional selectivity of EE-induced changes may indicate that early exposure to EE induces changes in the ECS that could result in reduced responses to stress, as confirmed in EE mice in a novelty-induced suppression of feeding test, and, ultimately, in resistance to addiction.
authors.affiliation: Institut de Physiologie et Biologie Cellulaires, University of Poitiers, CNRS, 1 rue Georges Bonnet, Poitiers, F-86022, France.
authors.forename: Rana
authors.initials: R
authors.lastname: El Rawas
authors.forename: Nathalie
authors.initials: N
authors.lastname: Thiriet
authors.forename: Joëlle
authors.initials: J
authors.lastname: Nader
authors.forename: Virginie
authors.initials: V
authors.lastname: Lardeux
authors.forename: Mohamed
authors.initials: M
authors.lastname: Jaber
authors.forename: Marcello
authors.initials: M
authors.lastname: Solinas
mesh_terms: D000367:Age Factors; D000581:Amidohydrolases / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D016739:Behavior, Addictive / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control; D063385:Cannabinoid Receptor Modulators / Q000096:biosynthesis / Q000235:genetics*; D063388:Endocannabinoids; D004777:Environment; D018507:Gene Expression Regulation, Developmental; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008994:Monoacylglycerol Lipases / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011897:Random Allocation; D043884:Receptor, Cannabinoid, CB1 / Q000096:biosynthesis / Q000235:genetics*; D000099252:Fatty Acid Amide Hydrolases
chemical_list: D000581:Amidohydrolases; D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D008994:Monoacylglycerol Lipases; D012333:RNA, Messenger; D043884:Receptor, Cannabinoid, CB1; D000099252:Fatty Acid Amide Hydrolases