title: Involvement of the orexin/hypocretin system in the pharmacological effects induced by Δ(9) -tetrahydrocannabinol.
abstract: OBJECTIVE
  Anatomical, biochemical and pharmacological evidence suggest the existence of a crosstalk between the orexinergic and endocannabinoid systems. While the orexin receptor 1 (OX1 receptor) modulates the reinforcing properties of cannabinoids, the participation of orexins in the acute pharmacological effects of Δ(9) -tetrahydrocannabinol (THC) remains unexplored.
  
  
  METHODS
  We assessed the possible role of orexins in THC-induced hypolocomotion, hypothermia, antinociception, anxiolytic- and anxiogenic-like effects and memory impairment. Selective OX1 and OX2 receptor antagonists and OX1 knockout (KO) mice as well as prepro-orexin (PPO) KO mice were used as pharmacological and genetic approaches. CB1 receptor levels in control and PPO KO mice were evaluated by immunoblot analysis. The expression of c-Fos after THC treatment was analysed in several brain areas in wild-type mice and in mice lacking the PPO gene.
  
  
  RESULTS
  The hypothermia, supraspinal antinociception and anxiolytic-like effects induced by THC were modulated by orexins through OX2 receptor signalling. OX1 receptors did not seem to be involved in these THC responses. No differences in CB1 receptor levels were found between wild-type and PPO KO mice. THC-induced increase in c-Fos expression was reduced in the central amygdala, medial preoptic area and lateral septum in these mutant mice.
  
  
  CONCLUSIONS
  Our results provide new findings to further clarify the interaction between orexins and cannabinoids. OX1 and OX2 receptors are differently implicated in the pharmacological effects of cannabinoids.
authors.affiliation: Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, PRBB, Barcelona, Spain.
authors.forename: África
authors.initials: Á
authors.lastname: Flores
authors.affiliation: Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, PRBB, Barcelona, Spain.
authors.forename: Marina
authors.initials: M
authors.lastname: Julià-Hernández
authors.affiliation: Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, PRBB, Barcelona, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Maldonado
authors.affiliation: Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, PRBB, Barcelona, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Berrendero
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D013759:Dronabinol / Q000494:pharmacology*; D005455:Fluorescent Antibody Technique; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D064446:Orexin Receptors / Q000172:deficiency / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis / Q000096:biosynthesis
chemical_list: C501103:Cd200r1 protein, mouse; C497459:Hcrtr1 protein, mouse; D064446:Orexin Receptors; D016760:Proto-Oncogene Proteins c-fos; D013759:Dronabinol