title: Lack of presynaptic interaction between glucocorticoid and CB1 cannabinoid receptors in GABA- and glutamatergic terminals in the frontal cortex of laboratory rodents.
abstract: Corticosteroid and endocannabinoid actions converge on prefrontocortical circuits associated with neuropsychiatric illnesses. Corticosteroids can also modulate forebrain synapses by using endocannabinoid effector systems. Here, we determined whether corticosteroids can modulate transmitter release directly in the frontal cortex and, in doing so, whether they affect presynaptic CB1 cannabinoid receptor- (CB1R) mediated neuromodulation. By Western blotting of purified subcellular fractions of the rat frontal cortex, we found glucocorticoid receptors (GcRs) and CB1Rs enriched in isolated frontocortical nerve terminals (synaptosomes). CB1Rs were predominantly presynaptically located while GcRs showed preference for the post-synaptic fraction. Additional confocal microscopy analysis of cortical and hippocampal regions revealed vesicular GABA transporter-positive and vesicular glutamate transporter 1-positive nerve terminals endowed with CB1R immunoreactivity, apposing GcR-positive post-synaptic compartments. In functional transmitter release assay, corticosteroids, corticosterone (0.1-10 microM) and dexamethasone (0.1-10 microM) did not significantly affect the evoked release of [(3)H]GABA and [(14)C]glutamate in superfused synaptosomes, isolated from both rats and mice. In contrast, the synthetic cannabinoid, WIN55212-2 (1 microM) diminished the release of both [(3)H]GABA and [(14)C]glutamate, evoked with various depolarization paradigms. This effect of WIN55212-2 was abolished by the CB1R neutral antagonist, O-2050 (1 microM), and was absent in the CB1R KO mice. CB2R-selective agonists did not affect the release of either neurotransmitter. The lack of robust presynaptic neuromodulation by corticosteroids was unchanged upon either CB1R activation or genetic inactivation. Altogether, corticosteroids are unlikely to exert direct non-genomic presynaptic neuromodulation in the frontal cortex, but they may do so indirectly, via the stimulation of trans-synaptic endocannabinoid signaling.
authors.affiliation: CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; Laboratory of Psychopharmacology, Dept. Pharmacology, Universidade Federal de Santa Catarina, Florianopolis 88049-900, Brazil.
authors.forename: Rafael M
authors.initials: RM
authors.lastname: Bitencourt
authors.affiliation: Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-17177 Stockholm, Sweden.
authors.forename: Alán
authors.initials: A
authors.lastname: Alpár
authors.affiliation: Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, A-1090 Vienna, Austria; University of Insubria, Via Ravasi, 2, 21100 Varese, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Cinquina
authors.affiliation: CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; FMUC, Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal.
authors.forename: Samira G
authors.initials: SG
authors.lastname: Ferreira
authors.affiliation: CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal.
authors.forename: Bárbara S
authors.initials: BS
authors.lastname: Pinheiro
authors.affiliation: CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal.
authors.forename: Cristina
authors.initials: C
authors.lastname: Lemos
authors.affiliation: IRIBHM, Université Libre de Bruxelles, Brussels B-1070, Belgium.
authors.forename: Catherine
authors.initials: C
authors.lastname: Ledent
authors.affiliation: Laboratory of Psychopharmacology, Dept. Pharmacology, Universidade Federal de Santa Catarina, Florianopolis 88049-900, Brazil.
authors.forename: Reinaldo N
authors.initials: RN
authors.lastname: Takahashi
authors.affiliation: Department of Pediatrics, Medical University of Vienna, Währinger Gürtel 18, A-1090 Vienna, Austria; CeMM Research Center for Molecular Medicine of the Austrian Academy of Science, Lazarettgasse 14, AKH BT 25.3, A-1090 Vienna, Austria.
authors.forename: Fernando J
authors.initials: FJ
authors.lastname: Sialana
authors.affiliation: Department of Pediatrics, Medical University of Vienna, Währinger Gürtel 18, A-1090 Vienna, Austria.
authors.forename: Gert
authors.initials: G
authors.lastname: Lubec
authors.affiliation: CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; FMUC, Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal.
authors.forename: Rodrigo A
authors.initials: RA
authors.lastname: Cunha
authors.affiliation: Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-17177 Stockholm, Sweden; Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, A-1090 Vienna, Austria.
authors.forename: Tibor
authors.initials: T
authors.lastname: Harkany
authors.affiliation: CNC, Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra, 3030-789 Coimbra, Portugal. Electronic address: akofalvi@uc.pt.
authors.forename: Attila
authors.initials: A
authors.lastname: Köfalvi
mesh_terms: D000818:Animals; D048588:Benzoxazines / Q000494:pharmacology*; D063388:Endocannabinoids / Q000378:metabolism; D005625:Frontal Lobe / Q000187:drug effects* / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D008297:Male; D051379:Mice; D009025:Morpholines / Q000494:pharmacology*; D009281:Naphthalenes / Q000494:pharmacology*; D017729:Presynaptic Terminals / Q000378:metabolism; D017208:Rats, Wistar; D043884:Receptor, Cannabinoid, CB1 / Q000172:deficiency / Q000187:drug effects* / Q000378:metabolism; D017661:Receptors, Presynaptic / Q000378:metabolism; D013569:Synapses / Q000187:drug effects* / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D048588:Benzoxazines; D063388:Endocannabinoids; D009025:Morpholines; D009281:Naphthalenes; D043884:Receptor, Cannabinoid, CB1; D017661:Receptors, Presynaptic; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone
keywords: CB(1) cannabinoid receptor; Frontal cortex; GABA; Glucocorticoid receptor; Glutamate; Presynaptic