title: Nongenomic glucocorticoid inhibition via endocannabinoid release in the hypothalamus: a fast feedback mechanism.
abstract: Glucocorticoid negative feedback in the brain controls stress, feeding, and neural-immune interactions by regulating the hypothalamic-pituitary-adrenal axis, but the mechanisms of inhibition of hypothalamic neurosecretory cells have never been elucidated. Using whole-cell patch-clamp recordings in an acute hypothalamic slice preparation, we demonstrate a rapid suppression of excitatory glutamatergic synaptic inputs to parvocellular neurosecretory neurons of the hypothalamic paraventricular nucleus (PVN) by the glucocorticoids dexamethasone and corticosterone. The effect was maintained with dexamethasone conjugated to bovine serum albumin and was not seen with direct intracellular glucocorticoid perfusion via the patch pipette, suggesting actions at a membrane receptor. The presynaptic inhibition of glutamate release by glucocorticoids was blocked by postsynaptic inhibition of G-protein activity with intracellular GDP-beta-S application, implicating a postsynaptic G-protein-coupled receptor and the release of a retrograde messenger. The glucocorticoid effect was not blocked by the nitric oxide synthesis antagonist N(G)-nitro-L-arginine methyl ester hydrochloride or by hemoglobin but was blocked completely by the CB1 cannabinoid receptor antagonists AM251 [N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide] and AM281 [1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide] and mimicked and occluded by the cannabinoid receptor agonist WIN55,212-2 [(beta)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone mesylate], indicating that it was mediated by retrograde endocannabinoid release. Several peptidergic subtypes of parvocellular neuron, identified by single-cell reverse transcripton-PCR analysis, were subject to rapid inhibitory glucocorticoid regulation, including corticotropin-releasing hormone-, thyrotropin-releasing hormone-, vasopressin-, and oxytocin-expressing neurons. Therefore, our findings reveal a mechanism of rapid glucocorticoid feedback inhibition of hypothalamic hormone secretion via endocannabinoid release in the PVN and provide a link between the actions of glucocorticoids and cannabinoids in the hypothalamus that regulate stress and energy homeostasis.
authors.affiliation: Division of Neurobiology, Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118-5698, USA.
authors.forename: Shi
authors.initials: S
authors.lastname: Di
authors.forename: Renato
authors.initials: R
authors.lastname: Malcher-Lopes
authors.forename: Katalin Cs
authors.initials: KC
authors.lastname: Halmos
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Tasker
mesh_terms: D000818:Animals; D063385:Cannabinoid Receptor Modulators; D003345:Corticosterone / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D063388:Endocannabinoids; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology*; D018756:GABA Antagonists / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D005938:Glucocorticoids / Q000494:pharmacology / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000145:classification / Q000187:drug effects / Q000378:metabolism; D009490:Neurosecretory Systems / Q000187:drug effects / Q000378:metabolism; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction; D051381:Rats; D017207:Rats, Sprague-Dawley; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D005231:Fatty Acids, Unsaturated; D018756:GABA Antagonists; D005938:Glucocorticoids; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D018698:Glutamic Acid; C023427:guanosine 5'-O-(2-thiodiphosphate); D003907:Dexamethasone; D019204:GTP-Binding Proteins; D003345:Corticosterone