title: Retrograde opioid signaling regulates glutamatergic transmission in the hypothalamus.
abstract: Opioid signaling in the CNS is critical for controlling cellular excitability, yet the conditions under which endogenous opioid peptides are released and the precise mechanisms by which they affect synaptic transmission remain poorly understood. The opioid peptide dynorphin is present in the soma and dendrites of vasopressin neurons in the hypothalamus and dynamically controls the excitability of these cells in vivo. Here, we show that dynorphin is released from dendritic vesicles in response to postsynaptic activity and acts in a retrograde manner to inhibit excitatory synaptic transmission. This inhibition, which requires the activation of kappa-opioid receptors, results from a reduction in presynaptic release of glutamate vesicles. The opioid inhibition is downstream of Ca(2+) entry and is likely mediated by a direct modulation of presynaptic fusion machinery. These findings demonstrate that neurons may self-regulate their excitability through the dendritic release of opioids to inhibit excitatory synaptic transmission.
authors.affiliation: Hotchkiss Brain Institute and Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Iremonger
authors.forename: Jaideep S
authors.initials: JS
authors.lastname: Bains
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D030801:Animals, Genetically Modified; D000831:Animals, Newborn; D044482:Benzeneacetamides / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003712:Dendrites / Q000187:drug effects / Q000502:physiology; D004399:Dynorphins / Q000235:genetics / Q000378:metabolism*; D004558:Electric Stimulation / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects; D008297:Male; D009292:Narcotic Antagonists; D009433:Neural Inhibition / Q000187:drug effects; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology*; D018408:Patch-Clamp Techniques / Q000379:methods; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000819:agonists / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
chemical_list: D044482:Benzeneacetamides; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D009292:Narcotic Antagonists; D026902:Potassium Channel Blockers; D011759:Pyrrolidines; D011957:Receptors, Opioid; D049452:Green Fluorescent Proteins; D018698:Glutamic Acid; D004399:Dynorphins; D020866:omega-Conotoxin GVIA; D015761:4-Aminopyridine; C045444:U 69593; D002118:Calcium