title: Mechanisms of G protein-coupled estrogen receptor-mediated spinal nociception.
abstract: Human and animal studies suggest that estrogens are involved in the processing of nociceptive sensory information and analgesic responses in the central nervous system. Rapid pronociceptive estrogenic effects have been reported, some of which likely involve G protein-coupled estrogen receptor (GPER) activation. Membrane depolarization and increases in cytosolic calcium and reactive oxygen species (ROS) levels are markers of neuronal activation, underlying pain sensitization in the spinal cord. Using behavioral, electrophysiological, and fluorescent imaging studies, we evaluated GPER involvement in spinal nociceptive processing. Intrathecal challenging of mice with the GPER agonist G-1 results in pain-related behaviors. GPER antagonism with G15 reduces the G-1-induced response. Electrophysiological recordings from superficial dorsal horn neurons indicate neuronal membrane depolarization with G-1 application, which is G15 sensitive. In cultured spinal sensory neurons, G-1 increases intracellular calcium concentration and induces mitochondrial and cytosolic ROS accumulation. In the presence of G15, G-1 does not elicit the calcium and ROS responses, confirming specific GPER involvement in this process. Cytosolic calcium concentration elevates faster and with higher amplitude following G-1 intracellular microinjections compared to extracellular exposure, suggesting subcellular GPER functionality. Thus, GPER activation results in spinal nociception, and the downstream mechanisms involve cytosolic calcium increase, ROS accumulation, and neuronal membrane depolarization.
  
  
  CONCLUSIONS
  Our results suggest that GPER modulates pain processing in spinal sensory neurons via cytosolic calcium increase and ROS accumulation. These findings extend the current knowledge on GPER involvement in physiology and disease, providing the first evidence of its pronociceptive effects at central levels and characterizing some of the underlying mechanisms.
authors.affiliation: Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Deliu
authors.forename: G Cristina
authors.initials: GC
authors.lastname: Brailoiu
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Arterburn
authors.forename: Tudor I
authors.initials: TI
authors.lastname: Oprea
authors.forename: Khalid
authors.initials: K
authors.lastname: Benamar
authors.forename: Nae J
authors.initials: NJ
authors.lastname: Dun
authors.forename: Eugen
authors.initials: E
authors.lastname: Brailoiu
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000701:Analgesics, Opioid / Q000008:administration & dosage; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal / Q000187:drug effects; D052117:Benzodioxoles / Q000008:administration & dosage; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003517:Cyclopentanes / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004347:Drug Interactions; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008845:Microinjections; D009020:Morphine / Q000008:administration & dosage; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D059225:Nociception / Q000187:drug effects / Q000502:physiology*; D059226:Nociceptive Pain / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D010147:Pain Measurement; D018408:Patch-Clamp Techniques; D011804:Quinolines / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D011960:Receptors, Estrogen / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology / Q000473:pathology*; D013481:Superoxides / Q000378:metabolism
chemical_list: C517943:1-(4-(6-bromobenzo(1,3)dioxol-5-yl)-3a,4,5,9b-tetrahydro-3H-cyclopenta(c)quinolin-8-yl)ethanone; C568862:4-(6-bromo-1,3-benzodioxol-5-yl)-3a,4,5,9b-3H-cyclopenta(c)quinoline; D000701:Analgesics, Opioid; D052117:Benzodioxoles; D003517:Cyclopentanes; D011804:Quinolines; D017382:Reactive Oxygen Species; D011960:Receptors, Estrogen; D043562:Receptors, G-Protein-Coupled; D013481:Superoxides; D009020:Morphine; D002118:Calcium