title: Role of spinal 5-HT2 receptor subtypes in quipazine-induced hindlimb movements after a low-thoracic spinal cord transection.
abstract: A role of serotonin receptors (5-HTRs) in spinal rhythmogenesis has been proposed several years ago based mainly upon data showing that bath-applied 5-HT could elicit locomotor-like rhythms in in vitro isolated spinal cord preparations. Such a role was partially confirmed in vivo after revealing that systemically administered 5-HTR(2) agonists, such as quipazine, could induce some locomotor-like movements (LM) in completely spinal cord-transected (Tx) rodents. However, given the limited binding selectivity of currently available 5-HTR(2) agonists, it has remained difficult to determine clearly if one receptor subtype is specifically associated with LM induction. In situ hybridization, data using tissues from L1-L2 spinal cord segments, where critical locomotor network elements have been identified in mice, revealed greater 5-HTR(2A) mRNA levels in low-thoracic Tx than non-Tx animals. This expression level remained elevated for several days, specifically in the lateral intermediate zone, where peak values were detected at 1 week post-Tx and returned to normal at 3 weeks post-Tx. Behavioral and kinematic analyses revealed quipazine-induced LM in 1-week Tx mice either non-pretreated or pretreated with selective 5-HTR(2B) and/or 5-HTR(2C) antagonists. In contrast, LM completely failed to be induced by quipazine in animals pretreated with selective 5-HTR(2A) antagonists. Altogether, these results provide strong evidence suggesting that 5-HTR(2A) are specifically associated with spinal locomotor network activation and LM generation induced by quipazine in Tx animals. These findings may contribute to design drug treatments aimed at promoting locomotor function recovery in chronic spinal cord-injured patients.
authors.affiliation: Neuroscience Unit, Laval University Medical Center, Quebec City, QC, Canada.
authors.forename: Roth-V
authors.initials: RV
authors.lastname: Ung
authors.forename: Eric S
authors.initials: ES
authors.lastname: Landry
authors.forename: Pascal
authors.initials: P
authors.lastname: Rouleau
authors.forename: Nicolas P
authors.initials: NP
authors.lastname: Lapointe
authors.forename: Claude
authors.initials: C
authors.lastname: Rouillard
authors.forename: Pierre A
authors.initials: PA
authors.lastname: Guertin
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D006614:Hindlimb / Q000294:innervation / Q000503:physiopathology; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009068:Movement / Q000187:drug effects / Q000502:physiology; D009415:Nerve Net / Q000187:drug effects / Q000378:metabolism; D010243:Paralysis / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D011814:Quipazine / Q000494:pharmacology*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D044402:Receptor, Serotonin, 5-HT2A / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D044403:Receptor, Serotonin, 5-HT2B / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D044405:Receptor, Serotonin, 5-HT2C / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020127:Recovery of Function / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000378:metabolism; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D013119:Spinal Cord Injuries / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013904:Thoracic Vertebrae; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D044402:Receptor, Serotonin, 5-HT2A; D044403:Receptor, Serotonin, 5-HT2B; D044405:Receptor, Serotonin, 5-HT2C; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D011814:Quipazine