title: The small GTPase RhoA, but not Rac1, is essential for conditioned aversive memory formation through regulation of actin rearrangements in rat dorsal hippocampus.
abstract: OBJECTIVE
  Actin rearrangements are induced in the dorsal hippocampus after conditioned morphine withdrawal, and involved in the formation of conditioned place aversion. In the present study, we investigated the mechanisms underlying the actin rearrangements in rat dorsal hippocampus induced by conditioned morphine withdrawal.
  
  
  METHODS
  The RhoA-ROCK pathway inhibitor Y27632 (8.56 μg/1 μL per side) or the Rac1 inhibitor NSC23766 (25 μg/1 μL per side) was microinjected into the dorsal hippocampus of rats. Conditioned place aversion (CPA) induced by naloxone-precipitated morphine withdrawal was assessed. Crude synaptosomal fraction of hippocampus was prepared, and the amount of F-actin and G-actin was measured with an Actin Polymerization Assay Kit.
  
  
  RESULTS
  Conditioned morphine withdrawal significantly increased actin polymerization in the dorsal hippocampus at 1 h following the naloxone injection. Preconditioning with microinjection of Y27632, but not NSC23766, attenuated CPA, and blocked the increase in actin polymerization in the dorsal hippocampus.
  
  
  CONCLUSIONS
  Our results suggest that the small GTPase RhoA, but not Rac1, in the dorsal hippocampus is responsible for CPA formation, mainly through its regulation of actin rearrangements.
authors.affiliation: Biotechnology Center, School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Yu-hua
authors.initials: YH
authors.lastname: Wang
authors.forename: Yuan-yuan
authors.initials: YY
authors.lastname: Hou
authors.forename: Tao
authors.initials: T
authors.lastname: Xi
authors.forename: Yao
authors.initials: Y
authors.lastname: Liu
authors.forename: Jing-gen
authors.initials: JG
authors.lastname: Liu
mesh_terms: D000199:Actins / Q000378:metabolism*; D000577:Amides / Q000494:pharmacology; D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D001362:Avoidance Learning / Q000502:physiology; D006624:Hippocampus / Q000378:metabolism; D008297:Male; D008568:Memory / Q000502:physiology; D008845:Microinjections; D009020:Morphine / Q000008:administration & dosage*; D009270:Naloxone / Q000494:pharmacology; D058105:Polymerization / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013375:Substance Withdrawal Syndrome / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; D000577:Amides; D000634:Aminoquinolines; C487513:NSC 23766; D011725:Pyridines; D011743:Pyrimidines; C108830:Y 27632; D009270:Naloxone; D009020:Morphine; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein
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