title: Paired-housing selectively facilitates within-session extinction of avoidance behavior, and increases c-Fos expression in the medial prefrontal cortex, in anxiety vulnerable Wistar-Kyoto rats.
abstract: The perseveration of avoidance behavior, even in the absence of once threatening stimuli, is a key feature of anxiety and related psychiatric conditions. This phenomenon can be observed in the Wistar-Kyoto (WKY) rat which, in comparison to outbred controls, demonstrates impaired extinction of avoidance behavior. Also characteristic of the WKY rat is abnormalities of the neurocircuitry and neuroplasticity of the medial prefrontal cortex (mPFC). One means of reducing physiological responses to anxiety, and conditioned fear, in social species is the presence of a conspecific animal. The current study investigates whether or not pair-housed WKY rats would show facilitated extinction of avoidance in comparison to individual-housed WKY rats, and whether or not pair-housing influences mPFC activation during lever-press avoidance.
  
  
  
  Male WKY rats were assigned to individual-housed and pair-housed conditions. Rats were trained in lever-press avoidance. Each session of lever-press avoidance consisted of 20 trials, where pressing a lever in response to a warning tone prevented foot-shocks. Rats received 12 acquisition sessions over 4weeks; followed by 6 extinction sessions over 2weeks, where foot-shocks ceased to be delivered. Brains were harvested 90min after trials 1 and 10 of extinction sessions 1 and 6, and mPFC sections underwent c-Fos staining as a measure of activation.
  
  
  
  Pair-housed rats showed facilitated lever-press avoidance extinction rates, but the main cause for this overall difference was a selective facilitation of within-session extinction. Similar to individual-housed rats, pair-housed rats continued to avoid during trial 1 of extinction even when the avoidance responding had been significantly reduced by the end of the previous session. Pair-housed rats sacrificed on trial 1 showed greater c-Fos expression in the anterior cingulate cortex and prelimbic cortex subregions of the mPFC compared individual-housed rats sacrificed on trial 1.
  
  
  
  This data shows pair-housing to facilitate the extinction of avoidance, and to influence activity of the mPFC, in WKY rats. Despite this environmental manipulation, the pair-housed WKY rats continued to show avoidance responding on trial 1 of extinction sessions. This demonstrates that within-session extinction can be dissociated from between-session extinction-resistance in WKY rats. Furthermore, it suggests the individual-housing of WKY rats selectively slows within-session extinction, possibly by reducing neuronal activity of the mPFC during the testing situation.
authors.affiliation: Neurobehavioral Research Laboratory, VA New Jersey Health Care System, East Orange, NJ 07018, United States; Veterans Biomedical Research Institute, East Orange, NJ 07018, United States.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Smith
authors.affiliation: Neurobehavioral Research Laboratory, VA New Jersey Health Care System, East Orange, NJ 07018, United States; Department of Pharmacology, Physiology, & Neuroscience, Rutgers-New Jersey Medical School, Rutgers Biomedical and Health Sciences, Rutgers, The State University of New Jersey, Newark, NJ 07103, United States.
authors.forename: Kevin C H
authors.initials: KC
authors.lastname: Pang
authors.affiliation: Research Service, Syracuse VA Medical Center, Department of Veteran's Affairs, Syracuse, NY, 13210, United States; Department of Pharmacology, Physiology, & Neuroscience, Rutgers-New Jersey Medical School, Rutgers Biomedical and Health Sciences, Rutgers, The State University of New Jersey, Newark, NJ 07103, United States.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Servatius
authors.affiliation: Neurobehavioral Research Laboratory, VA New Jersey Health Care System, East Orange, NJ 07018, United States; Veterans Biomedical Research Institute, East Orange, NJ 07018, United States.
authors.forename: Xilu
authors.initials: X
authors.lastname: Jiao
authors.affiliation: Neurobehavioral Research Laboratory, VA New Jersey Health Care System, East Orange, NJ 07018, United States; Department of Pharmacology, Physiology, & Neuroscience, Rutgers-New Jersey Medical School, Rutgers Biomedical and Health Sciences, Rutgers, The State University of New Jersey, Newark, NJ 07103, United States.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Beck
mesh_terms: D000818:Animals; D001007:Anxiety / Q000378:metabolism* / Q000473:pathology; D001362:Avoidance Learning / Q000502:physiology*; D004597:Electroshock; D005108:Extinction, Psychological / Q000502:physiology*; D005528:Foot; D006799:Housing, Animal; D007150:Immunohistochemistry; D008297:Male; D009483:Neuropsychological Tests; D017397:Prefrontal Cortex / Q000378:metabolism* / Q000473:pathology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D011897:Random Allocation; D011921:Rats, Inbred WKY; D012919:Social Behavior
chemical_list: D016760:Proto-Oncogene Proteins c-fos
keywords: Anxiety; Avoidance learning; Medial prefrontal cortex; Social buffering; Wistar-Kyoto rat