title: The effect of chronic phenytoin administration on single prolonged stress induced extinction retention deficits and glucocorticoid upregulation in the rat medial prefrontal cortex.
abstract: BACKGROUND
  Post-traumatic stress disorder (PTSD) is a chronic, debilitating disorder. Only two pharmacological agents are approved for PTSD treatment, and they often do not address the full range of symptoms nor are they equally effective in all cases. Animal models of PTSD are critical for understanding the neurobiology involved and for identification of novel therapeutic targets. Using the rodent PTSD model, single prolonged stress (SPS), we have implicated aberrant excitatory neural transmission and glucocorticoid receptor (GR) upregulation in the medial prefrontal cortex (mPFC) and hippocampus (HPC) in fear memory abnormalities associated with PTSD.
  
  
  OBJECTIVE
  The objective of this study is to examine the potential protective effect of antiepileptic phenytoin (PHE) administration on SPS-induced extinction retention deficits and GR expression.
  
  
  METHODS
  Forty-eight SPS-treated male Sprague Dawley rats or controls were administered PHE (40, 20 mg/kg, vehicle) for 7 days following SPS stressors; then, fear conditioning, extinction, and extinction retention were tested.
  
  
  RESULTS
  Fear conditioning and extinction were unaffected by SPS or PHE, but SPS impaired extinction retention, and both doses of PHE rescued this impairment. Similarly, SPS increased GR expression in the mPFC and dorsal HPC, and PHE prevented SPS-induced GR upregulation in the mPFC.
  
  
  CONCLUSIONS
  These data demonstrate that PHE administration can prevent the development of extinction retention deficits and upregulation of GR. PHE exerts inhibitory effects on voltage-gated sodium channels and decreases excitatory neural transmission via glutamate antagonism. If glutamate hyperactivity in the days following SPS contributes to SPS-induced deficits, then these data may suggest that the glutamatergic system constitutes a target for secondary prevention.
authors.affiliation: Department of Psychiatry, University of Michigan, 4250 Plymouth Road, Ann Arbor, MI, 48109, USA, alicegeo@med.umich.edu.
authors.forename: Sophie A
authors.initials: SA
authors.lastname: George
authors.forename: Mariana
authors.initials: M
authors.lastname: Rodriguez-Santiago
authors.forename: John
authors.initials: J
authors.lastname: Riley
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Rodriguez
authors.forename: Israel
authors.initials: I
authors.lastname: Liberzon
mesh_terms: D000818:Animals; D005108:Extinction, Psychological / Q000187:drug effects / Q000502:physiology*; D005239:Fear / Q000187:drug effects / Q000502:physiology / Q000523:psychology; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology; D010672:Phenytoin / Q000008:administration & dosage*; D017397:Prefrontal Cortex / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D013315:Stress, Psychological / Q000378:metabolism* / Q000517:prevention & control / Q000523:psychology; D016896:Treatment Outcome; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*
chemical_list: D011965:Receptors, Glucocorticoid; D010672:Phenytoin