title: Amplified reacquisition of nicotine self-administration in rats by repeated stress during abstinence.
abstract: BACKGROUND
  Quitting smoking is often very challenging, leading to frequent relapse. Exposure to acute and chronic stress during abstinence increases the likelihood of relapse to smoking. In rodents, stress acutely reinstates nicotine seeking after extinction of nicotine self-administration (SA). However, whether reacquisition of nicotine taking is amplified by chronic stress during abstinence from nicotine SA has not been determined in animals.
  
  
  OBJECTIVE
  We sought to determine effects of repeated restraint stress during abstinence on reacquisition of nicotine SA.
  
  
  METHODS
  Rats acquired nicotine SA (23 h/day) under a fixed-ratio (FR) 5 schedule of reinforcement, which was followed by an abstinence phase. Restraint (0, 2, and 4 times) was administered during abstinence. Animals reacquired nicotine SA, first under a progressive ratio (PR) schedule, beginning immediately after the final stress, followed by an FR5 schedule. In another experiment, reacquisition (FR5) began 24 h after the final stress. No PR testing was conducted.
  
  
  RESULTS
  Four restraint stress exposures during abstinence, but not only two, enhanced reacquisition of nicotine SA by increasing nicotine injections under a PR schedule beginning immediately after the final stress (p < 0.05) followed by increasing nicotine intake under an FR5 schedule (p < 0.05). This was observed even when the final stress and reacquisition trial were separated by 24 h. Moreover, repeated stress-induced nicotine taking during the behaviorally inactive phase (i.e., lights on) of the 24-h diurnal cycle.
  
  
  CONCLUSIONS
  Chronic (i.e., repeated) stress during abstinence promotes reacquisition of nicotine SA and affects diurnal pattern of nicotine intake.
authors.affiliation: Department of Pharmacology, University of Tennessee Health Science Center, 874 Union Ave., Memphis, TN, 38163, USA.
authors.forename: Guoliang
authors.initials: G
authors.lastname: Yu
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
authors.forename: Burt M
authors.initials: BM
authors.lastname: Sharp
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D003216:Conditioning, Operant / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D008297:Male; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012008:Recurrence; D012055:Reinforcement Schedule; D012149:Restraint, Physical; D012646:Self Administration; D016540:Smoking Cessation / Q000523:psychology*; D013315:Stress, Psychological / Q000517:prevention & control*; D013375:Substance Withdrawal Syndrome / Q000523:psychology*; D014029:Tobacco Use Disorder / Q000523:psychology*
chemical_list: D018722:Nicotinic Agonists; D009538:Nicotine