title: Reinforcement enhancing effect of nicotine and its attenuation by nicotinic antagonists in rats.
abstract: BACKGROUND
  Recent studies have demonstrated that nicotine can enhance operant responding for other nonpharmacological reinforcing stimuli. However, the nature of the reinforcement-enhancing effect of nicotine remains largely unknown.
  
  
  OBJECTIVE
  The present study determined the dose dependency of the ability of nicotine to increase lever-pressing responses maintained by a compound visual stimulus (VS) in rats and examined its sensitivity to pharmacological antagonism of nicotinic acetylcholine receptors (nAChRs).
  
  
  METHODS
  Male Sprague-Dawley rats were trained in daily 1-h sessions to lever press for delivery of a VS (1 s lever light on and 60 s house light off) on a fixed ratio 5 schedule. During these sessions, eight scheduled response-independent intravenous infusions of nicotine (total amount: 0, 0.06, 0.12, 0.24, 0.48 mg kg(-1) h(-1)) were delivered. In pharmacological tests, a nonselective nAChR antagonist mecamylamine, alpha4beta2-selective antagonist dihydro-beta-erythroidine (DHbetaE), and alpha7-selective antagonist methyllycaconitine (MLA) were administered in different groups of rats 30 min before the session.
  
  
  RESULTS
  The VS maintained a moderate level of lever-pressing responses and nicotine dose-dependently increased responses for the VS presentations. Preteatment of mecamylamine and DHbetaE but not MLA significantly attenuated the nicotine-enhanced responding. However, mecamylamine had no effect on responding for the VS in rats that received scheduled saline infusions.
  
  
  CONCLUSIONS
  These results demonstrate dose dependency of the reinforcement-enhancing effect of nicotine and suggest that activation of the alpha4beta2- but not alpha7-containing nAChRs may mediate this effect.
authors.affiliation: Department of Psychology, University of Pittsburgh, Pittsburgh, PA 15260, USA. xiuliu@pitt.edu
authors.forename: Xiu
authors.initials: X
authors.lastname: Liu
authors.forename: Matthew I
authors.initials: MI
authors.lastname: Palmatier
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Caggiula
authors.forename: Eric C
authors.initials: EC
authors.lastname: Donny
authors.forename: Alan F
authors.initials: AF
authors.lastname: Sved
mesh_terms: D000157:Aconitine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D004079:Dihydro-beta-Erythroidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007260:Infusion Pumps; D007262:Infusions, Intravenous; D007274:Injections, Intraperitoneal; D007279:Injections, Subcutaneous; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000008:administration & dosage / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D010775:Photic Stimulation / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000378:metabolism; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D014796:Visual Perception / Q000187:drug effects
chemical_list: D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011978:Receptors, Nicotinic; C403531:nicotinic receptor alpha4beta2; C054634:methyllycaconitine; D004079:Dihydro-beta-Erythroidine; D008464:Mecamylamine; D009538:Nicotine; D000157:Aconitine