title: Mecamylamine elicits withdrawal-like signs in rats following a single dose of nicotine.
abstract: BACKGROUND
  The ability of nicotine to induce dependence (result in a withdrawal syndrome) is typically thought to require long-term, daily smoking. Emerging evidence suggests that symptoms of nicotine withdrawal may occur following only a few cigarettes. Whether acute exposure to nicotine can induce dependence in animals has not been well established.
  
  
  OBJECTIVE
  The objective of this paper is to examine whether the nicotinic acetylcholine receptor antagonist mecamylamine elicits withdrawal-like signs in rats following acute nicotine exposure.
  
  
  RESULTS
  Mecamylamine (3.0 mg/kg, s.c.) administered ≈2 h after a single dose of nicotine (0.5 mg/kg, s.c.) elicited increases in intracranial self-stimulation (ICSS) thresholds and somatic signs, two well-established effects of withdrawal from long-term (chronic) nicotine exposure. The magnitude of these effects remained constant across five daily test sessions. A lower dose of mecamylamine (1.5 mg/kg, s.c.) had little or no effect on ICSS thresholds or somatic signs following acute nicotine exposure, but precipitated robust increases in these measures during a chronic nicotine infusion. Finally, rats exhibited a small increase in ICSS thresholds over time following a single nicotine injection (0.5 mg/kg, s.c.), possibly reflecting a modest spontaneous withdrawal-like effect.
  
  
  CONCLUSIONS
  Mecamylamine elicited withdrawal-like signs in rats following a single dose of nicotine. The different effects of mecamylamine 1.5 mg/kg following acute versus chronic nicotine exposure supports the notion that these models simulate the early and more advanced stages of nicotine dependence, respectively. While further optimization and validation of these models is necessary, they may provide a novel approach for studying the earliest stages of nicotine dependence.
authors.affiliation: Minneapolis Medical Research Foundation, 914 South 8th St. S-3 Labs, 860, Minneapolis, MN 55404, USA. harr0547@umn.edu
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Harris
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Manbeck
authors.forename: Clare E
authors.initials: CE
authors.lastname: Schmidt
authors.forename: David
authors.initials: D
authors.lastname: Shelley
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D007279:Injections, Subcutaneous; D008297:Male; D008464:Mecamylamine / Q000008:administration & dosage / 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*; D051381:Rats; D017208:Rats, Wistar; D012653:Self Stimulation / Q000187:drug effects; D013375:Substance Withdrawal Syndrome / Q000209:etiology; D014029:Tobacco Use Disorder / Q000503:physiopathology
chemical_list: D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D008464:Mecamylamine; D009538:Nicotine