title: Nicotine exposure beginning in adolescence enhances the acquisition of methamphetamine self-administration, but not methamphetamine-primed reinstatement in male rats.
abstract: BACKGROUND
  Nicotine is commonly abused in adolescence and is believed to be a "gateway" to other drugs of abuse [e.g., methamphetamine (METH)]. The relationship between early nicotine exposure and later METH use is complicated because the majority of juvenile smokers continue to use cigarettes into adulthood. Thus, the present investigation examined the individual and combined contribution of adolescent and adult nicotine exposure on METH self-administration.
  
  
  METHODS
  Forty-three male rats were pretreated with saline or nicotine (0.16 or 0.64 mg/kg, SC) from postnatal day (PD) 35-50. On PD 51, subjects were split into the following groups: SAL-SAL, 0.16-0.16, 0.16-SAL, 0.64-0.64, and 0.64-SAL. Rats were then trained to lever press for METH (0.05 mg/kg) for seven days on an FR1 and seven days on an FR3 reinforcement schedule. After acquisition training, rats underwent 14 days of extinction and were then tested for METH-induced primed reinstatement (1.0mg/kg, IP).
  
  
  RESULTS
  Data showed that rats receiving continuous injections of the low dose of nicotine (0.16-0.16) obtained more METH infusions versus the control group (SAL-SAL) on an FR1 and FR3 schedule. In addition, rats on the FR3 schedule that received a low dose of nicotine during the adolescent period only (0.16-SAL) had more METH intake than the control group (SAL-SAL). Interestingly, the high dose of nicotine exposure had no effect on METH intake and neither nicotine dose altered METH seeking behavior.
  
  
  CONCLUSIONS
  Low dose exposure to nicotine during adolescence enhances the reinforcing effects of METH, while heavier exposure has no effect on METH intake.
authors.affiliation: Department of Psychology, California State University, San Bernardino, 5500 University Parkway, San Bernardino, CA 92407, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Pipkin
authors.affiliation: Department of Psychology, California State University, San Bernardino, 5500 University Parkway, San Bernardino, CA 92407, USA.
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Kaplan
authors.affiliation: Department of Psychology, California State University, San Bernardino, 5500 University Parkway, San Bernardino, CA 92407, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Plant
authors.affiliation: Department of Psychology, California State University, San Bernardino, 5500 University Parkway, San Bernardino, CA 92407, USA.
authors.forename: Shannon E
authors.initials: SE
authors.lastname: Eaton
authors.affiliation: Department of Psychology, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, CA 90840, USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Gil
authors.affiliation: Department of Psychology, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, CA 90840, USA.
authors.forename: Arturo R
authors.initials: AR
authors.lastname: Zavala
authors.affiliation: Department of Psychology, California State University, San Bernardino, 5500 University Parkway, San Bernardino, CA 92407, USA. Electronic address: ccrawfor@csusb.edu.
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Crawford
mesh_terms: D000818:Animals; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D003216:Conditioning, Operant / Q000187:drug effects*; D005108:Extinction, Psychological / Q000187:drug effects; D008297:Male; D008694:Methamphetamine / Q000008:administration & dosage*; D009538:Nicotine / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012055:Reinforcement Schedule; D012646:Self Administration
chemical_list: D000697:Central Nervous System Stimulants; D008694:Methamphetamine; D009538:Nicotine
keywords: Adolescence; Methamphetamine; Nicotine; Self-administration