title: Sex differences in escalation of methamphetamine self-administration: cognitive and motivational consequences in rats.
abstract: BACKGROUND
  Male rats escalate methamphetamine (meth) intake during long-access meth self-administration, show enhanced reinstatement of meth-seeking, and exhibit meth-induced memory impairments. However, the impact of long-access daily meth self-administration on reinstatement and cognitive dysfunction has not been assessed in females, even though clinical studies on meth addiction have shown differences between men and women.
  
  
  OBJECTIVE
  This study determined whether male and freely cycling female rats: (1) escalate meth intake in a 6-h daily-access period relative to 1-h access; (2) show different sensitivity to meth primed reinstatement after short- and long-access conditions; and (3) show deficits in novel object and object in place recognition memory.
  
  
  METHODS
  Male and female Long-Evans rats self-administered meth in limited (1-h/day) or extended (6-h/day) daily access sessions. After 21 days, meth access was discontinued, and rats entered an abstinence period. On the seventh and 14th days of abstinence, rats were assessed for recognition memory using tests for: (a) novel object recognition memory and (b) object-in-place memory. Rats were tested for reinstatement of meth-seeking following extinction of responding.
  
  
  RESULTS
  Female rats self-administered more meth and escalated intake faster than males during extended, but not limited, daily access. Both males and females in the extended, but not limited, access groups showed memory deficits on both tasks. Female rats showed greater reinstatement to meth-seeking with lower doses of meth priming injections than males.
  
  
  CONCLUSIONS
  Relative to males, females were equally susceptible to meth-induced memory deficits but exhibited higher meth intake and greater relapse to meth-seeking.
authors.affiliation: Department of Neurosciences, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA. reichel@musc.edu
authors.forename: Carmela M
authors.initials: CM
authors.lastname: Reichel
authors.forename: Clifford H
authors.initials: CH
authors.lastname: Chan
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Ghee
authors.forename: Ronald E
authors.initials: RE
authors.lastname: See
mesh_terms: D000818:Animals; D003072:Cognition Disorders / Q000139:chemically induced*; D003216:Conditioning, Operant; D058999:Drug-Seeking Behavior; D005260:Female; D008297:Male; D008569:Memory Disorders / Q000139:chemically induced*; D008694:Methamphetamine / Q000008:administration & dosage* / Q000009:adverse effects; D009042:Motivation; D051381:Rats; D020318:Rats, Long-Evans; D021641:Recognition, Psychology / Q000187:drug effects; D012646:Self Administration; D012737:Sex Factors; D013997:Time Factors
chemical_list: D008694:Methamphetamine