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Psychopharmacology

, Volume 152, Issue 2, pp 132–139 | Cite as

Effects of sex and the estrous cycle on regulation of intravenously self-administered cocaine in rats

  • Wendy J. Lynch
  • Maria N. Arizzi
  • Marilyn E. Carroll
Original Investigation

Abstract.

Rationale: Previous research with both humans and animals suggests that there are sex differences in cocaine self-administration; in rodents, ovarian hormones may underlie these differences. Objectives: A two-lever drug self-administration procedure was used to compare regulation of intravenously self-administered cocaine in male and female rats and among females in different phases of the estrous cycle. Methods: Eleven female and seven male age-matched Wistar rats were trained to self-administer nine doses of cocaine (0.0–2.4 mg/kg) during daily 5-h sessions. Experimental test chambers were equipped with two levers and associated stimulus lights. A response on the lever with stimuli signaling an increase in cocaine dose increased the infusion duration by 3 s, and a response on the other lever decreased the infusion duration by 3 s. Results: After responding for cocaine stabilized, regulation was disrupted more in females than in males (r2=78.9, r2=92.6, respectively) with the greatest disruption observed in females during the estrus phase (r2=48.5). Mean dose size varied considerably for males and for females in the metestrus/diestrus and proestrus phases; however, estrus females responded almost exclusively on the lever associated with an increase in cocaine dose. Conclusions: These findings indicate sex differences in the regulation of cocaine self-administration, and they suggest that ovarian hormones may be responsible for the observed sex differences.

Cocaine Estrous cycle Intravenous regulation Self-administration Sex difference 

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Copyright information

© Springer-Verlag 2000

Authors and Affiliations

  • Wendy J. Lynch
    • 1
  • Maria N. Arizzi
    • 1
  • Marilyn E. Carroll
    • 1
  1. 1.Department of Psychiatry, Box 392, University of Minnesota, Minneapolis, MN 55455, USA

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