title: The effects of sex, estrous cycle, and social contact on cocaine and heroin self-administration in rats.
abstract: Preclinical studies indicate that gonadal hormones are important determinants of drug self-administration. To date, little is known about the influence of sex and estrous cycle on drug self-administration in ecologically relevant social contexts.
  
  
  
  The objective of this study was to examine the role of sex and estrous cycle in a rat model during cocaine and heroin self-administration with male-female and female-female social dyads.
  
  
  
  Male and female virgin rats were trained to self-administer cocaine and heroin in operant conditioning chambers that permitted two rats to self-administer concurrently, but prevented physical contact. Experiment 1 examined cocaine self-administration on a progressive ratio schedule in male-female dyads. Experiments 2 and 3 examined heroin self-administration on a fixed ratio schedule in male-female dyads at constant and varying doses, respectively. Experiment 4 examined heroin self-administration in female-female dyads on a fixed ratio schedule.
  
  
  
  Cocaine-maintained breakpoints increased by ∼17 % in females during estrus, but remained consistent in males. Heroin self-administration decreased by ∼70 % during proestrus in females whether they were isolated, housed with males, or housed with females. Heroin self-administration was lower in males than females under some conditions and was not consistently associated with the responding of females.
  
  
  
  Cocaine and heroin self-administration is influenced by the estrous cycle in females when in the presence of a male partner. As a novel finding, these data illustrate that heroin self-administration is reduced in females during proestrus regardless of the social context tested. Finally, these data suggest that drug self-administration in males is only minimally influenced by the hormonal status of a female partner.
authors.affiliation: Department of Psychology, Franklin and Marshall College, Lancaster, PA, 17603, USA.|Department of Psychology, Davidson College, Campus Box 7136, Davidson, NC, 28035-7037, USA.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Lacy
authors.affiliation: Department of Psychology, University of Kentucky, Lexington, KY, 40506, USA.
authors.forename: Justin C
authors.initials: JC
authors.lastname: Strickland
authors.affiliation: Program in Neuroscience, Davidson College, Davidson, 28035, USA.
authors.forename: Max A
authors.initials: MA
authors.lastname: Feinstein
authors.affiliation: Department of Psychology, Davidson College, Campus Box 7136, Davidson, NC, 28035-7037, USA.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Robinson
authors.affiliation: Department of Psychology, Davidson College, Campus Box 7136, Davidson, NC, 28035-7037, USA. masmith@davidson.edu.|Program in Neuroscience, Davidson College, Davidson, 28035, USA. masmith@davidson.edu.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Smith
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D003042:Cocaine / Q000008:administration & dosage*; D003216:Conditioning, Operant; D018765:Dopamine Uptake Inhibitors / Q000008:administration & dosage*; D030762:Estrous Cycle; D004971:Estrus; D005260:Female; D003932:Heroin / Q000008:administration & dosage*; D008297:Male; D051381:Rats; D012646:Self Administration; D012737:Sex Factors; D012919:Social Behavior
chemical_list: D018765:Dopamine Uptake Inhibitors; D003932:Heroin; D003042:Cocaine
keywords: Cocaine; Estrous; Heroin; Self-administration; Sex; Social