The effects of social contact on cocaine intake in female rats

Abstract

Background Studies conducted in male rats report that social contact can either facilitate or inhibit drug intake depending on the behavior of social partners. The purpose of the present study was to: (1) examine the effects of social contact on cocaine intake in female rats, (2) examine the behavioral mechanisms by which social contact influences cocaine intake, and (3) examine whether the estrous cycle moderates the effects of social contact on cocaine intake. Methods Female rats were assigned to either isolated or pair-housed conditions in which a social partner either had access to cocaine (cocaine partner) or did not have access to cocaine (abstinent partner). Pair-housed rats were tested in custom-built operant conditioning chambers that allowed both rats to be tested simultaneously in the same chamber. Results Rats housed with a cocaine partner self-administered more cocaine than isolated rats and rats housed with an abstinent partner. A behavioral economic analysis indicated that these differences were driven by a greater intensity of cocaine demand (i.e., greater intake at lower unit prices) in rats housed with a cocaine partner. Multivariate modeling revealed that the estrous cycle did not moderate the effects of social contact on cocaine intake. Conclusions These findings indicate that: (1) social contact influences cocaine self-administration in females in a manner similar to that reported in males, (2) these effects are due to differences in the effects of social contact on the intensity of cocaine demand, and (3) these effects are consistent across all phases of the estrous cycle.

Considering the context: social factors in responses to drugs in humans

“…How do various social contexts (e.g., strangers vs. friends or romantic partners) differentially influence drug effects (see Fairbairn, 2017)? To what extent are the findings with humans consistent with data from studies with laboratory animals, where there is also strong evidence for social factors in self-administration (e.g., Robinson et al, 2017)? Finally, there are critical questions about the neurobiological mechanisms that underlie the context-drug interactions, including questions about overlapping neurobiological pathways supporting both psychosocial function and drug use.…”

Drug-taking in a socio-sexual context enhances vulnerability for addiction in male rats

“…In addition, effects of social contact during drug taking behavior have been demonstrated. Specifically, cocaine selfadministration is enhanced in socially housed male or female rats if both members of the same-sex pair have simultaneous access to the drug in the same chamber using modified operant conditioning chambers, and in comparison to either socially isolated animals or socially housed animals that were paired with a drug abstinent partner [38][39][40]. The current study thus further extends these previous findings and provides a unique perspective in that it models the initial voluntary recreational drug taking in a sociosexual context with a sexual partner that was not part of the housing conditions.…”

Social Contact Reinforces Cocaine Self-Administration in Young Adult Male Rats: The Role of Social Reinforcement in Vulnerability to Drug Use

“…Social partners did not have access to either response levers or intravenous cocaine, thus limiting their ability to increase the salience of any component of the lever-press/cocaine infusion contingency. Social facilitation or reinforcement enhancement represent two potential explanations for these findings, but multiple studies report the presence of a non-intoxicated social partner reliably decreases drug intake across a range of experimental conditions (Smith, 2012;Peitz et al, 2013;Smith et al, 2014;Robinson et al, 2016Robinson et al, , 2017Venniro et al, 2018Venniro et al, , 2019Venniro et al, , 2021. The experimental design of the present study specified that social contact was contingent on pressing a response lever and self-administering cocaine; consequently, social reinforcement reflects the most parsimonious explanation for the observed findings, especially after other explanations are ruled out.…”

“…Recently, several studies have described the use of modified operant conditioning chambers that permit one or more animals to intravenously self-administer drugs in proximity to a social partner, which has rapidly advanced our understanding of how social contact can increase or decrease drug intake. For instance, these studies have shown that drug intake is increased in the presence of a partner self-administering drugs (Smith, 2012;Smith et al, 2014;Robinson et al, 2016Robinson et al, , 2017, drug intake is decreased in the presence of a partner without access to drugs (Smith, 2012;Smith et al, 2014;Peitz et al, 2013;Robinson et al, 2016Robinson et al, , 2017, patterns of drug intake between partners become more similar over time (Lacy et al, 2014), and subjects will maintain voluntary abstinence when given a choice between drugs and access to a social partner (Venniro et al, 2018(Venniro et al, , 2019(Venniro et al, , 2021. Importantly, social contact serves as a positive reinforcer in laboratory animals, and contingent access to a social partner can establish responding in experimentally naïve rats (Angermeier, 1960) and maintain rates of responding similar to those of consummatory reinforcers (e.g., food; Evans et al, 1994).…”