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Raymond JS, Rehn S, James MH, Everett NA, Bowen MT. Sex differences in the social motivation of rats: Insights from social operant conditioning, behavioural economics, and video tracking. Biol Sex Differ 2024; 15:57. [PMID: 39030614 DOI: 10.1186/s13293-024-00612-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Accepted: 04/09/2024] [Indexed: 07/21/2024] Open
Abstract
BACKGROUND Social behaviour plays a key role in mental health and wellbeing, and developing greater understanding of mechanisms underlying social interaction-particularly social motivation-holds substantial transdiagnostic impact. Common rodent behavioural assays used to assess social behaviour are limited in their assessment of social motivation, whereas the social operant conditioning model can provide unique and valuable insights into social motivation. Further characterisation of common experimental parameters that may influence social motivation within the social operant model, as well as complementary methodological and analytical approaches, are warranted. METHODS This study investigated the effects of biological sex, housing condition, and time-of-day, on social motivation using the social operant model. This involved training rats to lever press (FR1) for 60-s access to a social reward (same-sex conspecific stimulus). Subjects were male and female Wistar rats, housed under individual or paired conditions, and sessions were conducted either in the mid-late light phase (ZT6-10) or early-mid dark phase (ZT13-17). A behavioural economics approach was implemented to measure social demand and the influence of stimulus partner sex (same- vs. opposite-sex stimulus) on social operant responding. Additionally, video tracking analyses were conducted to assess the degree of convergence between social appetitive and consummatory behaviours. RESULTS Biological sex, housing conditions, the interaction between sex and housing, and stimulus partner sex potently influenced social motivation, whereas time-of-day did not. Behavioural economics demonstrated that sex, housing, and their interaction influence both the hedonic set-point and elasticity of social demand. Video analysis of social interaction during social operant sessions revealed that social appetitive and consummatory behaviours are not necessarily convergent, and indicate potential social satiety. Lastly, oestrus phase of female experimental and stimulus rats did not impact social motivation within the model. CONCLUSIONS Social isolation-dependent sex differences exist in social motivation for rats, as assessed by social operant conditioning. The social operant model represents an optimal preclinical assay that comprehensively evaluates social motivation and offers a platform for future investigations of neurobiological mechanisms underlying sex differences in social motivation. These findings highlight the importance of continued consideration and inclusion of sex as a biological variable in future social operant conditioning studies. Humans are social creatures-our everyday interactions with others and the support this provides play a key role in our wellbeing. For those experiencing mental health conditions, people's motivation to engage with others can wane, which can lead them to withdraw from those who support them. Therefore, to develop better treatment strategies for these conditions, we need to gain a deeper understanding of social motivation. Studying social behaviour in animals can facilitate this investigation of social motivation as it allows for a causal understanding of underlying neurobiology that is not possible in human experiments. An optimal way to study social motivation in animals is using the social operant conditioning model, where rats learn to press a lever that opens a door and allows them to interact with another rat for a short time. This study characterised the social operant model by testing whether sex, housing conditions, time-of-day, and the sex of the stimulus partner influence rats' motivation to seek interaction with another rat. We found that female rats were more socially motivated than males, and that rats living alone were more motivated than those living with another rat; interestingly, this effect of housing affected females more than males. Regardless of sex, rats were more motivated to interact with a rat of the opposite sex. These findings provide insights into sex differences in social motivation in rats and new insights into the social operant model which will help guide future research into social motivation and other mental health conditions.
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Affiliation(s)
- Joel S Raymond
- School of Psychology, Faculty of Science, The University of Sydney, Sydney, NSW, Australia
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, 2050, Sydney, NSW, Australia
| | - Simone Rehn
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW, Australia
| | - Morgan H James
- Brain Health Institute, Rutgers Biomedical and Health Sciences, Rutgers University, Piscataway, NJ, USA
- Department of Psychiatry, Robert Wood Johnson Medical School, Rutgers Biomedical Health Sciences, Rutgers University, Piscataway, NJ, USA
| | - Nicholas A Everett
- School of Psychology, Faculty of Science, The University of Sydney, Sydney, NSW, Australia
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, 2050, Sydney, NSW, Australia
| | - Michael T Bowen
- School of Psychology, Faculty of Science, The University of Sydney, Sydney, NSW, Australia.
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, 2050, Sydney, NSW, Australia.
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Smith MA, Armas SP, Camp JD, Carlson HN. The positive reinforcing effects of cocaine and opposite-sex social contact: roles of biological sex and estrus. Psychopharmacology (Berl) 2024:10.1007/s00213-024-06648-z. [PMID: 38992255 DOI: 10.1007/s00213-024-06648-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 07/03/2024] [Indexed: 07/13/2024]
Abstract
RATIONALE Preclinical studies report that drug use and social contact mutually influence the reinforcing effects of one another. Most of these studies have used same-sex dyads exclusively, and the role of factors related to biological sex and hormonal fluctuations are not well understood. OBJECTIVES The purpose of this study was to examine the reinforcing effects of cocaine and social contact with an opposite-sex partner in male and female rats, and how these effects are modulated by ovarian hormones. METHODS Male and female rats were trained in a nonexclusive choice procedure in which cocaine and social contact with an opposite-sex partner were simultaneously available on concurrent progressive ratio schedules of reinforcement. To examine the effects of ovarian hormones related to estrous cycling, Experiment 1 used naturally cycling, gonadally intact females, whereas Experiment 2 used ovariectomized females, and estrus was artificially induced with exogenous hormones. RESULTS In both experiments, cocaine and social contact functioned as robust reinforcers, and there were no significant effects of biological sex or estrus status of the females. The positive reinforcing effects of both cocaine and social contact increased as a function of cocaine dose, indicating that contingent cocaine administration increases the reinforcing effects of social contact. CONCLUSIONS These data suggest that cocaine use among opposite-sex partners may enhance factors that contribute to social bonding.
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Affiliation(s)
- Mark A Smith
- Department of Psychology and Program in Neuroscience, Davidson College, 209 Ridge Road, PO Box 5000, Davidson, NC, 28035, USA.
| | - Samantha P Armas
- Department of Psychology and Program in Neuroscience, Davidson College, 209 Ridge Road, PO Box 5000, Davidson, NC, 28035, USA
| | - Jacob D Camp
- Department of Psychology and Program in Neuroscience, Davidson College, 209 Ridge Road, PO Box 5000, Davidson, NC, 28035, USA
| | - Hannah N Carlson
- Department of Psychology and Program in Neuroscience, Davidson College, 209 Ridge Road, PO Box 5000, Davidson, NC, 28035, USA
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Beasley MM, Amantini S, Gunawan T, Silberberg A, Kearns DN. Cocaine and heroin interact differently with nondrug reinforcers in a choice situation. Exp Clin Psychopharmacol 2024; 32:158-172. [PMID: 37535523 PMCID: PMC10837314 DOI: 10.1037/pha0000674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
The present study used a rat choice model to test how cocaine or heroin economically interacted with two different nondrug reinforcers along the substitute-to-complement continuum. In Experiment 1, the nondrug alternative was the negative reinforcer timeout-from-avoidance (TOA)-that is, rats could press a lever to obtain a period of safety from footshock. One group of rats chose between cocaine and TOA and another group chose between heroin and TOA. The relative prices of the reinforcers were manipulated across phases while controlling for potential income effects. When cocaine was the reinforcer, rats reacted to price changes by increasing their allocation of behavior to the more expensive option, thereby maintaining relatively proportional intake of cocaine and TOA reinforcers across prices, suggesting these reinforcers were complements here. In contrast, when heroin became relatively cheap, rats increased allocation of income to heroin and decreased allocation of income to TOA, suggesting that heroin substituted for safety. Additionally, rats were willing to accept more footshocks when heroin was easily available. In Experiment 2, the nondrug alternative was saccharin, a positive reinforcer. Heroin and saccharin were complements, but there was no consistent effect of price changes on the allocation of behavior between cocaine and saccharin. As a model of the processes that could be involved in human drug use, these results show that drug-taking behavior depends on the type of drug, the type of nondrug alternative available, and the prices of both. (PsycInfo Database Record (c) 2024 APA, all rights reserved).
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Affiliation(s)
| | - Sarah Amantini
- Psychology Department, American University, Washington, DC
| | - Tommy Gunawan
- Human Psychopharmacology Laboratory, NIAAA/NIH, Bethesda, MD
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Chow JJ, Pitts KM, Schoenbaum A, Costa KM, Schoenbaum G, Shaham Y. Different Effects of Peer Sex on Operant Responding for Social Interaction and Striatal Dopamine Activity. J Neurosci 2024; 44:e1887232024. [PMID: 38346894 PMCID: PMC10919252 DOI: 10.1523/jneurosci.1887-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 01/05/2024] [Accepted: 01/08/2024] [Indexed: 03/08/2024] Open
Abstract
When rats are given discrete choices between social interactions with a peer and opioid or psychostimulant drugs, they choose social interaction, even after extensive drug self-administration experience. Studies show that like drug and nondrug food reinforcers, social interaction is an operant reinforcer and induces dopamine release. However, these studies were conducted with same-sex peers. We examined if peer sex influences operant social interaction and the role of estrous cycle and striatal dopamine in same- versus opposite-sex social interaction. We trained male and female rats (n = 13 responders/12 peers) to lever-press (fixed-ratio 1 [FR1] schedule) for 15 s access to a same- or opposite-sex peer for 16 d (8 d/sex) while tracking females' estrous cycle. Next, we transfected GRAB-DA2m and implanted optic fibers into nucleus accumbens (NAc) core and dorsomedial striatum (DMS). We then retrained the rats for 15 s social interaction (FR1 schedule) for 16 d (8 d/sex) and recorded striatal dopamine during operant responding for a peer for 8 d (4 d/sex). Finally, we assessed economic demand by manipulating FR requirements for a peer (10 d/sex). In male, but not female rats, operant responding was higher for the opposite-sex peer. Female's estrous cycle fluctuations had no effect on operant social interaction. Striatal dopamine signals for operant social interaction were dependent on the peer's sex and striatal region (NAc core vs DMS). Results indicate that estrous cycle fluctuations did not influence operant social interaction and that NAc core and DMS dopamine activity reflect sex-dependent features of volitional social interaction.
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Affiliation(s)
- Jonathan J Chow
- Intramural Research Program, NIDA, NIH, Baltimore, Maryland 21230
| | - Kayla M Pitts
- Intramural Research Program, NIDA, NIH, Baltimore, Maryland 21230
| | - Ansel Schoenbaum
- Intramural Research Program, NIDA, NIH, Baltimore, Maryland 21230
| | - Kauê M Costa
- Intramural Research Program, NIDA, NIH, Baltimore, Maryland 21230
| | | | - Yavin Shaham
- Intramural Research Program, NIDA, NIH, Baltimore, Maryland 21230
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Smith M, Kirkpatrick MG, Gipson CD. The role of social variables in drug use and addiction. Pharmacol Biochem Behav 2023; 232:173656. [PMID: 37802394 DOI: 10.1016/j.pbb.2023.173656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Affiliation(s)
- Mark Smith
- Department of Psychology and Program in Neuroscience, Davidson College, Davidson, NC, USA.
| | - Matthew G Kirkpatrick
- Department of Population and Public Health Sciences, Department of Psychology, University of Southern California, CA, USA
| | - Cassandra D Gipson
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
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Strickland JC, Acuff SF. Role of social context in addiction etiology and recovery. Pharmacol Biochem Behav 2023; 229:173603. [PMID: 37487953 PMCID: PMC10528354 DOI: 10.1016/j.pbb.2023.173603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 06/07/2023] [Accepted: 07/17/2023] [Indexed: 07/26/2023]
Abstract
While social context has long been considered central to substance use disorder prevention and treatment and many drug-taking events occur in social settings, experimental research on social context has historically been limited. Recent years have seen an emergence of concerted preclinical and human laboratory research documenting the direct impact of social context on substance use, delineating behavioral and neurobiological mechanisms underlying social influence's role. We review this emerging preclinical and human laboratory literature from a theoretical lens that considers distinct stages of the addiction process including drug initiation/acquisition, escalation, and recovery. A key conclusion of existing research is that the impact of the social environment is critically moderated by the drug-taking behavior and drug use history of a social peer. Specifically, while drug-free social contexts can reduce the likelihood of drug use initiation and act as a competitive non-drug alternative preventing escalation, drug-using peers can equally facilitate initiation and escalation through peer modeling as a contingent reward of use. Likewise, social context may facilitate recovery or serve as a barrier that increases the chances of a return to regular use. We conclude by discussing evidence-based treatments and recovery support services that explicitly target social mechanisms or that have identified social context as a mechanism of change within treatment. Ultimately, new areas for research including the expansion of drug classes studied and novel human laboratory designs are needed to further translate emerging findings into clinical practice.
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Affiliation(s)
- Justin C Strickland
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, 5510 Nathan Shock Drive, Baltimore, MD 21224, USA.
| | - Samuel F Acuff
- Department of Psychology, The University of Memphis, 202 Psychology Building, Memphis, TN 38152, USA; Recovery Research Institute, Massachusetts General Hospital and Harvard Medical School, 152 Merrimac St, Boston MA, 02135 USA
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Schulingkamp R, Wan H, Hackenberg TD. Social familiarity and reinforcement value: a behavioral-economic analysis of demand for social interaction with cagemate and non-cagemate female rats. Front Psychol 2023; 14:1158365. [PMID: 37251070 PMCID: PMC10213623 DOI: 10.3389/fpsyg.2023.1158365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 04/21/2023] [Indexed: 05/31/2023] Open
Abstract
Rats were studied in social reinforcement procedures in which lever presses opened a door separating two adjacent spaces, permitting access to social interaction with a partner rat. The number of lever presses required for social interaction was systematically increased across blocks of sessions according to fixed-ratio schedules, generating demand functions at three different social reinforcement durations: 10 s, 30 s, and 60 s. The social partner rats were cagemates in one phase, and non-cagemates in a second phase. The rate at which social interactions were produced declined with the fixed-ratio price, and was well described by an exponential model that has been successfully employed with a range of social and non-social reinforcers. None of the main parameters of the model varied systematically with social interaction duration or with the social familiarity of the partner rat. On the whole, the results provide further evidence of the reinforcing value of social interaction, and its functional parallels with non-social reinforcers.
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Affiliation(s)
| | - Haoran Wan
- Department of Psychology, Reed College, Portland, OR, United States
- Department of Psychological and Brain Sciences, Washington University in St. Louis, St. Louis, MO, United States
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