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Joel D, Smith CJ, Veenema AH. Beyond the binary: Characterizing the relationships between sex and neuropeptide receptor binding density measures in the rat brain. Horm Behav 2024; 159:105471. [PMID: 38128247 DOI: 10.1016/j.yhbeh.2023.105471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 10/30/2023] [Accepted: 12/09/2023] [Indexed: 12/23/2023]
Abstract
Sex differences exist in numerous parameters of the brain. Yet, sex-related factors are part of a large set of variables that interact to affect many aspects of brain structure and function. This raises questions regarding how to interpret findings of sex differences at the level of single brain measures and the brain as a whole. In the present study, we reanalyzed two datasets consisting of measures of oxytocin, vasopressin V1a, and mu opioid receptor binding densities in multiple brain regions in rats. At the level of single brain measures, we found that sex differences were rarely dimorphic and were largely persistent across estrous stage and parental status but not across age or context. At the level of aggregates of brain measures showing sex differences, we tested whether individual brains are 'mosaics' of female-typical and male-typical measures or are internally consistent, having either only female-typical or only male-typical measures. We found mosaicism for measures showing overlap between females and males. Mosaicism was higher a) with a larger number of measures, b) with smaller effect sizes of the sex difference in these measures, and c) in rats with more diverse life experiences. Together, these results highlight the limitations of the binary framework for interpreting sex effects on the brain and suggest two complementary pathways to studying the contribution of sex to brain function: (1) focusing on measures showing dimorphic and persistent sex differences and (2) exploring the relations between specific brain mosaics and specific endpoints.
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Affiliation(s)
- Daphna Joel
- School of Psychological Sciences and Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv, Israel.
| | - Caroline J Smith
- Department of Psychology and Neuroscience, Boston College, Chestnut Hill, MA, USA.
| | - Alexa H Veenema
- Neurobiology of Social Behavior Laboratory, Department of Psychology & Neuroscience Program, Michigan State University, East Lansing, USA.
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Olazábal DE, Pillay N, Sandberg N, Hartman KJ. Description and comparison of brain distribution of oxytocin receptors in Rhabdomys pumillio and Rhabdomys dilectus. Gen Comp Endocrinol 2023; 335:114224. [PMID: 36702289 DOI: 10.1016/j.ygcen.2023.114224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 01/20/2023] [Accepted: 01/21/2023] [Indexed: 01/25/2023]
Abstract
Oxytocin receptor (OXTR) distribution in the brain has been associated with different reproductive and social strategies of species. Rhabdomys pumilio (R. pumilio) and Rhabdomys dilectus (R. dilectus) are two sister rodent species that live in large/medium (but flexible) or small (mostly solitary) social groups respectively. In this study, we describe and compare the distribution of OXTR in these two species. OXTR binding in the brain of R. pumilio (8 females and 5 males) and R. dilectus (8 females and 5 males) adults was determined using autoradiography. Our results revealed significant differences in the nucleus accumbens, diagonal band, medial preoptic area, lateral habenula, superior colliculus, periaqueductal area and anterior paraventricular nucleus (higher in R. dilectus), and the dorsal lateral septum and anterior bed nucleus of the stria terminalis (higher in R. pumilio). OXTR density in other brain regions, such as the amygdala nuclei and hippocampus, did not differ between the two species. Sex differences were found in the medial preoptic area and ventral region of the lateral septum in R. pumilio (OXTR density higher in males) and in the anterior paraventricular thalamic nucleus, ventromedial nucleus of the hypothalamus and basolateral amygdala of R. dilectus (OXTR density higher in females). A sex difference in the density of OXTR was also found in the posterior region of the bed nucleus of the stria terminalis, where it was higher in males than in females of both species. This study shows species-specific brain distribution of OXTR in R. pumilio and R. dilectus that are unique, but with similarities with other polygynous or promiscuous rodent species that live in variable size groups, such as R. norvergicus, C. sociabilis, S. teguina and M. musculus.
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Affiliation(s)
- D E Olazábal
- Departamento de Fisiología, Facultad de Medicina, Udelar, Montevideo, Uruguay.
| | - N Pillay
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - N Sandberg
- Departamento de Fisiología, Facultad de Medicina, Udelar, Montevideo, Uruguay
| | - K-J Hartman
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
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Lu Q, Hu S. Sex differences of oxytocin and vasopressin in social behaviors. HANDBOOK OF CLINICAL NEUROLOGY 2021; 180:65-88. [PMID: 34225950 DOI: 10.1016/b978-0-12-820107-7.00005-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The neuropeptides oxytocin (OT) and vasopressin (VP) are known to mediate social cognition and behaviors in a sex-dependent manner. This chapter reviews the sex-dependent influence of OT and VP on social behaviors, focusing on (1) partner preference and sexual orientation, (2) memory modulation, (3) emotion regulation, and (4) trust-related behaviors. Most studies suggest that OT promotes familiar (opposite-sex) partner preference, strengthens memory, relieves anxiety, and increases trust. However, VP-regulated social cognition has been studied less than OT. VP facilitates familiar (opposite-sex) partner preference, enhances memory, induces anxiety, and influences happiness/anger perception. Detailed sex differences of these effects are reviewed. There is a male preponderance in the use of animal models and many study results are too complex to draw firm conclusions. Clarifying the complex interplay between the OT/VP system and sex hormones in the regulation of social behaviors is needed.
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Affiliation(s)
- Qiaoqiao Lu
- Department of Psychiatry, Hangzhou Seventh People's Hospital, Hangzhou, China
| | - Shaohua Hu
- Department of Psychiatry, First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China; The Key Laboratory of Mental Disorder Management in Zhejiang Province, Hangzhou, China; Brain Research Institute of Zhejiang University, Hangzhou, China.
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Smith CJ, Bilbo SD. Sickness and the Social Brain: Love in the Time of COVID. Front Psychiatry 2021; 12:633664. [PMID: 33692712 PMCID: PMC7937950 DOI: 10.3389/fpsyt.2021.633664] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 01/26/2021] [Indexed: 12/11/2022] Open
Abstract
As a highly social species, inclusion in social networks and the presence of strong social bonds are critical to our health and well-being. Indeed, impaired social functioning is a component of numerous neuropsychiatric disorders including depression, anxiety, and substance use disorder. During the current COVID-19 pandemic, our social networks are at risk of fracture and many are vulnerable to the negative consequences of social isolation. Importantly, infection itself leads to changes in social behavior as a component of "sickness behavior." Furthermore, as in the case of COVID-19, males and females often differ in their immunological response to infection, and, therefore, in their susceptibility to negative outcomes. In this review, we discuss the many ways in which infection changes social behavior-sometimes to the benefit of the host, and in some instances for the sake of the pathogen-in species ranging from eusocial insects to humans. We also explore the neuroimmune mechanisms by which these changes in social behavior occur. Finally, we touch upon the ways in which the social environment (group living, social isolation, etc.) shapes the immune system and its ability to respond to challenge. Throughout we emphasize how males and females differ in their response to immune activation, both behaviorally and physiologically.
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Affiliation(s)
- Caroline J Smith
- Department of Psychology and Neuroscience, Duke University, Durham, NC, United States
| | - Staci D Bilbo
- Department of Psychology and Neuroscience, Duke University, Durham, NC, United States
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Liu CM, Davis EA, Suarez AN, Wood RI, Noble EE, Kanoski SE. Sex Differences and Estrous Influences on Oxytocin Control of Food Intake. Neuroscience 2019; 447:63-73. [PMID: 31738883 DOI: 10.1016/j.neuroscience.2019.10.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 10/08/2019] [Accepted: 10/10/2019] [Indexed: 10/25/2022]
Abstract
Central oxytocin potently reduces food intake and is being pursued as a clinical treatment for obesity. While sexually dimorphic effects have been described for the effects of oxytocin on several behavioral outcomes, the role of sex in central oxytocin modulation of feeding behavior is poorly understood. Here we investigated the effects of sex, estrous cycle stage, and female sex hormones (estrogen, progesterone) on central oxytocin-mediated reduction of food intake in rats. Results show that while intracerebroventricular (ICV) oxytocin potently reduces chow intake in both male and female rats, these effects were more pronounced in males than in females. We next examined whether estrous cycle stage affects oxytocin's food intake-reducing effects in females. Results show that ICV oxytocin administration significantly reduces food intake during all estrous cycle stages except proestrous, suggesting that female sex hormones may modulate the feeding effects of oxytocin. Indeed, additional results reveal that estrogen, but not progesterone replacement, in ovariectomized rats abolishes oxytocin-mediated reductions in chow intake. Lastly, oxytocin receptor mRNA (Oxtr) quantification (via quantitative PCR) and anatomical localization (via fluorescent in situ hybridization) in previously established sites of action for oxytocin control of food intake revealed comparable Oxtr expression between male and female rats, suggesting that observed sex and estrous differences may be based on variations in ligand availability and/or binding. Overall, these data show that estrogen reduces the effectiveness of central oxytocin to inhibit food intake, suggesting that sex hormones and estrous cycle should be considered in clinical investigations of oxytocin for obesity treatment.
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Affiliation(s)
- Clarissa M Liu
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, United States; Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, CA, United States
| | - Elizabeth A Davis
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, CA, United States
| | - Andrea N Suarez
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, CA, United States
| | - Ruth I Wood
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, United States; Department of Integrative Anatomical Sciences, Keck School of Medicine of University of Southern California, Los Angeles, CA, United States
| | - Emily E Noble
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, CA, United States; Department of Foods and Nutrition, University of Georgia, Athens, GA, United States.
| | - Scott E Kanoski
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, United States; Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, CA, United States.
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