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Roggenbuck EC, Hall EA, Hanson IB, Roby AA, Zhang KK, Alkatib KA, Carter JA, Clewner JE, Gelfius AL, Gong S, Gordon FR, Iseler JN, Kotapati S, Li M, Maysun A, McCormick EO, Rastogi G, Sengupta S, Uzoma CU, Wolkov MA, Clowney EJ. Let's talk about sex: Mechanisms of neural sexual differentiation in Bilateria. WIREs Mech Dis 2024; 16:e1636. [PMID: 38185860 DOI: 10.1002/wsbm.1636] [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: 05/09/2023] [Revised: 11/20/2023] [Accepted: 11/21/2023] [Indexed: 01/09/2024]
Abstract
In multicellular organisms, sexed gonads have evolved that facilitate release of sperm versus eggs, and bilaterian animals purposefully combine their gametes via mating behaviors. Distinct neural circuits have evolved that control these physically different mating events for animals producing eggs from ovaries versus sperm from testis. In this review, we will describe the developmental mechanisms that sexually differentiate neural circuits across three major clades of bilaterian animals-Ecdysozoa, Deuterosomia, and Lophotrochozoa. While many of the mechanisms inducing somatic and neuronal sex differentiation across these diverse organisms are clade-specific rather than evolutionarily conserved, we develop a common framework for considering the developmental logic of these events and the types of neuronal differences that produce sex-differentiated behaviors. This article is categorized under: Congenital Diseases > Stem Cells and Development Neurological Diseases > Stem Cells and Development.
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Affiliation(s)
- Emma C Roggenbuck
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Elijah A Hall
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Isabel B Hanson
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Alyssa A Roby
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Katherine K Zhang
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Kyle A Alkatib
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Joseph A Carter
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jarred E Clewner
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Anna L Gelfius
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Shiyuan Gong
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Finley R Gordon
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jolene N Iseler
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Samhita Kotapati
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Marilyn Li
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Areeba Maysun
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Elise O McCormick
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Geetanjali Rastogi
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Srijani Sengupta
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Chantal U Uzoma
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - Madison A Wolkov
- MCDB 464 - Cellular Diversity: Sex Differentiation of the Brain, University of Michigan, Ann Arbor, Michigan, USA
| | - E Josephine Clowney
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
- Michigan Neuroscience Institute Affiliate, University of Michigan, Ann Arbor, Michigan, USA
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Gaytán-Tocavén L, Aguilar-Moreno A, Ortiz J, Alcauter S, Antonio-Cabrera E, Paredes RG. Identification of neural circuits controlling male sexual behavior and sexual motivation by manganese-enhanced magnetic resonance imaging. Front Behav Neurosci 2023; 17:1301406. [PMID: 38187924 PMCID: PMC10768062 DOI: 10.3389/fnbeh.2023.1301406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Accepted: 11/27/2023] [Indexed: 01/09/2024] Open
Abstract
Introduction Different techniques have been used to identify the brain regions that control sexual motivation and sexual behavior. However, the influence of sexual experience on the activation of these brain regions in the same subject is unknown. Using manganese-enhanced magnetic resonance imaging (MEMRI), we analyzed the activation of brain regions in the sexual incentive motivation (SIM) and the partner preference PP (tests) on weeks 1, 5, and 10 in male rats tested for 10 weeks. AIM. In experiment 1, we analyzed the possible toxic effects of 16 mg/kg of MnCl2 on male sexual behavior, running wheel, and motor execution. In experiment 2, subjects were tested for SIM and PP using MEMRI. Methods In both experiments, a dose of 16 mg/kg (s.c) of chloride manganese (MnCl2) was administered 24 h before subjects were tested and placed immediately thereafter in a 7-Tesla Bruker scanner. Results In experiment 1, the dose of 16 mg/kg of MnCl2 did not induce behavioral alterations that could interfere with interpreting the imaging data. In experiment 2, we found a clear preference for the female in both the SIM and PP tests. We found a higher signal intensity in the olfactory bulb (OB) in week 1 of the SIM test compared to the control group. We also found increased signal intensity in the socio-sexual behavior and mesolimbic reward circuits in the SIM test in week 1. In the PP test, we found a higher signal intensity in the ventral tegmental area (VTA) in week 10 compared to the control group. In the same test, we found increased signal intensity in the socio-sexual and mesolimbic reward circuits in week 5 compared to the control group. Cohen's d analysis of the whole brain revealed that as the subjects gained sexual experience we observed a higher brain activation in the OB in the SIM group. The PP group showed higher brain activation in the cortex and subcortical structures as they acquired sexual experience. Discussion As the subjects gain sexual experience, more structures of the reward and socio-sexual circuits are recruited, resulting in different, and large brain activations.
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Affiliation(s)
| | | | - Juan Ortiz
- Instituto de Neurobiología, UNAM, Querétaro, Mexico
| | | | | | - Raúl G. Paredes
- Escuela Nacional de Estudios Superiores, Unidad Juriquilla, UNAM, Querétaro, Mexico
- Instituto de Neurobiología, UNAM, Querétaro, Mexico
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Edwards PD, Toor I, Holmes MM. The Curious Case of the Naked Mole-Rat: How Extreme Social and Reproductive Adaptations Might Influence Sex Differences in the Brain. Curr Top Behav Neurosci 2023; 62:47-70. [PMID: 35301704 DOI: 10.1007/7854_2022_310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Research in the neurobiology of sex differences is inherently influenced by the study species that are used. Some traditional animal research models, such as rats and mice, show certain sex differences in the brain that have been foundational to neurobiological research. However, subsequent work has demonstrated that these differences are not always generalizable, especially to species with different social structures and sex-associated roles or behaviors. One such example is the naked mole-rat (Heterocephalus glaber), which has an unusual social structure among mammals. Naked mole-rats live in large groups where reproduction is restricted to a dominant female, called the "queen," and often only one breeding male. All other animals in the group, the "subordinates," are socially suppressed from reproduction and remain in a prepubescent state as adults, unless they are removed from the presence of the queen. These subordinates show little to no sex differences in external morphology, neural morphology, or behavior. However, there are a suite of neurobiological differences between subordinate and breeding naked mole-rats. After naked mole-rats attain breeding status, many of the classically sexually differentiated brain regions increase in volume (paraventricular nucleus, medial amygdala, bed nucleus of the stria terminalis). There are additionally social status differences in sex hormone receptor expression in the brain, as well as other changes in gene expression, some of which also show sex differences - though not always in the predicted direction based on other rodent studies. Data from naked mole-rats show that it is critical to consider the evolved social structure of a species when studying sex differences in the brain.
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Affiliation(s)
- Phoebe D Edwards
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Ilapreet Toor
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Melissa M Holmes
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada.
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Serrano Nájera G, Kin K. Unusual occurrence of domestication syndrome amongst African mole-rats: Is the naked mole-rat a domestic animal? Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.987177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The Naked mole-rat (NMR) is becoming a prominent model organism due to its peculiar traits, such as eusociality, extreme longevity, cancer resistance, and reduced pain sensitivity. It belongs to the African mole-rats (AMR), a family of subterranean rodents that includes solitary, cooperative breeding and eusocial species. We identified and quantified the domestication syndrome (DS) across AMR, a set of morphological and behavioural traits significantly more common and pronounced amongst domesticated animals than in their wild counterparts. Surprisingly, the NMR shows apparent DS traits when compared to the solitary AMR. Animals can self-domesticate when a reduction of the fear response is naturally selected, such as in islands with no predators, or to improve the group’s harmony in cooperative breeding species. The DS may be caused by alterations in the physiology of the neural crest cells (NCC), a transient population of cells that generate a full range of tissues during development. The NCC contribute to organs responsible for transmitting the fear response and various other tissues, including craniofacial bones. Therefore, mutations affecting the NCC can manifest as behavioural and morphological alterations in many structures across the body, as seen in neurocristopathies. We observed that all social AMRs are chisel-tooth diggers, an adaption to hard soils that requires the flattening of the skull. We hypothesise that chisel-tooth digging could impose a selective pressure on the NCC that triggered the DS’s appearance, possibly facilitating the evolution of sociality. Finally, we discuss how DS traits are neutral or beneficial for the subterranean niche, strategies to test this hypothesis and report well-studied mutations in the NMR that are associated with the NCC physiology or with the control of the fear response. In conclusion, we argue that many of the NMR’s unconventional traits are compatible with the DS and provide a hypothesis about its origins. Our model proposes a novel avenue to enhance the understanding of the extraordinary biology of the NMR.
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Adult Neural Plasticity in Naked Mole-Rats: Implications of Fossoriality, Longevity and Sociality on the Brain's Capacity for Change. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1319:105-135. [PMID: 34424514 DOI: 10.1007/978-3-030-65943-1_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Naked mole-rats (Heterocephalus glaber) are small African rodents that have many unique behavioral and physiological adaptations well-suited for testing hypotheses about mammalian neural plasticity. In this chapter, we focus on three features of naked mole-rat biology and how they impact neural plasticity in this species: (1) their fossorial lifestyle, (2) their extreme longevity with a lack of demonstrable senescence, and (3) their unusual social structure. Critically, each of these features requires some degree of biological flexibility. First, their fossorial habitat situates them in an environment with characteristics to which the central nervous system is particularly sensitive (e.g., oxygen content, photoperiod, spatial complexity). Second, their long lifespan requires adaptations to combat senescence and declines in neural functioning. Finally, their extreme reproductive skew and sustained ability for release from reproductive suppression indicates remarkable neural sensitivity to the sociosexual environment that is distinct from chronological age. These three features of naked mole-rat life are not mutually exclusive, but they do each offer unique considerations for the possibilities, constraints, and mechanisms associated with adult neural plasticity.
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Coen CW, Bennett NC, Holmes MM, Faulkes CG. Neuropeptidergic and Neuroendocrine Systems Underlying Eusociality and the Concomitant Social Regulation of Reproduction in Naked Mole-Rats: A Comparative Approach. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1319:59-103. [PMID: 34424513 DOI: 10.1007/978-3-030-65943-1_3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The African mole-rat family (Bathyergidae) includes the first mammalian species identified as eusocial: naked mole-rats. Comparative studies of eusocial and solitary mole-rat species have identified differences in neuropeptidergic systems that may underlie the phenomenon of eusociality. These differences are found in the oxytocin, vasopressin and corticotrophin-releasing factor (CRF) systems within the nucleus accumbens, amygdala, bed nucleus of the stria terminalis and lateral septal nucleus. As a corollary of their eusociality, most naked mole-rats remain pre-pubertal throughout life because of the presence of the colony's only reproductive female, the queen. To elucidate the neuroendocrine mechanisms that mediate this social regulation of reproduction, research on the hypothalamo-pituitary-gonadal axis in naked mole-rats has identified differences between the many individuals that are reproductively suppressed and the few that are reproductively mature: the queen and her male consorts. These differences involve gonadal steroids, gonadotrophin-releasing hormone-1 (GnRH-1), kisspeptin, gonadotrophin-inhibitory hormone/RFamide-related peptide-3 (GnIH/RFRP-3) and prolactin. The comparative findings in eusocial and solitary mole-rat species are assessed with reference to a broad range of studies on other mammals.
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Affiliation(s)
- Clive W Coen
- Reproductive Neurobiology, Division of Women's Health, Faculty of Life Sciences & Medicine, King's College London, London, UK.
| | - Nigel C Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Melissa M Holmes
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada.,Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Canada.,Department of Cell & Systems Biology, University of Toronto, Toronto, Canada
| | - Christopher G Faulkes
- School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
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Goddings AL, Beltz A, Peper JS, Crone EA, Braams BR. Understanding the Role of Puberty in Structural and Functional Development of the Adolescent Brain. JOURNAL OF RESEARCH ON ADOLESCENCE : THE OFFICIAL JOURNAL OF THE SOCIETY FOR RESEARCH ON ADOLESCENCE 2019; 29:32-53. [PMID: 30869842 DOI: 10.1111/jora.12408] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Over the past two decades, there has been a tremendous increase in our understanding of structural and functional brain development in adolescence. However, understanding the role of puberty in this process has received much less attention. This review examines this relationship by summarizing recent research studies where the role of puberty was investigated in relation to brain structure, connectivity, and task-related functional magnetic resonance imaging (fMRI). The studies together suggest that puberty may contribute to adolescent neural reorganization and maturational advancement, and sex differences also emerge in puberty. The current body of work shows some mixed results regarding impact and exact direction of pubertal influence. We discuss several limitations of current studies and propose future directions on how to move the field forward.
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Affiliation(s)
| | | | - Jiska S Peper
- Leiden University
- Leiden Institute for Brain and Cognition
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Williamson CM, Klein IS, Lee W, Curley JP. Immediate early gene activation throughout the brain is associated with dynamic changes in social context. Soc Neurosci 2018; 14:253-265. [PMID: 29781376 DOI: 10.1080/17470919.2018.1479303] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Social competence is dependent on successful processing of social context information. The social opportunity paradigm is a methodology in which dynamic shifts in social context are induced through removal of the alpha male in a dominance hierarchy, leading to rapid ascent in the hierarchy of the beta male and of other subordinate males in the social group. In the current study, we use the social opportunity paradigm to determine what brain regions respond to this dynamic change in social context, allowing an individual to recognize the absence of the alpha male and subsequently perform status-appropriate social behaviors. Replicating our previous work, we show that following removal of the alpha male, beta males rapidly ascend the social hierarchy and attain dominant status by increasing aggression towards more subordinate individuals. Analysis of patterns of Fos immunoreactivity throughout the brain indicates that in individuals undergoing social ascent, there is increased activity in regions of the social behavior network, as well as the infralimbic and prelimbic regions of the prefrontal cortex and areas of the hippocampus. Our findings demonstrate that male mice are able to respond to changes in social context and provide insight into the how the brain processes these complex behavioral changes.
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Affiliation(s)
- Cait M Williamson
- a Department of Psychology , Columbia University , New York , NY , USA
| | - Inbal S Klein
- a Department of Psychology , Columbia University , New York , NY , USA
| | - Won Lee
- a Department of Psychology , Columbia University , New York , NY , USA
| | - James P Curley
- a Department of Psychology , Columbia University , New York , NY , USA.,b Department of Psychology , UT Austin , Austin , TX , USA
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Increased brain glucocorticoid actions following social defeat in rats facilitates the long-term establishment of social subordination. Physiol Behav 2018; 186:31-36. [DOI: 10.1016/j.physbeh.2018.01.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 01/09/2018] [Accepted: 01/09/2018] [Indexed: 12/22/2022]
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Faykoo-Martinez M, Monks DA, Zovkic IB, Holmes MM. Sex- and brain region-specific patterns of gene expression associated with socially-mediated puberty in a eusocial mammal. PLoS One 2018; 13:e0193417. [PMID: 29474488 PMCID: PMC5825099 DOI: 10.1371/journal.pone.0193417] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 02/09/2018] [Indexed: 12/13/2022] Open
Abstract
The social environment can alter pubertal timing through neuroendocrine mechanisms that are not fully understood; it is thought that stress hormones (e.g., glucocorticoids or corticotropin-releasing hormone) influence the hypothalamic-pituitary-gonadal axis to inhibit puberty. Here, we use the eusocial naked mole-rat, a unique species in which social interactions in a colony (i.e. dominance of a breeding female) suppress puberty in subordinate animals. Removing subordinate naked mole-rats from this social context initiates puberty, allowing for experimental control of pubertal timing. The present study quantified gene expression for reproduction- and stress-relevant genes acting upstream of gonadotropin-releasing hormone in brain regions with reproductive and social functions in pre-pubertal, post-pubertal, and opposite sex-paired animals (which are in various stages of pubertal transition). Results indicate sex differences in patterns of neural gene expression. Known functions of genes in brain suggest stress as a key contributing factor in regulating male pubertal delay. Network analysis implicates neurokinin B (Tac3) in the arcuate nucleus of the hypothalamus as a key node in this pathway. Results also suggest an unappreciated role for the nucleus accumbens in regulating puberty.
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Affiliation(s)
| | - D. Ashley Monks
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Iva B. Zovkic
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Melissa M. Holmes
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
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Peragine DE, Yousuf Y, Fu Y, Swift-Gallant A, Ginzberg K, Holmes MM. Contrasting effects of opposite- versus same-sex housing on hormones, behavior and neurogenesis in a eusocial mammal. Horm Behav 2016; 81:28-37. [PMID: 27018426 DOI: 10.1016/j.yhbeh.2016.03.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 02/29/2016] [Accepted: 03/18/2016] [Indexed: 12/22/2022]
Abstract
Competitive interactions can have striking and enduring effects on behavior, but the mechanisms underlying this experience-induced plasticity are unclear, particularly in females. Naked mole-rat (NMR) colonies are characterized by the strictest social and reproductive hierarchy among mammals, and represent an ideal system for studies of social competition. In large matriarchal colonies, breeding is monopolized by one female and 1-3 males, with other colony members being socially subordinate and reproductively suppressed. To date, competition for breeding status has been examined in-colony, with female, but not male, aggression observed following the death/removal of established queens. To determine whether this sex difference extends to colony-founding contexts, and clarify neural and endocrine mechanisms underlying behavioral change in females competing for status, we examined neurogenesis and steroid hormone concentrations in colony-housed subordinates, and NMRs given the opportunity to transition status via pair-housing. To this end, Ki-67 and doublecortin immunoreactivity were compared in the hippocampal dentate gyrus (DG) and basolateral amygdala (BLA) of colony-housed subordinates, and subordinates housed with a same-sex (SS) or opposite-sex (OS) conspecific. Results suggest that OS pairing in eusocial mammals promotes cooperation and enhances hippocampal plasticity, while SS pairing is stressful, resulting in enhanced HPA activation and muted hippocampal neurogenesis relative to OS pairs. Data further indicate that competition for status is confined to females, with female-female housing exerting contrasting effects on hippocampal and amygdalar neurogenesis. These findings advance understanding of social stress effects on neuroplasticity and behavior, and highlight the importance of including female-dominated species in research on aggression and intrasexual competition.
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Affiliation(s)
- Deane E Peragine
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Yusef Yousuf
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Yi Fu
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Ashlyn Swift-Gallant
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Keren Ginzberg
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Melissa M Holmes
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada; Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3G5, Canada.
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12
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Social behavior, hormones and adult neurogenesis. Front Neuroendocrinol 2016; 41:71-86. [PMID: 26996817 DOI: 10.1016/j.yfrne.2016.02.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 02/08/2016] [Accepted: 02/11/2016] [Indexed: 01/31/2023]
Abstract
A variety of experiences have been shown to affect the production of neurons in the adult hippocampus. These effects may be mediated by experience-driven hormonal changes, which, in turn, interact with factors such as sex, age and life history to alter brain plasticity. Although the effects of physical experience and stress have been extensively characterized, various types of social experience across the lifespan trigger profound neuroendocrine changes in parallel with changes in adult neurogenesis. This review article focuses on the influence of specific social experiences on adult neurogenesis in the dentate gyrus and the potential role of hormones in these effects.
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Swift-Gallant A, Mo K, Peragine DE, Monks DA, Holmes MM. Removal of reproductive suppression reveals latent sex differences in brain steroid hormone receptors in naked mole-rats, Heterocephalus glaber. Biol Sex Differ 2015; 6:31. [PMID: 26693002 PMCID: PMC4676092 DOI: 10.1186/s13293-015-0050-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 12/01/2015] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Naked mole-rats are eusocial mammals, living in large colonies with a single breeding female and 1-3 breeding males. Breeders are socially dominant, and only the breeders exhibit traditional sex differences in circulating gonadal steroid hormones and reproductive behaviors. Non-reproductive subordinates also fail to show sex differences in overall body size, external genital morphology, and non-reproductive behaviors. However, subordinates can transition to breeding status if removed from their colony and housed with an opposite-sex conspecific, suggesting the presence of latent sex differences. Here, we assessed the expression of steroid hormone receptor and aromatase messenger RNA (mRNA) in the brains of males and females as they transitioned in social and reproductive status. METHODS We compared in-colony subordinates to opposite-sex subordinate pairs that were removed from their colony for either 1 day, 1 week, 1 month, or until they became breeders (i.e., produced a litter). Diencephalic tissue was collected and mRNA of androgen receptor (Ar), estrogen receptor alpha (Esr1), progesterone receptor (Pgr), and aromatase (Cyp19a1) was measured using qPCR. Testosterone, 17β-estradiol, and progesterone from serum were also measured. RESULTS As early as 1 week post-removal, males exhibited increased diencephalic Ar mRNA and circulating testosterone, whereas females had increased Cyp19a1 mRNA in the diencephalon. At 1 month post-removal, females exhibited increased 17β-estradiol and progesterone. The largest changes in steroid hormone receptors were observed in breeders. Breeding females had a threefold increase in Cyp19a1 and fivefold increases in Esr1 and Pgr, whereas breeding males had reduced Pgr and increased Ar. CONCLUSIONS These data demonstrate that sex differences in circulating gonadal steroids and hypothalamic gene expression emerge weeks to months after subordinate animals are removed from reproductive suppression in their home colony.
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Affiliation(s)
- Ashlyn Swift-Gallant
- Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6 Canada
| | - Kaiguo Mo
- Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6 Canada
| | - Deane E Peragine
- Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6 Canada
| | - D Ashley Monks
- Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6 Canada ; Department of Cell and Systems Biology, University of Toronto, 100 St. George Street, Toronto, ON M5S 3G3 Canada
| | - Melissa M Holmes
- Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6 Canada ; Department of Cell and Systems Biology, University of Toronto, 100 St. George Street, Toronto, ON M5S 3G3 Canada ; Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2 Canada
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Voigt C, Leitner S, Bennett NC. Breeding status affects the expression of androgen and progesterone receptor
mRNA
in the brain of male Damaraland mole‐rats. J Zool (1987) 2015. [DOI: 10.1111/jzo.12303] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- C. Voigt
- Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | - S. Leitner
- Department of Behavioural Neurobiology Max Planck Institute for Ornithology Seewiesen Germany
| | - N. C. Bennett
- Department of Zoology and Entomology University of Pretoria Pretoria South Africa
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15
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Mooney S, Coen C, Holmes M, Beery A. Region-specific associations between sex, social status, and oxytocin receptor density in the brains of eusocial rodents. Neuroscience 2015; 303:261-9. [DOI: 10.1016/j.neuroscience.2015.06.043] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 06/03/2015] [Accepted: 06/22/2015] [Indexed: 12/22/2022]
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16
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Beery AK, Bicks L, Mooney SJ, Goodwin NL, Holmes MM. Sex, social status, and CRF receptor densities in naked mole-rats. J Comp Neurol 2015; 524:228-43. [DOI: 10.1002/cne.23834] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 06/13/2015] [Accepted: 06/16/2015] [Indexed: 12/13/2022]
Affiliation(s)
- Annaliese K. Beery
- Department of Psychology, Department of Biology, Program in Neuroscience; Smith College; Northampton Massachusetts 01063 USA
| | - Lucy Bicks
- Department of Psychology, Department of Biology, Program in Neuroscience; Smith College; Northampton Massachusetts 01063 USA
| | - Skyler J. Mooney
- Department of Psychology; University of Toronto Mississauga; Mississauga Ontario L5L 1C6 Canada
| | - Nastacia L. Goodwin
- Department of Psychology, Department of Biology, Program in Neuroscience; Smith College; Northampton Massachusetts 01063 USA
| | - Melissa M. Holmes
- Department of Psychology; University of Toronto Mississauga; Mississauga Ontario L5L 1C6 Canada
- Departments of Cell and Systems Biology & Ecology and Evolutionary Biology; University of Toronto; Toronto Ontario M5S 3G5 Canada
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17
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A single testosterone pulse rapidly reduces urinary marking behaviour in subordinate, but not dominant, white-footed mice. Anim Behav 2015. [DOI: 10.1016/j.anbehav.2014.11.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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18
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Voigt C, Gahr M, Leitner S, Lutermann H, Bennett N. Breeding status and social environment differentially affect the expression of sex steroid receptor and aromatase mRNA in the brain of female Damaraland mole-rats. Front Zool 2014; 11:38. [PMID: 24839456 PMCID: PMC4024188 DOI: 10.1186/1742-9994-11-38] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 05/01/2014] [Indexed: 11/21/2022] Open
Abstract
Introduction The Damaraland mole-rat (Fukomys damarensis) is a eusocial, subterranean mammal, which exhibits an extreme reproductive skew with a single female (queen) monopolizing reproduction in each colony. Non-reproductive females in the presence of the queen are physiologically suppressed to the extent that they are anovulatory. This blockade is thought to be caused by a disruption in the normal gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus. In order to understand the underlying physiological mechanisms of reproductive suppression in subordinate females we studied the expression of steroid hormone receptors and the androgen-converting enzyme aromatase in forebrain regions involved in the control of reproductive behaviour in female breeders and non-breeders from intact colonies. Additionally, we included in our analysis females that experienced the release from social suppression by being removed from the presence of the queen. Results We found expression of androgen receptor, estrogen receptor α and aromatase in several forebrain regions of female Damaraland mole-rats. Their distribution matches previous findings in other mammals. Quantification of the hybridisation signal revealed that queens had increased expression of androgen receptors compared to non-breeders and removed non-breeders in most brain regions examined, which include the medial preoptic area (MPOA), the principal nucleus of the bed nucleus of the stria terminalis (BSTp), the ventromedial nucleus of the hypothalamus (VMH), the arcuate nucleus (ARC) and the medial amygdala (MeA). Furthermore, breeders had increased estrogen receptor α expression in the anteroventral periventricular nucleus (AVPV) and in the MeA, while aromatase expression in the AVPV was significantly reduced compared to non-breeders. Absence of social suppression was associated with increased androgen receptor expression in the ARC, increased estrogen receptor α expression in the MeA and BSTp and reduced aromatase expression in the AVPV. Conclusion This study shows that social suppression and breeding differentially affect the neuroendocrine phenotype of female Damaraland mole-rats. The differential expression pattern of estrogen receptor α and aromatase in the AVPV between breeders and non-breeders supports the view that this region plays an important role in mediating the physiological suppression in subordinate females.
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Affiliation(s)
- Cornelia Voigt
- Department of Zoology and Entomology, University of Pretoria, 0028 Pretoria, South Africa
| | - Manfred Gahr
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, D-82319 Seewiesen, Germany
| | - Stefan Leitner
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, D-82319 Seewiesen, Germany
| | - Heike Lutermann
- Department of Zoology and Entomology, University of Pretoria, 0028 Pretoria, South Africa
| | - Nigel Bennett
- Department of Zoology and Entomology, University of Pretoria, 0028 Pretoria, South Africa
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19
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Peragine D, Simpson J, Mooney S, Lovern M, Holmes M. Social regulation of adult neurogenesis in a eusocial mammal. Neuroscience 2014; 268:10-20. [DOI: 10.1016/j.neuroscience.2014.02.044] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 01/27/2014] [Accepted: 02/26/2014] [Indexed: 12/17/2022]
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20
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Mooney SJ, Peragine DE, Hathaway GA, Holmes MM. A game of thrones: Neural plasticity in mammalian social hierarchies. Soc Neurosci 2014; 9:108-17. [DOI: 10.1080/17470919.2014.882862] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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21
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Holmes MM, Van Mil S, Bulkowski C, Goldman SL, Goldman BD, Forger NG. Androgen receptor distribution in the social decision-making network of eusocial naked mole-rats. Behav Brain Res 2013; 256:214-8. [DOI: 10.1016/j.bbr.2013.08.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2013] [Revised: 08/13/2013] [Accepted: 08/15/2013] [Indexed: 10/26/2022]
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22
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French JA, Mustoe AC, Cavanaugh J, Birnie AK. The influence of androgenic steroid hormones on female aggression in 'atypical' mammals. Philos Trans R Soc Lond B Biol Sci 2013; 368:20130084. [PMID: 24167314 PMCID: PMC3826213 DOI: 10.1098/rstb.2013.0084] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Dimorphism on dominance and agonistic behaviour in mammals tends to be strongly biased toward males. In this review, we focus on a select few species of mammals in which females are as or more aggressive than males, and/or are dominant to males, and explore the role of androgenic hormones in mediating this important difference. While the data are not as clear-cut as those published on traditional laboratory mammals, our review highlights important endocrine substrates for both organizational and activational influences of steroids on female aggressive behaviour. We highlight areas in which further observations and experiments are crucial, especially the potential facilitative effects of androgens on female aggression. Finally, new and innovative techniques, including molecular genetics and receptor pharmacology, portend important insights into the ways in which androgenic hormones regulate aggressive behaviour in 'atypical' female mammals.
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Affiliation(s)
- Jeffrey A. French
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
- Department of Biology, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Aaryn C. Mustoe
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Jon Cavanaugh
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Andrew K. Birnie
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
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23
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Campi KL, Jameson CE, Trainor BC. Sexual Dimorphism in the Brain of the Monogamous California Mouse (Peromyscus californicus). BRAIN, BEHAVIOR AND EVOLUTION 2013; 81:236-49. [PMID: 23881046 PMCID: PMC3915401 DOI: 10.1159/000353260] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 01/04/2013] [Indexed: 11/19/2022]
Abstract
Sex differences in behavior and morphology are usually assumed to be stronger in polygynous species compared to monogamous species. A few brain structures have been identified as sexually dimorphic in polygynous rodent species, but it is less clear whether these differences persist in monogamous species. California mice are among the 5% or less of mammals that are considered to be monogamous and as such provide an ideal model to examine sexual dimorphism in neuroanatomy. In the present study we compared the volume of hypothalamic- and limbic-associated regions in female and male California mice for sexual dimorphism. We also used tyrosine hydroxylase (TH) immunohistochemistry to compare the number of dopamine neurons in the ventral tegmental area (VTA) in female and male California mice. Additionally, tract tracing was used to accurately delineate the boundaries of the VTA. The total volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA), the principal nucleus of the bed nucleus of the stria terminalis (BNST), and the posterodorsal medial amygdala (MEA) was larger in males compared to females. In the SDN-POA we found that the magnitude of sex differences in the California mouse were intermediate between the large differences observed in promiscuous meadow voles and rats and the absence of significant differences in monogamous prairie voles. However, the magnitude of sex differences in MEA and the BNST were comparable to polygynous species. No sex differences were observed in the volume of the whole brain, the VTA, the nucleus accumbens or the number of TH-ir neurons in the VTA. These data show that despite a monogamous social organization, sexual dimorphisms that have been reported in polygynous rodents extend to California mice. Our data suggest that sex differences in brain structures such as the SDN-POA persist across species with different social organizations and may be an evolutionarily conserved characteristic of mammalian brains.
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Affiliation(s)
- Katharine L Campi
- Department of Psychology and Center for Neuroscience, University of California Davis, Davis, CA 95616, USA.
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24
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Zhou S, Holmes MM, Forger NG, Goldman BD, Lovern MB, Caraty A, Kalló I, Faulkes CG, Coen CW. Socially regulated reproductive development: Analysis of GnRH-1 and kisspeptin neuronal systems in cooperatively breeding naked mole-rats (Heterocephalus glaber). J Comp Neurol 2013; 521:3003-29. [DOI: 10.1002/cne.23327] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 02/20/2013] [Accepted: 02/26/2013] [Indexed: 12/18/2022]
Affiliation(s)
- Shuzhi Zhou
- Reproductive Neurobiology; Division of Women's Health; School of Medicine; King's College London; London; UK
| | | | | | | | | | - Alain Caraty
- INRA; Physiology of Reproduction; Nouzilly; France
| | | | | | - Clive W. Coen
- Reproductive Neurobiology; Division of Women's Health; School of Medicine; King's College London; London; UK
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25
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Abstract
Animals evaluate and respond to their social environment with adaptive decisions. Revealing the neural mechanisms of such decisions is a major goal in biology. We analyzed expression profiles for 10 neurochemical genes across 12 brain regions important for decision-making in 88 species representing five vertebrate lineages. We found that behaviorally relevant brain regions are remarkably conserved over 450 million years of evolution. We also find evidence that different brain regions have experienced different selection pressures, because spatial distribution of neuroendocrine ligands are more flexible than their receptors across vertebrates. Our analysis suggests that the diversity of social behavior in vertebrates can be explained, in part, by variations on a theme of conserved neural and gene expression networks.
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Affiliation(s)
- Lauren A O'Connell
- Institute for Cellular and Molecular Biology and Section of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
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26
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Hews DK, Hara E, Anderson MC. Sex and species differences in plasma testosterone and in counts of androgen receptor-positive cells in key brain regions of Sceloporus lizard species that differ in aggression. Gen Comp Endocrinol 2012; 176:493-9. [PMID: 22230767 PMCID: PMC3334410 DOI: 10.1016/j.ygcen.2011.12.028] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 12/21/2011] [Indexed: 11/15/2022]
Abstract
We studied neuroendocrine correlates of aggression differences in adults of two Sceloporus lizard species. These species differ in the degree of sex difference in aggressive color signals (belly patches) and in aggression: Sceloporus undulatus (males blue, high aggression; females white, low aggression) and Sceloporus virgatus (both sexes white, lower aggression). We measured plasma testosterone and counted cells expressing androgen receptor-like immunoreactivity to the affinity-purified polyclonal AR antibody, PG-21, in three brain regions of breeding season adults. Male S. undulatus had the highest mean plasma testosterone and differed significantly from conspecific females. In contrast, there was no sex difference in plasma testosterone concentrations in S. virgatus. Male S. undulatus also had the highest mean number of AR-positive cells in the preoptic area: the sexes differed in S. undulatus but not in S. virgatus, and females of the two species did not differ. In the ventral medial hypothalamus, S. undulatus males had higher mean AR cell counts compared to females, but again there was no sex difference in S. virgatus. In the habenula, a control brain region, the sexes did not differ, and although the sex by species interaction significant was not significant, there was a trend (p=0.050) for S. virgatus to have higher mean AR cell counts than S. undulatus. Thus hypothalamic AR cell counts paralleled sex and species differences in aggression, as did mean plasma testosterone levels in these breeding-season animals.
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Affiliation(s)
- Diana K Hews
- Dept. Biology, Indiana State Univ., Terre Haute, IN 47809, USA.
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27
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O'Connell LA, Hofmann HA. The vertebrate mesolimbic reward system and social behavior network: a comparative synthesis. J Comp Neurol 2012; 519:3599-639. [PMID: 21800319 DOI: 10.1002/cne.22735] [Citation(s) in RCA: 691] [Impact Index Per Article: 57.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
All animals evaluate the salience of external stimuli and integrate them with internal physiological information into adaptive behavior. Natural and sexual selection impinge on these processes, yet our understanding of behavioral decision-making mechanisms and their evolution is still very limited. Insights from mammals indicate that two neural circuits are of crucial importance in this context: the social behavior network and the mesolimbic reward system. Here we review evidence from neurochemical, tract-tracing, developmental, and functional lesion/stimulation studies that delineates homology relationships for most of the nodes of these two circuits across the five major vertebrate lineages: mammals, birds, reptiles, amphibians, and teleost fish. We provide for the first time a comprehensive comparative analysis of the two neural circuits and conclude that they were already present in early vertebrates. We also propose that these circuits form a larger social decision-making (SDM) network that regulates adaptive behavior. Our synthesis thus provides an important foundation for understanding the evolution of the neural mechanisms underlying reward processing and behavioral regulation.
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Affiliation(s)
- Lauren A O'Connell
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712, USA
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28
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Endocrine function and neurobiology of the longest-living rodent, the naked mole-rat. Exp Gerontol 2011; 46:116-23. [DOI: 10.1016/j.exger.2010.09.005] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 09/02/2010] [Accepted: 09/09/2010] [Indexed: 02/04/2023]
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29
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Holmes MM, Seney ML, Goldman BD, Forger NG. Social and hormonal triggers of neural plasticity in naked mole-rats. Behav Brain Res 2010; 218:234-9. [PMID: 21130812 DOI: 10.1016/j.bbr.2010.11.056] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Revised: 11/22/2010] [Accepted: 11/28/2010] [Indexed: 11/25/2022]
Abstract
Naked mole-rats are eusocial rodents that live in large social groups with a strict reproductive hierarchy. In each colony only a few individuals breed; all others are non-reproductive subordinates. We previously showed that breeders have increased volume of several brain regions linked to reproduction: the paraventricular nucleus of the hypothalamus (PVN), the principal nucleus of the bed nucleus of the stria terminalis (BSTp), and the medial amygdala (MeA). Breeders also have more large motoneurons in Onuf's nucleus (ON) in the spinal cord, a cell group innervating perineal muscles that attach to the genitalia. Here, we sought to determine triggers for the neural changes seen in breeders. Specifically, we compared four groups of animals: subordinates, paired animals that did not reproduce, gonadally intact breeders, and gonadectomized breeders. We find that pairing alone is sufficient to cause breeder-like changes in volume of the PVN and cell size distribution in ON. In contrast, increases in BSTp volume were seen only in animals that actually reproduced. Those changes that were seen in successful breeders appear to be independent of gonadal steroids because long-term gonadectomy did not reverse the breeder-like neural changes in the PVN, BSTp or ON, although a trend for gonadectomized animals having larger MeA volumes was detected. Thus, neural changes associated with breeding status in naked mole-rats may be triggered by different aspects of the social and reproductive environment; once changes occur they are largely independent of gonadal hormones and may be permanent.
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Affiliation(s)
- Melissa M Holmes
- Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Road North, Mississauga, ON, L5L 1C6, Canada.
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30
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Munchrath LA, Hofmann HA. Distribution of sex steroid hormone receptors in the brain of an African cichlid fish, Astatotilapia burtoni. J Comp Neurol 2010; 518:3302-26. [PMID: 20575061 DOI: 10.1002/cne.22401] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Sex steroid hormones released from the gonads play an important role in mediating social behavior across all vertebrates. Many effects of these gonadal hormones are mediated by nuclear steroid hormone receptors, which are crucial for integration in the brain of external (e.g., social) signals with internal physiological cues to produce an appropriate behavioral output. The African cichlid fish Astatotilapia burtoni presents an attractive model system for the study of how internal cues and external social signals are integrated in the brain as males display robust plasticity in the form of two distinct, yet reversible, behavioral and physiological phenotypes depending on the social environment. In order to better understand where sex steroid hormones act to regulate social behavior in this species, we have determined the distribution of the androgen receptor, estrogen receptor alpha, estrogen receptor beta, and progesterone receptor mRNA and protein throughout the telencephalon and diencephalon and some mesencephalic structures of A. burtoni. All steroid hormone receptors were found in key brain regions known to modulate social behavior in other vertebrates including the proposed teleost homologs of the mammalian amygdalar complex, hippocampus, striatum, preoptic area, anterior hypothalamus, ventromedial hypothalamus, and ventral tegmental area. Overall, there is high concordance of mRNA and protein labeling. Our results significantly extend our understanding of sex steroid pathways in the cichlid brain and support the important role of nuclear sex steroid hormone receptors in modulating social behaviors in teleosts and across vertebrates.
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Affiliation(s)
- Lauren A Munchrath
- Section of Integrative Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78705, USA
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31
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Cell death and sexual differentiation of behavior: worms, flies, and mammals. Curr Opin Neurobiol 2010; 20:776-83. [PMID: 20934320 DOI: 10.1016/j.conb.2010.09.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 09/08/2010] [Accepted: 09/09/2010] [Indexed: 11/24/2022]
Abstract
Sex differences in the nervous system are found throughout the animal kingdom. Here, we discuss three prominent genetic models: nematodes, fruit flies, and mice. In all three, differential cell death is central to sexual differentiation and shared molecular mechanisms have been identified. Our knowledge of the precise function of neural sex differences lags behind. One fruitful approach to the 'function' question is to contrast sexual differentiation in standard laboratory animals with differentiation in species exhibiting unique social and reproductive organizations. Advanced genetic strategies are also addressing this question in worms and flies, and may soon be applicable to vertebrates.
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32
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Winning territorial disputes selectively enhances androgen sensitivity in neural pathways related to motivation and social aggression. Proc Natl Acad Sci U S A 2010; 107:12393-8. [PMID: 20616093 DOI: 10.1073/pnas.1001394107] [Citation(s) in RCA: 162] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Winning aggressive disputes can enhance future fighting ability and the desire to seek out additional contests. In some instances, these effects are long lasting and vary in response to the physical location of a fight. Thus, in principle, winning aggressive encounters may cause long-term and context-dependent changes to brain areas that control the output of antagonistic behavior or the motivation to fight (or both). We examined this issue in the territorial California mouse (Peromyscus californicus) because males of this species are more likely to win fights after accruing victories in their home territory but not after accruing victories in unfamiliar locations. Using immunocytochemistry and real-time quantitative PCR, we found that winning fights either at home or away increases the expression of androgen receptors (AR) in the medial anterior bed nucleus of the stria terminalis, a key brain area that controls social aggression. We also found that AR expression in brain regions that mediate motivation and reward, nucleus accumbens (NAcc) and ventral tegmental area (VTA), increases only in response to fights in the home territory. These effects of winning were likely exclusive to the neural androgenic system because they have no detectible impact on the expression of progestin receptors. Finally, we demonstrated that the observed changes in androgen sensitivity in the NAcc and VTA are positively associated with the ability to win aggressive contests. Thus, winning fights can change brain phenotype in a manner that likely promotes future victory and possibly primes neural circuits that motivate individuals to fight.
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33
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Pinto M, Jepsen KJ, Terranova CJ, Buffenstein R. Lack of sexual dimorphism in femora of the eusocial and hypogonadic naked mole-rat: a novel animal model for the study of delayed puberty on the skeletal system. Bone 2010; 46:112-20. [PMID: 19761882 PMCID: PMC4783644 DOI: 10.1016/j.bone.2009.08.060] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Revised: 07/18/2009] [Accepted: 08/12/2009] [Indexed: 12/22/2022]
Abstract
Sex steroid hormones are major determinants of bone morphology and quality and are responsible for sexually dimorphic skeletal traits. Hypogonadism results in suboptimal skeletal development and may lead to an increased risk of bone fracture later in life. The etiology of delayed puberty and/or hypothalamic amenorrhea is poorly understood, and experimental animal models addressing this issue are predominantly based upon short-term experimental induction of hormonal suppression via gonadotropin releasing hormone antagonists (GnRH-a). This acute change in hormone profile does not necessarily emulate the natural progression of hypogonadic bone disorders. We propose a novel animal model with which to explore the effects of chronic hypogonadism on bone quality, the naked mole-rat (NMR; Heterocephalus glaber). This mouse-size rodent may remain reproductively suppressed throughout its life, if it remains as a subordinate within the eusocial mole-rat colony. NMRs live in large colonies with a single dominant breeding female. She, primarily by using aggressive social contact, naturally suppresses the hypothalamic gonadotropic axis of subordinate NMRs and thereby their reproductive expression. However, should an NMR be separated from the dominant breeder, within less than a week reproductive hormones may become elevated and the animal attains breeding status. We questioned if sexual suppression of subordinates impact upon the development and maintenance of the femora and lead to a sexually indistinct monomorphic skeleton. Femora were obtained from male and female NMRs that were either non-breeders (subordinate) or breeders at the time of sacrifice. Diaphyseal cross-sectional morphology, metaphyseal trabecular micro-architecture and tissue mineral density of the femur were measured using microcomputed tomography and diaphyseal mechanical properties were assessed by four-point bending tests to failure. Subordinates were sexually monomorphic and showed no significant differences in body weight or femoral bone structure and quality between males and females. Femora of subordinate females differed significantly from that of breeding animals, whereas in males, the divergent trend among breeders and non-breeders did not reach statistical significance. Subordinate NMRs, naturally suppressed from entering puberty, may prove to be a useful model to tease apart the relationship between bone morphology and hypogonadism and evaluate skeletal development during pubertal maturation.
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Affiliation(s)
- M Pinto
- City College of CUNY, New York, NY, USA
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34
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Jazin E, Cahill L. Sex differences in molecular neuroscience: from fruit flies to humans. Nat Rev Neurosci 2010; 11:9-17. [DOI: 10.1038/nrn2754] [Citation(s) in RCA: 182] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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35
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Holmes MM, Goldman BD, Goldman SL, Seney ML, Forger NG. Neuroendocrinology and sexual differentiation in eusocial mammals. Front Neuroendocrinol 2009; 30:519-533. [PMID: 19416733 PMCID: PMC2748139 DOI: 10.1016/j.yfrne.2009.04.010] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 04/21/2009] [Accepted: 04/23/2009] [Indexed: 12/21/2022]
Abstract
Sexual differentiation of the mammalian nervous system has been studied intensively for over 25 years. Most of what we know, however, comes from work on relatively non-social species in which direct reproduction (i.e., production of offspring) is virtually the only route to reproductive success. In social species, an individual's inclusive fitness may include contributions to the gene pool that are achieved by supporting the reproductive efforts of close relatives; this feature is most evident in eusocial organisms. Here, we review what is known about neuroendocrine mechanisms, sexual differentiation, and effects of social status on the brain and spinal cord in two eusocial mammals: the naked mole-rat and Damaraland mole-rat. These small rodents exhibit the most rigidly organized reproductive hierarchy among mammals, with reproduction suppressed in a majority of individuals. Our findings suggest that eusociality may be associated with a relative lack of sex differences and a reduced influence of gonadal hormones on some functions to which these hormones are usually tightly linked. We also identify neural changes accompanying a change in social and reproductive status, and discuss the implications of our findings for understanding the evolution of sex differences and the neuroendocrinology of reproductive suppression.
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Affiliation(s)
- Melissa M Holmes
- Center for Neuroendocrine Studies and Department of Psychology, University of Massachusetts, Amherst, MA 01003, USA
| | - Bruce D Goldman
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Sharry L Goldman
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Marianne L Seney
- Center for Neuroendocrine Studies and Department of Psychology, University of Massachusetts, Amherst, MA 01003, USA
| | - Nancy G Forger
- Center for Neuroendocrine Studies and Department of Psychology, University of Massachusetts, Amherst, MA 01003, USA.
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Current world literature. Curr Opin Endocrinol Diabetes Obes 2009; 16:260-77. [PMID: 19390324 DOI: 10.1097/med.0b013e32832c937e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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