101
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Allieri F, Spigolon G, Melcangi R, Collado P, Guillamón A, Gotti S, Panzica G. Androgen receptor deficiency alters the arginine-vasopressin sexually dimorphic system in Tfm rats. Neuroscience 2013; 253:67-77. [DOI: 10.1016/j.neuroscience.2013.08.036] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 08/06/2013] [Accepted: 08/20/2013] [Indexed: 11/24/2022]
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102
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Johnson RT, Breedlove SM, Jordan CL. Androgen receptors mediate masculinization of astrocytes in the rat posterodorsal medial amygdala during puberty. J Comp Neurol 2013; 521:2298-309. [PMID: 23239016 DOI: 10.1002/cne.23286] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 12/03/2012] [Accepted: 12/11/2012] [Indexed: 11/07/2022]
Abstract
Astrocytes in the posterodorsal portion of the medial amygdala (MePD) are sexually dimorphic in adult rats: males have more astrocytes in the right MePD and more elaborate processes in the left MePD than do females. Functional androgen receptors (ARs) are required for masculinization of MePD astrocytes, as these measures are demasculinized in adult males carrying the testicular feminization mutation (Tfm) of the AR gene, which renders AR dysfunctional. We now report that the number of astrocytes is already sexually dimorphic in the right MePD of juvenile 25-day-old (P25) rats. Because Tfm males have as many astrocytes as wild-type males at this age, this prepubertal sexual dimorphism is independent of ARs. After P25, astrocyte number increases in the MePD of all groups, but activation of ARs augments this increase in the right MePD, where more astrocytes are added in males than in Tfm males. Consequently, by adulthood, females and Tfm males have equivalent numbers of astrocytes in the right MePD. Sexual dimorphism in astrocyte arbor complexity in the left MePD arises after P25, and is entirely AR-dependent. Thus, masculinization of MePD astrocytes is a result of both AR-independent processes before the juvenile period and AR-dependent processes afterward.
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Affiliation(s)
- Ryan T Johnson
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824-1101, USA.
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103
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Zorrilla EP, Koob GF. Amygdalostriatal projections in the neurocircuitry for motivation: a neuroanatomical thread through the career of Ann Kelley. Neurosci Biobehav Rev 2013; 37:1932-45. [PMID: 23220696 PMCID: PMC3838492 DOI: 10.1016/j.neubiorev.2012.11.019] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 11/28/2012] [Indexed: 01/25/2023]
Abstract
In MacLean's triune brain, the amygdala putatively subserves motivated behavior by modulating the "reptilian" basal ganglia. Accordingly, Ann Kelley, with Domesick and Nauta, influentially showed that amygdalostriatal projections are much more extensive than were appreciated. They highlighted that amygdalar projections to the rostral ventromedial striatum converged with projections from the ventral tegmental area and cingulate cortex, forming a "limbic striatum". Caudal of the anterior commissure, the entire striatum receives afferents from deep basal nuclei of the amygdala. Orthologous topographic projections subsequently were observed in fish, amphibians, and reptiles. Subsequent functional studies linked acquired value to action via this neuroanatomical substrate. From Dr. Kelley's work evolved insights into components of the distributed, interconnected network that subserves motivated behavior, including the nucleus accumbens shell and core and the striatal-like extended amygdala macrostructure. These heuristic frameworks provide a neuroanatomical basis for adaptively translating motivation into behavior. The ancient amygdala-to-striatum pathways remain a current functional thread not only for stimulus-response valuation, but also for the psychopathological plasticity that underlies addiction-related memory, craving and relapse.
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Affiliation(s)
- Eric P Zorrilla
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA.
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104
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Kelly DA, Varnum MM, Krentzel AA, Krug S, Forger NG. Differential control of sex differences in estrogen receptor α in the bed nucleus of the stria terminalis and anteroventral periventricular nucleus. Endocrinology 2013; 154:3836-46. [PMID: 24025225 PMCID: PMC3776875 DOI: 10.1210/en.2013-1239] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The principal nucleus of the bed nucleus of the stria terminalis (BNSTp) and anteroventral periventricular nucleus of the hypothalamus (AVPV) are sexually dimorphic, hormone-sensitive forebrain regions. Here we report a profound sex difference in estrogen receptor-α (ERα) immunoreactivity (IR) in the BNSTp, with robust ERα IR in females and the near absence of labeling in males. This sex difference is due to the suppression of ERα IR by testicular hormones in adulthood: it was not present at birth and was not altered by neonatal treatment of females with estradiol; gonadectomy of adult males increased ERα IR to that of females, whereas gonadectomy of adult females had no effect. Treating gonadally intact males with an aromatase inhibitor partially feminized ERα IR in the BNSTp, suggesting that testicular suppression required aromatization. By contrast, in AVPV we found a modest sex difference in ERα IR that was relatively insensitive to steroid manipulations in adulthood. ERα IR in AVPV was, however, masculinized in females treated with estradiol at birth, suggesting that the sex difference is due to organizational effects of estrogens. The difference in ERα IR in the BNSTp of males and females appears to be at least in part due to greater expression of mRNA of the ERα gene (Esr1) in females. The sex difference in message is smaller than the difference in immunoreactivity, however, suggesting that posttranscriptional mechanisms also contribute to the pronounced suppression of ERα IR and presumably to functions mediated by ERα in the male BNSTp.
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Affiliation(s)
- D A Kelly
- PhD, Department of Psychology, University of Massachusetts, Amherst, Massachusetts 01003.
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105
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Sexually dimorphic patterns of neural activity in response to juvenile social subjugation. Behav Brain Res 2013; 256:464-71. [PMID: 24004849 DOI: 10.1016/j.bbr.2013.08.042] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 08/20/2013] [Accepted: 08/24/2013] [Indexed: 12/26/2022]
Abstract
After experiencing juvenile social subjugation (JSS), adult female rats display more severe depression- and anxiety-like behaviors than adult males, suggesting that JSS is encoded in a sex-specific manner. To test this hypothesis, prepubertal rats (P28-33) were subjected to 10 aggressive acts in ≤10 min from an aggressive adult male, a 10 min encounter with a non-aggressive adult male, or to 10 min in an empty, clean cage (handled control) and were sacrificed one hour later. We then used unbiased stereology to estimate the total number and proportion of neurons immunoreactive for the immediate early gene product Fos bilaterally in the basolateral amygdala (BLA), the anterior and posterior subdivisions of the bed nucleus of the stria terminalis, and the paraventricular nucleus of the hypothalamus (PVN). Overall, females' Fos responses were less selective than males'. The BLA in males displayed a selective Fos response to the non-aggressive male, whereas no such selectivity occurred in the BLA of females. Additionally, there were more neurons overall in the left BLA than the right and this lateralization was specific to males. The principal subdivision of the BST (BSTpr) in males responded selectively to JSS, whereas the BSTpr in females responded to both the non-aggressive and aggressive males. We also found that the regional volume and neuron number of the BSTpr is greater in males than in females. Finally, the PVN in males was, like the BLA, selective for the non-aggressive male, whereas none of the experiences elicited a selective response in females. The greater selectivity for non-threatening stimuli in males in three stress-responsive brain regions may be a clue as to why males are less susceptible to the anxiogenic effects of JSS.
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106
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Karaismailoğlu S, Erdem A. The effects of prenatal sex steroid hormones on sexual differentiation of the brain. J Turk Ger Gynecol Assoc 2013; 14:163-7. [PMID: 24592097 DOI: 10.5152/jtgga.2013.86836] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 05/26/2013] [Indexed: 12/11/2022] Open
Abstract
Most of the anatomical, physiological and neurochemical gender-related differences in the brain occur prenatally. The sexual differences in the brain are affected by sex steroid hormones, which play important roles in the differentiation of neuroendocrine system and behavior. Testosterone, estrogen and dihydrotestosterone are the main steroid hormones responsible for the organization and sexual differentiation of brain structures during early development. The structural and behavioral differences in the female and male brains are observed in many animal species; however, these differences are variable between species. Animal and human (in vivo imaging and postmortem) studies on sex differences in the brain have shown many differences in the local distribution of the cortex, the gray-white matter ratio, corpus callosum, anterior commissure, hypothalamus, bed nucleus of the stria terminalis, limbic system and neurotransmitter systems. This review aims to evaluate the anatomical, physiological and neurochemical differences in the female and male brains and to assess the effect of prenatal exposure to sex steroid hormones on the developing brain.
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Affiliation(s)
| | - Ayşen Erdem
- Department of Physiology, Hacettepe University Faculty of Medicine, Ankara, Turkey
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107
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The amygdala in the guinea pig is sexually dimorphic—A morphometric study. Brain Res 2013; 1524:44-53. [DOI: 10.1016/j.brainres.2013.06.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 05/24/2013] [Accepted: 06/04/2013] [Indexed: 11/22/2022]
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108
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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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109
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Shaw AZ. The effect of prenatal androgen exposure on the development of neural reactivity systems: A study of the HEXACO Personality Inventory. PERSONALITY AND INDIVIDUAL DIFFERENCES 2013. [DOI: 10.1016/j.paid.2013.01.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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110
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Chung WCJ, Auger AP. Gender differences in neurodevelopment and epigenetics. Pflugers Arch 2013; 465:573-84. [PMID: 23503727 DOI: 10.1007/s00424-013-1258-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 02/26/2013] [Accepted: 02/27/2013] [Indexed: 01/19/2023]
Abstract
The concept that the brain differs in make-up between males and females is not new. For example, it is well established that anatomists in the nineteenth century found sex differences in human brain weight. The importance of sex differences in the organization of the brain cannot be overstated as they may directly affect cognitive functions, such as verbal skills and visuospatial tasks in a sex-dependent fashion. Moreover, the incidence of neurological and psychiatric diseases is also highly dependent on sex. These clinical observations reiterate the importance that gender must be taken into account as a relevant possible contributing factor in order to understand the pathogenesis of neurological and psychiatric disorders. Gender-dependent differentiation of the brain has been detected at every level of organization--morphological, neurochemical, and functional--and has been shown to be primarily controlled by sex differences in gonadal steroid hormone levels during perinatal development. In this review, we discuss howthe gonadal steroid hormone testosterone and its metabolites affect downstream signaling cascades, including gonadal steroid receptor activation, and epigenetic events in order to differentiate the brain in a gender-dependent fashion.
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Affiliation(s)
- Wilson C J Chung
- Department of Biological Sciences and School of Biomedical Sciences, Kent State University, Kent, OH 44242, USA.
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111
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Cao J, Rebuli ME, Rogers J, Todd KL, Leyrer SM, Ferguson SA, Patisaul HB. Prenatal bisphenol A exposure alters sex-specific estrogen receptor expression in the neonatal rat hypothalamus and amygdala. Toxicol Sci 2013; 133:157-73. [PMID: 23457122 DOI: 10.1093/toxsci/kft035] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Bisphenol A (BPA) exposure is ubiquitous, and in laboratory animals, early-life BPA exposure has been shown to alter sex-specific neural organization, neuroendocrine physiology, and behavior. The specific mechanisms underlying these brain-related outcomes, however, remain largely unknown, constraining the capacity to ascertain the potential human relevance of neural effects observed in animal models. In the perinatal rat brain, estrogen is masculinizing, suggesting that BPA-induced perturbation of estrogen receptor (ESR) expression may underpin later in-life neuroendocrine effects. We hypothesized that prenatal BPA exposure alters sex-specific ESR1 (ERα) and ESR2 (ERβ) expression in postnatal limbic nuclei. Sprague Dawley rats were mated and gavaged on gestational days (GDs) 6-21 with vehicle, 2.5 or 25 μg/kg bw/day BPA, or 5 or 10 μg/kg bw/day ethinyl estradiol. An additional group was restrained but not gavaged (naïve control). Offspring were sacrificed the day after birth to quantify ESR gene expression throughout the hypothalamus and amygdala by in situ hybridization. Relative to the vehicle group, significant effects of BPA were observed on ESR1 and ESR2 expression throughout the mediobasal hypothalamus and amygdala in both sexes. Significant differences in ESR expression were also observed in the mediobasal hypothalamus and amygdala of the naïve control group compared with the vehicle group, highlighting the potential for gavage to influence gene expression in the developing brain. These results indicate that ESR expression in the neonatal brain of both sexes can be altered by low-dose prenatal BPA exposure.
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Affiliation(s)
- Jinyan Cao
- Department of Biology, NCSU, Raleigh, North Carolina 27695, USA
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112
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Cao J, Patisaul HB. Sex-specific expression of estrogen receptors α and β and Kiss1 in the postnatal rat amygdala. J Comp Neurol 2013; 521:465-78. [PMID: 22791648 PMCID: PMC3492514 DOI: 10.1002/cne.23185] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 05/16/2012] [Accepted: 07/06/2012] [Indexed: 12/11/2022]
Abstract
The rodent amygdaloid complex is composed of numerous subnuclei important for the sex-specific regulation of sociosexual behavior. Although estrogen receptors (ERs) are critical for organizing functional and cytoarchitectural sex differences in these subnuclei, a detailed developmental profile of ER expression in the amygdaloid complex is not available. Moreover, the kisspeptin gene (Kiss1) was recently identified in the adult amygdala, but it remains unknown if it is expressed during development. To fill these data gaps, rat brains (5-7/group) were assessed on postnatal days (PNDs) 0, 2, 4, 7, and 19 for ER alpha (ERα; Esr1), beta (ERβ; Esr2), and Kiss1 expression using in situ hybridization. Expression was quantified in the posterodorsal portion of the medial amygdala posterodorsal (MePD), lateral (PLCo), and medial (PMCo) components of the posterior cortical nucleus, and the amygdalohippocampal area (AHi). ERα expression was high throughout the amygdala at birth, but sexually dimorphic only in the AHi. ERα expression in the MePD and the PLCo showed a U-shaped expression pattern over time. In the PMCo, ERα expression decreased from PND 2 and remained low through PND 19. Sexually dimorphic expression of ERβ in the MePD was observed on PND 0, with higher levels in females, but reversed by PND 4 due to declining levels in females. No Kiss1 signal was observed in the postnatal amygdala, suggesting that expression arises after puberty. These data reveal that ER expression is region-specific within the neonatal amygdala. These differences likely contribute to sex differences in sociosexual behavior across the lifespan.
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Affiliation(s)
- Jinyan Cao
- Department of Biology, North Carolina State University, Raleigh, North Carolina 27695, USA
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113
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Fukushima A, Furuta M, Kimura F, Akema T, Funabashi T. Testosterone exposure during the critical period decreases corticotropin-releasing hormone-immunoreactive neurons in the bed nucleus of the stria terminalis of female rats. Neurosci Lett 2013; 534:64-8. [DOI: 10.1016/j.neulet.2012.11.065] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2012] [Revised: 10/16/2012] [Accepted: 11/16/2012] [Indexed: 11/25/2022]
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114
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Social condition and oxytocin neuron number in the hypothalamus of naked mole-rats (Heterocephalus glaber). Neuroscience 2013. [DOI: 10.1016/j.neuroscience.2012.11.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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115
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Calabrese E, Johnson GA, Watson C. An ontology-based segmentation scheme for tracking postnatal changes in the developing rodent brain with MRI. Neuroimage 2012; 67:375-84. [PMID: 23246176 DOI: 10.1016/j.neuroimage.2012.11.037] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 10/11/2012] [Accepted: 11/15/2012] [Indexed: 10/27/2022] Open
Abstract
The postnatal period of neurodevelopment has been implicated in a number of brain disorders including autism and schizophrenia. Rodent models have proven to be invaluable in advancing our understanding of the human brain, and will almost certainly play a pivotal role in future studies on postnatal neurodevelopment. The growing field of magnetic resonance microscopy has the potential to revolutionize our understanding of neurodevelopment, if it can be successfully and appropriately assimilated into the vast body of existing neuroscience research. In this study, we demonstrate the utility of a developmental neuro-ontology designed specifically for tracking regional changes in MR biomarkers throughout postnatal neurodevelopment. Using this ontological classification as a segmentation guide, we track regional changes in brain volume in rats between postnatal day zero and postnatal day 80 and demonstrate differential growth rates in axial versus paraxial brain regions. Both the ontology and the associated label volumes are provided as a foundation for future MR-based studies of postnatal neurodevelopment in normal and disease states.
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Affiliation(s)
- Evan Calabrese
- Center for In Vivo Microscopy, Department of Radiology, Box 3302 Duke University Medical Center, Durham, NC 27710, USA
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116
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Welkenhuysen M, Gligorijevic I, Ameye L, Prodanov D, Van Huffel S, Nuttin B. Neuronal activity in the bed nucleus of the stria terminalis in a rat model for obsessive-compulsive disorder. Behav Brain Res 2012. [PMID: 23195114 DOI: 10.1016/j.bbr.2012.11.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In search of a new potential target for deep brain stimulation in patients with obsessive-compulsive disorder (OCD), we evaluated the single-cell activity of neurons in the bed nucleus of the stria terminalis (BST) in urethane-anesthetized rats in an animal model for OCD, the schedule-induced polydipsia (SIP) model, and compared this to the BST activity in control rats and to a third group of rats which were introduced in the model but did not develop the SIP, and thus were considered resistant. We compared the firing rate and firing pattern of BST neurons between these groups, between hemispheres and made a correlation of the firing rate and firing pattern to the position in the BST. The variability of BST neurons in SIP rats was lower and the randomness higher than BST neurons in control rats or resistant rats. The firing rate of BST neurons in SIP rats was significantly higher and the burst index lower than BST neurons in resistant rats but not in control rats. Also, neurons from the right hemisphere in the SIP group had a higher burst index than neurons from the left hemisphere. However, this is opposite in the resistant and control group. Third, we found a higher bursting index with increasing (more ventral) depth of recording. These findings suggest that schedule-induced polydipsia, which models compulsive behavior in humans, induces a change in firing behavior of BST neurons.
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Affiliation(s)
- Marleen Welkenhuysen
- Laboratory of Experimental Functional Neurosurgery, Department of Neurosciences, K.U. Leuven, Provisorium II, Minderbroedersstraat 19 Box 1033, 3000 Leuven, Belgium.
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117
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Hiraki T, Takeuchi A, Tsumaki T, Zempo B, Kanda S, Oka Y, Nagahama Y, Okubo K. Female-specific target sites for both oestrogen and androgen in the teleost brain. Proc Biol Sci 2012; 279:5014-23. [PMID: 23075834 DOI: 10.1098/rspb.2012.2011] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
To dissect the molecular and cellular basis of sexual differentiation of the teleost brain, which maintains marked sexual plasticity throughout life, we examined sex differences in neural expression of all subtypes of nuclear oestrogen and androgen receptors (ER and AR) in medaka. All receptors were differentially expressed between the sexes in specific nuclei in the forebrain. The most pronounced sex differences were found in several nuclei in the ventral telencephalic and preoptic areas, where ER and AR expression were prominent in females but almost completely absent in males, indicating that these nuclei represent female-specific target sites for both oestrogen and androgen in the brain. Subsequent analyses revealed that the female-specific expression of ER and AR is not under the direct control of sex-linked genes but is instead regulated positively by oestrogen and negatively by androgen in a transient and reversible manner. Taken together, the present study demonstrates that sex-specific target sites for both oestrogen and androgen occur in the brain as a result of the activational effects of gonadal steroids. The consequent sex-specific but reversible steroid sensitivity of the adult brain probably contributes substantially to the process of sexual differentiation and the persistent sexual plasticity of the teleost brain.
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Affiliation(s)
- Towako Hiraki
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan
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118
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Johnson RT, Schneider A, DonCarlos LL, Breedlove SM, Jordan CL. Astrocytes in the rat medial amygdala are responsive to adult androgens. J Comp Neurol 2012; 520:2531-44. [PMID: 22581688 PMCID: PMC4209966 DOI: 10.1002/cne.23061] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The posterodorsal medial amygdala (MePD) exhibits numerous sex differences including differences in volume and in the number and morphology of neurons and astroctyes. In adulthood, gonadal hormones, including both androgens and estrogens, have been shown to play a role in maintaining the masculine character of many of these sex differences, but whether adult gonadal hormones maintain the increased number and complexity of astrocytes in the male MePD was unknown. To answer this question we examined astrocytes in the MePD of male and female Long Evans rats that were gonadectomized as adults and treated for 30 days with either testosterone or a control treatment. At the end of treatment brains were collected and immunostained for glial fibrillary acidic protein. Stereological analysis revealed that adult androgen levels influenced the number and complexity of astrocytes in the MePD of both sexes, but the specific effects of androgens were different in males and females. However, sex differences in the number and complexity of adult astrocytes persisted even in the absence of gonadal hormones in adulthood, suggesting that androgens also act earlier in life to determine these adult sex differences. Using immunofluorescence and confocal microscopy, we found robust androgen receptor immunostaining in a subpopulation of MePD astrocytes, suggesting that testosterone may act directly on MePD astrocytes to influence their structure and function.
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Affiliation(s)
- Ryan T Johnson
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824-1101, USA.
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119
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Weathington JM, Strahan JA, Cooke BM. Social experience induces sex-specific fos expression in the amygdala of the juvenile rat. Horm Behav 2012; 62:154-61. [PMID: 22771954 DOI: 10.1016/j.yhbeh.2012.06.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 06/23/2012] [Accepted: 06/25/2012] [Indexed: 11/19/2022]
Abstract
To compare the response of the medial amygdala and central amygdala to juvenile social subjugation (JSS), we used unbiased stereology to quantify the immediate early gene product Fos in prepubertal rats after aggressive or benign social encounters or handling. We estimated the overall number of neurons and the proportion of Fos immunoreactive neurons in the posterodorsal (MePD) and posteroventral medial amygdala (MePV) and the central amygdala (CeA). Experience elicited Fos in a sex- and hemisphere-dependent manner in the MePD. The left MePD was selective for JSS in both sexes, but the right MePD showed a specific Fos response to JSS in males only. In the MePV, irrespective of hemisphere or sex, JSS elicited the greatest amount of Fos, benign social experience elicited an intermediate level, and handling the least. None of the experiential conditions elicited significant levels of Fos in the CeA. We found a previously unreported sex difference in the number of CeA neurons (M>F) that was highly significant and a strong trend toward a sex difference (M>F) in the MePD. These data show that the posterior MeA subnuclei are more responsive to JSS than to benign social interaction, that sex interacts with hemispheric laterality to determine the response of the MePD to JSS and that the MePV responds to social experience and JSS. Taken together, these findings support the hypothesis that juvenile rats process JSS in a sex-specific manner.
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Affiliation(s)
- Jill M Weathington
- Neuroscience Institute, Georgia State University, 100 Piedmont Avenue, SE, Atlanta, GA 30303‐5030, USA
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120
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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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121
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Waddell J, McCarthy MM. Sexual differentiation of the brain and ADHD: what is a sex difference in prevalence telling us? Curr Top Behav Neurosci 2012; 9:341-60. [PMID: 21120649 PMCID: PMC4841632 DOI: 10.1007/7854_2010_114] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Sexual differentiation of the brain is a function of various processes that prepare the organism for successful reproduction in adulthood. Release of gonadal steroids during both the perinatal and the pubertal stages of development organizes many sex differences, producing changes in brain excitability and morphology that endure across the lifespan. To achieve these sexual dimorphisms, gonadal steroids capitalize on a number of distinct mechanisms across brain regions. Comparison of the developing male and female brain provides insight into the mechanisms through which synaptic connections are made, and circuits are organized that mediate sexually dimorphic behaviors. The prevalence of most psychiatric and neurological disorders differ in males versus females, including disorders of attention, activity and impulse control. While there is a strong male bias in incidence of attention deficit and hyperactivity disorders, the source of that bias remains controversial. By elucidating the biological underpinnings of male versus female brain development, we gain a greater understanding of how hormones and genes do and do not contribute to the differential vulnerability in one sex versus the other.
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Affiliation(s)
- Jaylyn Waddell
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, 21201, USA,
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122
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Funayama R, Sugiura M, Sassa Y, Jeong H, Wakusawa K, Horie K, Sato S, Kawashima R. Neural bases of human mate choice: Multiple value dimensions, sex difference, and self-assessment system. Soc Neurosci 2012; 7:59-73. [DOI: 10.1080/17470919.2011.580120] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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123
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Zhou L, Ghee SM, Chan C, Lin L, Cameron MD, Kenny PJ, See RE. Orexin-1 receptor mediation of cocaine seeking in male and female rats. J Pharmacol Exp Ther 2011; 340:801-9. [PMID: 22186370 DOI: 10.1124/jpet.111.187567] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies have shown that female rats exhibit enhanced cocaine seeking during multiple phases of cocaine addiction compared with males. The orexin/hypocretin system recently has been implicated in drug addiction in male rats. Based on the known sex differences in cocaine addiction, in the current study we examined orexin-mediated cocaine seeking during self-administration, extinction, and reinstatement in age-matched male (initial weight 250-300 g) and female (initial weight 175-225 g) Sprague-Dawley rats by using the orexin-1 receptor (OX1R) antagonist 1-(2-methylbenzoxazol-6-yl)-3-[1,5]naphthyridin-4-yl urea (SB-334867) (10-30 mg/kg). OX1R blockade had no effect on established cocaine self-administration, but attenuated cocaine seeking during extinction in both male and female rats. It is noteworthy that OX1R blockade potently attenuated cue-induced reinstatement in males but had no effect on females. SB-334867 also reduced cocaine seeking during pharmacological stress-induced (yohimbine, 2.5 mg/kg) and yohimbine + cue-induced reinstatement in both sexes. SB-334867 failed to affect reinstatement induced by cocaine (10 mg/kg) in either male or female rats, but selectively reduced cocaine + cue-induced reinstatement only in males. In separate experiments examining basal and cocaine-induced locomotion, SB-334867 attenuated locomotion in both male and female rats. Finally, assessment of plasma and brain levels of SB-334867 showed that estrus females had slightly higher plasma levels than diestrus females, but no overall sex differences or estrous cycle differences were observed in plasma or brain SB-334867 concentrations. These results show that OX1R signaling plays a role in mediating cocaine seeking, but differs between the sexes for cue-induced reinstatement.
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Affiliation(s)
- Luyi Zhou
- Department of Neurosciences, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
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124
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Abstract
Convincing evidence indicates that prenatal exposure to the gonadal hormone, testosterone, influences the development of children's sex-typical toy and activity interests. In addition, growing evidence shows that testosterone exposure contributes similarly to the development of other human behaviors that show sex differences, including sexual orientation, core gender identity, and some, though not all, sex-related cognitive and personality characteristics. In addition to these prenatal hormonal influences, early infancy and puberty may provide additional critical periods when hormones influence human neurobehavioral organization. Sex-linked genes could also contribute to human gender development, and most sex-related characteristics are influenced by socialization and other aspects of postnatal experience, as well. Neural mechanisms underlying the influences of gonadal hormones on human behavior are beginning to be identified. Although the neural mechanisms underlying experiential influences remain largely uninvestigated, they could involve the same neural circuitry as that affected by hormones.
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Affiliation(s)
- Melissa Hines
- Department of Social and Developmental Psychology, University of Cambridge, Cambridge, CB2 3RQ, United Kingdom.
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125
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Lin LC, Lewis DA, Sibille E. A human-mouse conserved sex bias in amygdala gene expression related to circadian clock and energy metabolism. Mol Brain 2011; 4:18. [PMID: 21542937 PMCID: PMC3098780 DOI: 10.1186/1756-6606-4-18] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Accepted: 05/04/2011] [Indexed: 11/16/2022] Open
Abstract
Background Major depression affects twice as many women as men, but the underlying molecular mechanisms responsible for the heightened female vulnerability are not known. The amygdala, composed of heterogeneous subnuclei, participates in multiple functional circuits regulating emotional responses to stress. We hypothesized that sex differences in molecular structure may contribute to differential mood regulation and disease vulnerability. Findings Using gene arrays followed by quantitative PCR validation, we compared the transcriptome profiles between sexes in human and mouse amygdala. We now report sexually dimorphic features of transcriptomes in the basolateral nucleus of the amygdala, and these features are highly conserved across species. A functional analysis of differential gene expression showed that mitochondrial-related gene groups were identified as the top biological pathways associated with sexual dimorphism in both species. Conclusions These results suggest that the basolateral amygdala is a sexually dimorphic structure, featuring a regulatory cascade of mitochondrial function and circadian rhythm, potentially linked through sirtuins and hormone nuclear receptors. Hence, baseline differences in amygdalar circadian regulation of cellular metabolism may contribute to sex-related differences in mood regulation and vulnerability to major depression.
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Affiliation(s)
- Li-Chun Lin
- Translational Neuroscience Program, Department of Psychiatry, and Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15213, USA
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126
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Naninck EFG, Lucassen PJ, Bakker J. Sex differences in adolescent depression: do sex hormones determine vulnerability? J Neuroendocrinol 2011; 23:383-92. [PMID: 21418338 DOI: 10.1111/j.1365-2826.2011.02125.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Depression is one of the most common, costly and severe psychopathologies worldwide. Its incidence, however, differs significantly between the sexes, and depression rates in women are twice those of men. Interestingly, this sex difference emerges during adolescence. Although the adolescent period is characterised by major physical and behavioural transformations, it is unclear why the incidence of depression increases so dramatically in girls during this otherwise generally healthy developmental period. Although psychological and environmental factors are also involved, we discuss the neuroendocrinological factors determining adolescent vulnerability to depression. In particular, we address the role of sex steroids in mood regulation, hypothalamic-pituitary-adrenal axis maturation and sexual differentiation of the brain, with a focus on hippocampal plasticity.
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Affiliation(s)
- E F G Naninck
- Centre for Neuroscience, Swammerdam Institute of Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
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127
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The genetics of sex differences in brain and behavior. Front Neuroendocrinol 2011; 32:227-46. [PMID: 20951723 PMCID: PMC3030621 DOI: 10.1016/j.yfrne.2010.10.001] [Citation(s) in RCA: 216] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Revised: 10/04/2010] [Accepted: 10/06/2010] [Indexed: 11/22/2022]
Abstract
Biological differences between men and women contribute to many sex-specific illnesses and disorders. Historically, it was argued that such differences were largely, if not exclusively, due to gonadal hormone secretions. However, emerging research has shown that some differences are mediated by mechanisms other than the action of these hormone secretions and in particular by products of genes located on the X and Y chromosomes, which we refer to as direct genetic effects. This paper reviews the evidence for direct genetic effects in behavioral and brain sex differences. We highlight the 'four core genotypes' model and sex differences in the midbrain dopaminergic system, specifically focusing on the role of Sry. We also discuss novel research being done on unique populations including people attracted to the same sex and people with a cross-gender identity. As science continues to advance our understanding of biological sex differences, a new field is emerging that is aimed at better addressing the needs of both sexes: gender-based biology and medicine. Ultimately, the study of the biological basis for sex differences will improve healthcare for both men and women.
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128
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Nugent BM, McCarthy MM. Epigenetic underpinnings of developmental sex differences in the brain. Neuroendocrinology 2011; 93:150-8. [PMID: 21411982 PMCID: PMC7068790 DOI: 10.1159/000325264] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 01/28/2011] [Indexed: 12/12/2022]
Abstract
Sexual differentiation of the brain is a crucial developmental process that enables the lifelong expression of sexually dimorphic behaviors, including those necessary for successful reproduction. During a perinatal sensitive period, gonadal hormones defeminize and masculinize the male brain, and a lack of gonadal steroids allows for feminization in the female. This hormonally-induced differentiation permanently alters neural structures, creating highly dimorphic brain regions; however, the mechanism by which hormones exert their long-lasting effects are still largely unknown. Epigenetic processes such as DNA methylation and histone modifications serve as an interface for environmental stimuli to exert control over the genome. These modifications have the capacity to activate or repress gene expression, thereby shaping the developmental outcomes of cells, circuits, and structures in the brain. Sex differences in methylation, methyl-binding proteins, and chromatin modifications indicate that epigenetic mechanism may be important for sexual differentiation of the brain. The data outlined in this review provide evidence that gonadal hormones in the neonatal brain influence epigenetic processes such as DNA methylation and histone acetylation, but also emphasize the primitive status of our current understanding of epigenetics and sexual differentiation and the brain.
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Affiliation(s)
- Bridget M Nugent
- Program in Neuroscience, University of Maryland, School of Medicine, Baltimore, MD, USA.
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129
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Blockade of androgen receptor in the medial amygdala inhibits noncontact erections in male rats. Physiol Behav 2011; 103:295-301. [PMID: 21315100 DOI: 10.1016/j.physbeh.2011.02.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 01/27/2011] [Accepted: 02/02/2011] [Indexed: 11/21/2022]
Abstract
Our previous work demonstrated that androgens in the medial amygdala (MeA) of castrated male rats maintained noncontact erections (NCEs), which occur during exposure to an inaccessible receptive female, for one week after implantation. The present experiments investigated the effects of implantation into the MeA of either flutamide (F), a blocker of androgen receptors, or of 1,4,6-androstatrien-3,17-dione (ATD), which blocks aromatization of testosterone. One day after implantation of F, fewer males displayed NCEs, and had longer latencies to the first NCE and fewer NCEs, and spent less total time in genital grooming, compared to the control group. ATD had only weak facilitative effects on some measures of NCEs. These results suggest that androgen receptors in the MeA play a major role in the regulation of NCEs and that the MeA is one of the neuronal structures that regulate male sexual arousal. Furthermore, it is sensitive to relatively fast changes in the level of androgen receptors stimulation.
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130
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Tsukahara S, Tsuda MC, Kurihara R, Kato Y, Kuroda Y, Nakata M, Xiao K, Nagata K, Toda K, Ogawa S. Effects of aromatase or estrogen receptor gene deletion on masculinization of the principal nucleus of the bed nucleus of the stria terminalis of mice. Neuroendocrinology 2011; 94:137-47. [PMID: 21525731 DOI: 10.1159/000327541] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Accepted: 03/15/2011] [Indexed: 11/19/2022]
Abstract
The principal nucleus of the bed nucleus of the stria terminalis (BNSTp) is a sexually dimorphic nucleus, and the male BNSTp is larger and has more neurons than the female BNSTp. To assess the roles of neuroestrogen synthesized from testicular androgen by brain aromatase in masculinization of the BNSTp, we performed morphometrical analyses of the adult BNSTp in aromatase knockout (ArKO), estrogen receptor-α knockout (αERKO), and estrogen receptor-β knockout (βERKO) mice and their respective wild-type littermates. In wild-type littermates, the BNSTp of males had a larger volume and greater numbers of neuronal and glial cells than did that of females. The volume and neuron number of the BNSTp in ArKO and αERKO males and glial cell number of the BNSTp in αERKO males were significantly smaller than those of wild-type male littermates, and they were not significantly different from those in female mice with either gene knockout. In contrast, there was no significant morphological difference in the BNSTp between βERKO and wild-type mice. Next, we examined the BNSTp of ArKO males subcutaneously injected with estradiol benzoate (EB) on postnatal days 1, 2, and 3 (1.5 μg/day). EB-treated ArKO males had a significantly greater number of BNSTp neurons than did oil-treated ArKO males. The number of BNSTp neurons in EB-treated ArKO males was comparable to that in wild-type males. These findings suggested that masculinization of the BNSTp in mice involves the actions of neuroestrogen that was synthesized by aromatase and that this estrogen mostly binds to ERα during the postnatal period.
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Affiliation(s)
- Shinji Tsukahara
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama City, Japan.
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131
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Sex difference in cell proliferation in developing rat amygdala mediated by endocannabinoids has implications for social behavior. Proc Natl Acad Sci U S A 2010; 107:20535-40. [PMID: 21059913 DOI: 10.1073/pnas.1005003107] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The amygdala is a sexually dimorphic brain region critical for the regulation of social, cognitive, and emotional behaviors, but both the nature and the source of sex differences in the amygdala are largely unknown. We have identified a unique sex difference in the developing rat medial amygdala (MeA) that is regulated by cannabinoids. Newborn females had higher rates of cell proliferation than males. Treatment of neonates with the cannabinoid receptor agonist, WIN 55,212-2 (WIN), reduced cell proliferation in females to that of males and a wide range of WIN doses had no effect on cell proliferation in males. The effect of WIN on cell proliferation in the MeA was prevented by coinfusions of a CB2 but not CB1 receptor antagonist. Females had higher amygdala content of the endocannabinoid degradation enzymes, fatty acid amid hydrolase, and monoacylglycerol lipase than males, and lower amounts of the endocannabinoids 2-arachidonoylglycerol and N-arachidonylethanolamide (anandamide). Inhibition of the degradation of 2-arachidonoylglycerol in females occluded the sex difference in cell proliferation. Analyses of cell fate revealed that females had significantly more newly generated glial cells but not more newly generated neurons than males, and treatment with WIN significantly decreased glial cell genesis in females but not males. Finally, early exposure to cannabinoids masculinized juvenile play behavior in females but did not alter this behavior in males. Collectively, our findings suggest that sex differences in endocannabinoids mediate a sex difference in glial cell genesis in the developing MeA that impacts sex-specific behaviors in adolescence.
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132
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Amygdalar shape analysis method using surface contour aligning, spherical mapping, and probabilistic subregional segmentation. Neurosci Lett 2010; 488:65-9. [PMID: 21056631 DOI: 10.1016/j.neulet.2010.11.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2010] [Accepted: 11/01/2010] [Indexed: 02/05/2023]
Abstract
The objective of this study was to develop a reliable method for the shape analysis of the amygdala, a structure that is important in gaining a better understanding of the limbic system in the human brain. The goal of this study was threefold; to develop (1) a robust method for aligning the contour of the amygdala; (2) a reproducible method for extracting surface parameters of the amygdala using a spherical mapping technique; and (3) a standardized approach for statistical assessment and visualization of shape alterations by applying the probabilistic maps of amygdalar subregions. This technique was validated by conducting an artificial phantom study and by assessing sex-related amygdalar shape differences using T1-weighted images from healthy volunteers. In the phantom study, the region with atrophy was detected successfully through the shape analysis process. In the human study, the average radii of the centromedial (CM) subregion in the left amygdala and laterobasal (LB), superficial (SF) and CM subregions in the right amygdala were different between sexes (t-tests, p=0.02, 0.04, 0.04, and 0.002, respectively). In addition, focal regions with larger radii in amygdalae of men than those of women were found predominantly on the surfaces of bilateral SF and bilateral CM subregions, after the volumes of the amygdala had been scaled to the unit volume (1000mm(3)) (Mann-Whitney U-test, false discovery rate corrected p<0.05, clustered vertex points>25). Regions with smaller radii in amygdalae of men were found predominantly on the anterior surfaces of the right LB and SF subregions (Mann-Whitney U-test, false discovery rate corrected p<0.05, clustered vertex points>25). This is generally in agreement with previous findings from animal studies. The current method may be used for measuring subtle local shape changes of the amygdala in various psychiatric or neurologic disorders.
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133
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Abstract
The amygdala has received considerable attention because of its established role in specific behaviors and disorders such as anxiety, depression, and autism. Studies have revealed that the amygdala is a complex and dynamic brain region that is highly connected with other areas of the brain. Previous works have focused on neurons, demonstrating that the amygdala in rodents is highly plastic and sexually dimorphic. However, our more recent work explores sex differences in nonneuronal cells, joining a rich literature concerning glia in the amygdala. Prior investigation of glia in the amygdala can generally be divided into disease-related and hormone-related categories, with both areas of research producing interesting findings concerning glia in this important brain region. Despite a wide range of research topics, the collected findings make it clear that glia in the amygdala are sensitive and plastic cells that respond and develop in a highly region specific manner.
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134
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Chou KH, Cheng Y, Chen IY, Lin CP, Chu WC. Sex-linked white matter microstructure of the social and analytic brain. Neuroimage 2010; 54:725-33. [PMID: 20633662 DOI: 10.1016/j.neuroimage.2010.07.010] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2010] [Revised: 05/23/2010] [Accepted: 07/06/2010] [Indexed: 11/17/2022] Open
Abstract
Sexual dimorphism in the brain is known to underpin sex differences in neuropsychological behaviors. The white matter (WM) microstructure appears to be coupled with cognitive performances. However, the issues concerning sex differences in WM remains to be determined. This study used the tract-based spatial statistics on diffusion tensor imaging concurrently with the assessments of Empathizing Quotient (EQ) and Systemizing Quotient (SQ) in forty healthy female and forty male adults. Females exhibited greater fractional anisotropy (FA) in the fronto-occipital fasciculus, body of the corpus callosum, and WM underlying the parahippocampal gyrus. Males exhibited larger FA in the bilateral internal capsule, WM underlying the medial frontal gyrus, fusiform gyrus, hippocampus, insula, postcentral gyrus, frontal and temporal lobe. Interestingly, the interaction analysis of dispositional measures by sex showed that females had a positive correlation between FA of the WM underlying the inferior parietal lobule and superior temporal gyrus and EQ but a negative correlation between FA of the occipital and postcentral gyrus and SQ. Males displayed the opposite effect. The findings indicate a sexual dimorphism of WM microstructure. Divergent correlations of WM microstructure and neuropsychological behaviors between sexes may account for the higher prevalence of autism spectrum disorders in males.
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Affiliation(s)
- Kun-Hsien Chou
- Institute of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan
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135
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Semaan SJ, Kauffman AS. Sexual differentiation and development of forebrain reproductive circuits. Curr Opin Neurobiol 2010; 20:424-31. [PMID: 20471241 DOI: 10.1016/j.conb.2010.04.004] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 04/08/2010] [Accepted: 04/09/2010] [Indexed: 11/19/2022]
Abstract
Males and females exhibit numerous anatomical and physiological differences in the brain that often underlie important sex differences in physiology or behavior, including aspects relating to reproduction. Neural sex differences are both region-specific and trait-specific and may consist of divergences in synapse morphology, neuron size and number, and specific gene expression levels. In most cases, sex differences are induced by the sex steroid hormonal milieu during early perinatal development. In rodents, the hypothalamic anteroventral periventricular nucleus (AVPV) is sexually differentiated as a result of postnatal sex steroids, and also specific neuronal populations in this nucleus are sexually dimorphic, with females possessing more kisspeptin, dopaminergic, and GABA/glutamate neurons than males. The ability of female rodents, but not males, to display an estrogen-induced luteinizing hormone (LH) surge is consistent with the higher levels of these neuropeptides in the AVPV of females. Of these AVPV populations, the recently identified kisspeptin system has been most strongly implicated as a crucial component of the sexually dimorphic LH surge mechanism, though GABA and glutamate have also received some attention. New findings have suggested that the sexual differentiation and development of kisspeptin neurons in the AVPV is mediated by developmental estradiol signaling. Although apoptosis is the most common process implicated in neuronal sexual differentiation, it is currently unknown how developmental estradiol acts to differentiate specific neuronal populations in the AVPV, such as kisspeptin or dopaminergic neurons.
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Affiliation(s)
- Sheila J Semaan
- Department of Reproductive Medicine, University of California, San Diego, La Jolla, CA, USA
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136
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Keller M, Pawluski JL, Brock O, Douhard Q, Bakker J. The alpha-fetoprotein knock-out mouse model suggests that parental behavior is sexually differentiated under the influence of prenatal estradiol. Horm Behav 2010; 57:434-40. [PMID: 20109458 PMCID: PMC4298041 DOI: 10.1016/j.yhbeh.2010.01.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Revised: 01/20/2010] [Accepted: 01/21/2010] [Indexed: 11/28/2022]
Abstract
In rodent species, sexual differentiation of the brain for many reproductive processes depends largely on estradiol. This was recently confirmed again by using the alpha-fetoprotein knockout (AFP-KO) mouse model, which lacks the protective actions of alpha-fetoprotein against maternal estradiol and as a result represents a good model to determine the contribution of prenatal estradiol to the sexual differentiation of the brain and behavior. Female AFP-KO mice were defeminized and masculinized with regard to their neuroendocrine responses as well as sexual behavior. Since parental behavior is also strongly sexually differentiated in mice, we used the AFP-KO mouse model here to ask whether parental responses are differentiated prenatally under the influence of estradiol. It was found that AFP-KO females showed longer latencies to retrieve pups to the nest and also exhibited lower levels of crouching over the pups in the nest in comparison to WT females. In fact, they resembled males (WT and AFP-KO). Other measures of maternal behavior, for example the incidence of infanticide, tended to be higher in AFP-KO females than in WT females but this increase failed to reach statistical significance. The deficits observed in parental behavior of AFP-KO females could not be explained by any changes in olfactory function, novelty recognition or anxiety. Thus our results suggest that prenatal estradiol defeminizes the parental brain in mice.
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Affiliation(s)
- Matthieu Keller
- INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France.
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137
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Neumann ID, Veenema AH, Beiderbeck DI. Aggression and anxiety: social context and neurobiological links. Front Behav Neurosci 2010; 4:12. [PMID: 20407578 PMCID: PMC2854527 DOI: 10.3389/fnbeh.2010.00012] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Accepted: 03/07/2010] [Indexed: 01/29/2023] Open
Abstract
Psychopathologies such as anxiety- and depression-related disorders are often characterized by impaired social behaviours including excessive aggression and violence. Excessive aggression and violence likely develop as a consequence of generally disturbed emotional regulation, such as abnormally high or low levels of anxiety. This suggests an overlap between brain circuitries and neurochemical systems regulating aggression and anxiety. In this review, we will discuss different forms of male aggression, rodent models of excessive aggression, and neurobiological mechanisms underlying male aggression in the context of anxiety. We will summarize our attempts to establish an animal model of high and abnormal aggression using rats selected for high (HAB) vs. low (LAB) anxiety-related behaviour. Briefly, male LAB rats and, to a lesser extent, male HAB rats show high and abnormal forms of aggression compared with non-selected (NAB) rats, making them a suitable animal model for studying excessive aggression in the context of extremes in innate anxiety. In addition, we will discuss differences in the activity of the hypothalamic–pituitary–adrenal axis, brain arginine vasopressin, and the serotonin systems, among others, which contribute to the distinct behavioural phenotypes related to aggression and anxiety. Further investigation of the neurobiological systems in animals with distinct anxiety phenotypes might provide valuable information about the link between excessive aggression and disturbed emotional regulation, which is essential for understanding the social and emotional deficits that are characteristic of many human psychiatric disorders.
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Affiliation(s)
- Inga D Neumann
- Department of Behavioural and Molecular Neuroendocrinology, University of Regensburg Regensburg, Germany
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138
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Barker JM, Galea LAM. Males show stronger contextual fear conditioning than females after context pre-exposure. Physiol Behav 2010; 99:82-90. [PMID: 19879284 DOI: 10.1016/j.physbeh.2009.10.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Revised: 10/17/2009] [Accepted: 10/22/2009] [Indexed: 10/20/2022]
Abstract
Estradiol affects the structure and function of the hippocampus. We have found that repeated estradiol affects neurogenesis and cell death in the hippocampus of adult female, but not male rats. In the present study we sought to determine whether using the same regimen of estradiol would influence hippocampus-dependent behaviour. Adult male and female rats were given estradiol or sesame oil for 15 days, and then tested using a contextual pre-exposure paradigm in which performance depends on the hippocampus. The time spent freezing displayed by rats was scored on subsequent days in (1) the training context, (2) a novel context in which rats had never been shocked, and (3) the training context a second time. Irrespective of treatment, males showed stronger memory for the context by exhibiting greater freezing in both the training context exposures and the novel context. Previous estradiol treatment, in either sex, did not affect the ability to learn and retain information about the training context. However, female rats treated with estradiol and exposed to a novel context after fear conditioning exhibited less freezing behaviour than controls. Taken together, our results demonstrate that gonadectomized male rats outperform females, regardless of previous treatment with estradiol, on a hippocampus-contextual fear conditioning test, and that previous estradiol treatment has a subtle effect on performance in female but not male rats.
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Affiliation(s)
- Jennifer M Barker
- Graduate Program in Neuroscience, Brain Research Centre, Department of Psychology, University of British Columbia, Vancouver, British Columbia, Canada
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139
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Abstract
Epigenetic changes in the nervous system are emerging as a critical component of enduring effects induced by early life experience, hormonal exposure, trauma and injury, or learning and memory. Sex differences in the brain are largely determined by steroid hormone exposure during a perinatal sensitive period that alters subsequent hormonal and nonhormonal responses throughout the lifespan. Steroid receptors are members of a nuclear receptor transcription factor superfamily and recruit multiple proteins that possess enzymatic activity relevant to epigenetic changes such as acetylation and methylation. Thus steroid hormones are uniquely poised to exert epigenetic effects on the developing nervous system to dictate adult sex differences in brain and behavior. Sex differences in the methylation pattern in the promoter of estrogen and progesterone receptor genes are evident in newborns and persist in adults but with a different pattern. Changes in response to injury and in methyl-binding proteins and steroid receptor coregulatory proteins are also reported. Many steroid-induced epigenetic changes are opportunistic and restricted to a single lifespan, but new evidence suggests endocrine-disrupting compounds can exert multigenerational effects. Similarly, maternal diet also induces transgenerational effects, but the impact is sex specific. The study of epigenetics of sex differences is in its earliest stages, with needed advances in understanding of the hormonal regulation of enzymes controlling acetylation and methylation, coregulatory proteins, transient versus stable DNA methylation patterns, and sex differences across the epigenome to fully understand sex differences in brain and behavior.
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140
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Wu MV, Manoli DS, Fraser EJ, Coats JK, Tollkuhn J, Honda SI, Harada N, Shah NM. Estrogen masculinizes neural pathways and sex-specific behaviors. Cell 2009; 139:61-72. [PMID: 19804754 DOI: 10.1016/j.cell.2009.07.036] [Citation(s) in RCA: 295] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2009] [Revised: 05/18/2009] [Accepted: 07/10/2009] [Indexed: 10/20/2022]
Abstract
Sex hormones are essential for neural circuit development and sex-specific behaviors. Male behaviors require both testosterone and estrogen, but it is unclear how the two hormonal pathways intersect. Circulating testosterone activates the androgen receptor (AR) and is also converted into estrogen in the brain via aromatase. We demonstrate extensive sexual dimorphism in the number and projections of aromatase-expressing neurons. The masculinization of these cells is independent of AR but can be induced in females by either testosterone or estrogen, indicating a role for aromatase in sexual differentiation of these neurons. We provide evidence suggesting that aromatase is also important in activating male-specific aggression and urine marking because these behaviors can be elicited by testosterone in males mutant for AR and in females subjected to neonatal estrogen exposure. Our results suggest that aromatization of testosterone into estrogen is important for the development and activation of neural circuits that control male territorial behaviors.
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Affiliation(s)
- Melody V Wu
- Program in Neuroscience, University of California-San Francisco, San Francisco, CA 94158, USA
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141
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Barker JM, Galea LAM. Sex and regional differences in estradiol content in the prefrontal cortex, amygdala and hippocampus of adult male and female rats. Gen Comp Endocrinol 2009; 164:77-84. [PMID: 19457436 DOI: 10.1016/j.ygcen.2009.05.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2009] [Revised: 05/09/2009] [Accepted: 05/12/2009] [Indexed: 12/11/2022]
Abstract
In general, the behavioral and neural effects of estradiol administration to males and females differ. While much attention has been paid to the potential structural, cellular and sub-cellular mechanisms that may underlie such differences, as of yet there has been no examination of whether the differences observed may be related to differential uptake or storage of estradiol within the brain itself. We administered estradiol benzoate to gonadectomized male and female rats, and compared the concentration of estradiol in serum and brain tissue found in these rats to those of gonadectomized, oil-treated rats and intact rats of both sexes. Long-term gonadectomy (3 weeks) reduced estradiol concentration in the male and female hippocampus, but not in the male or female amygdala or in the female prefrontal cortex. Furthermore, exogenous treatment with estradiol increased estradiol content to levels above intact animals in the amygdala, prefrontal cortex and the male hippocampus. Levels of estradiol were undetectable in the prefrontal cortex of intact males, but were detectable in all other brain regions of intact rats. Here we demonstrate (1) that serum concentrations of estradiol are not necessarily reflective of brain tissue concentrations, (2) that within the brain, there are regional differences in the effects of gonadectomy and estradiol administration, and (3) that there is less evidence for local production of estradiol in males than females, particularly in the prefrontal cortex and perhaps the hippocampus. Thus there are regional differences in estradiol concentration in the prefrontal cortex, amygdala and hippocampus that are influenced by sex and hormone status.
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Affiliation(s)
- Jennifer M Barker
- Graduate Program in Neuroscience, Brain Research Centre, Department of Psychology, University of British Columbia, British Columbia, Canada
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142
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Murray EK, Hien A, de Vries GJ, Forger NG. Epigenetic control of sexual differentiation of the bed nucleus of the stria terminalis. Endocrinology 2009; 150:4241-7. [PMID: 19497973 PMCID: PMC2736071 DOI: 10.1210/en.2009-0458] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The principal nucleus of the bed nucleus of the stria terminalis (BNSTp) is larger in volume and contains more cells in male than female mice. These sex differences depend on testosterone and arise from a higher rate of cell death during early postnatal life in females. There is a delay of several days between the testosterone surge at birth and sexually dimorphic cell death in the BNSTp, suggesting that epigenetic mechanisms may be involved. We tested the hypothesis that chromatin remodeling plays a role in sexual differentiation of the BNSTp by manipulating the balance between histone acetylation and deacetylation using a histone deacetylase inhibitor. In the first experiment, a single injection of valproic acid (VPA) on the day of birth increased acetylation of histone H3 in the brain 24 h later. Next, males, females, and females treated neonatally with testosterone were administered VPA or saline on postnatal d 1 and 2 and killed at 21 d of age. VPA treatment did not influence volume or cell number of the BNSTp in control females but significantly reduced both parameters in males and testosterone-treated females. As a result, the sex differences were eliminated. VPA did not affect volume or cell number in the suprachiasmatic nucleus or the anterodorsal nucleus of the thalamus, which also did not differ between males and females. These findings suggest that a disruption in histone deacetylation may lead to long-term alterations in gene expression that block the masculinizing actions of testosterone in the BNSTp.
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Affiliation(s)
- Elaine K Murray
- Department of Psychology and Center for Neuroendocrine Studies, University of Massachusetts, Amherst, Massachusetts 01003, USA.
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143
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Fekete EM, Zhao Y, Li C, Sabino V, Vale WW, Zorrilla EP. Social defeat stress activates medial amygdala cells that express type 2 corticotropin-releasing factor receptor mRNA. Neuroscience 2009; 162:5-13. [PMID: 19358876 DOI: 10.1016/j.neuroscience.2009.03.078] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2008] [Revised: 02/24/2009] [Accepted: 03/28/2009] [Indexed: 11/17/2022]
Abstract
Defeat is a social stressor involving subordination by a threatening conspecific. Type 2 corticotropin-releasing factor receptors (CRF(2)) are abundant in brain regions implicated in defeat responses and are putative stress-related molecules. The present study sought to determine whether neuroactivation and CRF(2) expression co-occurred at brain region or cellular levels following acute defeat. Male "intruder" Wistar rats were placed into the cage of an aggressive "resident" Long-Evans rat (n=6). Upon defeat, intruders (n=6) were placed in a wire-mesh chamber and were returned to the resident's cage for an additional 75 min. Controls (n=6) were handled and returned to their home cage for the same duration. Coronal brain sections were stained for an immediate early gene product, Fos, as a neuronal activation marker. Combined immunohistochemistry with in situ hybridization was performed on a subset of brain sections from defeated intruders to visualize Fos immunoreactivity and CRF(2) mRNA jointly. Defeated rats had fivefold, sevenfold, and 10-fold more Fos-positive cells than controls in the arcuate, ventromedial nucleus of the hypothalamus, and medial amygdala post-defeat. Significant colocalization of CRF(2) mRNA and Fos-positive cells was observed in the posterior medial amygdala but not in the arcuate nucleus or ventromedial hypothalamus. The results indicate CRF(2) receptor-positive neurons in the posterior medial amygdala are involved in the neural response to social defeat.
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Affiliation(s)
- E M Fekete
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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144
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Doty RL, Cameron EL. Sex differences and reproductive hormone influences on human odor perception. Physiol Behav 2009; 97:213-28. [PMID: 19272398 DOI: 10.1016/j.physbeh.2009.02.032] [Citation(s) in RCA: 280] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Revised: 01/29/2009] [Accepted: 02/20/2009] [Indexed: 10/21/2022]
Abstract
The question of whether men and women differ in their ability to smell has been the topic of scientific investigation for over a hundred years. Although conflicting findings abound, most studies suggest that, for at least some odorants, women outperform men on tests of odor detection, identification, discrimination, and memory. Most functional imaging and electrophysiological studies similarly imply that, when sex differences are present, they favor women. In this review we examine what is known about sex-related alterations in human smell function, including influences of the menstrual cycle, pregnancy, gonadectomy, and hormone replacement therapy on a range of olfactory measures. We conclude that the relationship between reproductive hormones and human olfactory function is complex and that simple associations between circulating levels of gonadal hormones and measures of olfactory function are rarely present.
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Affiliation(s)
- Richard L Doty
- Smell & Taste Center, University of Pennsylvania School of Medicine, Philadelphia PA 19104, USA.
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145
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Tsukahara S. Sex differences and the roles of sex steroids in apoptosis of sexually dimorphic nuclei of the preoptic area in postnatal rats. J Neuroendocrinol 2009; 21:370-6. [PMID: 19226350 DOI: 10.1111/j.1365-2826.2009.01855.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The brain contains several sexually dimorphic nuclei that exhibit sex differences with respect to cell number. It is likely that the control of cell number by apoptotic cell death in the developing brain contributes to creating sex differences in cell number in sexually dimorphic nuclei, although the mechanisms responsible for this have not been determined completely. The milieu of sex steroids in the developing brain affects sexual differentiation in the brain. The preoptic region of rats has two sexually dimorphic nuclei. The sexually dimorphic nucleus of the preoptic area (SDN-POA) has more neurones in males, whereas the anteroventral periventricular nucleus (AVPV) has a higher cell density in females. Sex differences in apoptotic cell number arise in the SDN-POA and AVPV of rats in the early postnatal period, and an inverse correlation exists between sex differences in apoptotic cell number and the number of living cells in the mature period. The SDN-POA of postnatal male rats exhibits a higher expression of anti-apoptotic Bcl-2 and lower expression of pro-apoptotic Bax compared to that in females and, as a potential result, apoptotic cell death via caspase-3 activation more frequently occurs in the SDN-POA of females. The patterns of expression of Bcl-2 and Bax in the SDN-POA of postnatal female rats are changed to male-typical ones by treatment with oestrogen, which is normally synthesised from testicular androgen and affects the developing brain in males. In the AVPV of postnatal rats, apoptotic regulation also differs between the sexes, although Bcl-2 expression is increased and Bax expression and caspase-3 activity are decreased in females. The mechanisms of apoptosis possibly contributing to the creation of sex differences in cell number and the roles of sex steroids in apoptosis are discussed.
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Affiliation(s)
- S Tsukahara
- Research Centre for Environmental Risk, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan.
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146
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Akhmadeev AV, Kalimullina LB. Morphogenesis of the dorsomedial nucleus of the amygdaloid complex in early juvenile period in rats. Bull Exp Biol Med 2009; 146:372-4. [PMID: 19240863 DOI: 10.1007/s10517-008-0288-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
We studied the dynamics and gender differences in the formation of the dorsomedial nucleus of the amygdaloid complex in early juvenile period (postnatal days 21, 24, 28 and 31) by determining its planimetric parameters, count of neural and glial cells, and glial and apoptotic indexes.
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Affiliation(s)
- A V Akhmadeev
- Department of Human and Animal Morphology and Physiology, Bashkir State University, Ufa, Russia.
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147
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Rubinow MJ, Juraska JM. Neuron and glia numbers in the basolateral nucleus of the amygdala from preweaning through old age in male and female rats: a stereological study. J Comp Neurol 2009; 512:717-25. [PMID: 19065620 DOI: 10.1002/cne.21924] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The rat basolateral nucleus of the amygdala continues to develop connectivity with the frontal cortex through the periadolescent period and even into young adulthood. Although neuronal loss in the prefrontal cortex has been found during the periadolescent period, prior literature has not examined whether neuron number in the basolateral amygdala is stable through this period. In addition, aging of the rat basolateral nucleus is accompanied by significant increases in the dendritic tree of its principal neurons, but whether this occurs in the context of neuronal death has not been previously explored. In the present study, a stereological examination of neuron and glia numbers in the rat basolateral amygdalar nucleus was undertaken in male and female hooded rats at four ages across the lifespan. Our findings indicate 1) a significant decrease in the number of neurons and glia in the basolateral nucleus between adolescence and adulthood; and 2) the number of glia, as well as the volume of the basolateral nucleus, increases between adulthood and old age, whereas neuron number remains stable. These findings provide an important cellular context for interpretation of the neurochemical and other alterations documented in developmental and age-related literature on the rat basolateral amygdala, and underline the substantial development of this brain area during adolescence, as well as its comparative preservation during aging.
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Affiliation(s)
- Marisa J Rubinow
- Psychology Department, University of Illinois at Urbana-Champaign, Champaign, Illinois 61820, USA.
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148
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Rubinow MJ, Drogos LL, Juraska JM. Age-related dendritic hypertrophy and sexual dimorphism in rat basolateral amygdala. Neurobiol Aging 2009; 30:137-46. [PMID: 17570563 PMCID: PMC2647366 DOI: 10.1016/j.neurobiolaging.2007.05.006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2006] [Revised: 04/30/2007] [Accepted: 05/04/2007] [Indexed: 01/06/2023]
Abstract
Little research has examined the influence of aging or sex on anatomical measures in the basolateral amygdala. We quantified spine density and dendritic material in Golgi-Cox stained tissue of the basolateral nucleus in young adult (3-5 months) and aged (20-24 months) male and female Long-Evans rats. Dendritic branching and spine density were measured in principal neurons. Age, but not sex, influenced the dendritic tree, with aged animals displaying significantly more dendritic material. Previous findings from our laboratory in the same set of subjects indicate an opposite effect of aging on dendritic material in the medial prefrontal cortex and hippocampus. We also report here a sex difference across ages in dendritic spine density, favoring males.
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Affiliation(s)
- Marisa J. Rubinow
- Department of Psychology, University of Illinois at Urbana-Champaign
| | - Lauren L. Drogos
- Department of Psychology, University of Illinois at Urbana-Champaign
| | - Janice M. Juraska
- Department of Psychology, University of Illinois at Urbana-Champaign
- Neuroscience Program, University of Illinois at Urbana-Champaign
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149
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Johnson RT, Breedlove SM, Jordan CL. Sex differences and laterality in astrocyte number and complexity in the adult rat medial amygdala. J Comp Neurol 2008; 511:599-609. [PMID: 18853427 PMCID: PMC2592304 DOI: 10.1002/cne.21859] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The posterodorsal portion of the medial amygdala (MePD) is sexually dimorphic in several rodent species. In several other brain nuclei, astrocytes change morphology in response to steroid hormones. We visualized MePD astrocytes using glial-fibrillary acidic protein (GFAP) immunocytochemistry. We compared the number and process complexity of MePD astrocytes in adult wildtype male and female rats and testicular feminized mutant (TFM) male rats that lack functional androgen receptors (ARs) to determine whether MePD astrocytes are sexually differentiated and whether ARs have a role. Unbiased stereological methods revealed laterality and sex differences in MePD astrocyte number and complexity. The right MePD contained more astrocytes than the left in all three genotypes, and the number of astrocytes was also sexually differentiated in the right MePD, with males having more astrocytes than females. In contrast, the left MePD contained more complex astrocytes than did the right MePD in all three genotypes, and males had more complex astrocytes than females in this hemisphere. TFM males were comparable to wildtype females, having fewer astrocytes on the right and simpler astrocytes on the left than do wildtype males. Taken together, these results demonstrate that astrocytes are sexually dimorphic in the adult MePD and that the nature of the sex difference is hemisphere-dependent: a sex difference in astrocyte number in the right MePD and a sex difference in astrocyte complexity in the left MePD. Moreover, functional ARs appear to be critical in establishing these sex differences in MePD astrocyte morphology.
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Affiliation(s)
- Ryan T Johnson
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824-1101, USA.
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150
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Büdefeld T, Grgurevic N, Tobet SA, Majdic G. Sex differences in brain developing in the presence or absence of gonads. Dev Neurobiol 2008; 68:981-95. [PMID: 18418875 DOI: 10.1002/dneu.20638] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Brain sexual differentiation results from the interaction of genetic and hormonal influences. This study used a unique agonadal mouse model to determine relative contributions of genetic and gonadal hormone influences in the differentiation of selected brain regions. SF-1 knockout (SF-1 KO) mice are born without gonads and adrenal glands and are not exposed to endogenous sex steroids during fetal/neonatal development. Consequently, male and female SF-1 KO mice are born with female external genitalia and if left on their own, die shortly after birth due to adrenal insufficiency. In this study, SF-1 KO mice were rescued by neonatal adrenal transplantation to examine their brain morphology in adult life. To determine potential brain loci that might mediate functional sex differences, we examined the area and distribution of immunoreactive calbindin and neuronal nitric oxide synthase in the preoptic area (POA) and ventromedial nucleus of the hypothalamus, two areas previously reported to be sexually dimorphic in the mammalian brain. A sex difference in the positioning of cells containing immunoreactive calbindin in a group within the POA was clearly gonad dependent based on the elimination of the sex difference in SF-1 KO mice. Several other differences in the area of ventromedial hypothalamus and in POA were maintained in male and female SF-1 KO mice, suggesting gonad-independent genetic influences on sexually dimorphic brain development.
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Affiliation(s)
- Tomaz Büdefeld
- Center for Animal Genomics, Veterinary Faculty, University of Ljubljana, Ljubljana, Slovenia
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