1
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Hoops D, Whiting MJ, Keogh JS. A Smaller Habenula is Associated with Increasing Intensity of Sexual Selection. BRAIN, BEHAVIOR AND EVOLUTION 2022; 97:265-273. [PMID: 34983044 DOI: 10.1159/000521750] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 12/18/2021] [Indexed: 11/19/2022]
Abstract
The habenula is a small structure in the brain that acts as a relay station for neural information, helping to modulate behaviour in response to variable and unpredictable stimuli. Broadly, it is evolutionarily conserved in structure and connectivity across vertebrates and is the most prominent bilaterally asymmetric structure in the brain. Nonetheless, comparative evolutionary studies of the habenula are virtually non-existent. Here, we examine the volumes of the medial and lateral habenular subregions, in both hemispheres, across a group of Australian agamid lizards in the genus Ctenophorus. In males, we found bilaterally asymmetrical selection on the lateral habenula to become smaller with increasing intensity of sexual selection, possibly as a mechanism to increase aggressive responses. In females, we found bilaterally symmetrical selection on both the medial and lateral subregions to become smaller with increasing sexual selection. This is consistent with sexual selection increasing motivation to reproduce and the habenula's well-characterized role in controlling and modifying responses to rewarding stimuli. However, as there are currently no studies addressing habenular function in reptiles, it is difficult to draw more precise conclusions. As has happened recently in biomedical neuroscience, it is time for the habenula to receive greater attention in evolutionary neuroscience.
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Affiliation(s)
- Daniel Hoops
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Acton, Australian Capital Territory, Australia.,Mouse Imaging Centre, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Martin J Whiting
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - J Scott Keogh
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Acton, Australian Capital Territory, Australia
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2
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Sakata JT, Catalano I, Woolley SC. Mechanisms, development, and comparative perspectives on experience-dependent plasticity in social behavior. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2021; 337:35-49. [PMID: 34516724 DOI: 10.1002/jez.2539] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 08/08/2021] [Indexed: 11/09/2022]
Abstract
Revealing the mechanisms underlying experience-dependent plasticity is a hallmark of behavioral neuroscience. While the study of social behavior has focused primarily on the neuroendocrine and neural control of social behaviors, the plasticity of these innate behaviors has received relatively less attention. Here, we review studies on mating-dependent changes to social behavior and neural circuitry across mammals, birds, and reptiles. We provide an overview of species similarities and differences in the effects of mating experiences on motivational and performative aspects of sexual behaviors, on sensory processing and preferences, and on the experience-dependent consolidation of sexual behavior. We also discuss recent insights into the neural mechanisms of and developmental influences on mating-dependent changes and outline promising approaches to investigate evolutionary parallels and divergences in experience-dependent plasticity.
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Affiliation(s)
- Jon T Sakata
- Integrated Program in Neuroscience, McGill University, Montreal, Québec, Canada.,Department of Biology, McGill University, Montreal, Québec, Canada
| | - Isabella Catalano
- Integrated Program in Neuroscience, McGill University, Montreal, Québec, Canada
| | - Sarah C Woolley
- Integrated Program in Neuroscience, McGill University, Montreal, Québec, Canada.,Department of Biology, McGill University, Montreal, Québec, Canada
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3
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Hartline JT, Smith AN, Kabelik D. Serotonergic activation during courtship and aggression in the brown anole, Anolis sagrei. PeerJ 2017; 5:e3331. [PMID: 28533977 PMCID: PMC5436558 DOI: 10.7717/peerj.3331] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 04/19/2017] [Indexed: 11/20/2022] Open
Abstract
The role of serotonin (5-hydroxytryptamine, 5-HT) in social behavior regulation is not fully understood. While 5-HT release in nuclei of the social behavior network has generally been associated with inhibition of aggressive behavior across multiple classes of vertebrates, less is known about its effects on sexual, especially non-copulatory courtship display behaviors. Furthermore, most research has examined effects at 5-HT release sites, while studies examining the behavioral relevance of source cell populations have generated contradictory findings. This study utilized immunohistochemistry to examine the colocalization of 5-HT with Fos, an immediate early gene product and marker of neural activity, in the raphe and superior reticular nuclei of male brown anoles (Anolis sagrei) exposed to either aggression, courtship, or control social interactions. Supporting previous research, copulation was associated with a decrease in 5-HT activity, while a novel link between 5-HT activity and latency to non-copulatory courtship was also found. Within the aggression group, intensity and frequency of behavior were both associated with decreased 5-HT activity. An effect of social context was also seen, with anoles exposed to either courtship or aggression encounters showing decreased 5-HT activity in certain raphe and superior reticular nuclei populations compared to controls. Interestingly, context effects and behavioral effects were seen at separate brain nuclei, suggesting the presence of separate systems with distinct functional roles.
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Affiliation(s)
- Jacob T Hartline
- Department of Biology, Rhodes College, Memphis, TN, United States of America.,Program in Neuroscience, Rhodes College, Memphis, TN, United States of America
| | - Alexandra N Smith
- Department of Biology, Rhodes College, Memphis, TN, United States of America.,Program in Neuroscience, Rhodes College, Memphis, TN, United States of America
| | - David Kabelik
- Department of Biology, Rhodes College, Memphis, TN, United States of America.,Program in Neuroscience, Rhodes College, Memphis, TN, United States of America
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4
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Golinski A, Kubička L, John-Alder H, Kratochvíl L. Androgenic control of male-typical behavior, morphology and sex recognition is independent of the mode of sex determination: A case study on Lichtenfelder's gecko (Eublepharidae: Goniurosaurus lichtenfelderi). Horm Behav 2015; 72:49-59. [PMID: 25967849 DOI: 10.1016/j.yhbeh.2015.04.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2014] [Revised: 04/10/2015] [Accepted: 04/11/2015] [Indexed: 11/21/2022]
Abstract
Previous work on lizards has shown that many sexually dimorphic traits depend on testosterone (T), but the details of this control can vary among species. Here, we tested the role of T on the expression of morphological, physiological, and behavioral traits in Lichtenfelder's gecko (Goniurosaurus lichtenfelderi), from the lizard family Eublepharidae notable for interspecific variation in sexually dimorphic traits and the mode of sex determination. Experiments included three groups of males (intact control, surgically castrated, castrated with T replacement) and two groups of females (intact control, T supplemented). In males, castration caused reductions in 1) the size of hemipenes, 2) offensive aggression, 3) male sexual behavior in a neutral arena, 4) activity of precloacal glands, and 5) loss of male chemical cues for sex recognition. These reductions were not observed in castrated males with T replacement. Interestingly, castrated males performed sexual behavior in their home cages, which shows that the effect of T depends on the environmental context. Notably, tail vibration, previously reported as a courtship behavior in other eublepharids, is displayed by males of G. lichtenfelderi during interactions with conspecifics of both sexes, suggesting an evolutionary shift in the meaning of this signal. In females, T induced growth of hemipenes and male-typical courtship but did not induce precloacal pore activity, aggression, or mounting. In comparison to previous reports on Eublepharis macularius, our results indicate that effects of T do not depend on the mode of sex determination. Further, our results extend our understanding of the complexity of control of male traits and illustrate how lability in the effects of T can be a general mechanism causing evolutionary changes in the components of suites of functionally correlated traits.
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Affiliation(s)
- Alison Golinski
- Graduate Program in Endocrinology and Animal Biosciences, Rutgers University, 84 Lipman Drive, New Brunswick, NJ 08901, USA
| | - Lukáš Kubička
- Faculty of Science, Charles University in Prague, Department of Ecology, Viničná 7, 128 44 Praha 2, Czech Republic
| | - Henry John-Alder
- Department of Ecology, Evolution, and Natural Resources, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901, USA
| | - Lukáš Kratochvíl
- Faculty of Science, Charles University in Prague, Department of Ecology, Viničná 7, 128 44 Praha 2, Czech Republic.
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5
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Golinski A, John-Alder H, Kratochvíl L. Male sexual behavior does not require elevated testosterone in a lizard (Coleonyx elegans, Eublepharidae). Horm Behav 2011; 59:144-50. [PMID: 21081130 DOI: 10.1016/j.yhbeh.2010.11.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2010] [Revised: 10/31/2010] [Accepted: 11/07/2010] [Indexed: 11/28/2022]
Abstract
Male sexual behavior depends on gonadal androgens in species of all major vertebrate lineages, including reptiles. However, male sexual behavior includes distinct appetitive and consummatory phases, typically denoted as courtship and mounting, with potentially different hormonal control. Different proximate controls of courtship versus mounting could enable disconnected evolutionary losses and gains of various aspects of male sexual behavior. Male courtship display, which is activated by testosterone (T) in many species, is an ancestral trait in the lizard family Eublepharidae. However, Coleonyx elegans (Yucatan Banded Gecko) lost the courtship display, while retaining a highly simplified male sexual behavior that involves only mounting for copulation. We performed surgical manipulations (castration with and without T replacement in adult males; implantation of adult females with exogenous T) to investigate hormonal mechanisms involved in this evolutionary novelty. Our results indicate that the expression of simplified sexual behavior in C. elegans does not require elevated circulating levels of T, a finding that is previously unreported in lizards. In females, however, exogenous T induced male-like mounting. Thus, the mounting phase of sexual behavior is not activated by T in the traditional sense of this term but probably requires post-natal, maturational organization (if not periodic reorganization) by androgens. We conclude that the simplification of male sexual behavior and its independence from elevated levels of circulating androgens in C. elegans evolved via 1) evolutionary loss of the androgen-activated courtship display and 2) retention of the mounting phase, which has a longer "functional memory" for the effects of androgenic steroids.
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Affiliation(s)
- Alison Golinski
- Graduate Program in Endocrinology and Animal Biosciences, Rutgers University, 84 Lipman Drive, New Brunswick, NJ 08901, USA
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6
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Spivey JM, Padilla E, Shumake JD, Gonzalez-Lima F. Effects of maternal separation, early handling, and gonadal sex on regional metabolic capacity of the preweanling rat brain. Brain Res 2010; 1367:198-206. [PMID: 20969837 DOI: 10.1016/j.brainres.2010.10.038] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2010] [Revised: 10/05/2010] [Accepted: 10/12/2010] [Indexed: 02/04/2023]
Abstract
This is the first study to assess the effects of mother-infant separation on regional metabolic capacity in the preweanling rat brain. Mother-infant separation is generally known to be stressful for rat pups. Holtzman adolescent rats show a depressive-like behavioral phenotype after maternal separation during the preweanling period. However, information is lacking on the effects of maternal separation on the brains of rat pups. We addressed this issue by mapping the brains of preweanling Holtzman rat pups using cytochrome oxidase histochemistry, which reflects long-term changes in brain metabolic capacity, following two weeks of repeated, prolonged maternal separation, and compared this to both early handled and non-handled pups. Quantitative image analysis revealed that maternal separation reduced cytochrome oxidase activity in the medial prefrontal cortex and nucleus accumbens shell. Maternal separation reduced prefrontal cytochrome oxidase to a greater degree in female pups than in males. Early handling reduced cytochrome oxidase activity in the posterior parietal cortex, ventral tegmental area, and subiculum, but increased cytochrome oxidase activity in the lateral frontal cortex. The sex-dependent effects of early handling on cytochrome oxidase activity were limited to the medial prefrontal cortex. Regardless of separation group, females had greater cytochrome oxidase activity in the habenula and ventral tegmental area compared to males. These findings suggest that early life mother-infant separation results in dysfunction of prefrontal and mesolimbic regions in the preweanling rat brain that may contribute to behavioral changes later in life.
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Affiliation(s)
- Jaclyn M Spivey
- Department of Psychology and Institute for Neuroscience, University of Texas at Austin, 1 University Station A8000, Austin, TX 78712, USA
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7
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Spivey JM, Shumake J, Colorado RA, Conejo-Jimenez N, Gonzalez-Pardo H, Gonzalez-Lima F. Adolescent female rats are more resistant than males to the effects of early stress on prefrontal cortex and impulsive behavior. Dev Psychobiol 2009; 51:277-88. [PMID: 19125421 DOI: 10.1002/dev.20362] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We tested the hypothesis that adolescent Sprague-Dawley females may be more resistant than males to display impulsive behavior and lower prefrontal cortex thickness after mother-infant separation (MS). Starting at postnatal day 2 (P2), the MS group was separated 6 hr/day and the early handled (EH) group 15 min/day for 10 days, and another group was standard facility reared (SFR). Subjects were examined for novel open-field activity (P28), light-dark apparatus (P29), familiar open-field (P30) and frontal cortical thickness. This protocol resulted in impulsive behavior in MS rats relative to EH and SFR, but this effect was less pronounced in females than males. MS affected the two sexes differently in terms of decreased prefrontal cortex dorsoventral thickness, with this effect being significant in males but not females. Neuroanatomical and behavioral documentation that adolescent females are more resistant than males to ADHD-like effects of maternal separation have not been previously reported.
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Affiliation(s)
- Jaclyn M Spivey
- Department of Psychology, Pharmacology and Toxicology, University of Texas at Austin, 1 University Station A8000, Austin, Texas 78712, USA
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8
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Spivey JM, Colorado RA, Conejo-Jimenez N, Gonzalez-Pardo H, Gonzalez-Lima F. Juvenile male rats display lower cortical metabolic capacity than females. Neurosci Lett 2008; 440:255-9. [PMID: 18579304 DOI: 10.1016/j.neulet.2008.05.104] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Revised: 05/28/2008] [Accepted: 05/30/2008] [Indexed: 10/22/2022]
Abstract
The juvenile brain undergoes marked maturational changes accompanied by major sex hormone changes. In particular, sex differences in neural substrates could underlie male-specific dysfunction in behavioral responses related to the prefrontal cortex. Sex differences in regional metabolic capacity of the cerebral cortex were investigated in juvenile Sprague-Dawley rats. At 6 weeks of age the brains were processed for quantitative histochemistry of cytochrome oxidase, a rate-limiting enzyme in cellular respiration, which is an index of brain metabolic capacity. Quantitative image analysis revealed a main effect of sex with males displaying lower regional metabolic capacity than females in the dorsolateral and orbital prefrontal cortex and in the posterior parietal cortex. In addition, males separated for 6 h/day from their mothers as pups showed greater ambulatory behavior in the novel open field and higher metabolism in the posterior parietal cortex relative to males separated for 15 min/day. This is the first study to show sex differences in brain metabolic capacity in regions such as the prefrontal cortex that may be hypometabolic in juvenile males relative to females.
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Affiliation(s)
- Jaclyn M Spivey
- Departments of Psychology, Pharmacology and Toxicology, University of Texas at Austin, 1 University Station A8000, Austin, TX 78712, USA
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9
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Kustritz MVR. Determining the optimal age for gonadectomy of dogs and cats. J Am Vet Med Assoc 2007; 231:1665-75. [DOI: 10.2460/javma.231.11.1665] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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10
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Dias BG, Crews D. Serotonergic modulation of male-like pseudocopulatory behavior in the parthenogenetic whiptail lizard, Cnemidophorus uniparens. Horm Behav 2006; 50:401-9. [PMID: 16793042 PMCID: PMC2394198 DOI: 10.1016/j.yhbeh.2006.05.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Revised: 05/10/2006] [Accepted: 05/11/2006] [Indexed: 12/16/2022]
Abstract
Hormone-neurotransmitter interactions form an important link through which hormones influence a variety of behavioral processes. Typically, sexual behavior is dimorphic with males mounting receptive females. In the all-female lizard species Cnemidophorus uniparens, individuals display both male-like pseudocopulation and female-like receptivity. These respective behavioral states are correlated with high circulating concentrations of progesterone following ovulation and of estrogen preceding it. In sexual species, serotonin is involved in male-typical mounting, and, as reported here, in male-like pseudosexual behavior in this unisexual species. In the first study, C. uniparens were ovariectomized and treated systemically with exogenous androgen, a hormonal regimen that results in individuals displaying only male-like pseudosexual behavior. An increase in serotonin levels in the preoptic area coupled with the suppression of male-like pseudocopulation was observed in androgen-treated lizards injected with 5-hydroxytryptophan (the precursor of serotonin) and clorgyline (a monoamine oxidase inhibitor) compared to vehicle-treated controls. Our second experiment involved ovariectomizing lizards and either injecting them with estradiol or implanting them with either an empty (Blank) or a progesterone- or testosterone-containing Silastic capsule. Treatment with para-chlorophenylalanine (an inhibitor of tryptophan hydroxylase) facilitated male-like pseudosexual behavior depending on the circulating hormonal milieu and decreased serotonin levels in the preoptic area. Our data suggest that serotonin is inhibitory to male-like pseudosexual behavior in C. uniparens but more importantly that the hormonal environment modulates the serotonin system at the level of the preoptic area, with the serotonergic system then establishing behavioral thresholds that allow for this behavior to be "gated".
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Affiliation(s)
- Brian George Dias
- Institute for Neuroscience, University of Texas at Austin, Austin, TX 78712, USA
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11
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Wade J. Current research on the behavioral neuroendocrinology of reptiles. Horm Behav 2005; 48:451-60. [PMID: 16239163 DOI: 10.1016/j.yhbeh.2005.02.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2005] [Revised: 02/21/2005] [Accepted: 02/24/2005] [Indexed: 10/25/2022]
Abstract
Selected reptilian species have been the targets of investigations in behavioral neuroendocrinology for many years. Reptiles offer a particularly powerful set of traits that facilitate comparisons at multiple levels, including those within and between individuals of a particular species, between different environmental and social contexts, as well as across species. These types of studies, particularly as they are considered within the framework of results from other vertebrates, will enhance our understanding of the genetic and hormonal influences regulating changes in the structure and function of the nervous system. Work on the hormonal and environmental factors influencing courtship and copulatory behaviors in green anoles, including the development and maintenance of the neuromuscular structures critical for their display, is highlighted. Some very recent work on other model systems is also discussed to provide a context for suggested future research directions.
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Affiliation(s)
- Juli Wade
- Department of Psychology, Michigan State University, 108 Giltner Hall, East Lansing, MI 48824-1101, USA.
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12
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Sakata JT, Crews D, Gonzalez-Lima F. Behavioral correlates of differences in neural metabolic capacity. ACTA ACUST UNITED AC 2005; 48:1-15. [PMID: 15708625 DOI: 10.1016/j.brainresrev.2004.07.017] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2004] [Indexed: 11/21/2022]
Abstract
Cytochrome oxidase is a rate-limiting enzyme in oxidative phosphorylation, the major energy-synthesizing pathway used by the central nervous system, and cytochrome oxidase histochemistry has been extensively utilized to map changes in neural metabolism following experimental manipulations. However, the value of cytochrome oxidase activity in predicting behavior has not been analyzed. We argue that this endeavor is important because genetic composition and embryonic environment can engender differences in baseline neural metabolism in pertinent neural circuits, and these differences could represent differences in the degree to which specific behaviors are 'primed.' Here we review our studies in which differences in cytochrome oxidase activity and in behavior were studied in parallel. Using mammalian and reptilian models, we find that embryonic experiences that shape the propensity to display social behaviors also affect cytochrome oxidase activity in limbic brain areas, and elevated cytochrome oxidase activity in preoptic, hypothalamic, and amygdaloid nuclei correlates with heightened aggressive and sexual tendencies. Selective breeding regimes were used to create rodent genetic lines that differ in their susceptibility to display learned helplessness and in behavioral excitability. Differences in cytochrome oxidase activity in areas like the paraventricular hypothalamus, frontal cortex, habenula, septum, and hippocampus correlate with differences in susceptibility to display learned helplessness, and differences in activity in the dentate gyrus and perirhinal and posterior parietal cortex correlate with differences in hyperactivity. Thus, genetic and embryonic manipulations that engender specific behavioral differences produce specific neurometabolic profiles. We propose that knowledge of neurometabolic differences can yield valuable predictions about behavioral phenotype in other systems.
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Affiliation(s)
- Jon T Sakata
- Institute for Neuroscience, University of Texas at Austin, Austin, TX 78712, USA
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13
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Abstract
Evolutionary shifts in species-typical group size ('sociality') probably reflect natural selection on motivational processes such as social arousal, approach-avoidance, reward, stress/anxiety and dominance. Using four songbird species that differ selectively in sociality (one territorial, one modestly gregarious, and two highly gregarious species), we here examined immediate early gene (IEG) responses of relevant brain regions following exposure to a same-sex conspecific. The paradigm limited behavioural performance, thus species differences should reflect divergence in motivational and/or perceptual processes. Within the extended medial amygdala (which is involved in appetitive approach, social arousal and avoidance), we observed species differences in IEG response that are negatively graded in relation to sociality. In addition, brain areas that are involved in social stress and dominance-related behaviour (ventrolateral septum, anterior hypothalamus and lateral subdivision of the ventromedial hypothalamus) exhibited IEG responses that dichotomously distinguish the territorial species from the three gregarious species. The IEG responses of areas involved in reward (nucleus accumbens and ventral pallidum) and general stress processes (e.g. paraventricular hypothalamus, lateral bed nucleus of the stria terminalis and most areas of the lateral septum) do not correlate with sociality, indicating that social evolution has been accompanied by selection on a relatively discrete suite of motivational systems.
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Affiliation(s)
- James L Goodson
- Psychology Department, University of California, San Diego, La Jolla, CA 92093-0109, USA.
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14
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Woolley SC, Sakata JT, Crews D. Tyrosine hydroxylase expression is affected by sexual vigor and social environment in male Cnemidophorus inornatus. J Comp Neurol 2004; 476:429-39. [PMID: 15282714 DOI: 10.1002/cne.20236] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Although the distribution of catecholamine-synthesizing cells has been described for a variety of taxa, less is known about the functional significance of particular populations in nonmammalian species, especially reptiles. To understand the role of these populations in the display of social behaviors in lizards, we studied the interactive effects of sexual vigor (sexually vigorous vs. sluggish) and social condition (housing in isolation vs. with females) on the number and somal areas of cells expressing tyrosine hydroxylase (TH), a rate-limiting enzyme in catecholamine synthesis, in male whiptail lizards, Cnemidophorus inornatus. We found that, regardless of social condition, sexually vigorous males had more TH-immunoreactive (TH-ir) cells in the dorsal hypothalamus (DH) relative to sluggish males. Sexually vigorous males also had more TH-ir cells in the substantia nigra pars compacta (SNpc), but this difference was significant only among males housed with females. Sexually vigorous males that had been housed with females had smaller TH-ir cells in the preoptic area (POA) than vigorous males housed in isolation. On the other hand, no significant differences were found in the anterior hypothalamus. These results highlight the regional heterogeneity in the plasticity of TH expression and suggest that, just as in other species, the DH, SNpc, and POA might be involved in the expression of social behaviors and in behavioral plasticity following social experiences in lizards.
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Affiliation(s)
- S C Woolley
- Section of Integrative Biology, University of Texas at Austin, Austin, Texas 78712, USA.
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15
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Sakata JT, Crews D. Cytochrome oxidase activity in the preoptic area correlates with differences in sexual behavior of intact and castrated male leopard geckos (Eublepharis macularius). Behav Neurosci 2004; 118:857-62. [PMID: 15301612 DOI: 10.1037/0735-7044.118.4.857] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although the utility of analyzing behavioral experience effects on neural cytochrome oxidase (CO) activity is well recognized, the behavioral correlates of endogenous differences in CO activity have rarely been explored. In male leopard geckos (Eublepharis macularius), the incubation temperature experienced during embryogenesis (IncT) and age affect CO activity in the preoptic area (POA), an area that modulates copulatory behavior. In this study, the authors assessed whether differences in POA CO activity correlate with differences in sexual behavior in intact and castrated geckos. Males with IncT- and age-dependent increases in POA CO activity mounted females with shorter latencies while intact and after castration and ejaculated more frequently after castration. The authors discuss the predictive value of CO activity and propose similar parallels in other species.
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Affiliation(s)
- J T Sakata
- Institute for Neuroscience, University of Texas at Austin, Austin, TX, USA.
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16
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Sakata JT, Crews D. Developmental sculpting of social phenotype and plasticity. Neurosci Biobehav Rev 2004; 28:95-112. [PMID: 15172759 DOI: 10.1016/j.neubiorev.2004.01.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2003] [Revised: 12/23/2003] [Accepted: 01/05/2004] [Indexed: 11/16/2022]
Abstract
Early developmental variables engender behavioral and neural variation, especially in species in which embryonic environment determines gonadal sex. In the leopard gecko, Eublepharis macularius, the incubation temperature of the egg (IncT) determines gonadal sex. Moreover, IncT affects the sexual differentiation of the individual and, consequently, within-sex variation. Individuals hatched from eggs incubated at an IncT that produces predominantly males are more masculinized than same-sex counterparts from IncTs that produce predominantly females. Here we review how gonadal sex and IncT interact to affect behavioral, endocrinological, and neural phenotype in the leopard gecko and influence phenotypic plasticity following hormone administration or social experience. We discuss the hormonal dependence of sex- and IncT-dependent behavioral and neural morphological and metabolic differences and highlight the parallels between IncT effects in geckos and intrauterine position effects in rodents. We argue that the leopard gecko is an important model of how the process of sex determination can affect sexual differentiation and of selection forces underlying the evolution of sex ratios.
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Affiliation(s)
- Jon T Sakata
- Institute for Neuroscience, University of Texas at Austin, Austin, TX 78712, USA.
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17
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Woolley SC, Crews D. Species differences in the regulation of tyrosine hydroxylase inCnemidophorus whiptail lizards. ACTA ACUST UNITED AC 2004; 60:360-8. [PMID: 15281073 DOI: 10.1002/neu.20044] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Evolution of behavioral phenotype involves changes in the underlying neural substrates. Cnemidophorus whiptail lizards enable the study of behavioral and neural evolution because ancestral species involved in producing unisexual, hybrid species still exist. Catecholaminergic systems modulate the expression of social behaviors in a number of vertebrates, including whiptails, and therefore we investigated how changes in catecholamine production correlated with evolutionary changes in behavioral phenotype by measuring the size and number of catecholamine producing (tyrosine hydroxylase-immunoreactive, or TH-ir) cells across the reproductive cycle in females from two related whiptail species. Cnemidophorusuniparens is a triploid, parthenogenetic species that arose from hybridization events involving the diploid, sexual species C. inornatus. Prior to ovulation, females from both species display femalelike receptive behaviors. However, after ovulation, only parthenogenetic individuals display malelike mounting behavior. In all nuclei measured, we found larger TH-ir cells in the parthenogen, a difference consistent with species differences in ploidy. In contrast, species differences in the number of TH-ir cells were nucleus specific. In the preoptic area and anterior hypothalamus, parthenogens had fewer TH-ir cells than females of the sexual species. Reproductive state only affected TH-ir cell number in the substantia nigra pars compacta (SNpc), and C. uniparens individuals had more TH-ir cells after ovulation than when previtellogenic. Thus, species differences over the reproductive cycle in the SNpc are correlated with species differences in behavior, and it appears that the process of speciation may have produced a novel neural and behavioral phenotype in the parthenogen.
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Affiliation(s)
- Sarah C Woolley
- Section of Integrative Biology, Patterson 141, 2400 Speedway, University of Texas at Austin, Austin, Texas 78712, USA.
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Woolley SC, Sakata JT, Crews D. Tracing the Evolution of Brain and Behavior Using Two Related Species of Whiptail Lizards: Cnemidophorus uniparens and Cnemidophorus inornatus. ILAR J 2004; 45:46-53. [PMID: 14752207 DOI: 10.1093/ilar.45.1.46] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Cnemidophorus whiptail lizards offer a unique opportunity to study behavioral and neural evolution because unlike most genera, ancestral and descendant species are still extant, and comparisons between species provide a window into correlated changes in biological organization through speciation. This review focuses on the all-female or parthenogenetic species Cnemidophorus uniparens (descendant species), which evolved through several hybridization events involving the sexually reproducing species Cnemidophorus inornatus (ancestral species). Data compiled over more than 2 decades include behavioral, endocrine, and neural differences between these two related species of whiptail lizards. For example, unlike females of the ancestral species, individuals of the descendant species display male-like mounting behavior (pseudocopulatory behavior) after ovulation. Pseudocopulatory behavior in the parthenogen is triggered by the progesterone surge after ovulation, and the behavioral capacity to respond to progesterone appears to be an ancestral trait that was inherited from C. inornatus males through the hybridization events. Interestingly, the regulation of sex steroid hormone receptor mRNA in brain areas critical for the expression of sociosexual behaviors differs between females of the two species and suggests that evolutionary changes in the regulation of gene expression could be a proximate mechanism that underlies the evolution of a novel social behavior in the parthenogen. Finally, because the sexual species is diploid, whereas the parthenogen is triploid, differences between the species could directly assess the effect of ploidy. The behavioral and neuroendocrinological data are pertinent for considering this possibility.
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Affiliation(s)
- S C Woolley
- Keck Center for Integrative Neuroscience, University of California at San Francisco, CA, USA
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Affiliation(s)
- David Crews
- Section of Integrative Biology, University of Texas, Austin, Texas 78712, USA.
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Sakata JT, Woolley SC, Gupta A, Crews D. Differential effects of testosterone and progesterone on the activation and retention of courtship behavior in sexual and parthenogenetic whiptail lizards. Horm Behav 2003; 43:523-30. [PMID: 12799168 DOI: 10.1016/s0018-506x(03)00060-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Both testosterone (T) and progesterone (P) facilitate the expression of male-typical sexual behavior in a variety of animals, including rodents and lizards. In two species of whiptail lizards, Cnemidophorus inornatus and C. uniparens, both hormones elicit the full repertoire of courtship behavior. However, the relative efficacy of the two hormones is unknown. In Experiments 1 and 2 we assessed differences in capacity of exogenous T and P to induce male-typical courtship behavior in gonadectomized whiptail lizards. In both species, individuals implanted with T showed more frequent courtship behavior relative to those implanted with P or cholesterol. In Experiments 3 and 4 we examined whether T and P differentially affected the retention of courtship behavior following implant removal. In both species, individuals implanted with T showed more courtship behavior following implant removal than those previously given P. In these experiments, implants were removed at a time when individuals in both groups were behaviorally similar; therefore, the differences in behavior following implant removal were not due to differences in the amount of courtship experience. Taken together, the hormone that was more effective at activating courtship behavior was also more effective at maintaining courtship behavior following implant removal. In summary, though both T and P can elicit identical sexual behaviors in both whiptail species, T has a greater and more lasting effect on courtship behavior and possibly on the neural circuits underlying courtship behavior.
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Affiliation(s)
- Jon T Sakata
- Institute for Neuroscience, University of Texas at Austin, Austin, TX 78712, USA.
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