Abstracts for symposia presentations and other talks are listed chronologically according to their scheduled times during the meeting.
All talks—unless otherwise noted—will be in Alumni Hall in the Indiana Memorial Union.
Abstracts for symposia presentations and other talks are listed chronologically according to their scheduled times during the meeting.
All talks—unless otherwise noted—will be in Alumni Hall in the Indiana Memorial Union.
S1.1 A hypothalamic to PAG circuit controls aggressive motivation and action
Annegret Falkner, Princeton University USA
[abstract not available]
S1.2 Oxytocin in the bed nucleus of the stria terminalis induces social anxiety
Brian Trainor, University of California, Davis USA
Oxytocin is a well-known modulator of social behaviors, and has been put forth as a possible therapeutic for social anxiety disorder. However, studies in humans have found that oxytocin can either increase or decrease social anxiety. How can the same neuropeptide exert such different effects on behavior? In a series of studies using the California mouse model of social defeat, we demonstrate that oxytocin produced and acting within the bed nucleus of the stria terminalis promotes social avoidance and vigilance. Our results suggest that sex differences in how social stressors affect the activity of oxytocin producing neurons are a major contributing factor in determining sex differences in how stress affects social behavior. Consistent with work in other species, we also show oxytocin acting in the nucleus accumbens promotes social approach. Together, these results suggest that oxytocin works in complementary neural circuits to produce divergent effects on social behaviors.
S1.3 Understanding the neural basis of social attachment
Devanand Manoli, University of California, San Francisco USA
[abstract not available]
S1.4 Socially-transmitted motivation for maternal behavior
Ioana Carcea, Rutgers University USA
Maternal care is profoundly important for mammalian survival, and maternal behaviors can also be expressed by non-biological parents after experience with infants. One critical molecular signal for maternal behavior is oxytocin, released by hypothalamic paraventricular nucleus (PVN) and enabling plasticity within auditory cortex for recognizing infant vocalizations. To determine how these changes occur during natural experience, we continuously monitored homecage behavior of female virgin mice co-housed for days with an experienced mother and litter, synchronized with in vivo recordings from virgin PVN/oxytocin neurons. Mothers engaged virgins in maternal care by ensuring that virgins were in the nest, and demonstrated maternal behavior by self-generating pup retrieval episodes. These social interactions activated virgin PVN and gated behaviorally-relevant cortical plasticity for pup distress calls. Thus rodent maternal behavior can be learned by social transmission, and our results describe a mechanism for adapting the brains of new parents to infant needs via endogenous oxytocin.
Pleiotropic effects of testosterone on a sexually selected trait: birdsong
Gregory F. Ball, University of Maryland USA
Male birdsong functions as a courtship or territorial signal often in a reproductive context. Testosterone (T) increases during the reproductive phase of the annual cycle and can enhance song production. T can exert its effects in the brain on song and other reproductive behaviors via its estrogenic and androgenic metabolites. The neural control of birdsong is highly modular, with distinct regions and circuits regulating different aspects of song learning and production. The widespread distribution of nuclear androgen receptors in the song system as well as the occurrence of estrogen receptors in one key forebrain nucleus and the presence of both receptor types in the diencephalon and the midbrain raises questions as to where and how T is exerting its myriad effects on song. By selectively implanting T or androgen antagonists into specific brain regions or in the periphery of castrated male canaries, we have identified a modular organization of the androgenic activation of birdsong. T acting in the preoptic area (POM) induces singing at high rates, but song quality is impaired. Placing T in the song nucleus HVC and the POM rescues some of these effects. Blocking T action selectively in forebrain song nuclei can modulate independently effects on acoustic stereotypy of individual syllables and trills as opposed to effects on syllable-type usage or syllable-type sequence variability. Measures of song performance preferred by females can be modulated by selectively blocking T action in the syrinx. Thus, song behaviors are regulated by androgens acting at multiple levels in a non-redundant fashion
S2.1 Neuroepigenetic mechanisms of behavioural adaptation in the zebra finch
David Clayton, Queen Mary University of London UK
Behavioural adaptation is key to an organism’s success, on both proximal and evolutionary timescales. We are working on several models of behavioural adaptation in songbirds, testing the hypothesis that stable adaptations involve neuroepigenetic mechanisms – in particular changes in DNA methylation. In one model, we find that the experience of being placed alone overnight in a sound isolation chamber triggers changes in DNA methylation in the auditory forebrain of adult zebra finches. These genes including BDNF (a neurotrophic factor) and FKBP5 (a co-chaperone of the glucocorticoid receptor). We hypothesise that such changes support a broad re-tuning of the nervous system related to the shift in social context. In another model, we find that habituation of responses to song playbacks is correlated with other changes in DNA methylation, possibly related to formation of new song associations. Most recently we have begun studying developmental reprogramming of zebra finch embryos following parental “incubation calls” (Mariette & Buchanan, Science, 2016), testing the hypothesis of potential epigenetic mechanisms in this phenomenon, too. These observations suggest the deep involvement of epigenetic mechanisms in diverse behavioural adaptations and on multiple timescales.
S2.2 Epigenetic potential in introduced populations
Haley Hanson, University of South Florida USA
All organisms must respond to environmental stimuli and do so through alterations of the endocrine system. Phenotypic plasticity is common and the interconnectedness of the endocrine system makes it so many modifications can impact subsequent phenotypes and potentially the fitness of that organism, especially during development and vulnerable life-history stages. Epigenetic potential, defined as the capacity for epigenetically-mediated phenotypic plasticity, may be mediating endocrine phenotypes in response to environmental effects. Thus, epigenetic potential is expected to play an important role in range expansions, and other contexts in which the environment is novel or unpredictable, especially when it occurs in regulatory elements of the endocrine system. Here, we predicted which genes in the hypothalamic-pituitary-adrenal (HPA) axis are most likely to be epigenetically-regulated, and consequently, might be most impacted by epigenetic potential. Our top predicted components were mainly receptors: (in order) corticotropin-releasing hormone receptor 2, corticotropin-releasing receptor 1, adrenocorticotropic hormone receptor, and glucocorticoid receptor. This sparked a more intensive study into how one form of epigenetic potential (i.e. the abundance and/or position of CpG sites within gene promoters) varied among introduced populations of house sparrows (Passer domesticus) by targeting candidate genes and using epi- and ddRADseq methods.
S2.3 Transcriptomics of sexual differentiation of the brain
Margaret McCarthy, University of Maryland, Baltimore USA
In mammals, a perinatal surge in androgen production by the fetal testis initiates masculinization of the developing brain. The process is complete within days of birth but the consequences must endure for weeks, months or even decades depending upon the species. Exploration of epigenetic modifiers and sex differences in the transcriptome reveal multiple region specific mechanisms and profiles. These range from steroid modulation of the activity of enzymes that methylate DNA, divergent roles for chromatin versus DNA in males and females and the potential for sex-specific transcriptional networks underlying complex social behavior. Both the advantages and challenges of transcriptomic and epigenetic approaches will be discussed.
S2.4 Epigenetic development of the juvenile social brain
Anthony Auger, University of Wisconsin USA
[abstract not available]
S3.1 W.C. Young Lecture: Cancer and sleep—Understanding how tumors talk to the brain
Jeremy Borniger, Stanford University USA
[abstract not available]
S3.2 Lyn Clemens Lecture: Cross-species examination of the role of estradiol in sleep and memory in females
Nicole J. Gervais, University of Toronto Canada
Ovarian hormone deprivation following natural menopause is associated with sleep disturbance, memory complaints and increased risk of mild cognitive impairment and Alzheimer’s disease (AD) later in life. This risk is exacerbated following ovarian removal prior to natural menopause. Studies in humans and animals demonstrate the protective effects of estradiol (E2) on sleep and memory formation, and while sleep is known to promote memory and brain function, limited attention has been paid to understanding the contribution of poor sleep to memory decline following menopause. Our findings demonstrate the protective effects of E2 on both sleep and memory across three species (rat, marmosets, and humans). Our human studies provide novel insight into the importance of stratifying samples based on menopause type (e.g. natural vs surgical). Our discussion focuses on memory abilities that are dependent on structures within the medial temporal lobe or the prefrontal cortex. We show that E2 improves memory function across species, and promotes synaptic density and structural integrity of structures within the medial temporal lobe. We also show that menopause is associated with worse sleep in both marmosets and humans, which is protected by E2 use. Our recent data demonstrate that poor sleep is related to reduced hippocampal volume and lower memory performance in menopausal women. These studies take an integrative and translational approach to explore the contribution of ovarian hormone deprivation to menopausal symptoms and elevated dementia risk, and identify potential early markers associated with memory decline.
S3.3 Involvement of the ventral tegmental area in socially rewarding behavior in juvenile male and female rats
Christina J. Reppucci, Michigan State University USA
The ventral tegmental area (VTA) is an essential component of the mesocorticolimbic dopamine reward system and an important node of the Social Decision-Making Network. Yet, the role of the VTA in socially rewarding behaviors, especially during early adolescence, is understudied. Here, using juvenile male and female rats, we focused on social play, a highly rewarding behavior predominately displayed by juveniles and expressed by nearly all mammals. In Experiment 1, using combined Fos and tyrosine hydroxylase (TH) immunohistochemistry we found that subjects exposed to social play had greater activation of the VTA and its dopaminergic neurons than subjects in the no play control condition. In Experiment 2, temporary inactivation of the VTA via bilateral infusion of the GABAA agonist muscimol selectively decreased the expression of social play while leaving social investigation intact. In Experiment 3, using intra-VTA in vivo microdialysis we found that social play was associated with dynamic changes in the extracellular levels of glutamate, GABA, and dopamine. In Experiment 4, subjects were exposed to social play one week after unilateral injections of the retrograde tracer CTB into the VTA, and then Fos immunohistochemistry was used to determine activation of VTA afferents. Of note, subjects in the play condition had greater activation of VTA-projecting lateral septum neurons compared to the no play control condition. Together, these experiments provide evidence that the VTA is a key node in the network underlying social play, and that activation of the VTA supports the expression of social play behavior in juvenile rats.
S3.4 Noncanonical genomic imprinting reveals novel subpopulations of monoaminergic neurons in the brain
Paul Bonthuis, University of Utah USA
In published RNAseq studies, we discovered a network of monoamine neurotransmitter genes exhibiting “noncanonical” genomic imprinting effects in the mouse brain. Canonical imprinting involves complete silencing of a gene’s maternal or paternal allele, whereas noncanonical imprinting involves a bias to express either the maternal or paternal allele at the tissue level. Leading theories claim genomic imprinting in the brain functions to impact social behavior. Neurotransmitters known to regulate social behavior, including the monoamines dopamine, serotonin, and norepinephrine, are downstream products of dopa decarboxylase (Ddc), a monoamine synthesis enzyme, which exhibits a maternal allele bias in the brain. To investigate allelic bias at the cellular level in monoaminergic neurons, CRISPR-Cas9 mediated knockin made Ddc Allele-Tag mice expressing GFP and RFP from the maternal and paternal alleles (DdcGFP/RFP), respectively. These mice, and reciprocals (DdcRFP/GFP), were used to produce a brain atlas identifying imprinted monoamine cell populations. Fourteen (out of 52) high-confidence discrete regions, mostly in dopaminergic nuclei of the hypothalamus, contained subpopulations of DDC+ cells monoallelically expressing only the maternal allele. Also, Ddc maternal bias is enhanced in the hypothalamus of lactating females, and correlates with nursing litter size. Furthermore, compound heterozygous females that inherit multiple mutant monoamine synthesis alleles from their mother, as opposed to their father, display differences in maternal behavior phenotypes. These results indicate that noncanonical imprinting at the tissue level comprises a mixture of biallelic and imprinted monoallelic subpopulations at the cellular level, imprinting effects can change in response to environmental stimuli, and monoamine imprinting impacts social behavior.
S3.5 Regulation of fluid homeostasis during mammalian hibernation: Behavioral, hormonal, and neural mechanisms
Ni Y. Feng, Yale University USA
Hibernation is a fascinating physiological phenomenon during which animals rely solely on the management of internal resources for long-term survival. Winter hibernation in rodents can last up to nine months, during which animals cycle between weeks-long torpor bouts of severe hypothermia and hypometabolism interspersed by short interbout arousals (IBA), when major physiological parameters return to normal “active” levels. We use the thirteen-lined ground squirrel (Ictidomys tridecemlineatus) as a model to characterize how peripheral, central, and behavioral components of the fluid homeostatic pathway are tuned to enable hibernation. We show that despite not having access to external water, squirrels avoid dehydration and decrease serum concentration (osmolality) by 30 mOsmol/kg during torpor. This decrease is mainly due to changes in the internal distribution of ions, but not to increased drinking prior to hibernation or increased renal water retention via vasopressin or oxytocin production. During IBA, serum osmolality increase to active levels, but squirrels display lowered baseline drinking activity, suggesting an escape from the aversive drive of thirst during hibernation. However, acute dehydration via hypertonic saline injection is able to induce thirst in IBA animals, suggesting the underlying thirst neural circuit can be activated in hibernation. Supporting this conclusion, hypertonic saline injection elevates the expression of cFOS in the subfornical organ of both active and IBA animals. Together, our results demonstrate that during hibernation, squirrels escape dehydration by regulating the internal distribution of ions, exhibit lowered baseline thirst, but possess a functional thirst neural circuit capable of responding to signals of fluid imbalance.
The female power grid controlled by sex-dependent neurocircuits in the MBH
Holly Ingraham, University of California, San Francisco USA
We seek to discover sex-differences in the central control of female physiology across the lifespan. We found that central estrogen signaling is linked to sex-dependent anabolic bone responses in female mice. In our recently published work, a stunning increase in bone mass occurs after deleting estrogen hormone signaling in the female arcuate nucleus of the hypothalamus (ARC). In female mice, the robust increase in new bone formation stems from loss rather than gain of estrogen signaling in the ARC and is uncoupled from high circulating peripheral estradiol (E2). Four independent and intersectional models confirmed that ablating estrogen receptor alpha (ERa) signaling in ARC neurons leads to a robust increase in bone density and bone strength only in female mice. We identified ARC Kiss1 neurons in the medial basal hypothalamus (MBH) as the critical node for this powerful neuroskeletal circuit. These findings established that a sex-dependent brain-to-bone pathway normally restrains bone metabolism to divert energy resources elsewhere. When disrupted, a robust anabolic bone response is permanently triggered in young and old mutant female mice. In parallel studies we have identified a small cluster of ~100 estrogen-responsive neurons in the ventrolateral subregion of the ventromedial hypothalamus (VMHvl) that create an ancillary female-specific circuit to integrate melanocortin and estrogen signaling, promoting both activity and obsessive-like behaviors. Surprisingly, food intake was unaffected in all of our models that manipulate estrogen-signaling in the MBH. We conclude that hormone-sensitive, sex-dependent circuits in the hypothalamus are essential for coordinating energy allocation and utilization in females.
S4.1 Brain plasticity and perineuronal nets in songbirds
Jacques Balthazart, University of Liège Belgium
The morphology of the oscine song control system can be regulated by changes in the hormonal and social environment. This plasticity includes a modulation of neurogenesis in HVC, but also changes in cell size, long distance connectivity and perineuronal nets (PNN) density. PNN are aggregations of extracellular matrix components surrounding the soma of specific neurons that limit synaptogenesis and mark the end of sensitive periods. In zebra finches, PNN expression in HVC and the nucleus robustus arcopallialis (RA) is higher in males than in females and higher in adult than in juvenile males. PNN increase in the developing zebra finch brain correlates with the timing of sensitive periods for song learning and PNN maturation is delayed in birds deprived from a tutor. Similarly, in first year male canaries, PNN density reaches its maximum in the fall in HVC and in early winter in RA when birds are crystalizing their song. PNN are also more densely expressed in the song control system of zebra finches than in European starlings and canaries, two species that exhibit open-ended learning. Although PNN density did not change across conditions representing the different seasonal stages in starlings, testosterone increases the number of PNN in castrated male and in female canaries and their density seems to vary across seasons in some of the male song control nuclei. We are currently investigating whether dissolution of PNN in HVC by application of chondroitinase sulfate affects song structure and song (re)learning in adult male canaries.
S4.2 Do perineuronal nets close the postnatal sensitive period for steroid-dependent organization of behavior?
Kalynn Schulz, University of Tennessee USA
The factors mediating a successful transition from adolescence to adulthood range from social to biological. One factor that has received increased investigation in recent years is the timing of puberty. Whether individuals undergo pubertal development early or late relative to their peers increases risk for mental illness. Scientific explanations of the relationship between pubertal timing and mental illness tend to focus on the social and emotional consequences of developing earlier or later than one’s peers. However, our work demonstrates that gonadal hormones permanently alter neural networks and behavior during adolescence. We have also shown that sensitivity to the organizing actions of steroid hormones decreases across postnatal development, with adolescence marking the end of postnatal sensitive period. However, the mechanisms governing the timing of the postnatal sensitive period for steroid-dependent organization of behavior are unknown. My laboratory is currently investigating whether adolescent increases in perineuronal nets close the sensitive period for steroid-dependent organization of reproductive behavior in mice. Perineuronal nets (PNNs) are specialized extracellular matrix structures that preferentially wrap around parvalbumin-expressing GABAergic neurons as they mature. PNN increases are associated with the closing of many other sensitive periods of development such as visual acuity, fear conditioning, and song learning in birds. We are testing whether testosterone in males, and estradiol in females, directly impacts PNN development to close the postnatal sensitive period for steroid-dependent organization of reproductive behavior in mice. The outcomes will advance our understanding of the factors mediating the timing of postnatal brain sensitivity to gonadal steroid hormones.
S4.3 Role of perineuronal nets surrounding parvalbumin+GABAergic neurons in regulating learning and execution of maternal behavior
Keerthi Krishnan, University of Tennessee USA
Cohabitation of adult nulliparous mice with pups and mother induces maternal behavior in them in a hormone-independent manner. Such non-hormonal factors are important in mediating plasticity, likely through chromatin remodeling of specific neural circuitry (Stolzenberg and Champagne, 2016,). We have previously shown that nulliparous mice deficient in Methyl CpG-binding protein 2 (MECP2), an epigenetic regulator, display inefficient pup gathering behavior (Krishnan, Lau et al, 2017). We identified a crucial mechanism involving extracellular matrix structures called perineuronal nets (PNNs) which play a major role in structural plasticity of parvalbumin+ GABAergic networks in the auditory cortex. The auditory cortex of MECP2-deficient females had increased numbers of PNNs, which when removed, improved pup gathering performance, demonstrating the crucial structural role that PNNs provide in learning and plasticity.
Many questions remain: How do the nulliparous wild types learn and perform the behavior well? What stimuli and factors are critical for priming efficient retrieval? What neural circuits are essential for processing sensory information, motor outputs and context-specific responses? We answer these questions by utilizing integrative approaches from histology/microscopy to detailed behavioral coding, in order to gain a better understanding of the mechanisms underlying adult experience-dependent plasticity. I will be presenting our recent, unpublished data on somatosensory cortex plasticity, ultrasonic vocalizations during retrieval and detailed behavioral observations.
S4.4 Dynamic regulation of sound learning in adult auditory cortex
Robert Liu, Emory University USA
The mechanisms by which we learn from and reshape our perception of the world based on experience are of long-standing interest within the neuroscience community. One continuing mystery is how we manage to incorporate newly learned stimuli into our neural networks without drastically disrupting the processing of previously learned stimuli. We have been investigating such mechanisms in the context of more ethologically motivated sensory learning paradigms – both appetitive and aversive – in mice. An emerging picture based on work in both a maternal model for sensory learning of infant sounds, and an auditory fear conditioning model, suggests that context-dependent disinhibition of auditory cortex may be essential for plasticity to learn the behavioral relevance of new sounds from experiences. But how do these changes manage to persist despite further ongoing experiences? One contributing mechanism within auditory cortex appears to be the dynamic regulation of the extracellular matrix by sound learning. Although perineuronal nets (PNNs) are generally thought to be inhibitory to neural plasticity and stable in adulthood, we discovered that after an auditory fear conditioning session, PNN components are actually dynamically upregulated about 4 hours later before returning to baseline the next day. Moreover, digesting PNNs immediately after training impairs the consolidation of auditory fear memories, as assayed in subsequent fear expression tests. These results are consistent with a working model wherein the transient increase in PNNs might place a brake on further plasticity during a window of potential interference from new experiences during memory consolidation.
S5.1 Identifying a novel role for prolactin in the transition to paternal care
Kristina O. Smiley, University of Otago New Zealand
Paternal care is important for healthy offspring development. However, in comparison to maternal care, the neuroendocrine regulation of paternal care remains poorly understood. There is a well-established role for the hormone prolactin (PRL) in promoting mammalian maternal behavior through its actions on central prolactin receptors (PRLR). Although, male mice have a similar central PRLR distribution as females, it is unknown whether PRL plays a role in the induction of paternal behavior. To establish whether PRL-responsive neurons were active during paternal care, we examined c-fos (a marker for recent neural activation) immunolabelling in the brain of PRLR-IRES-Cre/tdtomato father mice. Fathers were separated from their pups for 24 hours on day 3 post-partum and then either exposed or not exposed to pups for 30 minutes in their home cage. We found that fathers exposed to pups showed increased c-fos expression in PRLR-expressing cells in the MPOA, as well as several other hypothalamic regions. Next, using mice with a conditional deletion of PRLR in CamK-Cre neurons to target forebrain neurons (Prlrlox/lox/CamK-Cre), we showed that paternal care behaviors (retrieving pups and crouching) were either eliminated or greatly reduced in knockout animals, compared to controls. In contrast, conditional deletion of PRLR from only glutamatergic or GABAergic neurons did not result in significant impairment in paternal behavior. These results are the first demonstration that PRL action in the brain is important for mammalian paternal behaviors.
S5.2 Effects of neural aromatase inhibition on auditory scene processing in songbirds
Marcela Fernández-Vargas, University of Massachusetts Amherst USA
Songbirds like humans are highly social and gregarious species that communicate under variable and often significant levels of background noise. In male songbirds, neurons in the secondary auditory cortex (caudomedial nidopallium, NCM) are tolerant to significant levels of background noise. They similarly encode song, as well as song embedded in noise and are thought to aid behavioral discrimination in noisy environments. In addition, NCM is characterized by a significant proportion of neurons that express the estrogen-synthesis enzyme, aromatase. Rapid synthesis of ‘neuroestrogens’ in NCM occurs in response to playback of conspecific song and enhances local gain and coding for song. Here we hypothesize that estrogens could facilitate discrimination of song embedded in noise by modulating neural processing in NCM. Using extracellular recordings in awake, restrained male and female zebra finches, we characterized single neuron responses to auditory scenes of incrementally varying signal-to-noise ratios. To examine the role neuroestrogens, we microinjected fadrozole (aromatase inhibitor, FAD) or artificial cerebrospinal fluid (vehicle, aCSF) into NCM and simultaneously recorded evoked-responses to auditory scenes at the site of drug application. As in males, female NCM cell types (identified by their action potential width) tolerated levels of background noise differentially during song encoding. Neurons exposed to FAD exhibited suppressed firing rates, less reliable encoding and discrimination of song embedded in chorus compared to neurons exposed to aCSF. Ongoing analysis is testing whether these patterns are cell type-specific in NCM. This research suggests a potential role of neuroestrogens in contextual processing of complex auditory scenes.
S5.3 Aggression and species differences in neural activity and gene expression in Lake Malawi cichlid fish
Nicole M. Baran, Georgia Institute of Technology USA
In Lake Malawi, two ecologically distinct lineages of cichlid fishes (rock- versus sand-dwelling ecotypes, each comprised of over 200 species) evolved from a single ancestral population within the last million years. The rock-dwelling species (Mbuna) are aggressively territorial year-round and males court and spawn with females over rocky substrate. In contrast, males of sand-dwelling species are not territorial and instead aggregate on seasonal breeding leks in which males construct courtship “bowers” in the sand. Previously, we demonstrated differences between species in both the quantity and quality of aggressive behavior in the lab using mirror-elicited aggression tests in seven species. Here, using one rock species (Petrotilapia chtimba, Petro), and one sand species (Mchenga conophoros, MC), we use phosphorylated ribosome immunoprecipitation of mRNA from whole brain followed by RNA-sequencing to compare the gene expression patterns activated by mirror-elicited aggression across the two species. We found 993 genes that show patterns of differential expression during aggression between MC and Petro, including neuromodulators, genes associated with steroid hormones, and glutamate/GABA activity. We then compare neural activity following mirror-elicited aggression using immunolabeling for pS6 and for neuropeptide Y (NPY), a differentially-expressed candidate neuropeptide which emerged from the pS6-RNA-seq analyses. NPY has previously implicated in territorial aggression in other species. This work lays the foundation for future experiments using this emerging genetic model system to investigate the genomic basis of evolved species differences in both brain and behavior.
S5.4 Early life stress primes future stress response through chromatin modifications
Catherine Jensen Peña, Mount Sinai and Princeton University USA
Early life stress (ELS) increases lifetime risk of depression and other mood, anxiety, and drug disorders by 2-4 -fold. Studies in humans and animals suggest that ELS sensitizes individuals to stress later in life, leading to a first appearance or synergistic worsening of depression-like symptoms after additional stress. To study the molecular correlates of lifelong stress vulnerability, we recently established a “two-hit” stress paradigm in mice in which early life stress in a sensitive window increases susceptibility for depression-like behavior, but only after experience of additional stress in adulthood. This latent behavioral vulnerability is accompanied by latent transcriptional alterations in key brain reward regions that are implicated in depression, including the ventral tegmental area (VTA). We hypothesized that such latent transcriptional alterations would be “primed” by chromatin modifications. We profiled all possible histone modifications simultaneously using bottom-up mass spectrometry. The proportions of 14 histone modifications were altered by ELS, a majority of which are associated with open chromatin, in which genes are more readily transcribed. Among these, ELS increased H3K4me3 and H3K4me1, marks of active and primed genomic regulatory elements. ChIP-seq for H3K4me1 revealed 209 differentially enriched peaks (FDR<0.05 and >20% fold-change), a majority of which were increased by ELS. Interestingly, there is greater correspondence between H3K4me1 enrichment and expression of putative enhancer-contacted genes after additional adult stress than after ELS alone, in support of a priming hypothesis. This research suggests novel epigenetic mechanisms mediating how ELS renders the VTA more reactive to future stress experience.
S5.5 Seasonal divergence in timing in a sparrow: Evidence from behavior to molecules
Devraj Singh, Indiana University USA
In anticipation of spring, dark eyed juncos living in the mountains of the eastern US begin to breed or migrate northward in a recurring seasonal pattern of biological activities and associated physiology underlying migration and reproduction. As photoperiod increases during spring, migratory juncos gain weight and prepare to initiate migration, while sedentary juncos undergo gonadal recrudescence and prepare to breed. We tested the divergence in behavior and physiology of migratory and sedentary juncos in captivity by exposing them to increasing photoperiod from nine to sixteen hours over four months. We observed a clear difference in the photoperiodic threshold of gonadal recrudescence and GnRH1 challenged testosterone (dT). We also observed significant elevation in the resident junco cloacal protuberance (CP) volume at 12.4h and GnRH1 challenged testosterone (dT) at 11h of light, as compared to migrants that exhibit similar elevation in CP at 13h and dT until 12L of light. In a second experiment conducted in the wild, we sampled the hypothalamic tissues of migrant (n=6) and resident (n=7) male juncos at the time of diverging behavior and physiology. Feather isotopes (dH) were used as a proxy to estimate breeding latitude. A comparison of the hypothalamic transcriptome of both forms showed gonadotrophin hormone 1 (GnRH1) as the only differentially expressed gene (FDR<0.05). Testing the photoperiodic threshold for gonadal recrudescence and hypothalamic transcriptome of migrants and residents living in the same environment reveals differential response to the photoperiodic cue and enables posing further questions to investigate cues influencing seasonal timekeeping.
S5.6 Lateral hypothalamic control of male and female sexual motivation
Kimberly J. Jennings, Stanford University USA
Stimulation of the lateral hypothalamus (LHA) has long been known to facilitate sexual motivation. Among the multiple cell types that populate the LHA, neurons that produce the neuropeptide hypocretin (Hcrt, also known as orexin) are strong candidates to mediate sexual motivation. Hcrt neurons drive arousal and reward-seeking behavior and are hypothesized to support expression of motivated behavior. However, evidence for a role in male sexual motivation has been discordant and the role of LHA-Hcrt in female sexual motivation remains unknown. To determine the role of LHA-Hcrt neurons in male and female sexual motivation, we first used fiber photometry to record calcium activity in LHA-Hcrt neurons while mice interacted with an opposite-sex conspecific. Resulting data indicate that LHA-Hcrt activity is specifically increased during appetitive sexual behavior and decreased during consummatory sexual behaviors in both sexes. We next used targeted optogenetic manipulation of LHA-Hcrt neurons during specific behaviors to probe the causal role of LHA-Hcrt neurons in male and female sexual behavior. To further determine the role of LHA-Hcrt in socio-sexual motivation, we manipulated LHA-Hcrt activity in a progressive ratio task for access to an opposite-sex mate. These data reveal the functional role of LHA-Hcrt neurons in male and female sexual motivation and broaden our understanding of LHA-Hcrt regulation of motivational and emotional states.
S5.7 Arginine vasotocin mediates social behavior via the chemosensory system
Stephanie M. Campos, Georgia State University USA
Social interactions are modulated by arginine vasotocin (AVT), which functions in nonmammalian vertebrates similarly to its homologue vasopressin in mammals. While AVT is known to impact the performance and perception of visual social signals in reptiles, whether AVT also operates within the chemosensory system as it does in mammals is unknown, despite social odors being potent modifiers of aggressive and reproductive behavior in many vertebrates. Previous studies in green anoles (Anolis carolinensis, which have highly stereotyped aggressive and courtship displays) link elevated levels of exogenous AVT in males (AVT-males) to lower rates of aggressive visual displays, whereas untreated females perform more visual displays towards AVT-males than Control-males. Here, we ask whether exogenous AVT levels impact rates of both chemical (e.g. tongue flicks) and visual display behavior (e.g. pushups) in adult male green anoles, and whether conspecific responses also depend on AVT levels of stimulus males or their display rates. We injected wild-caught males with either AVT or a saline (control) solution to serve as social stimuli. After 10mins in home tanks, we presented stimulus males with a conspecific and recorded 30min interactions. AVT-males responded to observer-females using a chemical display faster than Control-males, whereas observer-males performed more chemical behavior towards AVT-males than Control-males. In contrast, visual behavior did not differ between the two treatment groups for stimulus males or observers. These results demonstrate that AVT modulates chemical behavior in reptiles as it does in mammals, having important implications for the effects on animals that use multimodal communication.
Harnessing species diversity to understand the hormonal, genetic, and neural basis of pair bonding
Zoe Donaldson, University of Colorado USA
From hunting in groups to building empires, human advancements have depended on the crucial role of social bonds. However, it has been difficult to model complex social behaviors in a laboratory setting where traditional mouse and rat models do not form selective social bonds among adult individuals. My lab addresses a pressing need for new paradigms to study the neuronal and genetic basis of complex social behavior by comparing monogamous prairie voles, which form enduring bonds with their mating partner, to their promiscuous cousin, the meadow vole. My lab has pioneered advanced neurogenetic tools in voles in order to discover the neurons, genes, and molecules that contribute to bonding. In this talk, I will discuss genetic strategies for functionally investigating DNA elements implicated in monogamy, and I will present preliminary results from our ongoing in vivo calcium imaging studies in voles. Ultimately, my goal is to use these approaches to answer fundamental questions about the encoding of social bonds within the brain.
S6.1 The heat is on: Exposure to EDCs at elevated temperatures causes multigenerational effects in an estuarine fish with temperature sensitive sex determination
Susanne M. Brander, Oregon State University USA
Understanding anthropogenic impacts, such as climate change and pollution, on aquatic ecosystems is critical for preserving biodiversity and maintaining water quality. The pyrethroid pesticide bifenthrin is a known endocrine disrupting compound (EDC) that enters watersheds through urban and agricultural runoff. Ethinylestradiol (EE2) is a common pharmaceutical that enters watersheds via wastewater effluent. Little is known about how elevated temperatures associated with climate change may affect the estrogenic activity of these endocrine disruptors, which are widely established to alter molecular endpoints, fecundity, and behavior in fishes. Simultaneous exposure to increased temperature and EDCs in is of particular concern in organisms that exhibit temperature-dependent sex determination (TSD), such as the estuarine fish Menidia beryllina. This study investigated the effects of temperature and bifenthrin across multiple generations. Parental fish were exposed to environmentally relevant concentrations of bifenthrin and EE2 at 22°C and 28°C for 14 days prior to spawning. Embryos in the F1 generation were exposed as larvae and then reared to adulthood in clean water at experimental temperatures. F1 sex ratios were influenced by both temperature and EDCs, resulting in alteration of adaptive TSD. In F2 treatments, elevated temperature resulted in fewer viable offspring, with EDCs affecting offspring production at lower temperatures. Fish exposed to bifenthrin during development exhibited deformities. Changes in gene expression were observed across generations, including those exposed indirectly as germ cells within parents. Findings from this study will be useful in determining how EDCs will impact organisms and community structure in the face of global climate change.
S6.2 A neural circuit underlying the generation of hot flushes
Stephanie Padilla, University of California Los Angeles USA
Hot flushes are a sudden feeling of warmth commonly associated with the decline of gonadal hormones at menopause. Neurons in the arcuate nucleus of the hypothalamus that express kisspeptin and neurokinin B (Kiss1-ARH neurons) are candidates for mediating hot flushes because they are negatively regulated by sex hormones. We used a combination of genetic and viral technologies in mice to demonstrate that artificial activation of Kiss1-ARH neurons evokes a heat-dissipation response resulting in vasodilation (flushing) and a corresponding reduction of core-body temperature in both females and males. This response is sensitized by ovariectomy. Brief activation of Kiss1-ARH axon terminals in the preoptic area of the hypothalamus recapitulates this response, while pharmacological blockade of neurokinin B (NkB) receptors in the same brain region abolishes it. We conclude that transient activation of Kiss1-ARH neurons following sex-hormone withdrawal contributes to the occurrence of hot flushes via NkB release in the rostral preoptic area.
S6.3 Estrogen-sensitive neurons of the medial preoptic area potently regulate body temperature
Stephanie Correa, University of California, Los Angeles USA
Estrogen signaling in the hypothalamus modulates many aspects of homeostasis in female mice, including temperature. The medial preoptic area (MPA) is rich in estrogen receptor expression and contains temperature-sensitive neurons that regulate thermoregulatory behavior and physiology. Thus, we hypothesized that temperature-sensitive neurons in the MPA are sensitive to estrogen and could mediate the effects of estrogen on temperature regulation. To define estrogen-sensitive thermoregulatory neurons, we selectively ablated or activated neurons that express estrogen receptor alpha (ERa) in the MPA by delivering Cre-dependent virus expressing caspase 3 or Gq-coupled DREADDs to ERa-Cre mice. We monitored temperature changes using infrared thermal photography, thermo-loggers attached to the tail skin, and intraperitoneal telemetry probes. Ablation of ERa-expressing neurons in the MPA increased core temperature compared to controls. In contrast, chemogenetic activation of ERa neurons in the MPA showed a dramatic decrease (up to 10 degrees C) in core temperature. Interestingly, the effects of ERa+ neuron ablation were specific to females, whereas the effects of ERa+ neuron activation were stronger in females than in males and were modulated by ovariectomy and estradiol replacement. These complementary loss-of-function and gain-of-function studies suggest a critical thermoregulatory role for estrogen-sensitive neurons in the MPA. Ongoing studies will map the estrogen-sensitive neural circuits that alter thermogenesis or cutaneous vasodilation and dissect the ERa-dependent pathways that modulate these responses.
S6.4 A VMH ERα neural circuit controlling locomotion and energy expenditure
Yong Xu, Baylor College of Medicine USA
Multiple estrogen receptor α (ERα) neuron populations in the brain are required to maintain normal body weight. While the metabolic effects of these ERα neuron populations have been investigated, the neural circuit and associated neurotransmitter signaling underlying the regulatory effects of ERα neurons on energy balance are unknown. Here we combined retrograde and anterograde trans-synaptic tracers, chemogenetics, optogenetic circuit mapping and genetic mouse models to functionally map the downstream neural circuits of ERα neurons. We found that selective activation of ERα neurons in the ventral medial hypothalamus (VMH) stimulated locomotion and brown adipose tissue (BAT) thermogenesis without affecting food intake. We also showed that VMH ERα neurons provide monosynaptic glutamatergic inputs to serotonergic neurons in the dorsal Raphe nuclei (DRN). Inhibition of DRN serotonergic neurons partially attenuated the stimulatory effects of VMH ERα neurons on locomotion and BAT thermogenesis. More intriguingly, specific deletion of ERα or vesicular glutamate transporter 2 (vGluT2) from a subpopulation of VMH neurons projecting to the DRN results in decreased locomotion and BAT thermogenesis with normal food intake. Together, these findings suggest a model that VMH ERα neurons activate locomotion and BAT thermogenesis through stimulating DRN serotonergic neurons.