Hormones and Behavior最新文献

Given that double-brooding (rearing two broods within a season) can increase annual fecundity, it is unclear why some females in multi-brooded populations rear only one brood per season. The Quality Hypothesis proposes that double-brooded females are high quality and, thus, have sufficient energetic resources available to bear the costs of rearing two broods per season. Glucocorticoids - endocrine hormones that have a critical role in energy regulation - could reflect female quality, and, therefore, also have the potential to indicate whether a female will rear a second brood. Using 12 years of reproductive data on migratory Savannah sparrows (Passerculus sandwichensis) from a population in eastern Canada, we explored whether baseline corticosterone concentrations were correlated with measures of female quality (body condition and fat score) and whether a female's baseline corticosterone concentrations during her first brood would predict whether she attempted a second. We found weak evidence that baseline corticosterone was negatively correlated with female body condition and found strong evidence that baseline corticosterone was negatively correlated with fat score. There was weak evidence for a positive relationship between double-brooding and baseline corticosterone in females sampled during the first brood incubation stage. Additionally, there was moderate evidence to suggest that the probability of double-brooding was negatively related to baseline corticosterone in females sampled during the first brood nestling stage. Our results provide evidence that corticosterone can reflect female condition in the context of double-brooding and demonstrate the importance of considering breeding stage when assessing corticosterone concentrations in parents.

The benefits of estrogen treatment on cognition in middle-aged and older women are dependent on many factors, including the timing of treatment. Moreover, the potential interactive effects with other lifestyle factors, such as exercise, are poorly understood. In this study, we tested for lasting benefits of independent and combined treatment with estrogen and voluntary exercise initiated in midlife, using a rat model of menopause. Twelve-month-old, retired female breeders were bilaterally ovariectomized and received six weeks of 17β-estradiol (E2) treatment via subcutaneous implant, with or without access to running wheels. After E2 treatment, animals in the exercise groups had running wheel access for seven additional weeks, including a two-week period of cognitive and affective testing. Thereafter, hippocampal neuronal and cellular plasticity were assessed. E2 and exercise independently exerted effects on behavioral and cellular outcome measures. Transient E2 treatment enduringly increased motor output, lowered body weight, and increased behavioral plasticity. Exercise decreased total hippocampal microglia number and increased brain weight. No additive effects of exercise and E2 treatment were observed. E2 treatment may provide a means by which to enduringly increase physical activity in middle age, but combined E2 and exercise do not produce additive benefits on hippocampal behavioral or cellular plasticity.

Within dominance hierarchies, individuals must interact in a rank-appropriate manner, thus behavior and its underlying neural mechanisms must change with social status. One such potential neural mechanism is arginine vasotocin (AVT), a nonapeptide which has been implicated in the regulation of dominance and aggression across vertebrate taxa. We investigated the relationship between social status, dominance-related behaviors, and vasotocin neuron counts in daffodil cichlids (Neolamprologus pulcher). Daffodil cichlids live in stable, mixed-sex, cooperatively breeding social groups that are organised into linear dominance hierarchies. Group members of both sexes exhibit complex behavioral repertoires which differ depending on their current social status. We recorded agonistic behaviors within groups of daffodil cichlids and correlated these with the number of AVT cells within the three distinct neuronal populations in the preoptic area of the brain, comparing across social status and sex. We found that parvocellular AVT neurons were more abundant in dominant individuals than subordinates. We also found that numbers of both parvocellular and magnocellular AVT neurons were positively associated with aggression in dominant individuals. AVT neuron counts were unrelated to submissive behavior in subordinate fish. Our data emphasise the role of AVT in modulating status and aggression in social vertebrates.

An animal model of 4-vinylcyclohexene diepoxide (VCD)-induced premature ovarian failure was developed to mimic menopause; this model has been used in various field studies. However, detailed reports on the rodent model using VCD are lacking, and the animal species used, administration methods, and hormonal fluctuations in the creation of the VCD model have not been comprehensively elucidated. The aim of this study was to systematically review these aspects of the rodent model using VCD and elucidate its characteristics. Thirty-two studies were extracted; rats and mice (66 %/44 %) are the most commonly used animal species. In most of the studies involving mice, a dose of 160 mg/kg was administered, whereas in most rat studies, doses of 80 mg/kg and 160 mg/kg were administered. On most mice studies (70 %), the most frequently applied dosage duration was 15 days. In most rat studies (63 %), the most frequently applied duration was 25 days, followed by 14 and 15 days in 30 % of the studies. Meta-analysis indicated that the mouse model using VCD simulates significant hormonal changes, such as estradiol (E2), anti-Müllerian hormone (AMH), and follicle stimulating hormone (FSH) changes. In conclusion, although the VCD model has demonstrated significant promise in replicating menopausal hormonal conditions, further systematic studies are required to fully understand its potential applications and refine its methodologies. This comprehensive review of existing literature highlights the need for continued research to expand the use of the VCD model in diverse medical fields.

Estrogens are potent regulators of socioemotional behavior across species. Ubiquitous in human and animal diets, plant-derived phytoestrogens (PE) bind estrogen receptors. While prior work has examined the impact of PE exposure on socioemotional behavior, findings are inconsistent across studies. To investigate whether the timing of PE diet initiation may govern differential behavioral effects, we compared the impacts of PE-free (<20 mg/kg) versus PE-rich (810 mg/kg) diet exposure across the lifetime versus acutely in adulthood. Reproductive physiology was assessed through age at puberty onset and gonadal size. In adulthood, all mice underwent a behavioral battery consisting of the open field, elevated plus maze, and social interaction tests, followed by assessment of emotional memory dynamics with cued threat conditioning, extinction, recall, and renewal. Lifetime PE exposure delayed puberty onset and increased adult gonadal size selectively in males, whereas both lifetime and adult-only PE exposure decreased adult body weight in both sexes. In males, adult-only exposure increased open-arm avoidance in the elevated plus maze but enhanced threat memory extinction. In females, lifetime PE exposure increased open-arm avoidance, reduced sociability, and impaired threat memory extinction. Interestingly, lifetime PE exposure increased the context-dependent renewal of threat memory in both sexes. These findings demonstrate sex- and timing-dependent effects of PE exposure. Male lifetime PE exposure impacts reproductive measures with limited behavioral effects, whereas female lifetime exposure broadly impairs socioemotional behavior. Conversely, adult-only PE exposure altered behavior in males with limited impact in females. This study highlights the importance of diet composition, exposure period, and sex in rodent behavioral studies.

Encoding of emotional arousal in vocalisations is commonly observed in the animal kingdom, and provides a rapid means of information transfer about an individual's affective responses to internal and external stimuli. As a result, assessing affective arousal-related variation in the acoustic structure of vocalisations can provide insight into how animals perceive both internal and external stimuli, and how this is, in turn, communicated to con- or heterospecifics. However, the underlying physiological mechanisms driving arousal-related acoustic variation remains unclear. One potential driver of such variation in behaviour and vocal production are glucocorticoids. Through exogenous glucocorticoid manipulation, we aimed to gain insight on the relationship between arousal and physiological parameters, behaviour and vocal production in wild meerkats (Suricata suricatta). To this aim, we administered glucocorticoids to wild meerkats, and recorded their heart rate, vigilance behaviour, call rate and acoustic structure during natural behavioural contexts. The results suggest that, although the glucocorticoid treatment did increase plasma glucocorticoid levels, this did not result in observable changes in heart rate, vigilance, or vocal production. This lack of treatment effect suggests that, while glucocorticoids may be a significant component and correlate of the arousal response, they are not the direct drivers of affective arousal related changes in heart rate, behaviour, or vocal production.

Individual variation in stress coping styles is widespread and consequential to health and fitness. Proactive (bold behavior, low stress reactivity, low cognitive flexibility) and reactive (shy behavior, high stress reactivity, high cognitive flexibility) coping styles are found in many species, but the developmental forces shaping them remain elusive. We examined how social influences, specifically mating interactions, shape the development of adult female coping styles with a manipulative rearing experiment using El Abra swordtails, Xiphophorus nigrensis. We raised juvenile females in environments with different male reproductive phenotypes: coercive-only, courting-only, or complex (both coercive and courting males). At adulthood, we measured female stress reactivity (cortisol release following acute stress), boldness (scototaxis and open field responses), and cognitive flexibility (as inhibitory control in a detour task). Females raised in coercive and complex environments developed higher cortisol reactivity than females raised with only courtship. Stress coping trait correlations varied significantly across social environments producing different coping styles across treatments. Traditional proactive and reactive stress coping styles developed in the coercive-only environment with negative correlations between stress response and boldness, stress response and cognitive flexibility, and boldness and cognitive flexibility. Meanwhile, the courtship-only environment produced a negative correlation between stress response and boldness. We thus demonstrate that the relationship between stress response and boldness can be socially modulated. These findings suggest that developmental variation in social experiences can shape suites of traits with complex relationships; and that highly stressful social interactions, such as sexual coercion, can be a strong driver of stress coping styles.

Intraspecific competition with fellow group members represents an unavoidable cost of group living. However, the causes of competition can vary among group members, and ecological and reproductive challenges faced by individuals throughout the year can trigger physical conflicts and or physiological responses. To date, few studies in mammals have described both physiological and behavioral responses to competition simultaneously across the year in both males and females. However, such an approach may shed light on ultimate drivers of sex-specific competitive strategies. In this six-year study on multiple groups of wild redfronted lemurs (Eulemur rufifrons), a primate species from Madagascar, we intended to identify the relative importance of feeding vs. reproductive competition for both sexes. We combined data on fecal glucocorticoid metabolite (FGCM) levels, a proxy for the physiological stress response, with behavioral observations on agonistic interactions during ecologically and socially challenging phases across the year. We found that while FGCM levels increased in both sexes with decreasing fruit consumption, this increase was not accompanied by concomitant changes in agonistic behavior. Female aggression and FGCM levels instead peaked during the birth season, while for males, aggression remained fairly constant across the year. Our results suggest that redfronted lemurs have mechanisms to avoid direct competition through aggression at times when individuals may need to conserve energy.

Menopausal symptoms of sleep disturbances, cognitive deficits, and hot flashes are understudied, in part due to the lack of animal models in which they co-occur. Common marmosets (Callithrix jacchus) are valuable nonhuman primates for studying these symptoms, and we examined changes in cognition (reversal learning), sleep (48 h/wk of sleep recorded by telemetry), and thermoregulation (nose temperature in response to mild external warming) in middle-aged, surgically-induced menopausal marmosets studied at baseline, during 3-week phases of ethinyl estradiol (EE₂, 4 μg/kg/day, p.o.) treatment and after EE₂ withdrawal. We also assessed a brain-selective hormonal therapy devoid of estrogenic effects in peripheral tissues on the same measures (cognition, sleep, thermoregulation) after treatment with the estrogen prodrug 10β,17β-dihydroxyestra-1,4-dien-3-one (DHED, 100 μg/kg/day, p.o) and DHED withdrawal. Reversal learning performance was improved with EE₂ or DHED treatment relative to phases without hormone administration, as indicated by a faster reversal of the stimulus/reward contingencies. Both EE₂ and DHED increased non-REM sleep and reduced nighttime awakenings relative to baseline, but to the detriment of REM sleep which was highest at baseline. Nasal temperature in response to mild external warming was highest, and overnight core body temperature lowest, in the DHED treatment phase compared to both the EE₂ and baseline phases. These results suggest that low dose estradiol, delivered either peripherally or centrally via DHED, benefits selective aspects of cognition and sleep in a marmoset menopause model. DHED appears a promising therapeutic candidate for alleviating the cognitive and sleep disruptions associated with estrogen deficiency in primates.

Gonadal steroid hormones are thought to activate sexual behavior by actions on multiple organ systems, including the nervous system and genitalia. We previously characterized ovarian hormone dependent behavioral and neural responses to clitoral stimulation in female mice. Here we investigate whether sex differences exist in the responses to tactile genital stimulation, and whether these might depend on gonadal androgens. We measured conditioned place preference (CPP) in response to manual tactile stimulation of either the prepuce or dorsum and subsequently measured neural activation. Behavioral and neural responses to genital stimulation were sexually equivalent in gonadally intact mice, with males exhibiting CPP and neural activation responses similar to those previously reported in females, with the exception of the Arcuate nucleus, which was activated to a greater extent in females. An unexpected sex difference in response to dorsal stimulation was observed, with only males developing CPP and increased FOS expression in the nucleus accumbens. Unlike females, the reward value of tactile stimulation was unaffected by gonadectomy in males. However, neural responses to tactile stimulation were disrupted by gonadectomy in both sexes. Testosterone treatment was only partially effective in restoring neural responses to genital stimulation and did so in a sexually diffentiated manner. We conclude that behavioral and neural responses of sexually-naïve mice to genital stimulation are largely similar between males and females, but that non-genital tactile stimulation is more reinforcing to males. Further, the relationship between gonadal steroid hormones and genital reward is sexually differentiated.