Effects of the estrous cycle and ovarian hormones on behavioral indices of anxiety in female rats

Estrogen receptor beta activation prevents glucocorticoid receptor-dependent effects of the central nucleus of the amygdala on behavior and neuroendocrine function

Neuropsychiatric disorders such as anxiety and depression have formidable economic and societal impacts. A dysregulation of the hypothalamo-pituitary-adrenal (HPA) axis leading to elevated endogenous glucocorticoid levels is often associated with such disorders. Chronically high glucocorticoid levels may act upon the central nucleus of the amygdala (CeA) to alter normally adaptive responses into those that are maladaptive and detrimental. In addition to glucocorticoids, other steroid hormones such as estradiol and androgens can also modify hormonal and behavioral responses to threatening stimuli. In particular, estrogen receptor beta (ERbeta) agonists have been shown to be anxiolytic. Consequently, these experiments addressed the hypothesis that the selective stimulation of glucocorticoid receptor (GR) in the CeA would increase anxiety-like behaviors and HPA axis reactivity to stress, and further, that an ERbeta agonist could modulate these effects. Young adult female Sprague-Dawley rats were ovariectomized and bilaterally implanted via stereotaxic surgery with a wax pellet containing the selective GR agonist RU28362 or a blank pellet, to a region just dorsal to the CeA. Four days later, animals were administered the ERbeta agonist S-DPN or vehicle (with four daily sc injections). Anxiety-type behaviors were measured using the elevated plus maze (EPM). Central RU28362 implants caused significantly higher anxiety-type behaviors in the EPM and greater plasma CORT levels than controls given a blank central implant. Moreover, S-DPN treated animals, regardless of type of central implant, displayed significantly lower anxiety-type behaviors and post-EPM plasma CORT levels than vehicle treated controls or vehicle treated animals implanted with RU28362. These results indicate that selective activation of GR within the CeA is anxiogenic, and peripheral administration of an ERbeta agonist can overcome this effect. These data suggest that estradiol signaling via ERbeta prevents glucocorticoid-dependent effects of the CeA on behavior and neuroendocrine function.

A novel chronic social stress paradigm in female mice

Major depression is one of the most prevalent stress-related psychiatric diseases. Next to environmental influences such as chronic social stress, gender is among the strongest risk factors for major depression, with women having a twice as high risk to develop the disease compared to men. While there is abundant literature on the effects of chronic social stress in male rodents, there is a serious lack of information on gender-specific effects. Especially in mice, which due to the wide availability of transgenic lines offer a unique opportunity to study gene x environment interactions, there is no existing model of chronic social stress that is applicable to both sexes. We here describe the effects of chronic social stress based on the disruption of the social network in a group-housed situation in female mice, a model that was recently described and validated for male mice. In this model, the group composition of the mice is changed twice per week for a period of 7 weeks, covering the adolescent and early adulthood period. We observed that housing in an unpredictable social environment resulted in chronic stress in female mice. The observed effects, which included increased adrenal weight, decreased thymus weight, increased corticosterone levels, and increased anxiety-like behavior, were very similar to the described effects of this paradigm in male mice. In addition, we observed a distinct expression of stress system-related genes in female mice following chronic stress exposure. Our results validate this model as a suitable approach to study chronic social stress in female mice and open up the opportunity to use this model with transgenic or knockout mouse lines.

Cocaine withdrawal-induced anxiety in females: impact of circulating estrogen and potential use of delta-opioid receptor agonists for treatment

Sex differences in cocaine addiction warrants further research focused on examining the growing population of female cocaine addicts. As demonstrated in both clinical and preclinical research, females are more susceptible to drug relapse with anxiety being a contributing factor. In support of this, a recent clinical study from our laboratory highlights the importance of menstrual cycle phase and anxiety at treatment admission for cocaine addiction on treatment retention. In support of these trends in the clinical population, the purpose of the present study was to design an animal model to directly test the role of circulating hormone levels during cocaine withdrawal. To directly measure the influence of estrogen on anxiety-like behavior during early stages of withdrawal, both ovariectomized and intact female rodent models were employed. The elevated-plus maze and elevated-zero maze were used to assess anxiety-like behavior. Recent evidence in male rodents highlights a potential role for the delta opioid-receptor (DOR) system in the modulation of cocaine withdrawal-induced anxiety. In addition to the evaluation of hormonal effects, a potential anxiolytic specific for DOR was tested for its efficacy in females withdrawn from cocaine. Our results support the use of DOR agonists as a potential anxiolytic in females and highlight the importance of estrogen and other circulating hormones during all phases of cocaine addiction.

Males show stronger contextual fear conditioning than females after context pre-exposure

Estradiol affects the structure and function of the hippocampus. We have found that repeated estradiol affects neurogenesis and cell death in the hippocampus of adult female, but not male rats. In the present study we sought to determine whether using the same regimen of estradiol would influence hippocampus-dependent behaviour. Adult male and female rats were given estradiol or sesame oil for 15 days, and then tested using a contextual pre-exposure paradigm in which performance depends on the hippocampus. The time spent freezing displayed by rats was scored on subsequent days in (1) the training context, (2) a novel context in which rats had never been shocked, and (3) the training context a second time. Irrespective of treatment, males showed stronger memory for the context by exhibiting greater freezing in both the training context exposures and the novel context. Previous estradiol treatment, in either sex, did not affect the ability to learn and retain information about the training context. However, female rats treated with estradiol and exposed to a novel context after fear conditioning exhibited less freezing behaviour than controls. Taken together, our results demonstrate that gonadectomized male rats outperform females, regardless of previous treatment with estradiol, on a hippocampus-contextual fear conditioning test, and that previous estradiol treatment has a subtle effect on performance in female but not male rats.

The role of the estrogen receptor alpha in the medial amygdala and ventromedial nucleus of the hypothalamus in social recognition, anxiety and aggression

Social recognition manifests itself in decreased investigation of a previously encountered individual. Estrogen receptor alpha (ERalpha) knock out mice show deficient social recognition and anxiety. These data show that the ERalpha is involved in these effects, but they do not say anything about the brain sites important for these effects. In this study, an shRNA encoded within an AAV viral vector directed against the ERalpha receptor gene (or containing luciferase control), was injected bilaterally into the posterodorsal amygdala (MePDA) or the ventromedial nucleus of the hypothalamus (VMN) of female rats. An 81% reduction of ERalpha expression in the MePDA eliminated social recognition. Moreover, this diminution of ERalpha in the MePDA reduced anxiety in the light/dark choice test. In contrast, social recognition was unaffected after ERalpha knockdown in the VMN while aggressiveness against the juvenile was enhanced. In conclusion, social recognition and anxiety in female rats are modulated by the ERalpha in the amygdala. Moreover, aggression against juveniles but not against adults could, at least partly, depend on the ERalpha in the VMN.

Genetic mapping of social interaction behavior in B6/MSM consomic mouse strains

Genetic studies are indispensable for understanding the mechanisms by which individuals develop differences in social behavior. We report genetic mapping of social interaction behavior using inter-subspecific consomic strains established from MSM/Ms (MSM) and C57BL/6J (B6) mice. Two animals of the same strain and sex, aged 10 weeks, were introduced into a novel open-field for 10 min. Social contact was detected by an automated system when the distance between the centers of the two animals became less than ~12 cm. In addition, detailed behavioral observations were made of the males. The wild-derived mouse strain MSM showed significantly longer social contact as compared to B6. Analysis of the consomic panel identified two chromosomes (Chr 6 and Chr 17) with quantitative trait loci (QTL) responsible for lengthened social contact in MSM mice and two chromosomes (Chr 9 and Chr X) with QTL that inhibited social contact. Detailed behavioral analysis of males identified four additional chromosomes associated with social interaction behavior. B6 mice that contained Chr 13 from MSM showed more genital grooming and following than the parental B6 strain, whereas the presence of Chr 8 and Chr 12 from MSM resulted in a reduction of those behaviors. Longer social sniffing was observed in Chr 4 consomic strain than in B6 mice. Although the frequency was low, aggressive behavior was observed in a few pairs from consomic strains for Chrs 4, 13, 15 and 17, as well as from MSM. The social interaction test has been used as a model to measure anxiety, but genetic correlation analysis suggested that social interaction involves different aspects of anxiety than are measured by open-field test.

Neonatal lipopolysaccharide and adult stress exposure predisposes rats to anxiety-like behaviour and blunted corticosterone responses: implications for the double-hit hypothesis

The double-hit hypothesis posits that an early life genetic or environmental insult sets up a neural predisposition to psychopathology, which may emerge in the presence of a subsequent insult, or 'second hit' in later life. The current study assessed the effect of neonatal lipopolysaccharide (LPS) exposure on anxiety-like behaviours in the adult Wistar rat. Rats were administered either LPS (Salmonella enterica, serotype enteritidis, 0.05 mg/kg, i.p.) or saline (equivolume) on days 3 and 5 of life (birth=day 1). In adulthood (85 days), subjects were allocated to either "stress" or "no stress" treatment groups. For the "stress" group, subjects were exposed to a three-day stress protocol consisting of a 30 min period of restraint and isolation. The "no stress" group was left unperturbed but were handled during this period to control for handling effects between adult "stress" and "no stress" conditions. All animals then underwent behavioural testing using standardised tests of anxiety-like behaviour, including either the Hide Box/Open Field, Elevated Plus Maze (EPM) or Acoustic Startle Response (ASR). Time and event measures for restraint and isolation, the Hide Box/Open Field and EPM were recorded using automated tracking software. Startle amplitude and habituation across time was measured in the ASR test. Prior to and following behavioural test sessions, peripheral blood was collected to assess serum corticosterone and ACTH levels. Data analysis indicated that LPS-treated animals exposed to stress in adulthood exhibited increased anxiety-like behaviour across all behavioural tests compared to controls. Sexually dimorphic effects were observed with males exhibiting increased anxiety-related behaviours compared to females (p<.05). Neonatal LPS exposure induced a significant increase in corticosterone compared to controls (p<.05), whereas corticosterone responses to stress in adulthood were associated with a significantly blunted HPA axis response (p<.05). No differences in ACTH were observed. These results lend support to the double-hit hypothesis of anxiety-related behaviour, demonstrating that neonatal immune activation produces an enhanced propensity toward anxiety-related behaviour following stress in adulthood, and that this susceptibility is associated with alterations to HPA axis ontogeny.

The neurosteroid 3alphaDIOL modulates place preference when infused in the basolateral amygdala according to sex

Three different behavioral tasks were used to study the role of the neurosteroid 5alpha -androstane-3alpha, 17beta-diol (3alphaDIOL) in affective components of behavior when infused into the basolateral amygdala (BLA) of both sexes. Female rats were ovariectomized; half received implants containing estradiol benzoate (OVX-EB), whereas the other half received empty implants (OVX). Male rats were gonadally intact. No differences were noted in male behavior according to the conditioned place preference (CPP) test, the modified Vogel conflict test (VCT), or the elevated plus maze (EPM) upon infusion of 3alphaDIOL. In contrast, 3alphaDIOL modulated CPP and VCT performance among female rats. Therefore, the authors propose that 3alphaDIOL modulates affect through the BLA via a sex-specific mechanism.

Female fear: influence of estrus cycle on behavioral response and neuronal activation

Our observation that male rat's innate fear response differed with hormonal status, as well as the higher prevalence of fear and anxiety disorders in human females led to the current investigation of the impact of phases of the estrus cycle on innate fear responding. Female rats in different phases of the cycle were exposed to an innate fear-inducing stimulus (2,5-dihydro-2,4,5-trimethylthiazoline, TMT odor) and monitored for changes in behavior and brain activation. Behavioral data showed freezing responses to TMT were significantly enhanced during estrus as compared to other phases of the cycle. This data was supported by significant increases in pixel intensity in cortical and sub-cortical regions in estrus compared to proestrus and diestrus. Imaging results demonstrated significant increases in brain activation in the somatosensory and insular cortices when comparing estrus to diestrus. There were significant increases in neural activity in the bed nucleus of the stria terminals (BNST) and septum in estrus as compared to proestrus. Additionally, the hippocampus, hypothalamus, olfactory system, and cingulate cortex show significant increases in the estrus phase when compared to both diestrus and proestrus. Taken together, these results suggest that the female's hormonal status may be correlated with alterations in both neuronal and behavioral indices of fear.

Infusions of bicuculline to the ventral tegmental area attenuates sexual, exploratory, and anti-anxiety behavior of proestrous rats

Actions of 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP), in the midbrain ventral tegmental area (VTA) modulate sexual receptivity of female rats. Actions of 3alpha,5alpha-THP at GABAergic substrates in the VTA are known to modulate consummatory aspects of sexual behavior among rodents, such as lordosis. However, the extent to which GABA(A) receptors in the VTA are important for appetitive (exploratory, anti-anxiety, social) aspects of sexual receptivity is not well-understood. Proestrous rats were bilaterally-infused with saline or bicuculline (100 ng), a GABA(A) receptor antagonist, to the VTA or missed control sites. Rats were assessed for exploratory/anti-anxiety (open field/elevated plus maze), social (social interaction), and sexual (paced-mating) behavior. Compared to saline or missed site controls, intra-VTA bicuculline significantly reduced the number of central entries in an open field, time spent on the open arms of an elevated plus maze, frequency and intensity of lordosis, anti-aggression towards a male, pacing of sexual contacts, and 3alpha,5alpha-THP concentrations in midbrain and hippocampus. Bicuculline-infused rats also displayed less affiliation with a novel conspecific, fewer sexual solicitations, and had lower 3alpha,5alpha-THP concentrations in diencephalon and cortex, albeit these were not significant differences. Thus, actions at GABA(A) receptors in the midbrain VTA are essential for appetitive and consummatory aspects of sexual receptivity among rats.

Chronic estradiol replacement to aged female rats reduces anxiety-like and depression-like behavior and enhances cognitive performance

Decline in the ovarian steroid, estradiol (E(2)), with the menopause transition may influence cognitive and affective processing of older women and there is evidence that hormone replacement therapies (HRTs) with E(2)-mimetics may provide benefit in some, but not all, women. The parameters that play a role in determining whether the response to HRTs is positive are of interest. It may be that the likelihood for positive responses is related to the timing of E(2)-replacement following E(2) decline. As such, in the present study an animal model was utilized to investigate this. We investigated the effects of long- versus short-term E(2)-replacement by examining cognitive (object placement task), anxiety (open field, mirror maze, light-dark transition task), and depression (forced swim task) behavior of female rats that were ovariectomized (OVX) at middle-age (14 months) or older (19 months) and implanted with E(2)-filled implants at the time of surgery or after a delay of 5 months, or OVX at 14 months of age and never replaced with E(2). Rats were tested at 20 months of age. The hypothesis that was tested was that rats would have reduced anxiety and depression behavior and improved cognitive performance with E(2)-replacement at ovarian cessation, compared to a delay in E(2)-replacement. Performance in the object placement task was improved in rats that were OVX and then received continuous E(2)-replacement, compared to those that were OVX and continuously administered placebo vehicle. In the open field and forced swim task, there was an increase in anti-anxiety and anti-depression behavior, respectively, among rats that were OVX and then received continuous E(2)-replacement, compared to OVX rats administered vehicle or those that experienced a delay in E(2)-replacement. In the mirror maze and light-dark transition task, E(2)-replacement at OVX, or after a delay, reduced anxiety-like behavior. Thus, E(2)-replacement reduced anxiety and depression behavior and improved cognitive performance of aged female rats; however, delay in E(2) treatment influenced whether there were favorable effects of E(2) in some tasks.

Progestogens and estrogen influence impulsive burying and avoidant freezing behavior of naturally cycling and ovariectomized rats

Steroid hormones, progesterone and estradiol, may influence approach and/or anxiety behavior. Female rats in behavioral estrous, have elevated levels of these steroid hormones and demonstrate more approach and less anxiety behavior than do diestrous rats. Ovariectomy obviates these cyclic variations and systemic progesterone and/or estrogen replacement can enhance approach and anti-anxiety behavior. However, the role of progesterone and/or estrogen in mediating impulsive, avoidant and/or fear behaviors requires further investigation. We hypothesized that if progesterone and/or estrogen influences impulsivity and/or fear then rats in behavioral estrous would demonstrate less impulsive behavior in a burying task and freezing behavior in a conditioned fear task than will diestrous rats. Ovariectomized rats administered progesterone and/or estrogen would show less impulsive burying and freezing behaviors than will vehicle-administered rats. Experiment 1: Naturally cycling rats were tested in marble burying or conditioned fear when they were in behavioral estrous or diestrous. Experiment 2: Ovariectomized rats were administered progesterone, estrogen or vehicle, then tested in marble burying or conditioned fear. Results of Experiment 1 show rats in behavioral estrous demonstrate less impulsive burying and less freezing behavior than diestrous rats. Results of Experiment 2 show administration of progesterone or both estrogen and progesterone decreases impulsive burying and each decrease freezing behavior compared to vehicle. Thus, progesterone and/or estrogen may mediate impulsive and/or avoidant behavior.

Male but not female Wistar rats show increased anxiety-like behaviour in response to bright light in the defensive withdrawal test

The defensive withdrawal test (DWT) is used to model anxiety-like behaviour in rats. The aim of this study was to investigate whether an aversive stimulus, bright light, affects the behaviour in this test. Additionally, the effect of habituation to the apparatus was studied. Both male and female Wistar rats were used to study whether sex differences exist in the DWT, as reported for other tests of anxiety. On day 1 half of the rats were tested under low light and half under bright light. Two to seven days after trial one the same rats were repeatedly tested under the same light condition for five consecutive days. The male rats showed a higher degree of anxiety-like behaviour when tested under bright light than under low light. In contrast, the behaviour of the female rats was not affected by changes in illumination. Male rats also exhibited elevated anxiety-like behaviour compared to female rats under bright light, whereas under low light conditions no sex difference was seen. Males in low light habituated much faster than males tested under bright light, whereas in females there was little difference in habituation between low and bright light. In summary, we found that bright light is aversive for male but not female Wistar rats in the DWT. Whether this is due to sex differences in light sensitivity or if females respond with a different behavioural strategy in response to bright light, which could not be detected in the DWT, remains to be elucidated.

Sex differences in psychopathology: of gonads, adrenals and mental illness

Stress-related disorders such as anxiety and depression are disproportionately prevalent in women. Women are more likely to experience depression and anxiety disorders during periods of marked hormonal fluctuations, suggesting that gonadal hormones are involved in stress pathology. Depression and anxiety are both associated with aberrant secretion of glucocorticoids, which also show marked fluctuations across the reproductive cycle and in response to gonadal steroids. Thus, interactions between gonadal and stress hormones may play a major role in predisposing females to stress-related disease. The purpose of this brief review is to highlight preclinical data regarding the role of estrogens in depression and anxiety-like behaviors. While it is evident the exogenous estrogens modulate affective behavior in rodents, there is some disagreement in the literature, perhaps related to experimental designs that vary with respect to administration parameters and stress. Beneficial effects of estrogens on mood are most likely due to estrogen receptor (ER)beta signaling. The antidepressant and anxiolytic effects of ERbeta are consistent with its role in attenuating glucocorticoid responses to stress, suggesting that estrogens, acting at ERbeta, may improve mood by suppressing glucocorticoid hyperactivity. However, additional studies demonstrate that ERbeta signaling in the hippocampus is sufficient to induce antidepressant and anxiolytic behaviors. Thus, ERbeta may improve mood via primary actions on hypothalamic (i.e., paraventricular nucleus) and/or extra-hypothalamic sites. Overall, the preclinical research suggests that selective ER modulators targeting ERbeta may be an attractive alternative or adjunct treatment to currently prescribed antidepressants or anxiolytics.

Estradiol or diarylpropionitrile decrease anxiety-like behavior of wildtype, but not estrogen receptor beta knockout, mice

Clinical and basic studies demonstrate that estrogen (E-sub-2)-based therapies influence anxiety and mood, but the receptor targets (e.g., a or ss isoform of the estrogen receptor, ER) for these effects requires further investigation. To address the specificity of E2's anxiolytic-like effects through ERss, anxiety, motor, and nociceptive behavior of ovariectomized, wildtype (WT), and ERss knockout (ssERKO) mice was examined. Mice were administered oil vehicle or ER agonists, 17ss-E2 (E2; 0.1 mg/kg; similar affinity for ERa and ERss), and a selective ER modulator, diarylpropionitrile (DPN; 0.1 mg/kg; greater affinity for ERss than ERa). Performance of mice in anxiety (open field, elevated plus maze, elevated zero maze, social interaction), motor activity (activity monitor) and nociception (tailflick, pawlick) measures was compared. Results supported our hypothesis that ERss is important in modulation of anxiety-like behavior by E2 in some tasks. Administration of E2 or DPN to WT, but not ssERKO, mice increased open field central entries, plus maze open arm time, zero maze open quadrant time, and social interaction. This pattern was neither seen in motor activity nor pain threshold measures. Thus, actions of ERss may be important for modulating anxiety-like behavior of mice.

Effects of pretest manipulation on elevated plus-maze behavior in adolescent and adult male and female Sprague-Dawley rats

The elevated plus-maze (EPM) is vulnerable to variations in pretest circumstances when testing adult rodents. Because of an increasing interest in adolescence, the present experiments examined the impact of pretest manipulations on anxiety levels in the EPM among adolescent and adult Sprague-Dawley rats of both sexes. In Exp. 1, animals removed from their home cage and immediately placed on the EPM were compared to rats tested following 30 min of social isolation, or following 30-min exposure to a novel context. These pretest manipulations only modestly decreased anxiety levels at both ages. In Exp. 2, more varied pretest conditions were examined: testing directly from the home cage; testing following 30 min of social isolation in a novel environment; or a large saline injection and rehousing 18 h prior to a 30-min period of social isolation in a novelty situation before testing. In adults, anxiety levels decreased linearly as pretest perturbation increased, whereas adolescents showed comparable levels of anxiety with both the moderate and large perturbations. As a result, observed age differences in anxiety differed as a function of pretest circumstances. Therefore, caution is urged when using the EPM for across-age comparisons of anxiolytic and anxiogenic effects of pharmacological or other manipulations.

Decreased anxiety-like behavior and locomotor/exploratory activity, and modulation in hypothalamus, hippocampus, and frontal cortex redox profile in sexually receptive female rats after short-term exposure to male chemical cues

Chemical cues are widely used for intraspecific social communication in a vast majority of living organisms ranging from bacteria to mammals. As an example, mammals release olfactory cues with urine that promote neuroendocrine modulations with changes in behavior and physiology in the receiver. In this work, four-month-old Wistar (regular 4-day cyclic) virgin female rats were utilized in the proestrus-to-estrus phase of the reproductive cycle for experimental exposure. In an isolated room, female rats were exposed for 90 min to male-soiled bedding (MSB). Elevated plus-maze assay, open field test, and light/dark box task were performed to analyze behavioral alterations on females after exposure. For biochemical assays, female rats were killed and the hypothalamus, hippocampus, and frontal cortex were isolated for further analysis. Antioxidant enzyme activities (superoxide dismutase, catalase and glutathione peroxidase), non-enzymatic antioxidant defense measurements (TRAP and TAR), and the oxidative damage parameters (TBARS, Carbonyl and SH content) were analyzed. In behavioral analyses we observe that female rats show decreased anxiety and locomotory/exploratory activities after MSB exposure. In biochemical assays we observed an increase in both enzymatic and non-enzymatic antioxidant defenses in different central nervous system (CNS) structures analyzed 30 and 90 min after MSB exposure. Furthermore, hippocampus and frontal cortex showed diminished free radical oxidative damage at 180 and 240 min after exposure. These results provide the first evidence that oxidative profile of female CNS structures are altered by chemical cues present in the MSB, thus suggesting that pheromonal communication is able to modulate radical oxygen species production and/or clearance in the female brain.

Progesterone withdrawal-evoked plasticity of neural function in the female periaqueductal grey matter

Cyclical changes in production of neuroactive steroids during the oestrous cycle induce significant changes in GABA_A receptor expression in female rats. In the periaqueductal grey (PAG) matter, upregulation of α4β1δ GABA_A receptors occurs as progesterone levels fall during late dioestrus (LD) or during withdrawal from an exogenous progesterone dosing regime. The new receptors are likely to be extrasynaptically located on the GABAergic interneurone population and to mediate tonic currents. Electrophysiological studies showed that when α4β1δ GABA_A receptor expression was increased, the excitability of the output neurones in the PAG increased, due to a decrease in the level of ongoing inhibitory tone from the GABAergic interneurones. The functional consequences in terms of nociceptive processing were investigated in conscious rats. Baseline tail flick latencies were similar in all rats. However, acute exposure to mild vibration stress evoked hyperalgesia in rats in LD and after progesterone withdrawal, in line with the upregulation of α4β1δ GABA_A receptor expression.

Role of nitric oxide in the anticonvulsive effect of progesterone

Described here is an investigation of the potential interaction of the nitric oxide signaling pathway with the anticonvulsant effects of progesterone. In ovariectomized Swiss mice, the threshold for seizures induced by intravenous infusion of pentylenetetrazole was determined after treatment with progesterone (25, 50, or 75 mg/kg, given subcutaneously 6h before seizure testing) or vehicle. Progesterone induced significant anticonvulsive activity at moderate (50 mg/kg) and high (75 mg/kg) doses. This effect of progesterone was abolished by the NO precursor compound L-arginine (200 mg/kg). Moreover, when subeffective doses of progesterone (25 mg/kg) and the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (10 mg/kg) were injected, a strong anticonvulsant effect was observed. These findings suggest a potential role for NO signaling as an anticonvulsant target in females.

Effect of ER-beta gene disruption on estrogenic regulation of anxiety in female mice

It has been shown that long-term estrogen treatment in gonadectomized female mice increases anxiety levels. On the other hand, a recent study has reported that estrogen may down-regulate the levels of anxiety by acting through estrogen receptor (ER) beta. In the present study, we investigated the role of ER-beta in the regulation of anxiety levels in female mice after long-term estrogen treatment. Gonadectomized ER-beta knockout (betaERKO) female mice and their wild type (betaWT) littermates were implanted several different doses (experiment 1: 2.0 microg/day, experiment 2: 1.0, 0.4, 0.2 or 0.1 microg/day) of an estradiol benzoate (EB) or placebo pellet. Ten days after pellet implant, behavioral tests commenced to measure the anxiety levels (experiment 1: light-dark transition test (LDT), experiment 2: LDT, elevated plus maze test (EPM) and social investigation test (SIT)). We found that, at higher-doses, long-term treatment of EB had anxiogenic effects in both betaWT and betaERKO mice as indicated by a decrease of the time spent in the light side and the number of transitions between two sides during LDT. In contrast, several behavioral measurements indicated that the lower-doses treatment of EB might reduce the anxiety levels possibly through ER-beta. Particularly, the anxiolytic effects of EB in the SIT were more pronounced in betaWT mice than betaERKO mice. Together, the findings in the present study suggest that estrogen may have both anxiolytic and anxiogenic effects in female mice, and that ER-beta gene disruption did not affect anxiogenic regulation by estrogen in female mice, but partially affected anxiolytic regulation.

Pregnant rats show enhanced spatial memory, decreased anxiety, and altered levels of monoaminergic neurotransmitters

Spatial memory, anxiety and central monoaminergic activities were measured in non-pregnant (NP) and pregnant females during two time periods of pregnancy: gestational days 7-9 (GD7, GD9) and gestation days 16-18 (GD16, GD18). Pregnant females discriminated between object locations on both test days on an object placement task, whereas NP females were unable to discriminate between locations. Pregnant females displayed decreased anxiety on the elevated plus maze on GD9 compared to NP females, followed by increased anxiety-like behavior on the elevated plus maze on GD18. Monoamine levels and activity (as indexed by turnover ratio) were measured in prefrontal cortex (PFC), CA1 and CA3 regions of the hippocampus (areas important for memory), and medial preoptic area (mPOA, an area important in display of maternal behaviors). In the PFC, NP females generally had higher monoamine levels and turnover ratios; however, norepinephrine (NE) turnover was higher in pregnant females at GD18. In the CA1 and CA3 regions of the hippocampus, monoamine levels and turnover ratios were generally higher during pregnancy, particularly on GD9. In the mPOA, pregnancy was associated with increases in NE activity, a previously unreported finding. The present study expands upon existing research indicating that pregnancy is beneficial to spatial memory and may decrease anxiety. Changes in monoamine levels and activity in specific brain regions indicate that the dopamine, norepinephrine and serotonin systems may contribute to the observed behavioral differences.

Estrogen is necessary for 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) infusion to the ventral tegmental area to facilitate social and sexual, but neither exploratory nor affective behavior of ovariectomized rats

The progesterone metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP, allopregnanolone), acts in the ventral tegmental area (VTA) to facilitate exploratory, anti-anxiety, and socio-sexual behavior among ovariectomized (OVX), estrogen (E(2))-primed rats and gonadally-intact rats with high (proestrus) or low (diestrus) endogenous E(2) levels. The extent to which E(2) is required for these effects of 3alpha,5alpha-THP is not known. OVX rats were primed with systemic 17beta-estradiol (10 microg) or oil vehicle and were infused 44 h later with 3alpha,5alpha-THP (100 ng) or beta-cyclodextrin vehicle to the VTA, substantia nigra (SN), or central grey (CG). Rats were assessed in a battery of exploratory (open field), anxiety (elevated plus maze), social (partner preference, social interaction), and sexual (paced mating) tasks. E(2)-priming was necessary for 3alpha,5alpha-THP infusions to facilitate social interaction and mating and midbrain 3alpha,5alpha-THP levels were higher among E(2)-compared to vehicle-primed rats. Irrespective of E(2)-priming, rats infused with 3alpha,5alpha-THP to the VTA, but not SN or CG, demonstrated increased exploration in an open field, anti-anxiety behavior on an elevated plus maze, and preference for a male. Thus, actions of 3alpha,5alpha-THP in the VTA to enhance social and sexual behaviors were reliant on E(2) but increases in exploratory and anti-anxiety behavior were not.

The effects of sexual experience and estrus on male-seeking motivated behavior in the female rat

Ovariectomized (OVX) female rats were trained to traverse a straight alley and return to a goal box where they had previously encountered a male rat, a female rat or an empty goal box. The time required to run the alley was used as an index of the subjects' motivation to re-engage the goal box target. Subjects were tested in both estrus and non-estrus, first sexually naïve and then again after sexual experience. Female rats ran most quickly for a male target, most slowly for an empty goal box, and at intermediate speeds for a female target. Sexual experience tended to slow run times for all but male targets. Estrus enhanced approach behavior for males and an empty goal box, but tended to slow the approach toward females, both before and after sexual experience. This latter finding was further investigated in a second experiment in which sexually naïve OVX females were tested during estrus and non-estrus in a locomotor activity apparatus, a runway with an empty goal box, and an open field. Estrus produced no changes in spontaneous locomotion either in the activity box or the open field, but decreased run times in the alley and increased the number of center-square entries in the open-field. Thus, estrus produces increases in sexual motivation that selectively enhance exploratory, presumably male-seeking behavior, but not simple spontaneous locomotion.

Gender-specific behavioral and immunological alterations in an animal model of autism induced by prenatal exposure to valproic acid

Autism is a severe behavioral disorder characterized by pervasive impairments in social interactions, deficits in verbal and non-verbal communication, and stereotyped behaviors, with a four times higher incidence in boys than in girls. The core symptoms are frequently accompanied by a spectrum of neurobehavioral and immunological derangements, including: aberrant sensitivity to sensory stimulation, anxiety, and decreased cellular immune capacity. Recently, a new potential rodent model of autism induced by prenatal exposure to valproic acid (VPA rats) has been proposed. In order to determine if gender has an influence on alterations observed in VPA rats, male and female rats have been evaluated in a battery of behavioral, immunological, and endocrinological tests. A plethora of aberrations has been found in male VPA rats: lower sensitivity to pain, increased repetitive/stereotypic-like activity, higher anxiety, decreased level of social interaction, increased basal level of corticosterone, decreased weight of the thymus, decreased splenocytes proliferative response to concanavaline A, lower IFN-gamma/IL-10 ratio, and increased production of NO by peritoneal macrophages. Female VPA rats exhibited only increased repetitive/stereotypic-like activity and decreased IFN-gamma/IL-10 ratio. Sexual dimorphism characteristics for measured parameters have been observed in both groups of animals, except social interaction in VPA rats. Our results confirm existence of similarities between the observed pattern of aberrations in VPA rats and features of disturbed behavior and immune function in autistic patients, and suggest that they are gender-specific, which is intriguing in light of disproportion in boys to girls ratio in autism.

The effects of novelty-seeking phenotypes and sex differences on acquisition of cocaine self-administration in selectively bred High-Responder and Low-Responder rats

Individual differences in exploratory behavior can predictably influence psychostimulant self-administration behavior. Male rats that exhibit a high degree of locomotor activity in a novel environment (High Responders, HR) will self-administer cocaine more readily than males exhibiting low levels of novelty-induced locomotion (Low Responders, LR). The present experiment investigates the combined influences of the sex of an individual and individual phenotypes in novelty-induced locomotion to predispose animals to acquire cocaine self-administration behavior, in male and female rats selectively bred for the HR-LR phenotypes. We first established that HR females, like their male counterparts, exhibit a dramatically greater locomotor response to novelty and less anxiety-like behavior than do LR females. While locomotor behavior was subtly influenced by estrous stage, with both HR and LR females showing increased activity during metestrus and diestrus compared to proestrus and estrus, the effect did not obscure HR-LR differences. When male and female HR-LR animals were trained to self-administer cocaine (2 h/day, 5 days/wk x 3 wk, 0.2 mg cocaine/kg/infusion), HR males and females acquired cocaine self-administration significantly faster than their LR counterparts. Furthermore, HR females self-administered significantly more cocaine than all other groups. In conclusion, female rats, like males, exhibit HR-LR phenotypes that predict rapidity of acquiring cocaine self-administration. Moreover, HR females self-administer more cocaine than HR males and both LR groups.

Translational aspects of pharmacological research into anxiety disorders: the stress-induced hyperthermia (SIH) paradigm

In anxiety research, the search for models with sufficient clinical predictive validity to support the translation of animal studies on anxiolytic drugs to clinical research is often challenging. This review describes the stress-induced hyperthermia (SIH) paradigm, a model that studies the activation of the autonomic nervous system in response to stress by measuring body temperature. The reproducible and robust SIH response, combined with ease of testing, make the SIH paradigm very suitable for drug screening. We will review the current knowledge on the neurobiology of the SIH response, discuss the role of GABA(A) and serotonin (5-HT) pharmacology, as well as how the SIH response relates to infectious fever. Furthermore, we will present novel data on the SIH response variance across different mice and their sensitivity to anxiolytic drugs. The SIH response is an autonomic stress response that can be successfully studied at the level of its physiology, pharmacology, neurobiology and genetics and possesses excellent animal-to-human translational properties.

Involvement of nuclear progesterone receptors in the formation of anxiety in female mice

We report here studies on the delayed effects of exogenous progesterone on the formation of anxiety in female mice. Ovariectomized female mice were given seven days of replacement therapy either with the two main ovarian hormones-progesterone and estradiol benzoate-or with progesterone only; levels of anxiety were measured six hours later in the elevated plus-maze. The role of nuclear progesterone receptors in controlling the level of anxiety was assessed by giving some mice injections of the synthetic progesterone receptor blocker mifepristone 2 h before the last dose of hormones. An immunohistochemical method was used to study changes in the number of nuclear progesterone receptors in different areas of the brains of experimental animals. These studies showed that progesterone has a delayed enhancing effect on anxiety in female mice. The role of nuclear progesterone receptors in forming this behavioral characteristic was supported by a strong correlation between changes in the numbers of progesterone receptor-immunopositive cells in several brain structures and the level of anxiety. Prior blockade of progesterone receptors using mifepristone led to a maximal reduction in the level of anxiety, which was also evidence for a role for the genomic mechanisms of action of progesterone in controlling anxiety in females.

Progestin receptor-mediated reduction of anxiety-like behavior in male rats

Background

It is well known progesterone can have anxiolytic-like effects in animals in a number of different behavioral testing paradigms. Although progesterone is known to influence physiology and behavior by binding to classical intracellular progestin receptors, progesterone's anxiety reducing effects have solely been attributed to its rapid non-genomic effects at the GABA_A receptor. This modulation occurs following the bioconversion of progesterone to allopregnanolone. Seemingly paradoxical results from some studies suggested that the function of progesterone to reduce anxiety-like behavior may not be entirely clear; therefore, we hypothesized that progesterone might also act upon progestin receptors to regulate anxiety.

Methodology/Principal Findings

To test this, we examined the anxiolytic-like effects of progesterone in male rats using the elevated plus maze, a validated test of anxiety, and the light/dark chamber in the presence or absence of a progestin receptor antagonist, RU 486. Here we present evidence suggesting that the anxiolytic-like effects of progesterone in male rats can be mediated, in part, by progestin receptors, as these effects are blocked by prior treatment with a progestin receptor antagonist.

Conclusion/Significance

This indicates that progesterone can act upon progestin receptors to regulate anxiety-like behavior in the male rat brain.

Interactions between estrogen effects and hunger effects in ovariectomized female mice. I. Measures of arousal

Measures of arousal were used to study effects of estradiol and food restriction, and their potential interactions, in ovariectomized female C57Bl/6 mice. It was hypothesized based on a proposed theoretical equation [Pfaff, D.W., 2006a. Brain Arousal and Information Theory. Harvard University Press, Cambridge, Pfaff, D.W., (Ed.), 2006b. Knobil and Neill's The Physiology of Reproduction, 3rd edition. Elsevier/Academic Press, San Diego] that each treatment would increase arousal-related behaviors and that their combination would further increase arousal behavior. Following baseline testing, animals (n=28) were divided into 3 groups that, in different experimental phases, received either estradiol (in subcutaneous capsules), restricted diet (a liquid diet providing 60% of daily caloric requirements) or a combination of those two. An automated arousal behavior monitoring system was used to measure home cage voluntary motor activity and sensory responsiveness, these being components of a new operational definition of 'generalized arousal'.

KEY FINDINGS

(1) During the light, all treatments reduced voluntary activity. (2) In the dark, estrogens increased, while estrogens in combination with restricted diet decreased, horizontal activity. (3) In the dark, restricted diet alone had little effect on voluntary activity, but reduced it when combined with estrogen treatment. (4) All treatments reduced responses to the olfactory stimulus. The dependence of results on time of day was unexpected. Further, different patterns of results for the three treatments suggest that estrogens and food restriction did not have equivalent or additive effects on arousal. While contrary to the main prediction, these findings are discussed in terms of the animals' adaptive preparations for reproduction [Schneider, J.E., 2006. Metabolic and hormonal control of the desire for food and sex: implications for obesity and eating disorders. Horm. Behav. 50, 562-571].

The microinjection of AMPA receptor antagonist into the accumbens shell, but not into the accumbens core, induces anxiolysis in an animal model of anxiety

This study investigated the effect of the AMPA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) microinjected into the core and shell sub-regions of the accumbens nucleus (Acb), on the level of fear/anxiety and emotional learning, in female rats submitted to the elevated plus-maze (EPM), an animal model of anxiety. Bilateral microinjections of DNQX (330 and 660 ng) into the Acb shell (AP, +1.08 to +2.16) induced an anxiolytic-like effect in relation to rats microinjected with vehicle, since there was an increased percentage of entries in the open arms of the maze. The 660 ng DNQX microinjection into the Acb shell also increased the percentage of entries into the open arms in relation to 660 ng DNQX microinjection into the Acb core. Prior DNQX microinjections in both core and shell sub-regions of the Acb failed to impair the emotional learning, since the animals exhibited an increase of the open arm avoidance on EPM Trial 2 in relation to EPM trial 1. DNQX microinjections into both sub-regions of the Acb did not change the number of entries into the enclosed arms, either in the EPM Trial 1 or in the EPM Trial 2, which indicates an absence of drug-induced locomotor impairment. Similarly, DNQX microinjections into both sub-regions of the Acb failed to alter the total arm entries, rearing, grooming and head-dipping frequency. The anxiolytic-like effect induced by DNQX suggests that the AMPA receptor in the Acb shell, but not in the Acb core, may underlie anxiety regulation in the EPM.

Parity and estrogen-administration alter affective behavior of ovariectomized rats

Evidence from clinical and basic research studies demonstrates that estradiol (E(2)) reduces anxiety and/or depressive behavior; however, this effect is not observed in all studies. One factor that may mitigate differential responses to E(2) may be previous E(2) experience, i.e. parity. To investigate this, performance in tasks that are utilized to assess whether compounds, such as E(2), can alter anxiety-like behavior (elevated plus maze) and have anti-depressant-like effects (forced swim test) were determined. Performance of ovariectomized (ovx), young (3-6 months old) rats that had never had a litter (nulliparous) was compared to that of those that had several litters in their lifetime (multiparous) following 48 h of oil vehicle or E(2) (10 microg) administration. We predicted that E(2) would decrease anxiety-like behavior and increase anti-depressant-like effects of ovx rats and that this pattern may be influenced by parity. Multiparous rats, irrespective of E(2)-priming, had increased open arm time compared to nulliparous rats. Administration of E(2) to ovx, nulliparous or multiparous rats decreased immobility in the forced swim test compared to vehicle-administration. Together, these data suggest that E(2) can alter affective behavior and rats with greater reproductive experience have decreased anxiety-like behavior in the elevated plus maze, irrespective of E(2)-priming.

Neonatal tactile stimulation reverses the effect of neonatal isolation on open-field and anxiety-like behavior, and pain sensitivity in male and female adult Sprague-Dawley rats

It is well known that early life events induce long-lasting psychophysiological and psychobiological influences in later life. In rodent studies, environmental enrichment after weaning prevents the adulthood behavioral and emotional disturbances in response to early adversities. We compared the behavioral effect of neonatal isolation (NI) with the effect of NI accompanied by tactile stimulation (NTS) to determine whether NTS could reverse or prevent the effects of NI on the adulthood behavioral and emotional responses to environmental stimuli. In addition, we also examined the sex difference of the NTS effect. Measurements of body weights, an open-field locomotor test, an elevated plus maze test, a hot-plate test, and a contextual fear-conditioning test were performed on postnatal day 60. As compared with rats subjected to NI, rats subjected to NTS showed significantly higher activity and exploration in the open-field locomotor test, lower anxiety-like behavior in the elevated plus maze test, and significantly prolonged latencies in the hot-plate test, and this effect was equal among males and females. In the contextual fear-conditioning test, whereas NTS significantly reduced the enhanced freezing time due to NI in females, no significant difference in the freezing time between NI and NTS was found in males. These findings indicate that adequate tactile stimulation in early life plays an important role in the prevention of disturbances in the behavioral and emotional responses to environmental stimuli in adulthood induced by early adverse experiences.

Sex and estrous cycle differences in the display of conditioned defeat in Syrian hamsters

We have reported that there is a sex difference in the behavioral response to social defeat in hamsters. While previously defeated male hamsters fail to display normal territorial aggression and instead produce submissive/defensive behavior, a phenomenon that we have termed conditioned defeat (CD), only a small portion of previously defeated females exhibit CD. In Experiment 1, we tested the hypothesis that CD varies over the estrous cycle and found that previously defeated female hamsters tested on diestrus 2 and proestrus were more likely to exhibit CD than were females tested on diestrus 1 and estrus. In Experiment 2, we found that regardless of hormonal status, non-defeated females displayed normal territorial aggression, indicating that the behavioral changes observed in Experiment 1 were not due to a cyclic variation in submissive behavior independent of a previous defeat encounter. In Experiment 3, we found that females tested 4 days after defeat responded similarly to those tested 1 day after defeat suggesting that the hormonal status of females on the day of testing is a more important determinant of the behavioral response to defeat than is the hormonal status on the day of defeat training. Finally, in Experiment 4, we monitored anxiety-like behaviors in diestrous 1 and proestrous females in an open field arena and found that there was no effect of cycle on any of the observed behavioral measures, suggesting that the observed differences in CD are not the result of differences in generalized anxiety-like behaviors across the estrous cycle.

Estradiol decreases anxiety behavior and enhances inhibitory avoidance and gestational stress produces opposite effects

Although there is evidence that estradiol has effects in women and in animal models to reduce anxiety and depressive behavior and enhance performance in some cognitive tasks, this is not seen among all individuals. Given the interaction between estradiol and hypothalamic-pituitary-adrenal function, we hypothesized that an individual's prior exposure to stress may mitigate some of the subsequent effects of estradiol. To address this, rats were exposed to gestational stress, or not, to determine if stress exposure during development alters behavioral responses to estradiol in adulthood. If estradiol's effects on anxiety and cognitive behavior are modulated by prior stress experience, then gestationally-stressed rats administered estradiol should have decreased anti-anxiety (open field, elevated plus maze) behavior and cognitive performance in the inhibitory avoidance task. Offspring of dams that were exposed to restraint stress daily on gestational days 14-20, or no such manipulation, were used as adults either intact in behavioral estrus (high estradiol) or diestrus (low estradiol), or ovariectomized (OVX) with empty or estradiol-containing silastic implants. Rats were used for blood collection to determine plasma corticosterone and estradiol concentrations, or were used for behavioral testing. Compared with rats in diestrus or OVX and vehicle-replaced, rats in behavioral estrus and OVX rats with estradiol implants had higher estradiol concentrations, entered more central squares in an open field, spent more time on the open arms of the plus maze, and had a longer latency to crossover to the dark, shock-associated side of the inhibitory avoidance chamber. Gestational stress increased plasma corticosterone but not estradiol levels, decreased plus maze open arm time in cycling rats, and decreased inhibitory avoidance performance. Thus, estradiol and gestational stress can have opposite effects on anxiety and inhibitory avoidance performance.

Sex and diet affect the behavioral response of rats to chronic mild stressors

To investigate the interaction between sex, stressors, and dietary choice in rats, a preferred diet under the influence of chronic mild stressors was empirically determined to consist of soybeans and cookies in addition to lab chow. This preferred mixed diet was then tested for its influence on several behavioral tests at the end of prolonged exposure to the potential stressors. Rats of both sexes decreased their frequency of rearing but increased their attention to novelty in response to stressors. In the elevated plus maze, diet interacted with exposure to stressors to influence time spent in the open arm in females but not males. In the forced swim test, females but not males fed the mixed diet showed increased immobility, whether exposed to stressors or not. Finally, females but not males showed a differential effect of diet under stressors on the sucrose preference test, but this result was confounded by estrus cycling, demonstrating the importance of this factor in analyzing behavior in females. These results suggest that male and female rats differ in their susceptibility to the behavioral-modifying influences of stressors. And to the extent that diet serves as a coping mechanism, it does so differently in males and females.

Attenuation of estrous cycle-dependent marble burying in female rats by acute treatment with progesterone and antidepressants

Premenstrual dysphoric disorder (PMDD) is characterized by the recurrence of a cluster of physical and negative mood symptoms, especially irritability, appearing when estrogen and progesterone levels decrease during the late luteal phase of the menstrual cycle. The aim of the present study was to explore a new potential model of premenstrual irritability. It has been suggested that burying of harmless objects by rodents may reflect a form of impulsive or anxiety-like behavior. This study demonstrates changes in burying behavior during various phases of the estrous cycle in some but not all female rats. Burying behavior was found to be enhanced at metestrus and decreased at proestrus, characterized by low and high ovarian hormone levels, respectively. No habituation of the cycle-dependent burying was observed. Enhanced burying was not observed in reproductive senescent and ovariectomized females characterized by stable, low levels of ovarian hormones. Increased marble burying at metestrus was reversed by acute treatment with antidepressants fluoxetine, desipramine, nomifensine, the benzodiazepine agonist diazepam, and progesterone, while the neuroleptic chlorpromazine was without effect. Reversal of cycle-dependent burying was unrelated to the drugs' effects on locomotor activity. These results indicate that estrous cycle-dependent marble-burying behavior displayed by a subgroup of female rats might be a manifestation of ovarian hormone-dependent irritability. This manifestation may be used to elucidate the neuroendocrine mechanisms triggering premenstrual irritability, and the detailed mode of action of antidepressants when used for PMDD.

The use of the elevated plus maze as an assay of anxiety-related behavior in rodents

The elevated plus maze is a widely used behavioral assay for rodents and it has been validated to assess the anti-anxiety effects of pharmacological agents and steroid hormones, and to define brain regions and mechanisms underlying anxiety-related behavior. Briefly, rats or mice are placed at the junction of the four arms of the maze, facing an open arm, and entries/duration in each arm are recorded by a video-tracking system and observer simultaneously for 5 min. Other ethological parameters (i.e., rears, head dips and stretched-attend postures) can also be observed. An increase in open arm activity (duration and/or entries) reflects anti-anxiety behavior. In our laboratory, rats or mice are exposed to the plus maze on one occasion; thus, results can be obtained in 5 min per rodent.

Generalized anxiety disorder: a 40-year follow-up study

OBJECTIVE

There is insufficient knowledge of the long-term course of generalized anxiety disorder (GAD). We studied the course of this disorder in patients who were followed up for 40 years.

METHOD

Patients admitted with the diagnosis of anxiety states ('anxious thymopathy' ) to the Lopez Ibor Neuropsychiatric Research Institute between 1950 and 1961 were examined between 1984 and 1988 (n = 65). The retrospective diagnosis of GAD was made according to DSM-III-R criteria during 1984-1988 (first examination). A re-examination was performed by the same psychiatrist in the period 1997-2001 (n = 59; second examination).

RESULTS

At first and second examinations 20% and 17% of subjects were diagnosed as GAD. Improvement was observed in 83%. GAD tended to disappear around age 50, but was replaced by somatization disorders. Lack of regular treatment compliance, female sex, and onset of GAD before age 25 were variables associated with a worse outcome. Undifferentiated somatization disorder was the most prevalent clinical status at follow-up.

CONCLUSION

After several decades, participants improve with regard to GAD, although most continue to present somatizations.

Estrous cycle effects on behavior of C57BL/6J and BALB/cByJ female mice: implications for phenotyping strategies

Systematic behavioral phenotyping of genetically modified mice is a powerful method with which to identify the molecular factors implicated in control of animal behavior, with potential relevance for research into neuropsychiatric disorders. A number of such disorders display sex differences, yet the use of female mice in phenotyping strategies has been a rare practice because of the potential variability related to the estrous cycle. We have now investigated the behavioral effects of the estrous cycle in a battery of behavioral tests in C57BL/6J and BALB/cByJ inbred strains of mice. Whereas the performance of BALB/cByJ female mice varied significantly depending on the phase of the estrous cycle in the open field, tail flick and tail suspension tests, the behavior of C57BL/6J females, with the exception of the tail suspension performance, remained stable across all four phases of the estrous cycle in all of the tests including open field, rotarod, startle reflex and pre-pulse inhibition, tail flick and hot plate. We also found that irrespective of the estrous cycle, the behavior of C57BL/6J females was different from that of BALB/cByJ groups in all of the behavioral paradigms. Such strain differences were previously reported in male comparisons, suggesting that the same inter-group differences can be revealed by studying female or male mice. In addition, strain differences were evident even for behaviors that were susceptible to estrous cycle modulations, although their detection might necessitate the constitution of large experimental groups.

Administration of estrogen receptor beta-specific selective estrogen receptor modulators to the hippocampus decrease anxiety and depressive behavior of ovariectomized rats

Estradiol (E(2)) may influence some of the sex differences in neuropsychiatric disorders that emerge post-puberty. Studies in our laboratory, and others, have shown that actions at the beta isoform of estrogen receptor (ER) are important for E(2)'s effects for anxiety and/or depressive behavior. Whether ERbeta in the hippocampus is a target for these effects was investigated in the present study. We hypothesized that if actions at ERbeta in the hippocampus are important for the anti-anxiety and anti-depressive effects, then administration of selective ER modulator (SERMs) with greater affinity for ERbeta than ERalpha to the hippocampus, but not a control region/missed sites (i.e. the ventral tegmental area), should decrease anxiety and depressive behavior, compared to vehicle and that ERalpha-specific SERMs should not have the same effect. To investigate this, ovariectomized (ovx) rats were surgically-implanted with guide cannulae aimed at the hippocampus (target site) or ventral tegmental area (control site). Rats were administered vehicle, or 17beta-E(2) (equal affinity for ERalpha and ERbeta), SERMs with greater affinity for ERalpha vs. ERbeta (17alpha-E(2) or propyl pyrazole triol), or SERMs with greater affinity for ERbeta vs. ERalpha (coumestrol or diarylpropionitrile) to these sites (2 microg/microl/side) before testing in anxiety (open field, elevated plus maze) or depression (forced swim) tasks. ERbeta-selective SERMs to the hippocampus, but not the ventral tegmental area, decreased anxiety and depressive behavior. Rats administered 17beta-E(2) or ERbeta SERMs entered more central squares in an open field, spent more time on the open arms of the plus maze, and spent less time immobile compared to rats administered vehicle. Administration of ERalpha-specific SERMs produced similar effects as vehicle administration. Thus, E(2)'s anti-anxiety and anti-depressive effects may involve ERbeta in the hippocampus.

Nitric oxide involvement in estrous cycle-dependent changes of the behavioral responses of female rats in the elevated plus-maze test

Nitric oxide (NO)/cGMP pathway is known as a mediator in anxiety modulation. In this study, we assessed the involvement of NO pathway in the estrous cycle-related changes of anxiety level in rat. By using elevated plus-maze test, we studied the changes of serum nitrate and nitrite (NO(x)) levels in comparison to the estrous cycle-dependent changes of anxiety state. Then, we tested the effects of nitric oxide synthase (NOS) inhibitor, L-NAME (10, 60mg/kg, i.p.), and the NO precursor, l-arginine (100mg/kg, i.p.) on anxiety modulatory properties of exogenous ovarian hormones in ovariectomized (OVX) rats. Compared with other cycle phases and with OVX rats, cycling rats spent more time in open arms and had lower levels of serum NO(x) levels during metestrous while they spent less time in open arms and had lower levels of serum NO(x) levels during proestrous. In OVX rats, L-NAME (60mg/kg, i.p.) exerted anxiolytic effect while l-arginine showed no effect. In comparison with corn oil-treated controls, estradiol benzoate (10microg/kg, subcutaneously (s.c.)) significantly increased the serum NO(x) level and exerted anxiogenic effect, which was dose-dependently inhibited by L-NAME but was not changed by l-arginine. In contrast, progesterone (25mg/kg, s.c.) significantly decreased the serum NO(x) level and exerted anxiolytic effect, which was abolished by l-arginine but was not affected by L-NAME. These findings suggest that NO system might be involved in the estrous cycle-related changes of anxiety level, probably by mediating the effect of ovarian sex hormones.

Alterations in GABA(A) receptor alpha2 subunit mRNA expression following reproductive experience in rats

BACKGROUND/AIM

Reproductive experience (i.e., pregnancy and lactation) alters anxiety-like behavior. One neurotransmitter system that may mediate the effects of reproductive experience on anxiety-like behavior is gamma-aminobutyric acid (GABA). The purpose of the current study was to determine whether reproductive experience alters the mRNA expression of selective GABA(A) receptor subunits in brain regions associated with anxiety-like behaviors.

METHODS

Brains were collected from age-matched nulliparous and primiparous female rats in either diestrus or proestrus, and the subunit mRNA expression was determined using real-time reverse transcription-polymerase chain reaction with Taqman.

RESULTS

Increased alpha1 mRNA expression was found in proestrus within both medial preoptic area (MPOA) and medial amygdala (MeA) in nulliparous and primiparous females. The expression of alpha2 mRNA was also increased within the MPOA in proestrus in both nulliparous and primiparous females; however, within the MeA, an increased alpha2 mRNA expression in proestrus was only observed in nulliparous females, with primiparous females having a significantly reduced expression when compared to nulliparous controls. In addition, a significant increase in the expression of alpha2 mRNA expression was observed within the periaqueductal gray of reproductively experienced female rats.

CONCLUSION

These results indicate that reproductive experience results in significant shifts in the expression of GABA(A) alpha2 mRNA expression in the MeA.

Increased depressive-like traits in an animal model of premenstrual irritability

Women are at higher risk of anxiety and mood disorders, especially at transitions across the reproductive life cycle (premenstruum, postpartum, menopause). Premenstrual dysphoric disorder (PMDD) is one of female mood disorders associated with changing ovarian hormone levels. Because anxiety and depression frequently occur in women with PMDD, premenstrual dysphoria might be a manifestation of certain vulnerability traits increasing the risk of those disorders. The present study was conducted to elucidate a potential association between estrous cycle-dependent aggression, the rodent model of "premenstrual irritability" (resident-intruder test), and anxiety (elevated plus maze), depressive-like traits (forced swim test) as well as carbohydrate craving in female Wistar rats. Some aggressive and nonaggressive females were restraint-stressed before testing to determine their sensitivity to stress at different hormonal stages. The results revealed that females expressing the estrous cycle-dependent aggression but not those not expressing cycle-dependent aggression spent longer time immobile and shorter time swimming in the forced swim test at metestrus compared to proestrus phase of the estrous cycle. There was no difference between aggressive and nonaggressive females in anxiety, locomotor activity and sensitivity to restraint stress and sucrose consumption. The present study suggests a common neurobiological background for the estrous cycle-dependent aggression and depressive-like traits in rodents. This phenomenon could potentially aid the elucidation of premenstrual emotional dysfunctions and might be used as an ethological model to study a biochemical and genetic proneness to depression.

Aged rats: Sex differences and responses to chronic stress

Cognitive, as well as physiological, sex differences exist in young adult rats under both basal conditions and following chronic stress; however, few studies have examined whether sex differences remain in aged subjects and whether responses to stress are altered. We compared aged male and female Fischer 344 rats (21.5 months at testing) without stress and when given 21 days of restraint for 6 h/day on locomotion, anxiety-related behaviors, object recognition (non-spatial memory), object placement (spatial memory), body weight and serum steroid hormone levels. Control (unstressed) females had lower levels of estradiol and testosterone and higher corticosterone than males, and stress had no lasting effect on hormone concentrations. Females weighed less than males and showed less weight loss with stress. Locomotion measures on an open field were similar in the sexes and unaffected by stress. Anxiety-related behavior measures on the field showed that males were generally more anxious and that stress increased male, but decreased, female anxiety-related behaviors. In memory testing, exploration of objects was not different between the sexes, with or without stress, while stress increased exploration in both sexes during object recognition trials. Both males and females, regardless of treatment, discriminated between old and new objects at short, but not long, inter-trial delays. The typical advantage of young males for spatial memory performance was not observed in aged subjects on the object placement tasks. Stress-dependent enhancements in females and impairments in males for object placement are reported for young rats, but in aged rats, neither sex was altered by stress. Current data suggest that aging is associated with changes in the pattern of sex differences present in young adult rats in some behaviors and in the behavioral responses to stress.