Prolactin promotes the recruitment of main olfactory bulb cells and enhances the behavioral exploration toward a socio-sexual stimulus in female mice

Olfactory communication is triggered by pheromones that profoundly influence neuroendocrine responses to drive social interactions. Two principal olfactory systems process pheromones: the main and the vomeronasal or accessory system. Prolactin receptors are expressed in both systems suggesting a participation in the processing of olfactory information. We previously reported that prolactin participates in the sexual and olfactory bulb maturation of females. Therefore, we explored the expression of prolactin receptors within the olfactory bulb during sexual maturation and the direct responses of prolactin upon pheromonal exposure. Additionally, we assessed the behavioral response of adult females exposed to male sawdust after prolactin administration and the consequent activation of main and accessory olfactory bulb and their first central relays, the piriform cortex and the medial amygdala. Last, we investigated the intracellular pathway activated by prolactin within the olfactory bulb. Here, prolactin receptor expression remained constant during all maturation stages within the main olfactory bulb but decreased in adulthood in the accessory olfactory bulb. Behaviorally, females that received prolactin actively explored the male stimulus. An increased cFos activation in the amygdala and in the glomerular cells of the whole olfactory bulb was observed, but an augmented response in the mitral cells was only found within the main olfactory bulb after prolactin administration and the exposure to male stimulus. Interestingly, the ERK pathway was upregulated in the main olfactory bulb after exposure to a male stimulus. Overall, our results suggest that, in female mice, prolactin participates in the processing of chemosignals and behavioral responses by activating the main olfactory system and diminishing the classical vomeronasal response to pheromones.

Behavioural traits related with resilience or vulnerability to the development of cocaine-induced conditioned place preference after exposure of female mice to vicarious social defeat

Exposure to stress induced by intermittent repeated social defeat (IRSD) increases vulnerability to the development of cocaine-induced conditioned place preference (CPP) among male mice; however, some defeated mice are resilient to these effects of stress. In the present study we evaluated the effects of vicarious IRSD (VIRSD) in female mice and explored behavioural traits that are potentially predictive of resilience. C57BL/6 female mice (n = 28) were exposed to VIRSD, which consisted of the animals witnessing a short experience of social defeat by a male mouse on postnatal day (PND) 47, 50, 53 and 56. The control group (n = 10) was not exposed to stress. Blood samples were collected on PND 47 and 56 for corticosterone and interleukin-6 determinations. On PND 57-58, female mice performed several behavioural tests (elevated plus maze, hole-board, object recognition, social interaction, TST and splash tests). Three weeks later, the effects of cocaine (1.5 mg/kg) on the CPP paradigm were assessed. VIRSD decreased corticosterone levels (on PND 56), increased interleukin-6 levels, enhanced novelty-seeking, improved recognition memory and induced anxiety- and depression-like symptoms. Control and VIRSD female mice did not acquire CPP, although some stressed individuals with certain behavioural traits - including a high novelty-seeking profile or the development of depression-like behaviour in the splash test shortly after VIRSD - acquired cocaine CPP. Our results confirm that some behavioural traits of female mice are associated with vulnerability or resilience to the long-term effects of social stress on cocaine reward, as previously observed in males.

Unveiling the vulnerability of C57BL/6J female mice to HFpEF and its related complications

Introduction

The impact of female biological sex on the development of heart failure with preserved ejection fraction (HFpEF) and its associated kidney disease and vascular endothelial dysfunction is still controversial. Whether females are protected from HFpEF and associated complications is not well established. Previous studies report conflicting prevalence between genders. We hypothesize that female mice are unprotected from HFpEF and its associated kidney disease and vascular endothelial dysfunction.

Methods

Eight-week-old female mice were divided into four groups: control groups receiving a standard diet and water for either 5 or 16 weeks, and HFpEF groups fed a high-fat diet (HFD, Rodent Diet With 60 kcal% Fat) and N [w]-nitro-l-arginine methyl ester (L-NAME - 0.5 g/L) in the drinking water for 5 or 16 weeks. Various measurements and assessments were performed, including echocardiography, metabolic and hypertensive evaluations, markers of heart and kidney injury, and assessment of vascular endothelial function.

Results

Female mice with HFD and L-NAME developed HFpEF at 5 weeks, evidenced by increased E/E' ratio, reduced cardiac index, left ventricular mass, and unchanged ejection fraction. After 16 weeks, HFpEF worsened. Metabolic disorders, hypertension, lung wet/kidney weight increase, exercise intolerance, and cardiac/renal injury markers were observed. Vascular endothelial dysfunction was associated with ER stress and fibrosis induction.

Conclusions

We found that female mice are susceptible to the development of HFpEF and its associated kidney disease and vascular endothelial dysfunction. Our data support the concept that the female sex does not protect from HFpEF and its associated kidney disease and vascular endothelial dysfunction when disease risk factors are present.

Multiple integrated social stress induces depressive-like behavioral and neural adaptations in female C57BL/6J mice

Despite women representing most of those affected by major depression, preclinical studies have focused almost exclusively on male subjects, partially due to a lack of ideal animal paradigms. As the persistent need regarding the sex balance of neuroscience research and female-specific pathology of mental disorders surges, the establishment of natural etiology-based and systematically validated animal paradigms for depression with female subjects becomes an urgent scientific problem. This study aims to establish, characterize, and validate a "Multiple Integrated Social Stress (MISS)" model of depression in female C57BL/6J mice by manipulating and integrating daily social stressors that females are experiencing. Female C57BL/6J mice randomly experienced social competition failure in tube test, modified vicarious social defeat stress, unescapable overcrowding stress followed by social isolation on each day, for ten consecutive days. Compared with their controls, female MISS mice exhibited a relatively decreased preference for social interaction and sucrose, along with increased immobility in the tail suspension test, which could last for at least one month. These MISS mice also exhibited increased levels of blood serum corticosterone, interleukin-6 L and 1β. In the pharmacological experiment, MISS-induced dysfunctions in social interaction, sucrose preference, and tail suspension tests were amended by systematically administrating a single dose of sub-anesthetic ketamine, a rapid-onset antidepressant. Compared with controls, MISS females exhibited decreased c-Fos activation in their anterior cingulate cortex, prefrontal cortex, nucleus accumbens and some other depression-related brain regions. Furthermore, 24 h after the last exposure to the paradigm, MISS mice demonstrated a decreased center zone time in the open field test and decreased open arm time in the elevated plus-maze test, indicating anxiety-like behavioral phenotypes. Interestingly, MISS mice developed an excessive nesting ability, suggesting a likely behavioral phenotype of obsessive-compulsive disorder. These data showed that the MISS paradigm was sufficient to generate pathological profiles in female mice to mimic core symptoms, serum biochemistry and neural adaptations of depression in clinical patients. The present study offers a multiple integrated natural etiology-based animal model tool for studying female stress susceptibility.

The role of sociability in social instability stress: Behavioral, neuroendocrine and monoaminergic effects

Extensive literature has reported a link between social stress and mental health. In this complex relationship, individual strategies for coping with social stress are thought to have a possible modulating effect, with sociability being a key factor. Despite the higher incidence of affective disorders in females and sex-related neurochemical differences, female populations have been understudied. The aim of the present study was, therefore, to analyze the behavioral, neuroendocrine, and neurochemical effects of stress in female OF1 mice, paying special attention to social connectedness (female mice with high vs low sociability). To this end, subjects were exposed to the Chronic Social Instability Stress (CSIS) model for four weeks. Although female mice exposed to CSIS had increased arousal, there was no evidence of depressive-like behavior. Neither did exposure to CSIS affect corticosterone levels, although it did increase the MR/GR ratio by decreasing GR expression. Female mice exposed to CSIS had higher noradrenaline and dopamine levels in the hippocampus and striatum respectively, with a lower monoaminergic turnover, resulting in an increased arousal. CSIS increased serotonin levels in both the hippocampus and striatum. Similarly, CSIS was found to reduce kynurenic acid, 3-HK, and IDO and iNOS enzyme levels in the hippocampus. Interestingly, the observed decrease in IDO synthesis and the increased serotonin and dopamine levels in the striatum were only found in subjects with high sociability. These highly sociable female mice also had significantly lower levels of noradrenaline in the striatum after CSIS application. Overall, our model has produced neuroendocrine and neurochemical but not behavioral changes, so it has not allowed us to study sociability in depth. Therefore, a model that induces both molecular and behavioral phenotypes should be applied to determine the role of sociability.

Obese female mice do not exhibit overt hyperuricemia despite hepatic steatosis and impaired glucose tolerance

Recent reports have clearly demonstrated a tight correlation between obesity and elevated circulating uric acid levels (hyperuricemia). However, nearly all preclinical work in this area has been completed with male mice, leaving the field with a considerable gap in knowledge regarding female responses to obesity and hyperuricemia. This deficiency in sex as a biological variable extends beyond unknowns regarding uric acid (UA) to several important comorbidities associated with obesity including nonalcoholic fatty liver disease (NAFLD). To attempt to address this issue, herein we describe both phenotypic and metabolic responses to diet-induced obesity (DIO) in female mice. Six-week-old female C57BL/6J mice were fed a high-fat diet (60% calories derived from fat) for 32 weeks. The DIO female mice had significant weight gain over the course of the study, higher fasting blood glucose, impaired glucose tolerance, and elevated plasma insulin levels compared to age-matched on normal chow. While these classic indices of DIO and NAFLD were observed such as increased circulating levels of ALT and AST, there was no difference in circulating UA levels. Obese female mice also demonstrated increased hepatic triglyceride (TG), cholesterol, and cholesteryl ester. In addition, several markers of hepatic inflammation were significantly increased. Also, alterations in the expression of redox-related enzymes were observed in obese mice compared to lean controls including increases in extracellular superoxide dismutase (Sod3), heme oxygenase (Ho)-1, and xanthine dehydrogenase (Xdh). Interestingly, hepatic UA levels were significantly elevated (~2-fold) in obese mice compared to their lean counterparts. These data demonstrate female mice assume a similar metabolic profile to that reported in several male models of obesity in the context of alterations in glucose tolerance, hepatic steatosis, and elevated transaminases (ALT and AST) in the absence of hyperuricemia affirming the need for further study.

Chronic social instability stress down-regulates IL-10 and up-regulates CX3CR1 in tumor-bearing and non-tumor-bearing female mice

Extensive literature has reported a link between stress and tumor progression, and between both of these factors and mental health. Despite the higher incidence of affective disorders in females and the neurochemical differences according to sex, female populations have been understudied. The aim of this study was therefore to analyze the effect of stress on tumor development in female OF1 mice. For this purpose, subjects were inoculated with B16F10 melanoma cells and exposed to the Chronic Social Instability Stress (CSIS) model. Behavioral, neurochemical and neuroendocrine parameters were analyzed. Female mice exposed to CSIS exhibited reduced body weight and increased arousal, but there was no evidence of depressive behavior or anxiety. Exposure to CSIS did not affect either corticosterone levels or tumor development, although it did provoke an imbalance in cerebral inflammatory cytokines, decreasing IL-10 expression (IL-6/IL-10 and TNF-α/IL-10); chemokines, increasing CX3CR1 expression (CX3CL1/CX3CR1); and glucocorticoid receptors, decreasing GR expression (MR/GR). In contrast, tumor development did not alter body weight and, although it did alter behavior, it did so to a much lesser extent. Tumor inoculation did not affect corticosterone levels, but increased the MR/GR ratio in the hippocampus and provoked an imbalance in cerebral inflammatory cytokines and chemokines, although differently from stress. These results underscore the need for experimental approaches that allow us to take sex differences into account when exploring this issue, since these results appear to indicate that the female response to stress is mediated by mechanisms different from those often proposed in relation to male mice.

Prepulse inhibition can predict the motivational effects of cocaine in female mice exposed to maternal separation

The prepulse inhibition (PPI) of the startle response can identify the rodents that are more sensitive to the effects of cocaine. Mice with a lower PPI presented a higher vulnerability to the effects of cocaine and a higher susceptibility to developing a substance use disorder (SUD). Maternal separation with early weaning (MSEW) is a relevant animal model to induce motivational alterations throughout life. Nevertheless, only a few studies on females exist, even though they are more vulnerable to stress- and cocaine-related problems. Hence, the aim of the present study was to evaluate the ability of PPI to identify females with a greater vulnerability to the long-term consequences of early stress on the motivational effects of cocaine. Female mice underwent MSEW and were classified according to their high or low PPI. They were then assessed in the cocaine-induced locomotor sensitization test, the conditioned place preference paradigm or the operant self-administration paradigm. Additionally, they were also evaluated in the passive avoidance task, the tail-suspension and the splash tests. The results revealed that the females with lower PPI presented higher consequences of MSEW on the effects of cocaine and showed an increase in anhedonia-like behaviours. Our findings support that a PPI deficit could represent a biomarker of vulnerability to the effects of cocaine induced by MSEW.

Daily ingestion of Akkermansia mucciniphila for one month promotes healthy aging and increases lifespan in old female mice

The ingestion of certain probiotics has been suggested as a promising nutritional strategy to improve aging. The objective of this work was to evaluate the effects of the daily intake, for a month, of a new probiotic Akkermansia muciniphila (AKK) (2 × 10⁸ cfu/100µL PBS) on behavior, as well as function and redox state of immune cells of old female ICR-CD1 mice (OA group). For this, several behavioral tests were performed, and function and oxidative-inflammatory stress parameters of peritoneal leukocytes were analyzed in OA group, in a group of the same age that did not take AKK (old control, OC group) and in another adult control (AC) group. The results showed, in OA group, a significant improvement of several behavioral responses (coordination, balance, neuromuscular vigor, exploratory ability and anxiety like-behaviors), as well as in immune functions (chemotaxis, phagocytosis, NK activity and lymphoproliferation) and in oxidative stress parameters (glutathione peroxidase and reductase activities, oxidized glutathione and lipid oxidation concentrations) of the peritoneal leukocytes in comparison to those observed in OC group. In addition, peritoneal immune cells from the OA group released lower basal concentrations of pro-inflammatory cytokines (IL-2, IL-6 and TNF-α) compared to those from the OC group. The values of parameters in OA were similar to those in AC group. These improvements in the old mice receiving the probiotic were reflected in an increase in their lifespan. In conclusion, our data indicate that AKK supplementation for a short period could be a good nutritional strategy to promote healthy longevity.

Data on cecal and fecal microbiota and predicted metagenomes profiles of female mice receiving whole flaxseed or its oil and secoisolariciresinol diglucoside components

Dietary flaxseed (FS) and its components including FS oil (FSO), secoisolariciresinol diglucoside (SDG) and fiber, are processed by the gut microbiota. These data are in support of the article entitled “Discriminatory and cooperative effects within the mouse gut microbiota in response to flaxseed and its oil and lignan components”, Journal of Nutritional Biochemistry [1]. Here we describe data generated by 16S rRNA sequencing of DNA obtained from cecum contents and feces of C57BL/6 female mice fed either a basal diet (BD, AIN93G), or isocaloric diets containing 10% FS, or 10% FS-equivalent amounts of FSO or SDG for 21 days. These include bacterial community composition and inferred KEGG pathways; the raw data are publicly available at the NCBI SRA database (BioProject ID PRJNA683934). Furthermore, this work includes detailed experimentation procedures, total bacterial counts (qPCR) in the cecum content and feces, and correlation analysis between a selected bacterial genus, Bacteroides and a predicted metabolic pathway. FS is utilized worldwide, especially for the prevention and/or treatment of diseases including cardiovascular diseases, diabetes and cancer. These data will be valuable as a reference to study different FS cultivars and SDG- or FSO- enriched products on the gut microbiota, to study gut microbial responses to FS and its components in different mouse strains and mammalian hosts to elucidate individualized effects, and to understand the importance of the gut microbiota for FS benefits.

Uncoupling protein 1-independent effects of eicosapentaenoic acid in brown adipose tissue of diet-induced obese female mice

Brown adipose tissue (BAT) plays a key role in energy expenditure through its thermogenic function, making its activation a popular target to reduce obesity. We recently reported that male mice housed at thermoneutrality with uncoupling protein 1 (UCP1) deficiency had increased weight gain and glucose intolerance, but eicosapentaenoic acid (EPA) ameliorated these effects. Whether female mice respond similarly to lack of UCP1 and to EPA remains unknown. We hypothesize that the effects of EPA on BAT activation are independent of UCP1 expression. We used female wild type (WT) and UCP1 knockout (KO) mice housed at thermoneutrality (30°C) as an obesogenic environment and fed them high fat (HF) diets with or without EPA for up to 14 weeks. Body weight (BW), body composition, and insulin and glucose tolerance tests were performed during the feeding trial. At termination, serum and BAT were harvested for further analyses. Mice in the KO-EPA group had significantly lower BW than KO-HF mice. In addition, KO-HF mice displayed significantly impaired glucose tolerance compared to their WT-HF littermates. However, EPA significantly enhanced glucose clearance in the KO mice compared to KO-HF mice. Protein levels of the mitochondrial cytochrome C oxidase subunits I, II, and IV were significantly lower in KO mice compared to WT. Our findings support that ablation of UCP1 is detrimental to energy metabolism of female mice in thermoneutral conditions. However, unexpectedly, EPA's protective effects against diet-induced obesity and glucose intolerance in these mice were independent of UCP1.

Selecting antidepressants according to a drug-by-environment interaction: A comparison of fluoxetine and minocycline effects in mice living either in enriched or stressful conditions

Selective serotonin reuptake inhibitors (SSRIs) are the first-line treatment for major depressive disorder. It has been recently proposed that these drugs, by enhancing neural plasticity, amplify the influences of the living conditions on mood. Consequently, SSRI outcome depends on the quality of the environment, improving symptomatology mainly in individuals living in favorable conditions. In adverse conditions, drugs with a different mechanism of action might have higher efficacy. The antibiotic minocycline, with neuroprotective and anti-inflammatory properties, has been recently proposed as a novel potential antidepressant treatment. To explore the drug-by-environment interaction, we compared the effects on depressive-like behavior and neural plasticity of the SSRI fluoxetine and minocycline in enriched and stressful conditions. We first exposed C57BL/6 adult female mice to 14 days of chronic unpredictable mild stress to induce a depressive-like profile. Afterward, mice received vehicle, fluoxetine, or minocycline for 21 days, while exposed to either enriched or stressful conditions. During the first five days, fluoxetine led to an improvement in enrichment but not in stress. By contrast, minocycline led to an improvement in both conditions. After 21 days, all groups showed a significant improvement in enrichment while fluoxetine worsened the depressive like behavior in stress. The effects of the drugs on neural plasticity, measured as long-term potentiation, were also environment-dependent. Overall, we show that the environment affects fluoxetine but not minocycline outcome, indicating that the latter represents a potential alternative to SSRIs to treat depressed patients living in adverse conditions. From a translation perspective, our finding call for considering the drug-by-environment interaction to select the most effective pharmacological treatment.

Sex-Specific Role for Egr3 in Nucleus Accumbens D2-Medium Spiny Neurons Following Long-Term Abstinence From Cocaine Self-administration

BACKGROUND

We previously showed that the transcription factor Egr3 (early growth response 3) is oppositely regulated in nucleus accumbens (NAc) cell subtypes 24 hours following cocaine exposure and bidirectionally mediates cocaine-related behaviors in male rodents. Overexpressing Egr3 in D₂ receptor-containing medium spiny neurons (D2-MSNs) before drug exposure reduces the rewarding and psychomotor sensitization effects of cocaine. However, it is unknown if Egr3 plays a role in long-term neuroadaptations in the NAc and relapse to cocaine seeking.

METHODS

We measured EGR3 protein levels in the NAc following 20 days of forced abstinence from intravenous cocaine self-administration in 10-week-old Sprague Dawley rats and C57BL/6 mice. In 8- to 10-week-old A2A-Cre mice, we used virally mediated Egr3 overexpression in NAc D2-MSNs to test the role of Egr3 on operant responding during seeking, extinction, and drug-induced reinstatement of cocaine self-administration. To evaluate if Egr3 contributed to sex differences to cocaine relapse, we conducted these procedures in both male and female rodents.

RESULTS

We found that EGR3 expression was reduced only in female rodents after 20 days of forced abstinence. Additionally, we showed that our self-administration paradigm in mice recapitulated the sex differences in cocaine intake and relapse demonstrated in humans and rats. Finally, whereas Egr3 overexpression in D2-MSNs during forced abstinence facilitated extinction and blunted drug-induced reinstatement in female mice, it had the opposite effect in male mice.

CONCLUSIONS

We showed that the immediate early gene Egr3 has long-term effects on drug-related behaviors. Our work suggests that changes in Egr3 expression in D2-MSNs contributes to sex differences in cocaine relapse.

Copper Changes Intestinal Microbiota of the Cecum and Rectum in Female Mice by 16S rRNA Gene Sequencing

The aim of the present study was to investigate the effects of high concentrations of copper (Cu) on the cecum and rectum of intestinal microbiota in female mice. Twenty-four Kunming mice were weighed and randomly divided into two groups (n = 12 per group) including the control group and Cu group. Cu group was given drinking water with 5 mg/kg-bw copper chloride (CuCl₂), while the control group was treated with drinking water without CuCl₂. At the 90th day, results showed that compared with the control group, mice in the treatment group had a lower body weight, and the feces turned yellow and had a lower pH value. Histopathological lesions showed that the intestinal tissue from the treatment group had increased thickness of outer muscularis and smoothed muscle fiber, widened submucosa, decreased goblet cells, and showed blunting of intestinal villi and severe atrophy of central lacteal. In addition, at the genus level, 16S rRNA gene sequencing from the Cu group showed that Corynebacterium were significantly increased whereas Staphylococcaceae, Odoribacter, Rikenella, and Jeotgalicoccus were significantly decreased in the cecum. Dehalobacterium, Coprococcus, and Spirochaetales increased significantly whereas Salinicoccus, Bacillales, Staphylococcus, and Lactobacillales decreased sharply in the rectum. This study demonstrated that high concentrations of Cu could induce tissue injury and interrupt the homeostasis of microbiota.

Analgesic effects of optogenetic inhibition of basolateral amygdala inputs into the prefrontal cortex in nerve injured female mice

Peripheral nerve injury can lead to remodeling of brain circuits, and this can cause chronification of pain. We have recently reported that male mice subjected to spared injury of the sciatic nerve undergo changes in the function of the medial prefrontal cortex (mPFC) that culminate in reduced output of layer 5 pyramidal cells. More recently, we have shown that this is mediated by alterations in synaptic inputs from the basolateral amygdala (BLA) into GABAergic interneurons in the mPFC. Optogenetic inhibition of these inputs reversed mechanical allodynia and thermal hyperalgesia in male mice. It is known that the processing of pain signals can exhibit marked sex differences. We therefore tested whether the dysregulation of BLA to mPFC signaling is equally altered in female mice. Injection of AAV-Arch3.0 constructs into the BLA followed by implantation of a fiberoptic cannula into the mPFC in sham and SNI operated female mice was carried out, and pain behavioral responses were measured in response to yellow light mediated activation of this inhibitory opsin. Our data reveal that Arch3.0 activation leads to a marked increase in paw withdrawal thresholds and latencies in response to mechanical and thermal stimuli, respectively. However, we did not observe nerve injury-induced changes in mPFC layer 5 pyramidal cell output in female mice. Hence, the observed light-induced analgesic effects may be due to compensation for dysregulated neuronal circuits downstream of the mPFC.

No Difference Between Age-Matched Male and Female C57BL/6J Mice in Photopic and Scotopic Electroretinogram a- and b-Wave Amplitudes or in Peak Diurnal Outer Segment Phagocytosis by the Retinal Pigment Epithelium

Mice provide informative models of enormous utility for eye research. Sex as biological variable must be considered when conducting studies exploring mouse models. To determine if sex confounds neural retina or retinal pigment epithelium (RPE) activity in wild-type C57BL/6J mice, we compared male and female mice with respect to retinal light response and RPE phagocytosis. We tested 2-month-old mice at peak fertility and 12-month-old mice past fertility. Retinal function was assessed by quantifying a- and b-wave amplitudes of photopic and scotopic electroretinograms (ERGs). These experiments did not reveal differences between male and female mice at either age. As expected from earlier studies, 12-month-old mice showed reduced light responses compared to 2-month-old mice, but age-related decline was identical for male and female mice. RPE functionality was assessed by quantifying RPE phagosome content 1 h after light onset in mice 2 months of age, an age of maturity of the process of outer segment turnover that includes RPE phagocytosis. These experiments did not reveal differences in RPE phagocytosis between male and female mice. Altogether, male and female C57BL/6J mice do not differ in retinal light response and peak RPE phagocytic activity. Retinal activity is impaired with age to the same extent in male and female mice. Our results justify testing mixed-sex mouse cohorts in studies on outer segment renewal and RPE phagocytosis and illustrate the importance of careful consideration of cohort age.

Distinctive stress sensitivity and anxiety-like behavior in female mice: Strain differences matter

Epidemiologic studies have shown that the prevalence of stress-related mood disorders is higher in women, which suggests a different response of neuroendocrine circuits involved in the response to stressful events, as well as a genetic background influence. The aim of this study was to investigate the baseline differences in anxiety-like behaviors of females of two commonly used mice strains. Secondly, we have also aimed to study their behavioral and biochemical alterations following stress. Naïve 3-4 months-old Swiss and C57BL/6 female mice were evaluated in the elevated plus maze (EPM) and in the acoustic startle response (ASR) for anxiety-like behaviors. Besides, an independent group of animals from each strain was exposed to cold-restraint stress (30 min/4 °C, daily) for 21 consecutive days and then evaluated in EPM and in the sucrose consumption tests. Twenty-four hours following behavioral experimentation mice were decapitated and their hippocampi (HP) and cortex (CT) dissected for further Western blotting analysis of glucocorticoid receptor (GR) and glial fibrillary acid protein (GFAP). Subsequent to each behavioral protocol, animal blood samples were collected for further plasma corticosterone analysis. C57BL/6 presented a lower anxiety profile than Swiss female mice in both behavioral tests, EPM and ASR. These phenomena could be correlated with the fact that both strains have distinct corticosterone levels and GR expression in the HP at the baseline level. Moreover, C57BL/6 female mice were more vulnerable to the stress protocol, which was able to induce an anhedonic state characterized by lower preference for a sucrose solution. Behavioral anhedonic-like alterations in these animals coincide with reduced plasma corticosterone accompanied with increased GR and GFAP levels, both in the HP. Our data suggest that in C57BL/6 female mice a dysregulation of the hypothalamus-pituitary-adrenal axis (HPA-axis) occurs, in which corticosterone acting on GRs would possibly exert its pro-inflammatory role, ultimately leading to astrocyte activation in response to stress.

Tribulus terrestris improves metronidazole-induced impaired fertility in the male mice

INTRODUCTION

Fruit extract of Tribulus terrestris (TT) bears aphrodisiac and antioxidative properties. Antimicrobial drug, metronidazole (MTZ) impairs the spermatogenic activity and fertility in males.

OBJECTIVE

Validation of the use of fruit extract of TT as a supplement against MTZ-induced fertility impairment in males.

METHODS

Adult Swiss strain male mice were administered with 500mg/kgBW/day of MTZ for 28 days. Low (100mg/kgBW/day) and high (200mg/kgBW/day) doses of TT were administered simultaneously with MTZ (500mg/kgBW/day) for same duration. All males were cohabited with virgin proestrus females. Vaginal plug formation was observed to calculate the libido index. Cohabited females were sacrificed on fifteenth day of gestation to dissect out the ovaries and uteri. Fertility index, quantal pregnancy, pre-implantation and post-implantation losses were calculated.

RESULTS

MTZ-treated males showed unaltered mating ability, however, the females impregnated by such males exhibited marked alterations in the fertility index, quantal pregnancy and pre- and post-implantation losses. Supplementation with low dose of TT failed to restore such reproductive toxicities exhibited by administration of MTZ. However, the altered reproductive toxicities were reinstated to control values following supplementation with high dose of TT.

CONCLUSION

The fruit extract of TT may emerge as an effective herbal remedy, correcting the drug-induced fertility impairments in males.

Effects of monoamines on the intrinsic excitability of lateral orbitofrontal cortex neurons in alcohol-dependent and non-dependent female mice

Changes in brain reward and control systems of frontal cortical areas including the orbitofrontal cortex (OFC) are associated with alcohol use disorders (AUD). The OFC is extensively innervated by monoamines, and drugs that target monoamine receptors have been used to treat a number of neuropsychiatric diseases, including AUDs. Recent findings from this laboratory demonstrate that D2, α2-adrenergic and 5HT_1A receptors all decrease the intrinsic excitability of lateral OFC (lOFC) neurons in naïve male mice and that this effect is lost in mice exposed to repeated cycles of chronic intermittent ethanol (CIE) vapor. As biological sex differences may influence an individual's response to alcohol and contribute to the propensity to engage in addictive behaviors, we examined whether monoamines have similar effects on lOFC neurons in control and CIE exposed female mice. Dopamine, norepinephrine and serotonin all decreased spiking of lOFC neurons in naïve females via activation of G_iα-coupled D2, α2-adrenergic and 5HT_1A receptors, respectively. Firing was also inhibited by the direct GIRK channel activator ML297, while blocking these channels with barium eliminated the inhibitory actions of monoamines. Following CIE treatment, evoked spiking of lOFC neurons from female mice was significantly enhanced and monoamines and ML297 no longer inhibited firing. Unlike in male mice, the enhanced firing of neurons from CIE exposed female mice was not associated with changes in the after-hyperpolarization and the small-conductance potassium channel blocker apamin had no effect on current-evoked tail currents from either control or CIE exposed female mice. These results suggest that while CIE exposure alters monoamine regulation of OFC neuron firing similarly in males and female mice, there are sex-dependent differences in processes that regulate the intrinsic excitability of these neurons.

A longitudinal study

Aging is accompanied by impairment in the nervous, immune, and endocrine systems as well as in neuroimmunoendocrine communication. In this context, there is an age-related alteration of the physiological response to acute stress, which is modulated by catecholamine (CA), final products of the sympathetic-adreno-medullary axis. The involvement of CA in essential functions of the nervous system is consistent with the neuropsychological deficits found in mice with haploinsufficiency (hemizygous; HZ) of tyrosine hydroxylase (TH) enzyme (TH-HZ). However, other possible alterations in regulatory systems have not been studied in these animals. The aim of the present work was to analyze whether adult TH-HZ female mice presented the impairment of behavioral traits and immunological responses that occurs with aging and whether they had affected their mean lifespan. ICR-CD1 female TH-HZ and wild type (WT) mice were used in a longitudinal study. Behavioral tests were performed on adult and old mice in order to evaluate their sensorimotor abilities and exploratory capacity, as well as anxiety-like behaviors. At the ages of 2 ± 1, 4 ± 1, 9 ± 1, 13 ± 1 and 20 ± 1 months, peritoneal leukocytes were extracted and several immune functions were assessed (phagocytic capacity, Natural Killer (NK) cytotoxicity, and lymphoproliferative response to lipopolysaccharide (LPS) and concanavalin A (ConA)). In addition, several oxidative stress parameters (catalase, glutathione reductase and glutathione peroxidase activities, and reduced glutathione (GSH) concentrations as antioxidant compounds as well as xanthine oxidase activity, oxidized glutathione (GSSG) concentrations, and GSSG/GSH ratio as oxidants) were analyzed. As inflammatory stress parameters TNF-alpha and IL-10 concentrations, and TNF-alpha/IL-10 ratios as inflammatory/anti-inflammatory markers, were measured. Animals were maintained in standard conditions until their natural death. The results indicate that adult TH-HZ mice presented worse sensorimotor abilities and exploratory capacity than their WT littermates as well as greater anxiety-like behaviors. With regards to the immune system, adult TH-HZ animals exhibited lower values of phagocytic capacity, NK cytotoxicity, and lymphoproliferative response to LPS and ConA than WT mice. Moreover, immune cells of TH-HZ mice showed higher oxidative and inflammatory stress than those of WT animals. Although these differences between TH-HZ and WT, in general, decreased with aging, this premature immunosenescence and impairment of behavior of TH-HZ mice was accompanied by a shorter mean lifespan in comparison to WT counterparts. In conclusion, haploinsufficiency of th gene in female mice appears to provoke premature aging of the regulatory systems affecting mean lifespan.

Acute lung injury induced by intestinal ischemia and reperfusion is altered in obese female mice

RATIONAL

Acute lung injury (ALI) is a common complication after intestinal ischemia and reperfusion (I/R) injury that can lead to acute respiratory distress syndrome (ARDS). We have previously demonstrated that females are protected against lung damage induced by intestinal I/R through an estrogen mediated mechanism.

OBJECTIVES

To investigate the effect of obesity on ALI induced by intestinal I/R in female mice.

METHODS

C57Bl/6 female mice were fed with a standard low-fat diet (SD) or a high-fat diet (HFD) for 9 weeks. Intestinal I/R injury was induced by a 45 min occlusion of the mesenteric artery followed by 2 and 24 h of reperfusion.

RESULTS

Significant increase in lung myeloperoxidase expression (MPO) and neutrophil numbers of SD and HFD mice occurred at 2 h and 24 h of reperfusion. Furthermore, HFD mice presented a significant increase in lung eosinophil peroxidase (EPO) expression and eosinophil numbers compared to SD mice. Lung wet/dry weight ratio was significantly greater in HFD mice at 2 and 24 h of reperfusion, accompanied by a significant increase in the expression of inducible NO in the lung tissue and a significant decrease in arterial oxygen saturation at 24 h of reperfusion relative to SD mice.

CONCLUSION

Obesity predisposes female mice to increased pulmonary oedema and deterioration in gas exchange, which is accompanied by an increase in iNOS expression in the lung.

The MMP-9/TIMP-1 System is Involved in Fluoride-Induced Reproductive Dysfunctions in Female Mice

A total of 84 healthy female mice were kept with various concentrations of sodium fluoride (F) (0, 50, 100, 150 mg F^-/L in drinking water for 90 days) and were then mated with healthy male mice for 1 week to study the effect of excessive fluoride on female reproductive function, particularly in embryo implantation. The rate of pregnancy, litter size, and the birth weight of female mice were evaluated. Ultrastructural changes of uteri tissues were observed by transmission electron microscopy (TEM). The mRNA expression levels of MMP-9 and TIMP-1 were determined by quantitative real-time PCR. The protein expression levels of MMP-9 and TIMP-1 were analyzed by western blotting. Results showed a significant decrease of litter size in mice exposed to fluoride. TEM images of uteri tissue of mice that underwent a 150 mg/L F^- treatment for 90 days showed a vague nucleus, reduced microvilli, increased lysosomes, a dilated endoplasmic reticulum, and a vacuolization mitochondrion when compared with the control group. Following the damage of the structure, the expression levels of MMP-9 and TIMP-1 in uteri tissues were significantly unregulated in the F 150 group. These results show that MMP-9/TIMP-1 system disturbance and changes of histological structure in uteri tissue are involved in fluoride-induced reproductive dysfunctions.

Anti-oxidant and anti-inflammatory effects of hydrogen-rich water alleviate ethanol-induced fatty liver in mice

AIM

To investigate the effects of hydrogen-rich water (HRW) treatment on prevention of ethanol (EtOH)-induced early fatty liver in mice.

METHODS

In vitro reduction of hydrogen peroxide by HRW was determined with a chemiluminescence system. Female mice were randomly divided into five groups: control, EtOH, EtOH + silymarin, EtOH + HRW and EtOH + silymarin + HRW. Each group was fed a Lieber-DeCarli liquid diet containing EtOH or isocaloric maltose dextrin (control diet). Silymarin was used as a positive control to compare HRW efficacy against chronic EtOH-induced hepatotoxicity. HRW was freshly prepared and given at a dosage of 1.2 mL/mouse trice daily. Blood and liver tissue were collected after chronic-binge liquid-diet feeding for 12 wk.

RESULTS

The in vitro study showed that HRW directly scavenged hydrogen peroxide. The in vivo study showed that HRW increased expression of acyl ghrelin, which was correlated with food intake. HRW treatment significantly reduced EtOH-induced increases in serum alanine aminotransferase, aspartate aminotransferase, triglycerol and total cholesterol levels, hepatic lipid accumulation and inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6. HRW attenuated malondialdehyde level, restored glutathione depletion and increased superoxide dismutase, glutathione peroxidase and catalase activities in the liver. Moreover, HRW reduced TNF-α and IL-6 levels but increased IL-10 and IL-22 levels.

CONCLUSION

HRW protects against chronic EtOH-induced liver injury, possibly by inducing acyl ghrelin to suppress the pro-inflammatory cytokines TNF-α and IL-6 and induce IL-10 and IL-22, thus activating antioxidant enzymes against oxidative stress.

Effect of LA on the Growth and Development of the Main Organs in Female Mice

Effects of lead acetate (LA) on the growth and development of major organs in female mice were studied. Female mice were divided randomly into four treatment groups and one control group. In treatment groups, mice were injected with different concentrations of LA solution every 2 days; whereas control-group mice received equal volumes of sterile normal saline. Body weight (BW) and symptoms were recorded every 2 days. After LA exposure, mice were executed by cervical dislocation and main organs (heart, liver, spleen, lung, kidney) collected for evaluation of morphologic and histologic changes. LA could greatly affect increases in BW, and BW decreased with increasing dose and time of exposure to LA. Compared with the control group, organ coefficients in treatment groups were of the order kidney and spleen > liver and lung > heart and demonstrated obvious dose-time effects. LA exposure could damage the heart, liver, spleen, lung, and kidney. Damage to the kidney and spleen was the most severe, followed by that to the liver, heart, and lung. Damage was aggravated with increasing doses and exposure time to LA in an obvious dose-time relationship; when LA dose was ≥20 mg/kg, the growth and development of mice were obviously inhibited. These results suggest that long-term exposure to low-dose LA can result in universal pathologic damage to mouse organs and that severity is dependent on the dose and duration of LA exposure.

Enkephalin levels and the number of neuropeptide Y-containing interneurons in the hippocampus are decreased in female cannabinoid-receptor 1 knock-out mice

Drug addiction requires learning and memory processes that are facilitated by activation of cannabinoid-1 (CB1) and opioid receptors in the hippocampus. This involves activity-dependent synaptic plasticity that is partially regulated by endogenous opioid (enkephalin and dynorphin) and non-opioid peptides, specifically cholecystokinin, parvalbumin and neuropeptide Y, the neuropeptides present in inhibitory interneurons that co-express CB1 or selective opioid receptors. We tested the hypothesis that CB1 receptor expression is a determinant of the availability of one or more of these peptide modulators in the hippocampus. This was achieved by quantitatively analyzing the immunoperoxidase labeling for each of these neuropeptide in the dorsal hippocampus of female wild-type (CB1+/+) and cannabinoid receptor 1 knockout (CB1-/-) C57/BL6 mice. The levels of Leu(5)-enkephalin-immunoreactivity were significantly reduced in the hilus of the dentate gyrus and in stratum lucidum of CA3 in CB1-/- mice. Moreover, the numbers of neuropeptide Y-immunoreactive interneurons in the dentate hilus were significantly lower in the CB1-/- compared to wild-type mice. However, CB1+/+ and CB1-/- mice did not significantly differ in expression levels of either dynorphin or cholecystokinin, and showed no differences in numbers of parvalbumin-containing interneurons. These findings suggest that the cannabinoid and opioid systems have a nuanced, regulatory relationship that could affect the balance of excitation and inhibition in the hippocampus and thus processes such as learning that rely on this balance.

The reproductive toxicity of saponins isolated from Cortex Albiziae in female mice

Saponin frsom Cortex Albiziae (SCA) are extensively used in the clinical treatment of tumor and depression. However, SCA may cause several adverse effects, including reproductive toxicity. The present study was designed to assess the mechanism by which SCA cause reproductive toxicity in female mice. The general reproductive toxicity testing was accomplished in female Kunming mice. The animals were divided into four groups: three groups that were treated by oral gavage with 135, 270, and 540 mg·kg(-1)·d(-1) of SCA prepared in physiological saline, respectively, and one vehicle control group that was treated with physiological saline only. The gestational toxicity tests were conducted at 540 mg·kg(-1)·d(-1). The general reproductive toxicity results showed that the pregnancy rate of the SCA-treated group decreased with the pregnancy rate being decreased by 70% at 540 mg·kg(-1)·d(-1). SCA elicited maternal toxicity in the ovary and the uterus, but no fetal toxicity or teratogenicity was observed. The rates of implantation in the early, middle, and late pregnancy were all decreased, with stillbirths and maternal deaths being observed. Histopathological changes showed that SCA adversely affected the ovary and the uterus. In conclusion, SCA-induced reproductive toxicity in female mice is most likely caused by its damage to the ovary and the uterus.

Gene expression in the liver of female, but not male mice treated with rapamycin resembles changes observed under dietary restriction

It is well known that in mice the extension in lifespan by rapamycin is sexually dimorphic, in that it has a larger effect in females than males. In a previous study we showed that in male C57BL6 mice, rapamycin had less profound effects in both gene expression and liver metabolites when compared to dietary restriction (DR), but no data was available in females. Because recent studies showed that rapamycin increases longevity in a dose dependent manner and at every dose tested the effect remains larger in females than in males, we hypothesized that rapamycin should have a stronger effect on gene expression in females, and this effect could be dose dependent. To test this hypothesis, we measured the changes in liver gene expression induced by rapamycin (14 ppm) with a focus on several genes involved in pathways known to play a role in aging and that are altered by DR. To investigate whether any effects are dose dependent, we also analyzed females treated with two additional doses of rapamycin (22 and 42 ppm). We observed striking differences between male and female in gene expression at 14 ppm, where females have a larger response to rapamycin than males, and the effects of rapamycin in females resemble what we observed under DR. However, these effects were generally not dose dependent. These data support the notion that female mice respond better to rapamycin, and at least with the set of genes studied here, the effect of rapamycin in females resemble the effect of DR.

Disruption of running activity rhythm following restricted feeding in female mice: Preventive effects of antidepressants

Biological rhythms are critical in the etiology of mood disorders; therefore, effective mood disorder treatments should address rhythm disturbances. Among the variables synchronized with the light-dark cycle, spontaneous activity in rodents is useful for investigating circadian rhythms. However, previous studies have focused only on the increase of wheel-running activity under restricted feeding conditions, while little information is available on circadian rhythm of running activity. In this study, chronometrical analysis was used to assess whether circadian rhythms during wheel-running are altered by restricted feeding and affected by antidepressant drugs. Wheel revolutions were automatically recorded and analyzed using cosinor-rhythmometry in 8-week old ICR albino mice. When feeding was restricted to 1 h per day (21:00-22:00), wheel-running rhythms were reliably disrupted. Female mice exhibited marked alterations in the pattern and extent of wheel-running beginning on day 1. Subchronic treatment with imipramine or paroxetine, as well as tandospirone and (-)-DOI, prevented wheel-running rhythm disruption. Thus, altering the circadian activity rhythms of female mice on a 1-h feeding schedule may be useful for investigating disturbances in biological rhythms.

17β-Estradiol administration promotes delayed cutaneous wound healing in 40-week ovariectomised female mice

This study investigated the effect of 17β-estradiol on wound healing in 40-week ovariectomised female mice. Thirty-six-week-old female mice were divided into three groups: medication with 17β-estradiol after ovariectomy (OVX + 17β-estradiol), ovariectomy (OVX) and sham (SHAM). The mice received two full-thickness wounds, and the OVX + 17β-estradiol group was administered 17β-estradiol at 0·01 g/day until healing. In the OVX + 17β-estradiol group, the ratio of wound area was significantly smaller than those of the OVX and SHAM groups on days 1-3, 5, 6, 8-12 and 9-12, respectively, the numbers of neutrophils and macrophages were significantly smaller than those on days 3 and 7, the ratio of re-epithelialisation was significantly higher than those on days 3 and 11, the ratio of myofibroblasts was significantly higher than those on day 11 and smaller on day 14, and the ratio of collagen fibres was significantly larger than that of the OVX group on days 7-14. We found that 17β-estradiol administration promotes cutaneous wound healing in 40-week female mice by reducing wound area, shortening inflammatory response, and promoting re-epithelialisation, collagen deposition and wound contraction. Our results suggest that cutaneous wound healing that is delayed because of ageing is promoted by exogenous and continuous 17β-estradiol administration.

Peroxisome proliferator-activated receptor α mediates di-(2-ethylhexyl) phthalate transgenerational repression of ovarian Esr1 expression in female mice

Di-(2-ethylhexyl)-phthalate (DEHP) is a phthalate ester that binds peroxisome proliferator-activated receptor α (PPARα) to induce proliferation of peroxisomes and regulate the expression of specific target genes. The question of whether the effect of DEHP on female reproductive processes is mediated via PPARα-dependent signaling is controversial. In this study, we investigated the effect of exposure to DEHP on ovarian expression of estrogen receptor α (Esr1) and aromatase (Cyp19a1) in three generations of Sv/129 wild-type (WT, +/+) and PPARα (-/-) knockout mice. Compared with untreated controls, ovarian expression of Esr1 decreased in response to DEHP treatment in the F0 (0.56-fold, P=0.19), F1 (0.45-fold, P=0.023), and F2 (0.35-fold, P=0.014) generations of WT mice, but not PPARα-null mice. Our data indicate that transgenerational repression by DEHP of ovarian Esr1 gene expression is mediated by PPARα-dependent pathways. Further studies are required to elucidate the mechanisms underlying crosstalk between PPARα and Esr1 signaling in reproductive processes.

Milled Stress Reduces Morphine-Induced Locomotion in F2 NMRI Mice

In the present study, the effects of pregnant NMRI mice restraint stress on the responsibility of their children to the behavioral properties of morphine, sulpiride and dextromethorphan were investigated in the F2 generation.

TWENTY FOUR PREGNANT NMRI FEMALE MICE (W

25 g) were divided into the experimental and control groups (n = 12/group). Animals in the experimental group were kept in the restraint cylinder (ID = 6 cm, L = 20 cm) for 60 min/day for 15 consecutive days, while the control group did not receive stress. On the 8(th) day, blood samples were taken from the retro-orbital of both groups for corticosterone measurement (ELYSA method). After the F2 weight gained 20-25 g, their tendency for right-handedness or Left-handedness and response to the new environment was determined by T-maze and open field method, respectively. In addition, the effects of morphine, sulpiride and dextromethorphan on the animals' motor activity were studied. Results showed that plasma corticosterone level in the experimental group was elevated significantly with respect to the controls. In the off-springs, left-handedness was more frequent in both the male and female animals whose mothers experienced restrained stress. In the open field paradigm, however, the females of experimental group showed more activity compared to the others. While the females of the control group showed more response to morphine (50 mg/Kg), interestingly, both male and female animals in the experimental group showed hypo activity to morphine (0.5, 5, and 50 mg/Kg). Similarly, sulpiride (25 and 50 mg/Kg) reduced the animals' activity in both groups, while dextromethorphan did not cause any difference. In conclusion, it can be summarized that stress during the gestation period may change the response to the morphine-induced motor activity, in a sex-dependent manner.