Juvenile Female Rats Research Articles

H3K9 Acetylation of Tph2 Involved in Depression-like Behavior in Male, but not Female, Juvenile Offspring Rat Induced by Prenatal Stress

Increasing evidence has shown that prenatal stress (PS) could cause depression-like behavior in the offspring, which is sex-specific. However, the underlying mechanisms remain to be elucidated. This study is to investigate the involvement of tryptophan hydroxylase 2 (Tph2) H3K9 acetylation (H3K9ac) modification on PS-induced depression-like behavior in juvenile offspring rats (JOR). PS models were established, with or without trichostatin A (TSA) treatment. Animal behavior was assessed by the sucrose preference test (SPT) and forced swimming test (FST). The mRNA and protein expression levels of TPH2 in the dorsal raphenucleus (DRN), hippocampus, and prefrontal cortex were detected with quantitative real-time PCR and Western blot analysis, respectively. The Tph2 H3K9ac levels in the hippocampus were also analyzed. SPT and FST showed significantly reduced sucrose preference and significantly prolonged immobility in PS-induced male juvenile offspring rats (MJOR). Moreover, the mRNA and protein expression levels of TPH2 in the DRN and hippocampus were significantly declined, while the hippocampal Tph2 H3K9ac levels were significantly declined in the PS-induced MJOR. Furthermore, the PS-induced effects in MJOR could be reversed by the microinjection of TSA. However, no significant effects were observed for the female juvenile offspring rats (FJORs). In conclusion, our results showed that the Tph2 H3K9ac modification is only involved in PS-induced depression-like behavior in MJOR, in a sex-specific manner. These findings might contribute to the understanding of the disease pathogenesis and clinical treatment in future.

The Influence of Neonatal Pro-Inflammatory Stress on the Expression of Genes Associated with Stress in the Brains of Juvenile Rats: Septo-Temporal Specificity

We studied the long-term effects of neonatal pro-inflammatory stress (NPS) on the expression of corticoliberin and its receptors in the dorsal and ventral hippocampus of juvenile male and female rats. In the dorsal hippocampus of juvenile males, NPS increases the expression of corticoliberin mRNA. This effect is absent in females, where we found a tendency to an increase in the expression of CRHR2 receptor mRNA in the ventral hippocampus. Thus, NPS induces long-term changes in the expression of genes associated with stress, specifically in different parts of the hippocampus; these changes may be related the mechanism of “early programming” of the predisposition to depression and to the gender-related specificity of disease pathogenesis.

The effects of antipsychotics on the density of cannabinoid receptors in selected brain regions of male and female adolescent juvenile rats

Antipsychotic drugs have been increasingly prescribed to children and adolescents for treating various mental disorders, such as childhood-onset schizophrenia. The abnormality of endocannabinoid system is involved in the pathophysiology of these disorders in juveniles. This study investigated the effect of antipsychotics on the cannabinoid (CB) receptors in the brain of both male and female juvenile rats. The postnatal rats (PD23±1) were administered aripiprazole (1 mg/kg), olanzapine (1 mg/kg), risperidone (0.3 mg/kg) or vehicle (control) for 3 weeks. Quantitative autoradiography was used to investigate the binding densities of [3H]CP-55940 (an agonist for CB1R and CB2R) and [3H]SR141716A (a selective CB1R antagonist) in the rat brains. Risperidone significantly upregulated the [3H]CP55940 and [3H]SR141716A bindings in the prefrontal cortex (PFC), nucleus accumbens core (NAcC), nucleus accumbens shell (NAcS), cingulate cortex (Cg), and the caudate putamen (CPu) in male rats. Moreover, aripiprazole significantly elevated the [3H]SR141716A binding in the Cg and NAcS of female rats. Furthermore, there is an overall higher [3H]SR141716A binding level in the brain of female rats than male rats. Therefore, treatment with aripiprazole, olanzapine and risperidone could induce differential and gender specific effects on the binding density of cannabinoid receptors in the selected brain regions of childhood/adolescent rats.

Non-clinical assessment of safety and gadolinium deposition after cumulative administration of gadobenate dimeglumine (MultiHance®) to neonatal and juvenile rats

To determine the impact of single and cumulative doses of MultiHance on toxicity, pharmacokinetics, tissue gadolinium presence, behavior and neurological function in juvenile rats. Juvenile male and female rats received either physiological saline or MultiHance at 0.6, 1.25 or 2.5 mmol/kg bodyweight. Animals received either single or six consecutive MultiHance administrations and were sacrificed the day after the last administration or after a 60-day treatment-free period. Animals were assessed for behavior, cognitive function, grip strength, gait, pupillary reflex, and auditory reflex, as well as for physical development, sexual maturation and histopathology. Gadolinium presence in brain, femur, kidneys, liver and skin was determined using inductively coupled plasma-mass spectrometry (ICP-MS). No effects of MultiHance on behavior, cognitive function or any other parameter were noted, even for the highest administered cumulative dose (15 mmol/kg). Gadolinium presence was variable across tissues and decreased during the 60-day treatment-free period. The highest levels were noted in the femur and the lowest levels in the brain. Gadolinium presence in juvenile rat brain following single or repeated MultiHance administrations was minimal and non-impactful.

Developmental Exposure to Low Levels of Ethinylestradiol Affects Play Behavior in Juvenile Female Rats.

Juvenile social play contributes to the development of adult social and emotional skills in humans and non-human animals, and is therefore a useful endpoint to study the effects of endocrine disrupters on behavior in animal models. Ethinylestradiol (EE2) is a widely produced, powerful synthetic estrogen that is widespread in the environment mainly because is a component of the contraceptive pill. In addition, fetuses may be exposed to EE2 when pregnancy is undetected during contraceptive treatment. To understand whether exposure to EE2 during gestation or lactation affects social play, we exposed 72 female Sprague-Dawley rats to EE2 or vehicle either during gestation (gestation day (GD) 5 through GD 20) or during lactation (from postnatal day (PND) 1 through PND 21). Two doses of EE2 were used to treat the dams: a lower dose in the range of possible environmental exposure (4ng/kg/day) and a higher dose equivalent to that received during contraceptive treatment (400ng/kg/day). Behavioral testing was carried out between PND 40 and 45. A principal component analysis of frequencies of behavioral items observed during play sessions identified three main components: defensive-like play, aggressive-like play, and exploration. Aggressive-like play was significantly increased by both doses of EE2, and the gestational administration was in general more effective than the lactational one. Defensive-like play and exploration were not significantly affected by treatment. This research showed that low and very low doses of EE2 that mimic clinical or environmental exposure during development can affect important aspects of social behavior even during restricted time windows.

Juvenile female rats, but not male rats, show renewal, reinstatement, and spontaneous recovery following extinction of conditioned fear.

Anxiety disorders emerge early, and girls are significantly more likely to develop anxiety compared to boys. However, sex differences in fear during development are poorly understood. Therefore, we investigated juvenile male and female rats in the relapse behaviors following extinction of conditioned fear. In all experiments, 18-d-old rats first received three white-noise–footshock pairings on day 1. On day 2, extinction involved 60 white-noise alone trials. In experiment 1, we examined renewal by testing the rats in either the same or different context as extinction on day 3. Male rats did not show renewal, however, female rats showed renewal. Experiment 2 investigated reinstatement by giving rats either a mild reminder footshock or context exposure on day 3. When tested the next day, male rats did not show reinstatement, whereas female rats showed reinstatement. Experiment 3 investigated spontaneous recovery by testing the rats either 1 or 5 d following extinction. Male rats did not show any spontaneous recovery whereas female rats did. Taken together, fear regulation appear to be different in males versus females from early in development, which may explain why girls are more prone to suffer from anxiety disorders compared to boys.

Robust age, but limited sex, differences in mu-opioid receptors in the rat brain: relevance for reward and drug-seeking behaviors in juveniles

In the brain, the µ-opioid receptor (MOR) is involved in reward-seeking behaviors and plays a pivotal role in the mediation of opioid use disorders. Furthermore, reward-seeking behaviors and susceptibility to opioid addiction are particularly evident during the juvenile period, with a higher incidence of opioid use in males and higher sensitivity to opioids in females. Despite these age and sex differences in MOR-mediated behaviors, little is known regarding potential age and sex differences in the expression of MORs in the brain. Here, we used receptor autoradiography to compare MOR binding densities between juvenile and adult male and female rats. Age differences were found in MOR binding density in 12 out of 33 brain regions analyzed, with 11 regions showing higher MOR binding density in juveniles than in adults. These include the lateral septum, as well as sub-regions of the bed nucleus of the stria terminalis, hippocampus, and thalamus. Sex differences in MOR binding density were observed in only two brain regions, namely, the lateral septum (higher in males) and the posterior cortical nucleus of the amygdala (higher in females). Overall, these findings provide an important foundation for the generation of hypotheses regarding differential functional roles of MOR activation in juveniles versus adults. Specifically, we discuss the possibility that higher MOR binding densities in juveniles may allow for higher MOR activation, which could facilitate behaviors that are heightened during the juvenile period, such as reward and drug-seeking behaviors.

Neonatal infection produces significant changes in immune function with no associated learning deficits in juvenile rats

The current experiments examined the impact of early-life immune activation and a subsequent mild immune challenge with lipopolysaccharide (LPS; 25µg/kg) on hippocampal-dependent learning, proinflammatory cytokine expression in the brain, and peripheral immune function in juvenile male and female rats at P24, an age when hippocampal-dependent learning and memory first emerges. Our results indicate that neonatal infection did not produce learning deficits in the hippocampal-dependent context pre-exposure facilitation effect paradigm in juvenile males and females, contrary to what has been observed in adults. Neonatal infection produced an increase in baseline IL-1β expression in the hippocampus (HP) and medial prefrontal cortex (mPFC) of juvenile rats. Furthermore, neonatally infected rats showed exaggerated IL-1β expression in the HP following LPS treatment as juveniles; and juvenile females, but not males, showed exaggerated IL-1β expression in the mPFC following LPS treatment. Neonatal infection attenuated the production of IL-6 expression following LPS treatment in both the brain and the spleen, and neonatal infection decreased the numbers of circulating white blood cells in juvenile males and females, an effect that was further exacerbated by subsequent LPS treatment. Together, our data indicate that the consequences of neonatal infection are detectable even early in juvenile development, though we found no concomitant hippocampal-dependent learning deficits at this young age. These findings underscore the need to consider age and associated on-going neurodevelopmental processes as important factors contributing to the emergence of cognitive and behavioral disorders linked to early-life immune activation. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1221-1236, 2017.

Transgenerational Social Stress Alters Immune-Behavior Associations and the Response to Vaccination.

Similar to the multi-hit theory of schizophrenia, social behavior pathologies are mediated by multiple factors across generations, likely acting additively, synergistically, or antagonistically. Exposure to social adversity, especially during early life, has been proposed to induce depression symptoms through immune mediated mechanisms. Basal immune factors are altered in a variety of neurobehavioral models. In the current study, we assessed two aspects of a transgenerational chronic social stress (CSS) rat model and its effects on the immune system. First, we asked whether exposure of F0 dams and their F1 litters to CSS changes basal levels of IL-6, TNF, IFN-γ, and social behavior in CSS F1 female juvenile rats. Second, we asked whether the F2 generation could generate normal immunological responses following vaccination with Mycobacterium bovis Bacillus Calmette–Guérin (BCG). We report several changes in the associations between social behaviors and cytokines in the F1 juvenile offspring of the CSS model. It is suggested that changes in the immune–behavior relationships in F1 juveniles indicate the early stages of immune mediated disruption of social behavior that becomes more apparent in F1 dams and the F2 generation. We also report preliminary evidence of elevated IL-6 and impaired interferon-gamma responses in BCG-vaccinated F2 females. In conclusion, transgenerational social stress alters both immune–behavior associations and responses to vaccination. It is hypothesized that the effects of social stress may accumulate over generations through changes in the immune system, establishing the immune system as an effective preventative or treatment target for social behavior pathologies.

A high salt diet inhibits obesity and delays puberty in the female rat.

Background/ObjectivesProcessed foods are considered major contributors to the worldwide obesity epidemic. In addition to high sugar and fat contents, processed foods contain large amounts of salt. Due to correlations with rising adiposity, salt has recently been proposed to be obesogenic. This study investigated three hypotheses: i) high salt contributes to weight gain and adiposity in juvenile female rats, ii) puberty onset would be altered because salt is known to affect neuronal systems involved in activating the reproductive system, and iii) enhanced adiposity will act synergistically with salt to drive early puberty onset.DesignFemale weanling rats (post-natal day 21, n=105) were fed a low fat/low salt diet, low fat/high salt diet, high fat/low salt diet, or a high salt/high fat diet for 24 days. Metabolic measures, including weight gain, food intake, fecal output, activity, and temperature were recorded in subsets of animals.ResultsBody weight, retroperitoneal and perirenal fat pad weight, and adipocyte size were all lower in animals fed high fat/high salt compared to animals fed high fat alone. Leptin levels were reduced in high fat/high salt fed animals compared to high fat/low salt fed animals. Daily calorie intake was higher initially but declined with adjusted food intake and was not different among groups after 5 days. Osmolality and corticosterone were not different among groups. Fecal analysis showed excess fat excretion and a decreased digestive efficiency in animals fed high fat/low salt but not in animals fed high fat/high salt. Although respiratory exchange ratio was reduced by high dietary fat or salt, aerobic resting metabolic rate was not affected by diet. High salt delayed puberty onset, regardless of dietary fat content.ConclusionsSalt delays puberty and prevents the obesogenic effect of a high fat diet. The reduced weight gain evident in high salt fed animals is not due to differences in food intake or digestive efficiency.

Firing properties of pre‐inspiratory neurons are altered in female rats exposed to chronic intermittent hypoxia

Female rats submitted to chronic intermittent hypoxia (CIH) presented a reduced time of inspiration, sympathetic overactivity and hypertension. The increase in sympathetic nerve discharge in CIH‐female rats is associated to an increase in the inspiratory modulation of sympathetic activity. In this context, we hypothesized that inspiratory neurons at the brainstem have change their activity in CIH‐female rats, which in turn, modulates the presympathetic neurons producing an increase in sympathetic activity during inspiration. To test this hypothesis, juvenile female Wistar rats (P20–21) underwent intermittent hypoxia for 10 days. One day after CIH, we performed the extracellular single unit recordings of respiratory neurons at the ventral surface of the medulla using the ventral approach of the working heart‐brainstem preparation. All the experimental protocols were approved by the institutional ethical committee (#091/2013). Pre‐inspiratory neurons (Pre‐I/I) of CIH‐female rats (n=16) have reduced their firing frequency (58.3 ± 9 vs 107.6 ± 12Hz, p=0.0027) compared to Pre‐I/I neurons of control (n=15). Synaptic blockade demonstrated that Pre‐I/I neurons (n=3) have auto‐depolarization property. Ramp‐I, Early‐I and Late‐I neurons presented no changes in their firing properties after CIH. Regarding the expiratory neurons, post‐inspiratory neurons (Post‐I) have increased the firing time relative to duration of expiration (92.2 ± 2 vs 81.3 ± 3 % of total duration of expiration, p=0.0127) in CIH‐female rats (n=15) compared to control (n=17). We conclude that CIH produces a reduction in the activity of pacemaker Pre‐I/I neurons that could explain the reduced time of inspiration and the increase in inspiratory modulation of sympathetic activity in CIH‐female rats. These findings contribute to a better understanding of the respiratory network activity associated with sympathetic overactivity and hypertension in female rats exposed to CIH.Support or Funding InformationFapesp, CAPES and CNPq

Defensive burying as an ethological approach to studying anxiety: Influence of juvenile methamphetamine on adult defensive burying behavior in rats

The defensive burying test is an ethological approach that has both pharmacological and physiological validity in studying rodent anxiety-like behaviors. The defensive burying test measures the naturally occurring behavior of displacing bedding toward a noxious stimulus. Exposure to psychostimulants can alter anxiety behaviors in children and adults, however few studies have investigated the long-term effects of chronic juvenile stimulant exposure on anxiety behaviors in adulthood. Therefore, the current experiment tested the effects of juvenile methamphetamine exposure on defensive burying behavior in adulthood. Juvenile (PD20-34) male and female rats were either given intraperitoneal injections of 2.0mg/kg methamphetamine or saline or were not handled, and then all groups were left undisturbed until adulthood. As adults, rats’ anxiety-like behavior was assessed after exposure to a single shock probe in a defensive burying paradigm. Adult male rats that were exposed to methamphetamine as juveniles showed a significant increase in the latency to begin burying following the shock, indicative of decreased behavioral reactivity towards the shock. However, there were no other differences between treatment groups. Interestingly, there were no sex differences in any measure. These findings suggest that early exposure to the stimulant drug methamphetamine has limited effects on defensive burying behaviors when measured in adulthood. Defensive burying is an important ethological approach to assess rodent anxiety and can increase our understanding of coping behaviors in rodents following stimulant drug exposure.

Sex-Dependent Regulation of Aromatase-Mediated Synaptic Plasticity in the Basolateral Amygdala.

The basolateral amygdala (BLA) integrates sensory input from cortical and subcortical regions, a function that requires marked synaptic plasticity. Here we provide evidence that cytochrome P450 aromatase (AROM), the enzyme converting testosterone to 17β-estradiol (E2), contributes to the regulation of this plasticity in a sex-specific manner. We show that AROM is expressed in the BLA, particularly in the basolateral nucleus (BL), in male and female rodents. Systemic administration of the AROM inhibitor letrozole reduced spine synapse density in the BL of adult female mice but not in the BL of male mice. Similarly, in organotypic corticoamygdalar slice cultures from immature rats, treatment with letrozole significantly reduced spine synapses in the BL only in cultures derived from females. In addition, letrozole sex-specifically altered synaptic properties in the BL: in acute slices from juvenile (prepubertal) female rats, wash-in of letrozole virtually abolished long-term potentiation (LTP), whereas it did not prevent the generation of LTP in the slices from males. Together, these data indicate that neuron-derived E2 modulates synaptic plasticity in rodent BLA sex-dependently. As protein expression levels of AROM, estrogen and androgen receptors did not differ between males and females and were not sex-specifically altered by letrozole, the findings suggest sex-specific mechanisms of E2 signaling.SIGNIFICANCE STATEMENT The basolateral amygdala (BLA) is a key structure of the fear circuit. This research reveals a sexually dimorphic regulation of synaptic plasticity in the BLA involving neuronal aromatase, which produces the neurosteroid 17β-estradiol (E2). As male and female neurons in rodent BLA responded differently to aromatase inhibition both in vivo and in vitro, our findings suggest that E2 signaling in BLA neurons is regulated sex-dependently, presumably via mechanisms that have been established during sexual determination. These findings could be relevant for the understanding of sex differences in mood disorders and of the side effects of cytochrome P450 aromatase inhibitors, which are frequently used for breast cancer therapy.

Early Antipsychotic Treatment in Juvenile Rats Elicits Long-Term Alterations to the Dopamine Neurotransmitter System.

Prescription of antipsychotic drugs (APDs) to children has substantially increased in recent years. Whilst current investigations into potential long-term effects have uncovered some alterations to adult behaviours, further investigations into potential changes to neurotransmitter systems are required. The current study investigated potential long-term changes to the adult dopamine (DA) system following aripiprazole, olanzapine and risperidone treatment in female and male juvenile rats. Levels of tyrosine hydroxylase (TH), phosphorylated-TH (p-TH), dopamine active transporter (DAT), and D1 and D2 receptors were measured via Western blot and/or receptor autoradiography. Aripiprazole decreased TH and D1 receptor levels in the ventral tegmental area (VTA) and p-TH levels in the prefrontal cortex (PFC) of females, whilst TH levels decreased in the PFC of males. Olanzapine decreased PFC p-TH levels and increased D2 receptor expression in the PFC and nucleus accumbens (NAc) in females only. Additionally, risperidone treatment increased D1 receptor levels in the hippocampus of females, whilst, in males, p-TH levels increased in the PFC and hippocampus, D1 receptor expression decreased in the NAc, and DAT levels decreased in the caudate putamen (CPu), and elevated in the VTA. These results suggest that early treatment with various APDs can cause different long-term alterations in the adult brain, across both treatment groups and genders.

Inspiratory modulation of sympathetic activity is increased in female rats exposed to chronic intermittent hypoxia.

What is the central question of the study? There are sex differences in the respiratory network and in the regulation of arterial blood pressure. Female rats develop hypertension after chronic intermittent hypoxia (CIH). In this context, we evaluated the respiratory-related mechanism underlying the development of hypertension in CIH-exposed female rats. What is the main finding and its importance? Female rats exposed to CIH develop changes in the respiratory pattern related to inspiration and sympathetic overactivity phase locked to the inspiratory phase of the respiratory cycle, which is different from CIH-exposed male rats. These data suggest a specific respiratory mechanism for sympathetic overactivity in hypertensive CIH-exposed female rats. Chronic intermittent hypoxia (CIH) induces sympathetic overactivity and hypertension in male rats. Enhanced respiratory modulation of sympathetic activity in juvenile male rats exposed to CIH occurs in the expiratory phase of the respiratory cycle, characterizing changes in respiratory-sympathetic coupling. Different from other experimental models of hypertension, CIH induces an increase in arterial pressure in adult female rats similar to that observed in male rats. However, the mechanisms underlying the hypertensive phenotype in CIH-exposed female rats remain to be elucidated. Moreover, several lines of evidence have documented sex differences in respiratory network activity in response to hypoxia. Considering that CIH-exposed male rats present an increase in the respiratory modulation of sympathetic activity and there are sex differences in the respiratory network, we hypothesized that CIH-exposed female rats develop an increase in the respiratory modulation of sympathetic activity different from CIH-exposed male rats. In this study, we investigated sympathetic and respiratory activities in juvenile female rats exposed to CIH using an in situ working heart-brainstem preparation. The CIH-exposed female rats developed changes in the respiratory pattern and changes in the respiratory-sympathetic coupling marked by sympathetic overactivity phase locked to inspiration, which was different from male rats exposed to CIH. This study revealed a specific respiratory-related mechanism for sympathetic overactivity linked to inspiration that explains, at least in part, the hypertensive phenotype in female rats exposed to CIH.

Early antipsychotic exposure affects serotonin and dopamine receptor binding density differently in selected brain loci of male and female juvenile rats.

Antipsychotic drugs (APDs) were developed to treat schizophrenia in adults; however they have been increasingly prescribed (mostly "off-label") for children and adolescents. This study aimed to investigate the effects of aripiprazole, olanzapine and risperidone on the binding of serotonin (5-HT) and dopamine receptors in juvenile rat brain regions that are involved in antipsychotic efficacy. Male and female rats were treated orally with aripiprazole (1mg/kg), olanzapine (1mg/kg), risperidone (0.3mg/kg) or vehicle 3 times/day starting from postnatal day 23 (±1day) for 20 days. Quantitative autoradiography was performed to examine the receptor binding densities. Olanzapine significantly decreased 5-HT2A (5-HT2AR) and 5-HT2C receptor (5-HT2CR) binding in the prefrontal cortex (PFC), cingulate cortex (Cg) and nucleus accumbens (NAc) of both male and female rats. In the caudate putamen (CPu), olanzapine attenuated 5-HT2AR binding in both genders, and reduced 5-HT2CR binding in male rats. Olanzapine increased D2 receptor (D2R) binding in the NAcS of male rats, but decreased it in females. Olanzapine increased D1 receptor (D1R) binding in the Cg, while aripiprazole decreased D1R binding in the PFC of males. Aripiprazole significantly reduced 5-HT2AR binding in the male PFC. Risperidone decreased 5-HT2AR binding in the PFC of female rats, while attenuating D1R binding in the PFC and Cg of males. However, APDs have no effects on the binding of serotonin and dopamine transporters. This study revealed that aripiprazole, olanzapine and risperidone affected 5-HT2AR, 5-HT2CR, 5-HTT, D1R and D2R bindings differently in the brains of juvenile male and female rats.

Age and sex differences in oxytocin and vasopressin V1a receptor binding densities in the rat brain: focus on the social decision-making network

Oxytocin (OT) and vasopressin (AVP) regulate various social behaviors via activation of the OT receptor (OTR) and the AVP V1a receptor (V1aR) in the brain. Social behavior often differs across development and between the sexes, yet our understanding of age and sex differences in brain OTR and V1aR binding remains incomplete. Here, we provide an extensive analysis of OTR and V1aR binding density throughout the brain in juvenile and adult male and female rats, with a focus on regions within the social decision-making network. OTR and V1aR binding density were higher in juveniles than in adults in regions associated with reward and socio-spatial memory and higher in adults than in juveniles in key regions of the social decision-making network and in cortical regions. We discuss possible implications of these shifts in OTR and V1aR binding density for the age-specific regulation of social behavior. Furthermore, sex differences in OTR and V1aR binding density were less numerous than age differences. The direction of these sex differences was region-specific for OTR but consistently higher in females than in males for V1aR. Finally, almost all sex differences in OTR and V1aR binding density were already present in juveniles and occurred in regions with denser binding in adults compared to juveniles. Possible implications of these sex differences for the sex-specific regulation of behavior, as well potential underlying mechanisms, are discussed. Overall, these findings provide an important framework for testing age- and sex-specific roles of OTR and V1aR in the regulation of social behavior.

PM364. Early risperidone exposure affects serotonin, dopamine and cannabinoid receptors binding density differently in male and female juvenile rats

PM364. Early risperidone exposure affects serotonin, dopamine and cannabinoid receptors binding density differently in male and female juvenile rats

Changes in the Firing Frequency of Medullary Respiratory Neurons of Juvenile Female Rats Exposed to Chronic Intermittent Hypoxia

Juvenile female rats exposed to chronic intermittent hypoxia (CIH) presented a significant reduction in the time of inspiration and increase in sympathetic activity during this phase of respiratory cycle, characterizing changes in the respiratory‐sympathetic coupling. There is evidence that the firing frequency of the pre‐sympathetic neurons is modulated by the respiratory neurons activity. In this context, we hypothesized that: in CIH‐female rats, the enhanced sympathetic activity during inspiration is due to the increased inspiratory neurons activity that modulates the pre‐sympathetic neurons firing frequency. We aimed to evaluate the respiratory neurons activity in the ventral surface of the medulla in juvenile female rats exposed to CIH. For this purpose, juvenile female rats (P20–21) were exposed to CIH (FiO2=6%) for 10 days and after this protocol we performed extracellular single unit recordings of medullary respiratory neurons using the working heart‐brainstem preparation (ventral approach). The respiratory neurons were identified and classified by their activity (firing frequency) in relation to the phrenic nerve activity. All experimental protocols were approved by the institutional ethical committee (#091/2013). Pre‐inspiratory/Inspiratory (Pre‐I/I) neurons of CIH‐female rats (n=12) presented a reduced firing frequency (39.3 ±5 vs 61.5 ±8 Hz, p=0.027) when compared to control (n=10). Ramp‐I, Post‐I and Aug‐E neurons presented no significant changes in their firing frequency in CIH‐female rats compared to control. We concluded that Pre‐I/I neurons presented a reduced firing frequency in CIH‐female rats, which may explain the reduced time of inspiration.Support or Funding InformationFAPESP, CAPES and CNPq.

Natural and synthetic vocalizations of brown rat pups, Rattus norvegicus, enhance attractiveness of bait boxes in laboratory and field experiments.

Rats are often neophobic and thus do not readily enter trap boxes which are mandated in rodent management to help reduce the risk of accidental poisoning or capture of non-target animals. Working with brown rats, Rattus norvegicus, as a model species, our overall objective was to test whether sound cues from pups could be developed as a means to enhance captures of rats in trap boxes. Recording vocalizations from three-day-old pups after removal from their natal nest with both sonic and ultrasonic microphones revealed frequency components in the sonic range (1.8-7.5 kHz) and ultrasonic range (18-24 kHz, 33-55 kHz, 60-96 kHz). In two-choice laboratory bioassays, playback recordings of these vocalizations induced significant phonotactic and arrestment responses by juvenile, subadult and adult female and male rats. The effectiveness of engineered 'synthetic' rat pup sounds was dependent upon their frequency components, sound durations and the sound delivery system. Unlike other speakers, a piezoelectric transducer emitting sound bursts of 21 kHz with a 63-KHz harmonic, and persisting for 20-300 ms, proved highly effective in attracting and arresting adult female rats. In a field experiment, a battery-powered electronic device fitted with a piezoelectric transducer and driven by an algorithm that randomly generated sound cues resembling those recorded from rat pups and varying in fundamental frequency (19-23 kHz), duration (20-300 ms) and intermittent silence (300-5000 ms) significantly enhanced captures of rats in trap boxes baited with a food lure and soiled bedding material of adult female rats. Our study provides proof of concept that rat-specific sound cues or signals can be effectively reproduced and deployed as a means to enhance capture of wild rats. © 2016 Society of Chemical Industry.