Rats In Estrus Research Articles

Comparison of pain modulatory effect of the LPGi estragon receptor on inflammatory pain between pro-estrus and estrus phases and OVX rats.

The present study has investigated whether circulating estrogen level variations in the pro-estrus and estrus phases of the intact rats and estrogen depletion in the ovariectomized animals (OVX) adjust the formalin-induced nociceptive behaviors. During the pro-estrus and estrus phases of rats' estrus cycle and in the OVX rats, 17β-estradiol and ICI 182,780 (estrogen receptor antagonist) were administered into the right paragigantocellularis lateralis (LPGi) nucleus. Then, the formalin-induced flexing and licking responses were recorded for 60min. The findings of this study revealed that intra-LPGi administration of 17β-estradiol (0.8μmol) reduced the formalin-induced flexing and licking duration in pro-estrus and estrus rats (P < 0.001), suggesting an analgesic effect. 17β-Estradiol injection into the LPGi nucleus of OVX rats increased the flexing duration (P < 0.05) while decreasing the licking duration (P < 0.05) of the formalin test. The pain modulatory effect of 17β-estradiol on the flexing response was reversed by ICI 182,780 (15nmol) in the pro-estrus (P < 0.001) and estrus rats (P < 0.001) but not in the OVX rats. Also, pretreatment of LPGi nucleus with ICI 182,780 reversed the analgesic effect of 17β-estradiol on the licking response in the pro-estrus (P < 0.05), estrus (P < 0.001), and OVX rats (P < 0.001). These results suggest that the pain threshold in intact female rats is modulated independently of the estrus state. Still, the basal level of plasma estrogen and the activation of its receptors are necessary for pain modulation.

Infrared Thermal Imaging during the Estrous Cycle in Adult Wistar Rats.

The collection and examination method of vaginal smears is the standard for the determination of ovulation or phases of the estrous cycle of rodents used in research. However, this method is time consuming and may not be amenable to continual monitoring of a large number of animals. Infrared thermography has recently emerged as a noninvasive technique that requires relatively little handling of animals. The body temperature of rodents has been shown to correlate with the ocular surface temperature. This study aimed to evaluate the use of thermographic monitoring of the ocular surface for the identification of estrus in rats. Vaginal smears were collected from female Wistar rats (n = 22) for 14 consecutive days. Core body temperature was estimated by measuring ocular surface temperature using a thermal camera; vaginal temperature was measured using a digital thermometer. Average temperatures were calculated for each rat for each phase of the estrous cycle. The highest core body and vaginal temperature were measured during the estrus phase (37.2 ± 0.6 °C and 37.7 ± 0.6 °C, respectively). The temperatures then fell as the rat entered the diestrus phase (36.8 ± 0.5 °C and 37 ± 0.5 °C). The core body temperature was positively correlated with vaginal temperature (r = 0.697, P < 0.001). In conclusion, thermography is a less invasive method of determining estrus in rats as compared with vaginal smear collection. However, thermography is less accurate and requires at least a 12-d period of measurement.

Pharmacologic blockade of nicotinic receptors in the suprachiasmatic nucleus increases ovarian atresia and inhibits follicular growth.

Reproduction in all mammalian species depends on the growth and maturation of ovarian follicles, that is, folliculogenesis. Follicular development can culminate with the rupture of mature follicles and the consequent expulsion of their oocytes (ovulation) or in atresia, characterized by the arrest of development and eventual degeneration. These processes are regulated by different neuroendocrine signals arising at different hypothalamic nuclei, including the suprachiasmatic nucleus (SCN). In the later, the activation of muscarinic receptors (mAChRs) and nicotinic receptors (nAChRs) by acetylcholine is essential for the regulation of the pre-ovulatory signals that stimulate the rupture of mature follicles. To evaluate the participation of the nAChRs in the SCN throughout the oestrous cycle in the regulation of the hypothalamic-pituitary-ovarian axis. For this purpose, 90-day-old adult female rats in metoestrus, dioestrus, proestrus or oestrus were microinjected into the left- or right-SCN with 0.3 μL of saline solution as vehicle or with 0.225 μg of mecamylamine (Mec), a non-selective antagonist of the nicotinic receptors, diluted in 0.3 μL of vehicle. The animals were sacrificed when they presented vaginal cornification, indicative of oestrus stage, and the effects of the unilateral pharmacological blockade of the nAChRs in the SCN on follicular development, ovulation and secretion of oestradiol and follicle-stimulating hormone (FSH) were evaluated. The microinjection of Mec decreased the serum levels of FSH, which resulted in a lower number of growing and healthy follicles and an increase in atresia. The higher percentage of atresia in pre-ovulatory follicles was related to a decrease in the number of ova shed and abnormalities in oestradiol secretion. We also detected asymmetric responses between the left and right treatments that depended on the stage of the oestrous cycle. The present results allow us to suggest that during all the stages of the oestrous cycle, cholinergic signals that act on the nAChRs in the SCN are pivotal to modulate the secretion of gonadotropins and hence the physiology of the ovaries. Further research is needed to determine if such signals are generated by the cholinergic neurons in the SCN or by cholinergic afferents to the SCN.

Gonadotropic Activity of Pituitary Extract of African Catfish, Clarias gariepinus, in Mammals using Immature Wistar Rats as Models.

The pituitary glands normally produce and stores gonadotropic hormones (GnH) that are responsible for ovulation and spermiation in animals. However, whether fish pituitary extracts can elicit same effects in treated animals need elucidation as a prelude to their practical usage in animals. The aim of this study was to investigate the oestrus-inducing potential of the pituitary gland extract of the Africa Catfish (Clarias gariepinus) in immature Wistar rats. The experiment involved the use of 18 immature female Wistar rats and 10 male catfish brood stocks with the use of six Wistar rats per groups as follows: Group A had human chorionic gonadotropin (hCG) treatment. Group B had only normal saline treatment as the control whereas Group C had the C. gariepinus pituitary extract administration to induce oestrus with treatments occurring twice six hours apart in each group. There was an obvious expression of visible signs of heat and the presence of uterine horn oedema with significant (p < 0.05) increase in reproductive tract weight and uterine width and length. However, only progesterone levels increased significantly (p < 0.05) in the hCG and the C. gariepinus pituitary extract treated groups compared to other assayed hormones. These results showed that C. gariepinus pituitary extract has the capacity to induce oestrus in Wistar rats because of its gonadotropic effects, which needs further investigations at higher doses and for longer exposure periods for possible oestrus induction and synchronization in higher mammals. Further favourable results could herald the possible patent of the catfish pituitary extract for either experimental or commercial use in mammals.

Transplantation of the Uterus in the Male Rat.

Uterus transplantation (UTx) is one of the potential methods to cure absolute uterine factor infertility of transgender. However, this mostly comes with many technological challenges. Left inguinal UTx was performed in 13 castrated male rats. End-to-end anastomosis of donor common iliac vessels to recipient femoral vessels was used for transsexual UTx. Sampling was performed on day 30 after transplantation. Grafts were used to analyze the histological changes. TUNEL assay was applied to stain the apoptotic cells. Immunological rejection was judged by flow cytometry. Six uteri, 4 ovaries, and 4 upper vaginas were found at day 30 posttransplantation. Similar histological changes to proestrus, estrus, and diestrus of female rats were examined in the transplanted uteri. The histological changes of transplanted vaginas showed similarity to proestrus, estrus, and metestrus of the female rats. Follicles of different stages and corpus luteum with distinct morphological appearances were also observed. The TUNEL assay revealed a higher apoptosis of granulosa cells in transplanted ovaries compared with normal ovaries. A rat model of transsexual unilateral inguinal uterine transplantation in castrated rats was established, which will provide a reference for bilateral transsexual UTx in animals and genetically 46 XY individuals who wish to become real women through transsexual UTx.

Sex differences in the effects of mild traumatic brain injury and progesterone treatment on anxiety-like behavior and fear conditioning in rats

Mild traumatic brain injuries (mild TBIs) commonly occur in young adults of both sexes, oftentimes in high-stress environments. In humans, sex differences have been observed in the development of post-concussive anxiety and PTSD-like behaviors. Progesterone, a sex steroid that has neuroprotective properties, restores cognitive function in animal models following more severe TBI, but its effectiveness in preventing the psychological symptoms associated with mild TBI has not been evaluated. Using a model of mild TBI that pairs a social stressor (social defeat) with weight drop, male and naturally estrous-cycling female rats were treated with 4 mg/kg progesterone or vehicle once daily for 5 days after injury. Behavioral measures, including elevated plus maze (EPM), contextual fear conditioning, and novel object recognition (NOR) were assessed following progesterone treatment. Anxiety-like behavior was increased by mild TBI in male rats, with a smaller effect seen in female rats in the diestrus phase at the time of EPM testing. In contrast, mild TBI impaired fear learning in female rats in estrus at the time of fear acquisition. Progesterone treatment failed to attenuate post-mild TBI anxiety-like behavior in either sex. Furthermore, progesterone increased fear conditioning and impaired NOR discrimination in male rats, independent of TBI status. Overall, both sex and estrous cycle contributed to psychological outcomes following mild TBI, which were not ameliorated by post-TBI progesterone. This suggests sex steroids play an important role as a moderator of the expression of mild TBI-induced psychological symptoms, rather than as a potential treatment for their underlying etiology.

Estrous cycle impacts on dendritic spine plasticity in rat nucleus accumbens core and shell and caudate-putamen.

An important factor that can modulate neuron properties is sex-specific hormone fluctuations, including the human menstrual cycle and rat estrous cycle in adult females. Considering the striatal brain regions, the nucleus accumbens (NAc) core, NAc shell, and caudate-putamen (CPu), the estrous cycle has previously been shown to impact relevant behaviors and disorders, neuromodulator action, and medium spiny neuron (MSN) electrophysiology. Whether the estrous cycle impacts MSN dendritic spine attributes has not yet been examined, even though MSN spines and glutamatergic synapse properties are sensitive to exogenously applied estradiol. Thus, we hypothesized that MSN dendritic spine attributes would differ by estrous cycle phase. To test this hypothesis, brains from adult male rats and female rats in diestrus, proestrus AM, proestrus PM, and estrus were processed for Rapid Golgi-Cox staining. MSN dendritic spine density, size, and type were analyzed in the NAc core, NAc shell, and CPu. Overall spine size differed across estrous cycle phases in female NAc core and NAc shell, and spine length differed across estrous cycle phase in NAc shell and CPu. Consistent with previous work, dendritic spine density was increased in the NAc core compared to the NAc shell and CPu, independent of sex and estrous cycle. Spine attributes in all striatal regions did not differ by sex when estrous cycle was disregarded. These results indicate, for the first time, that estrous cycle phase impacts dendritic spine plasticity in striatal regions, providing a neuroanatomical avenue by which sex-specific hormone fluctuations can impact striatal function and disorders.

Superior mesenteric ganglion via ovarian plexus nerve involved in the cross-talk between noradrenaline and GnRH in rat ovaries

There is evidence of the existence of an intraovarian gonadotropin-releasing hormone (GnRH) system. There are also reports about the influence of extrinsic ovarian innervation in gonadal function. Therefore, it is interesting to study the relationship between ovarian sympathetic innervation and GnRH to shed light on possible physiological and pathophysiological implications. This work aimed to investigate whether noradrenergic stimulation of the superior mesenteric ganglion (SMG) can modify the levels of ovarian GnRH and cause functional and morphological changes in the gonad through the ovarian plexus nerve (OPN), during estrus and diestrus II in rats. The SMG-OPN-Ovary system and an ovary without extrinsic innervation were removed from Holtzman rats in estrus and diestrus II stages and placed in specially designed cuvettes containing Krebs-Ringer buffer. In the experimental groups, SMGs and denervated ovaries were stimulated with 10−6 M noradrenaline (NA). GnRH and progesterone levels (in the ovarian incubation medium) and the mRNA expression of 3beta-hydroxysteroid dehydrogenase (Hsd3b3), 20alpha-hydroxysteroid dehydrogenase (Akr1c18), Bax, and Bcl2 were analyzed. Histological studies of the ovaries were performed. In estrus, NA decreased GnRH levels in both experimental schemes. Furthermore, progesterone levels increased while the Akr1c18 expression and Bax/Bcl2 ratio decreased, without causing changes in ovarian morphology. In diestrus, the noradrenergic stimulation of the ganglion increased GnRH levels, decreased progesterone levels, and increased Akr1c18 expression and Bax/Bcl2 ratio. Follicles with histoarchitecture alterations and corpus luteum with signs of cell death were observed. In denervated ovaries, NA increased the levels of GnRH and progesterone. Furthermore, NA decreased the Bax/Bcl2 ratio and histological studies revealed signs compatible with a possible atretogenic effect. In conclusion, noradrenergic stimulation of the SMG-OPN pathway regulates ovarian cyclicity. The SMG modulates the cross-talk between NA and ovarian GnRH, protecting the ovary from atretogenic effects and luteal apoptosis during estrus while inducing luteal regression in the diestrus II.

Characterization, Phytochemical Screening of Phyllanthus emblica L. Fruit Nanoherbal and Determination of the Estrus Cycle of Female Rats

One of a plant that is thought to have quite high antioxidant activity is kemloko (Phyllanthus emblica L.). This plant is a material that is often used by the community as a traditional medicine. This plant in India has been used to treat cancer, diabetes, liver (liver), heart problems and anemia. This biological activity is thought to be caused by the presence of bioactive compounds from secondary metabolites contained therein, especially compounds from the phenolic and flavonoid groups. The short length of the estrus cycle of rats makes them ideal for investigation of changes occurring during the reproductive cycle. The estrus cycle lasts four days and is characterized as: proestrus, estrus, metestrus and diestrus, which may be determined according to the cell types observed in the vaginal smear. Since the collection of vaginal secretion and the use of stained material generally takes some time, the aim of the present work was to provide researchers with some helpful considerations about the determination of the rat estrus cycle phases in a fast and practical way. This study began with macroscopic examination, examination of water content, examination of water-soluble extract levels, examination of ethanol-soluble extracts, examination of total ash content, and also an examination of acid-insoluble ash levels, phytochemical screening of Phyllanthus emblica L. fruit nanoherbal and determination of the estrus cycle of female rats. The results of phytochemical screening showed that the compound of Phyllanthus emblica L. Fruit nanoherbal contained a class of secondary metabolites of alkaloids, flavonoids, tannins, saponins, steroids/triterpenoids, and glycosides. And the estrus cycle of female rats can be determined by observing changes in vaginal epithelial cells.

ODP428 The Effects of Asprosin Pubertal Maturation in Female Rats

Abstract Adipokines play an important role in sexual maturation and reproduction in a variety of ways. The central Asprosin administration of asprosin, a new adipokine secreted by white adipose tissue, has been found to have the potential to stimulatory effects influence on the hypothalamus-pituitary-gonadal axis (HPG)pubertal maturation in male rats. However, there is no study on the effects of asprosin on the HPG axis. Interestingly, peri-ovarian adipose tissues, which surround the ovaries and perform both autocrine and paracrine functions, suggest that asprosin may have a role in ovarian function. Asprosin has been also shown to cross the blood-brain barrier. However, the effects of asprosin, a novel adipokine, are not fully defined on the hypothalamus-pituitary-gonadal axis at the peripheral levels. The aim of the research study aims is to see how asprosin affects pubertal maturation in female rats when it is given parentally. For the experimental studies, totally a total of 24 female Sprague-Dawley rats, 21 days old and 35 ± 2 g weight, were used and randomly divided into two groups as control and asprosin groups (n=12). Asprosin (500 ng/kg) was given intraperitoneally daily in the animals in the asprosin group from postnatal day 21 for about 8 weeks. Similarly, the control group received only saline. For determining the puberty onset, vaginal opening (complete canalization of the vagina, an external index of puberty onset) was monitored daily in rats. Vaginal smears were performed daily from the date of puberty onset to determine the day of the first estrus. The ELISA method is used to analyze hormones in blood samples. Asprosin administration did not affect the onset of puberty or pubertal weight compared to the control group (p&amp;gt;0. 05). The first day of estrus in female rats administered with asprosin was shown to be significantly earlier than control rats (p&amp;lt;0. 05). Asprosin administration significantly increased the levels of FSH, oxytocin, and estradiol in the blood(p&amp;lt;0. 05). It significantly decreased inhibin B level (p&amp;lt;0. 05). There was no significant difference in LH level (p&amp;gt;0. 05). In conclusion, our findings suggest that asprosin may have stimulatory effects on pubertal maturation of the reproductive system in female rats. However, we believe that more research is needed to determine the mechanism by which asprosin affects the pubertal maturation of the reproductive system. This study was supported by TUBITAK (Project# 220S744). Presentation: No date and time listed

Expression of phoenixin-14 and nesfatin-1 in the hypothalamo–pituitary–gonadal axis in the phases of the estrous cycle

Phoenixin-14 (PNX-14) and nucleobindin 2 (NUCB2)/nesfatin-1 are regulatory neuropeptides expressed in the hypothalamus. These neuropeptides can be effective in hormonal regulation of the hypothalamo–pituitary–gonadal (HPG) axis and reproductive functions. In the present study, the distribution of PNX-14 and NUCB2/nesfatin-1 in the hypothalamus, pituitary, ovary, and uterus tissues during the phases of the estrous cycle in female rats was investigated. Eighteen Wistar Albino rats determined among animals showing regular estrous cycle by vaginal smear method were divided into three groups: proestrus (Group I), estrus (Group II) and diestrus (Group III). Serum gonadotropin-releasing hormone (GnRH), plasma PNX-14, and NUCB2/nesfatin-1 concentrations were the highest, moderate, and lowest in estrus, diestrus, and proestrus phases, respectively. PNX-14 immunoreactivity in the supraoptic and arcuate nuclei of the hypothalamus and NUCB2/nesfatin-1 immunoreactivity in the paraventricular nuclei were particularly evident in the estrus phase. These neuropeptide immunoreactivities were decreased in different cells of anterior pituitary during proestrus compared with those during estrus and diestrus. PNX-14 immunoreactivity in the ovary, especially during the estrus phase, was diffuse and intense in the granulosa and luteal cells and oocytes, and it was few and weak in theca cells. In addition, NUCB2/nesfatin-1 immunoreactivity was abundant and strong in granulosa and luteal cells, theca and interstitial cells, and oocytes during estrus. In the estrus phase, PNX-14 immunoreactivity was strong in the glandular epithelial cells and stromal cells of the endometrium, also NUCB2/nesfatin-1 immunoreactivity was strong in the epithelial and glandular epithelial cells. As a result, when the estrous cycle was evaluated, it was concluded that the changes in the distribution of PNX-14 and NUCB2/nesfatin-1 at all phases were related to GnRH and that these neuropeptides showed the highest immunoreactivity especially in the HPG axis and uterus tissues of estrus rats.

Uterine Microvascular Dysfunction After Plastic Particle Inhalation

Adverse cardiovascular and inflammatory outcomes after airborne particulate matter (PM) inhalation have long been a topic of epidemiological studies. Previous studies have identified, the microcirculation as particularly vulnerable to this insult. However, the mechanisms of microvascular dysfunction are complex and vary with each specific aerosol. Variations in neurohormonal and inflammatory status contribute to the complexity of defining mechanisms of microvascular dysfunction caused by aerosols. Given the recent identification and toxicological concerns surrounding micro‐ and nanoplastic exposures, we aimed to evaluate microvascular reactivity after acute plastic particle inhalation in this study. Virgin female Sprague Dawley rats in estrus were exposed to filtered air or aerosolized polyamide (i.e., nylon) particles in a whole‐body inhalation chamber. We hypothesized the uterine microvascular reactivity would achieve a vasoconstrictive state due to plastic particle inhalation. Exposure only during estrus served to control for neurohormonal differences within groups. 24h later, the radial arteriole of the uterus was selected as a representative vessel for the microcirculation. Ex vivouterine radial arteriole reactivity was assessed using pressure myography Living Systems Instrumentation, St. Albans, VT). Vascular reactivity was assessed based on responses to endothelium‐dependent (methacholine, MCh, 10‐9‐10‐4 M), –independent (sodium nitroprusside, SNP, 10‐9‐10‐4 M), and smooth muscle contractility (phenylephrine, PE, 10‐9‐10‐4 M). Inflammatory cytokines (IL‐4, IL‐6, MCP‐1, CXCL1; Sigma, St. Louis, MO and IL 5; Abcam, Cambridge, UK) were quantified in plasma with ELISA. Acute inhalation exposure to polyamide MNPs led to significantly impaired vascular reactivity through endothelium‐dependent and vascular smooth muscle mechanisms. Percent maximum dilation in response to 10‐9 M MCh was significantly reduced in exposed animals when compared to controls (‐9.44% ± 3.65 vs. 7.26% ± 4.61). Smooth muscle contraction was also impaired with percent maximum dilation in response to 10‐8 M PE being significantly increased in exposed animals compared to controls (‐9.56%±7.28 vs. ‐59.7±17.4). The levels of IL‐6 were not significant between groups which suggests systemic inflammation may not be a key component of plastic aerosol induced vascular dysfunction. In summary, exposure to polyamide MNPs resulted in less vascular reactivity to pharmacologic stimuli during estrus. However, the mechanisms attributing to disrupted microvascular function remain elusive. An important consideration for future studies will be the proper time point in which various cytokines can be assessed and the reproductive ramifications of these findings. Future studies should examine the impact of plastic particulate inhalation on endothelial inflammatory activation, metabolism, or apoptotic mechanisms. Altogether this information may give insight into how plastic particle inhalation could impair distal tissue health, including endometrial perfusion and ability to sustain pregnancy.

Estrogen modulation of the pronociceptive effects of serotonin on female rat trigeminal sensory neurons is timing dependent and dosage dependent and requires estrogen receptor alpha.

The role of the major estrogen estradiol (E2) on orofacial pain conditions remains controversial with studies reporting both a pronociceptive and antinociceptive role of E2. E2 modulation of peripheral serotonergic activity may be one mechanism underlying the female prevalence of orofacial pain disorders. We recently reported that female rats in proestrus and estrus exhibit greater serotonin (5HT)-evoked orofacial nocifensive behaviors compared with diestrus and male rats. Further coexpression of 5HT 2A receptor mRNA in nociceptive trigeminal sensory neurons that express transient receptor potential vanilloid 1 ion channels contributes to pain sensitization. E2 may exacerbate orofacial pain through 5HT-sensitive trigeminal nociceptors, but whether low or high E2 contributes to orofacial pain and by what mechanism remains unclear. We hypothesized that steady-state exposure to a proestrus level of E2 exacerbates 5HT-evoked orofacial nocifensive behaviors in female rats, explored the transcriptome of E2-treated female rats, and determined which E2 receptor contributes to sensitization of female trigeminal sensory neurons. We report that a diestrus level of E2 is protective against 5HT-evoked orofacial pain behaviors, which increase with increasing E2 concentrations, and that E2 differentially alters several pain genes in the trigeminal ganglia. Furthermore, E2 receptors coexpressed with 5HT 2A and transient receptor potential vanilloid 1 and enhanced capsaicin-evoked signaling in the trigeminal ganglia through estrogen receptor α. Overall, our data indicate that low, but not high, physiological levels of E2 protect against orofacial pain, and we provide evidence that estrogen receptor α receptor activation, but not others, contributes to sensitization of nociceptive signaling in trigeminal sensory neurons.

The role of perinatal testosterone on exploratory behavior, sexual motivation, and spatial working memory in adult rats

Aim: Sex differentiation occurs during the perinatal period (four days before and after birth) in the rat brain. The brain remains a female brain unless exposed to testosterone, which gets metabolized to 17β-estradiol and dihydrotestosterone. While aromatase converts testosterone to 17β-estradiol, 5α-reductase converts testosterone to dihydrotestosterone. 17β-estradiol exerts its effects by binding to an estrogen receptor, whereas dihydrotestosterone via an androgen receptor. The role of dihydrotestosterone and 17β-estradiol during the organizational phase of brain differentiation was tested using adult rat behaviors. The study sought to examine the effects of perinatal manipulations on adult rat behaviors. Materials and methods: Timed-pregnant rats received either the vehicle (5% ethanol and 95% sesame oil), exemestane (4 mg/kg/ml; aromatase inhibitor), or flutamide (20 mg/kg/ml; androgen receptor blocker) subcutaneously during the last four days of pregnancy. Pups from each group continued to receive their treatments during the first four days after birth. From postnatal day 65, these animals were subjected to open field, sexual motivation, and spatial working memory tests. Results: Male rats receiving flutamide exhibited exploratory behavior significantly more compared to exemestane and control groups. Male rats receiving exemestane had substantially higher plasma testosterone and displayed an increased interest in the estrus rat than the control and flutamide group. Conclusion: Androgen receptor blockade resulted in increased exploratory behavior in male rats where 17β-estradiol was testosterone's primary metabolite. The blocking of aromatase using exemestane resulted in higher levels of plasma testosterone and enhanced sexual motivation in male rats. Thus, 17β-estradiol and dihydrotestosterone's presence during the organizational phase is essential for normal socio-sexual and exploratory behaviors.

Acute LPS exposure increases synaptosomal metabolism during estrus but not diestrus

The hormones estrogen and progesterone alter physiological functions, including the estrus cycle and relevant neurological and synaptic activity. Here, we determined the extent to which estrus cycle stage interacts with an inflammatory stimulus, lipopolysaccharide (LPS), to alter synaptic mitochondrial respiration in female rats. LPS elevated synaptic mitochondrial respiration of rats in estrus, but not diestrus. Likewise, estrogen concentration correlated with multiple respiratory metrics in LPS treated females in estrus. These data suggest estrogen likely modulates synaptic mitochondrial respiration in a high progesterone environment.

Administration of a VIP-antagonist in vivo modifies ovarian hormone secretion in a rat model with polycystic ovary syndrome

AimsIn the cyclic rat in estrus, the vasoactive intestinal peptide (VIP) has an impact on ovarian function, which depends on the endocrine status of the animal. In this work, we aimed to clarify the participation of VIP in the pathophysiological condition of polycystic ovary syndrome (PCOS) using a model of PCOS induced by estradiol valerate (EV-PCOS) in rats. Main methodsIn the cyclic rat in estrus and in the EV-PCOS model, we analyzed the acute effects of blocking VIP receptors with the use of an antagonist (Ant-VIP) injected into the left or right ovarian bursa on the steroidogenic response and ovarian catecholamine levels. Key findingsIn the cyclic animal in estrus, the treatment with Ant-VIP in the left ovarian bursa resulted in a reduction in testosterone serum levels and in ovarian levels of dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC), without changes in 4-hydroxy-3-methoxyphenyl (MHPG) and norepinephrine (NE). When the treatment was applied on the right side, only MHPG levels increased.In the EV-PCOS model, the treatment with Ant-VIP in the left ovarian bursa increased testosterone, estradiol, MHPG, and NE levels. When the treatment was performed on the right side, progesterone levels decreased and estradiol increased, without changes in ovarian catecholamines. SignificanceThe binding of VIP to its receptors differentially regulates steroidogenesis in the cyclic animal in estrus and in the EV-PCOS model. The blocking of VIP signaling produces changes in ovarian catecholamines.

MON-002 The Effect of GNRHR Autoantibody on Reproduction Function and Insulin Signaling Intermediates in a New Animal Model of Polycystic Ovary Syndrome

Background: Polycystic ovary syndrome (PCOS), a metabolic and reproductive associated disease, defined as hyperandrogenism with reproductive dysfunction including menstrual disorder, anovulation, infertility, polycystic ovary and so on. We previously showed reported a high percentage of activating autoantibodies (AAb) directed toward the second extracellular loop (ECL2) of gonadotropin-releasing hormone receptor (GnRHR) in PCOS patients, and further demonstrated elevated GnRHR-autoantibody (GnRHR-AAb) could induced insulin resistance in energy storage and peripheral tissue in immunized animals. In the present study, we have now induced specific GnRHR-ECL2 AAb in rats and explored the underlying mechanisms of their resultant reproductive dysfunction. Methods: Sixteen SD rats were randomly divided into 2 groups: a GnRHR group (n=8) and a control group (n=8). Rats in the GnRHR group were immunized with GnRHR ECL2 peptide while the controls were not. Epitope mapping of GnRHR-ECL2-directed AAb was performed using octapeptide multipin solid-phase peptides. Rat estrus cycle was measured through pudendum appearance and vaginal smears. Ovarian and pituitary tissues were collected to observe ovarian morphological changes, to examine the expressions of proteins and genes of insulin signaling pathway by Quantitative real-time PCR respectively. The concentration of inflammatory cytokines in the ovary was detected by Bio-plex Pro™ magnetic bead-based assays on the Bio-plex®. Results: The GnRHR-AAb titers and activity in the GnRHR group were significantly higher than the control group, and the GnRHR-AAb from the immunized rats reacted predominantly with the peptide sequence FSQCVTHC of the GnRHR-ECL2. Numbers of LH pulses and concentration of testosterone in GnRHR group were significantly higher than control group. The GnRHR group exhibited lower frequency of in the appearance of proestrus and estrous phases while the control group represented had a higher frequency in the appearance of metestrus and diestrus stages on estrus cyclicity. The GnRHR-immunized group showed demonstrated increased atretic follicles, decreased corpora lutea, loosely packed granulosa cells, and thecal cell hyperplasia in ovarian tissue compared with controls group. There was GnRHR group represented increased expressions of IRS-1, PI3K and GLUT-1 in ovarian and pituitary tissues compared with control group. However, no obvious changes of inflammatory cytokines are observed in ovarian tissues between two groups. Conclusion: Chronic elevated GnRHR-AAb exerts induced reproductive dysfunction through increased ovarian LH secretion and androgen production, thus likely leading to compensatory hyperinsulinemia which ultimately enhanced insulin signaling in reproductive tissues to exert more and androgen production to, which may provide a novel etiological mechanism for PCOS.

The Effects of Pregnancy on the Sympathoexcitatory and Pressor Responses to Nanoinjection of Angiotensin II into the Arcuate Nucleus

Pregnancy induces profound increases in sympathetic nerve activity (SNA). Angiotensin II (AngII) may contribute, since systemic or central blockade of AngII production or receptors (AT1aR) decreases SNA in pregnant animals. However, the brain sites involved are unknown. One possibility is the arcuate nucleus (ArcN), since AngII binds to ArcN AT1aR to increase SNA, and the ArcN is a well‐established reproductive integrating center. To begin to test this hypothesis, we measured the changes in SNA and mean arterial pressure (MAP) in response to bilateral nanoinjections of AngII (30 pmol in 30 nL) into the ArcN of α‐chloralose anesthetized pregnant rats and virgin rats throughout the estrus cycle. ArcN AngII slowly increased (P&lt;0.05) lumbar SNA (LSNA) in pregnant rats (by 50±10 % after 90 min; n=6), and the rise was larger than in proestrus rats (‐1±8 %; n=5; P&lt;0.05), similar to diestrus rats (40±9 %; n=4), but less than estrus rats (72±12 %; n=6; P&lt;0.05). ArcN AngII rapidly increased (P&lt;0.05) MAP by ~10 mmHg (after 10 min) in all groups, but after 90 min the increase was sustained (P&lt;0.05) only in pregnant (13±2 mmHg) and estrus (11±4 mmHg) rats. A cohort of ArcN neurons projects to and stimulates vasopressinergic neurons in the hypothalamic paraventricular and supraoptic nuclei. Therefore, to test if the initial or sustained increases in MAP were mediated by vasopressin, another set of estrus and pregnant rats were pretreated with the Manning Compound (V1x; 5 μg iv) 15 min before ArcN AngII. In estrus rats (n=4), V1x had no effects on baseline LSNA or MAP, but completely blocked the initial rise in MAP induced by ArcN AngII (2±3 mmHg). Nevertheless, the increase in MAP at 90 min was unchanged (13±3 mmHg; P&lt;0.05). The LSNA response to ArcN AngII (83±9 %) was also not altered. In pregnant rats pretreated with V1x (n=4), baseline MAP decreased (P&lt;0.05) by 10±1 mmHg, and again ArcN AngII failed to increase MAP initially (2±1 mmHg). However, the increase in MAP 90 min after ArcN AngII (7±2 mmHg) was the same as the increase 90 min after injection of artificial cerebrospinal fluid into the ArcN of V1x‐treated pregnant rats (5±2 mmHg). Again, the increase in LSNA to ArcN AngII was unchanged (30±6 %). Finally, RNAScope was used to assay AT1aR mRNA expression in the ArcN in diestrus, proestrus, and pregnant rats. ArcN AT1aR were undetectable in proestrus rats and were expressed at low but detectable levels in diestrus rats. In contrast, pregnancy markedly increased the expression of AT1aR in the ArcN. In summary, during pregnancy, ArcN AngII produces substantial increases in LSNA in association with elevated AT1aR expression. Moreover, the increase in MAP in response to ArcN AngII was reduced or eliminated in estrus and pregnant rats pretreated with a vasopressin V1 receptor blocker. In conclusion, these data highlight the ArcN as a potential site at which AngII increases SNA during normal pregnancy. The data also suggest that AngII can elicit an increase in vasopressin secretion via an action in the ArcN and that vasopressin contributes to the pressor responses induced by ArcN AngII in both estrus and pregnant rats.Support or Funding InformationHL128181

In Female Rats, the Sympathoexcitatory and Pressor Actions of Arcuate Nucleus Angiotensin II Vary During the Estrus Cycle and are Mediated by Inhibition of Neuropeptide Y, and Excitation of α‐Melanocyte Stimulating Hormone, Projections to the Hypothalamic Paraventricular Nucleus

In male rats, nanoinjections of Angiotensin II (AngII) into the arcuate nucleus (ArcN) increases sympathetic nerve activity (SNA) by suppressing tonic sympathoinhibitory Neuropeptide Y (NPY) inputs, and activating excitatory pro‐opiomelanocortin (POMC) inputs that release alpha melanocyte stimulating hormone (α‐MSH), into the hypothalamic paraventricular nucleus (PVN). In female rats, ArcN AngII AT1a receptor (AT1aR) expression is generally higher than in males, but varies with the estrus cycle (highest during estrus; lowest during proestrus). However, whether ArcN AngII increases SNA in females, or if the response varies during the cycle, is unknown. Therefore, we tested bilateral ArcN AngII injections (30 pmol in 30 nL) in α‐chloralose anesthetized female rats throughout the reproductive cycle, and found that 90 min after ArcN AngII injections, LSNA increased (P&lt;0.05) in rats during estrus (by 72±12 %; n=6) and diestrus (by 40±9 %; n=4), but not proestrus (−1±8 %; n=5). ArcN AngII also induced an initial rapid rise (P&lt;0.05) in mean arterial pressure (MAP) in all groups (estrus: 13±2 mmHg; diestrus: 11±3 mmHg; proestrus: 13±3 mmHg), but the increase was sustained only in estrus rats (by 12±2 mmHg; P&lt;0.05). We next tested if ArcN AngII suppresses inhibitory NPY inputs by determining if blockade of PVN NPY Y1 receptors (Y1R) with bilateral nanoinjections of BIBO3304 (60 pmol/60nL) elicits smaller increases in MAP and LSNA 60 min after nanoinjection of AngII into the ArcN. As previously reported, PVN injections of BIBO3304 (without ArcN AngII; n=3) increased (P&lt;0.05) LSNA (by 34±6 %) and MAP (by 10±1 mmHg). However, the increases (P&lt;0.05) in LSNA (to 93±16 %) and MAP (by 19±1 mmHg) (n=4) following ArcN AngII and PVN BIBO3304 were the same as ArcN AngII followed by PVN artificial cerebrospinal fluid (n=3; LSNA by 107±30 % and MAP by 17±4 mmHg). Thus, ArcN AngII markedly attenuated the pressor and sympathoexcitatory effects of blockade of PVN Y1R, indicating that AngII increases LSNA and MAP in part by inhibition of NPY projections to the PVN. Finally, because suppression of tonic NPY inhibition of PVN presympathetic neurons permits increased activation of PVN α‐MSH receptors (MC4R), we tested if blockade of PVN MC4R with SHU9119 decreases LSNA and MAP 90 min after ArcN AngII (n=4). Indeed, bilateral PVN SHU9119 decreased (P&lt;0.05) LSNA (by 30±10 %) and MAP (by 10±1 mmHg). In conclusion, in females as in males, ArcN AngII increases SNA and MAP by inhibiting NPY inputs and increasing α‐MSH inputs into the PVN. However, these effects vary during the estrus cycle in parallel to AngII AT1aR expression: highest during estrus and undetectable during proestrus.Support or Funding InformationHL128181

Effects of Perinatal Inhibition of Gonadal Steroid Hormones on Behavioral Changes in Rats

Sex differentiation of a rat brain occurs during the perinatal period (four days prior to and four days after birth). The undifferentiated brain becomes a female brain unless it is exposed to testosterone (T) which gets metabolized to 17β‐estradiol (E2) and dihydrotestosterone (DHT). While aromatase converts T to E2, 5α‐reductase converts T to DHT. 17β‐estradiol exerts its effects by binding to an estrogen receptor (ER) whereas DHT via an androgen receptor (AR). We tested the significance of DHT and E2 during the organizational phase in the differentiation of the rat brain. During the last four days of pregnancy, seven timed‐pregnant rats received either the vehicle (5% ethanol and 95% sesame oil), exemestane (Aromasin; 4mg/kg/ml), or flutamide (20 mg/kg/ml) subcutaneously. Pups from each group continued to receive their specific treatments during the first four days after birth. From postnatal day 65, these animals were subjected to open field (OF), spatial working memory, and sexual motivation (SM) tests. Male rats receiving flutamide exhibited a significant increase in exploratory behavior. Additionally, male rats receiving exemestane exhibited significantly greater interest in the estrus rat compared to the control group. In conclusion, under AR blockade, where E2 becomes the main gonadal hormone, improvements in exploratory behavior in male rats were observed. Moreover, when exemestane was used to block E2 conversion, and DHT becomes the main gonadal hormone, increased SM in male rats was observed. Thus, the presence of both E2 and DHT during organizational phase appears to be essential for normal socio‐sexual and exploratory behaviors.