The effect of orexin on the hypoxic ventilatory response of female rats is greatest in the active phase during diestrus.

We recently showed that in male rats, orexin contributes to the hypoxic ventilatory response (HVR), with a stronger effect in the active phase. The effect of orexin on the HVR in females has not been investigated. As estrogen can inhibit orexin neurons, here we hypothesized that orexin neurons are activated by hypoxia and facilitate the HVR only in diestrus, when estrogen is low. We exposed female rats (n = 10) to near-isocapnic hypoxia ([Formula: see text] from 0.21 to 0.09) over ∼5 min, after vehicle and again after suvorexant (a dual OxR antagonist; 20 mg/kg ip), with ventilation measured using whole body plethysmography. Each rat was tested in proestrus or estrus (p/estrus), and again in diestrus, during both inactive and active phases. We also performed immunohistochemistry (IHC) to determine the proportion of orexin neurons activated by acute hypoxia during diestrus (n = 6) or proestrus/estrus (n = 6) in the active phase. In the inactive phase, the HVR was unaffected by OxR blockade, irrespective of estrus stage. In the active phase, the effect of OxR blockade depended on stage: the slope of the HVR was significantly reduced by OxR blockade only during diestrus. IHC revealed that hypoxia activated more orexin neurons during diestrus compared with p/estrus. We conclude that in females, orexin neurons are activated by hypoxia and contribute to the HVR only in diestrus when estrogen levels are low. Stage of the estrus cycle should be considered when examining the physiological function of orexin neurons in females.NEW & NOTEWORTHY We previously showed that orexin facilitates the hypoxic ventilatory response (HVR) of adult male rats during the active phase. Others have shown that estrogen inhibits orexin neurons. Here we show that orexin neurons are activated by hypoxia and facilitate the HVR of adult female rats during the active phase, but only in diestrus. These data suggest that orexin neurons facilitate the HVR in females when they are free from the inhibitory effects of estrogen.

Heat shock protein HSP90 immunoexpression in equine endometrium during oestrus, dioestrus and anoestrus.

Heat shock proteins play a crucial role in cellular development, proliferation, differentiation and apoptosis. Heat shock protein 90 (HSP90) has been localised in the human endometrium, where its immunoexpression changes during the menstrual cycle. Similar studies have not been done for the equid species, so the present study aimed to describe endometrial HSP90 immunoexpression in mare endometrium. Endometrial biopsies were formalin-fixed and paraffin-embedded, and sections were stained with haematoxylin-eosin in preparation for HSP90 immunohistochemistry. Immunostaining and morphometric analyses were performed on the epithelial lining, endometrial glands and connective stroma during oestrus, dioestrus phase and anoestrus period (n = 7 per phase or period). Immunoexpression was localised in the basal region of the epithelial cells lining the lumen. Immunoexpression was greater during oestrus than during either dioestrus or anoestrus. During anoestrus, there was little immunostaining in the endometrium, suggesting that HSP90 is involved in the functional modulation of sex steroid receptors in cyclic mares. Indeed, the function of HSP90 as a chaperone in the folding of proteins, such as steroid receptors, might explain the greater intensity of immunostaining during the oestrus and dioestrus phases, compared the anoestrus period. We conclude that, in the mare, HSP90 plays a role in endometrial function and that further studies are needed to test whether it is important in pathological conditions as endometritis.

Serum progesterone concentration, volume, and apoptosis of corpora lutea in early, middle and late diestrus in the bitch.

The aim was to study number, volume, apoptosis of corpora lutea (CL), and serum P4 concentrations in early, middle, and late diestrus of dogs. Thirty-six bitches were ovari-hysterectomized (OVX): Early Diestrus (Group [G]1; OVX 20 days after end of estrus [DEH]); Mid-diestrus (GII; OVX between 21 and 40 days after DEH), and Late-diestrus (GIII; OVX between 41 and 60 days after DEH). Before OVX a blood sample was collected to quantify P4. After OVX, the number of CL (NCL) was recorded, CL measured using both ultrasonography (US) and caliper (CAL), and the volume (mm3) was calculated. Based on abundances of caspase-3, apoptotic luteal cells were detected. Bitches in early-diestrus had greater P4 concentrations than bitches in mid- and late-diestrus (23.52 ±â€¯3.78 and 10.86 ±â€¯3.88 ng/mL; P < 0.05). The NCL, cumulative USCLV, and CALCLV were similar among diestrus stages (P > 0.30). Bitches with CL (≥5) had twice the serum P4 concentrations as bitches with CL1-2 and CL3-4 (22.71 ±â€¯3.70 and 10.97 ±â€¯4.06 ng/mL; P < 0.05). There were correlations between P4 concentrations with USCLV, CALCLV, and NCL (r = 0.64, r = 0.67, r = 0.44; P < 0.0001). When serum P4 concentrations were adjusted for stages of diestrus, however, there were only correlations during early diestrus. The percentage of apoptotic cells was greater in GIII compared with GI and GII (13.75 ±â€¯2.26 % compared with 4.5 ±â€¯0.68 % and 4.6 ±â€¯1.5 %, respectively; P < 0.05). As days of diestrus increased, number of apoptotic cells increased, and serum P4 concentrations decreased.

Role of the superior ovarian nerve in the regulation of follicular development and steroidogenesis in the morning of diestrus 1.

PURPOSE: Little is known about the role of the superior ovarian nerve (SON) in follicular development during the estrus cycle. The aim of the present study was to analyze the role of neural signals arriving through the SON at the ovaries in the regulation of follicular development and ovarian steroid secretion in diestrus 1 of cyclic rats. METHODS: Cyclic rats were subjected to left, right, or bilateral SON sectioning or to unilateral or bilateral laparotomy at diestrus 1 at 11:00 h. Animals were sacrificed 24 h after surgery. RESULTS: Compared to laparotomized animals, unilateral SON sectioning decreased the number of preovulatory follicles, while bilateral SON sectioning resulted in a decreased number of atretic preantral follicles. An important observation was the presence of invaginations in the follicular wall of large antral and preovulatory follicles in animals with denervation. Furthermore, left SON sectioning increased progesterone levels but decreased testosterone levels, which are effects that were not observed in animals that were subjected to right denervation. CONCLUSIONS: At 11:00 h of diestrus 1, the SON was found to stimulate follicle development, possibly via neural signals, such as noradrenaline and/or vasoactive intestinal peptide, and this stimulation induced the formation of follicle-stimulating hormone receptors. The role of the SON in the regulation of ovarian steroid secretion is asymmetric: the left SON inhibits the regulation of progesterone and stimulates testosterone secretion, and the right nerve does not participate in these processes.

Triplex doppler ultrasonography to describe the uterine arteries during diestrus and progesterone profile in pregnant and non-pregnant bitches of different sizes.

Hemodynamics of uterine vascularization is modified throughout pregnancy to meet the increasing demand of the growing fetuses and triplex doppler ultrasonography is widely used in human medicine to study the uterine arteries and assess the fetal and placental conditions. The aim of our study was to confirm this observation in the bitch, to evaluate differences between bitches of different sizes and to study abnormal pregnancies. Forty-four bitches were monitored during the estrous period to determine ovulation and every 10 days from ovulation to 50 days post-ovulation: the resistivity (RI) and pulsatility (PI) indexes of the right uterine artery were measured as well as usual assessment of fetal development and follow up of the luteal function. Thirty-three out of forty-four bitches were pregnant, including 6 abnormal pregnancies (resorption of more than 10% of the embryos). We also divided them in four weight categories: 8 were small (<10 kg), 13 medium (10-25 kg), 13 large (>25-40 kg) and 10 were giant breeds (>40 kg). We observed that RI and PI decreased over time and were significantly lower for pregnant bitches compared to non-pregnant ones from 30 days post-ovulation. In contrast, RI and PI did not significantly vary with the size of the bitches and we could not determine a significant impact of abnormal pregnancies either. In conclusion, we found no significant difference related to the size of bitches in the RI and PI. The only significant difference between pregnant and non-pregnant bitches was observed from 30 days post-ovulation.

Clinical diabetes mellitus in association with diestrus-induced acromegaly in 2 bitches.

Two intact bitches aged 9 and 11 years were referred due to chronic polyuria, polydipsia, vomiting, anorexia and progressive lethargy. On clinical examination, signs of tissue overgrowth (large paws, widened interdental space, pharyngeal stridor) were noticed. Diabetes mellitus (DM) was diagnosed in one dog (case 1) and diabetic ketoacidosis (DKA) in the other (case 2). There were increased IGF-1 values suggestive of hypersomatotropism. Progesterone values and pathological findings of the ovaries and uterus indicated diestrus. Diagnosis of diestrus-induced hypersomatotropism was made and ovariohysterectomy was performed in both dogs. Dog 1 also had multiple mammary neoplasms treated with bilateral mastectomy. Treatment resulted in diabetic remission in case 1 and improved glycaemic control in case 2. Overall, diestrus-induced hypersomatotropism is rare but should be considered in any intact diabetic bitch with acromegalic features. Ovariohysterectomy is recommended and associated with a fair to good prognosis.

Expression of Bcl-2 Family Proteins in the Ovarian Follicular Apparatus in the Acute Period after Experimental Hyperthermia.

The expression of apoptosis regulators (proapoptotic protein Bad and anti-apoptotic protein Bcl-2) was analyzed and Bcl-2/Bad ratio in the follicular apparatus of the rat ovary was determined on day 3 after hyperthermia (rectal temperature 43.5°C). Hyperthermia in the catabolic phase leads to different degrees of activation of the molecular "switches" of apoptosis in cells of ovarian follicular epithelium. This was seen from increased intensity of immunohistochemical staining for Bad protein against the background of more pronounced expression of Bcl-2 protein. On day 3 after exposure to hyperthermia, Bcl-2/Bad ratio increased, which reflects antiapoptotic protection of cells and conditions for blockade of mitochondrial pathway of apoptosis in the follicular apparatus of the ovaries during the acute period after hyperthermia.

Evaluation of cell proliferation and endometrial thickness of bitches in different periods of diestrus

ABSTRACT This study aimed to determine the histological features of the endometrium of bitches, as well as the cell proliferation at specific moments of diestrus, 10, 20, 30, 40, 50 and 60 days post ovulation, correlating the endometrial thickness with the uterine cell proliferation and the metabolic state (weight, blood glucose and plasma cholesterol) of the animals. Therefore, the right and left uterine horns of 26 clinically healthy bitches submitted to ovariohysterectomy were histologically analyzed 10, 20, 30, 40, 50 and 60 days post ovulation. The hematoxylin-eosin and AgNOR staining techniques were performed. All parameters were evaluated by ANOVA and post-hoc Tukey test (p<0.05). The correlation between endometrial thickness and uterine cell proliferation, weight, blood glucose and plasma cholesterol of animals was observed using the Pearson method (p<0.05). In the present study, it is concluded that endometrial thickness does not differ at any of the moments analyzed in diestrus. The endometrial thickness is not influenced by hormones, weight, blood glucose or serum cholesterol of bitches in this phase of the estrous cycle. However, there is greater cell proliferation in the endometrium at day 40 compared to day 60 post ovulation under the influence of the endocrine profile.

Evaluation of cell proliferation and endometrial thickness of bitches in different periods of diestrus.

This study aimed to determine the histological features of the endometrium of bitches, as well as the cell proliferation at specific moments of diestrus, 10, 20, 30, 40, 50 and 60 days post ovulation, correlating the endometrial thickness with the uterine cell proliferation and the metabolic state (weight, blood glucose and plasma cholesterol) of the animals. Therefore, the right and left uterine horns of 26 clinically healthy bitches submitted to ovariohysterectomy were histologically analyzed 10, 20, 30, 40, 50 and 60 days post ovulation. The hematoxylin-eosin and AgNOR staining techniques were performed. All parameters were evaluated by ANOVA and post-hoc Tukey test (p<0.05). The correlation between endometrial thickness and uterine cell proliferation, weight, blood glucose and plasma cholesterol of animals was observed using the Pearson method (p<0.05). In the present study, it is concluded that endometrial thickness does not differ at any of the moments analyzed in diestrus. The endometrial thickness is not influenced by hormones, weight, blood glucose or serum cholesterol of bitches in this phase of the estrous cycle. However, there is greater cell proliferation in the endometrium at day 40 compared to day 60 post ovulation under the influence of the endocrine profile.

Effect of GnRH and hCG on progesterone concentration and ovarian and luteal blood flow in diestrous mares.

The objective of the present study was to investigate the effect of reproductive hormones (GnRH, hCG, LH and progesterone) on the regulation of corpus luteum (CL) and ovarian blood flow. Diestrous mares received a single treatment of saline, 100µg gonadorelin (GnRH), or 1500IU hCG 10days after ovulation. Plasma LH and progesterone concentrations, resistance index (RI) for ovarian artery blood-flow, and percentage of corpus luteum (CL) with color-Doppler signals of blood flow were determined immediately before treatment (hour 0) and at hours 0.25, 0.5, 1, 1.5, 2, 3, 4, 5, and 6. In the GnRH group, LH increased (P<0.0001) between hours 0 and 0.25 and then progressively decreased; concentration of LH was not affected in the saline and hCG groups. Progesterone concentration was not different among groups. In the GnRH group, RI tended (P<0.07) to decrease between hours 0 and 1.5 and increased (P<0.01) between hours 1.5 and 4. In the hCG group, two transient RI decreases (P<0.05) occurred before hour 2. The percentage change from hour 0 in the percentage of CL with blood-flow signals was greater at hour 0.5 in the GnRH group than in the saline group and was intermediate in the hCG group. The similarity among groups in progesterone concentration indicated that changes in progesterone were not involved in the GnRH and hCG stimulation of ovarian vascular perfusion. Effects of treatment might have been mediated through LH; however, since hCG biological activity is primarily LH-like, the differences in timing and degree of ovarian and luteal blood flow changes after GnRH or hCG administration in the present study suggest that GnRH might have a direct effect on ovarian blood vessels and vascular control.

Alterations in the threshold of the potassium concentration to evoke cortical spreading depression during the natural estrous cycle in mice.

Cortical spreading depression (CSD) has been implicated in a variety of neurological disorders. However, the relationship between serum sex hormones and susceptibility to the development of CSD in naturally estrous cycling female animals is largely unknown. The natural estrous cycle of mice consists of four stages, namely, proestrus, estrus, metestrus and diestrus. We measured the serum concentration of estradiol and progesterone in estrus and diestrus and compared the minimum potassium concentrations necessary to evoke CSD in each stage and in males. In diestrus, the minimum potassium concentration required to evoke CSD was significantly lower compared to the other three phases and male animals. The serum level of estradiol is significantly higher and serum level of progesterone is significantly lower in diestrus compared to estrus. Furthermore, when we administered an estrogen receptor antagonist, the susceptibility to the development of CSD was decreased. Conversely, the administration of a progesterone receptor antagonist increased the susceptibility to CSD. Our results demonstrated that neuronal excitability related to CSD induction differs among the natural estrous phases in mice.

Expression of 3ß-hydroxysteroid dehydrogenase in ovarian and uterine tissue during diestrus and open cervix cystic endometrial hyperplasia-pyometra in the bitch.

The purpose of this study was to compare the expression of 3ß-hydroxystreroid dehydrogenase (3ß-HSD) in the uterus and ovary of healthy dogs and those with cystic endometrial hyperplasia and/or pyometra complex (CEH-pyometra). Eighteen female dogs were included in the study. Eleven bitches with open cervix CEH-pyometra were included in the CEH-pyometra group and seven diestrus bitches in the control group. For immunostaining a rabbit polyclonal, one raised against recombinant human type 2 (adrenal/gonadal) 3ß-HSD was used. Progesterone (P4) concentrations were not statistically different between the groups. Strongly stained large interstitial cell groups in the ovarian medulla were observed particularly in CEH-pyometra group although these cells in the control group were weakly or moderately stained and existed singly or paired. The expressions of 3ß-HSD in luminal epithelium (42.40 ± 22.40% vs. 18.42 ± 13.15%, P < 0.05) and glandular epithelium (32.80 ± 27.05% vs. 2.94 ± 7.79%, P < 0.01) of endometrium were significantly higher in CEH-pyometra group than those in the control group. The expression of 3ß-HSD in CL was higher (29.38 ± 9.58% vs. 22.94 ± 4.97%) in CEH-pyometra group than that of control group although the differences were not significant (P > 0.05). Similarly, the significant increase in the expression of 3ß-HSD in ovarian interstitial cells (33.86 ± 29.44 vs. 1.13 ± 2.97, P < 0.05) was found in CEH-pyometra group compared to the control group. The study revealed that 3ß-HSD expression in the endometrium of canine CEH-pyometra was significantly high.

Confirmed dioestrus in pseudopregnant mice using vaginal exfoliative cytology improves embryo transfer implantation rate.

Embryo transfer is a commonly performed surgical technique. In mice, protocols typically specify pairing recipient females with vasectomized males to induce a receptive uterine environment for embryo implantation. However, this induced receptive state is not always maintained until implantation occurs. The use of a well-characterized correlation between oestrous state and exfoliative vaginal cytology was therefore evaluated to assess uterine receptivity immediately before embryo transfer. Eight- to 12-week-old virgin female CD1 mice (n = 22) were paired overnight with vasectomized males and successfully mated, indicated by the presence of a vaginal plug. These dams underwent embryo transfer 3 days later with embryos obtained from superovulated 4-week-old F1 (C57BL/6 × CBA) females. Non-invasive vaginal lavage was conducted immediately before transfer. Dams were killed 6 days after transfer and the uterus collected for histological analysis. Embryo implantation rate in mice was 96% when cytological analysis of the lavage samples signified dioestrus (n = 6), whereas the implantation rate was <15% (n = 16) when cytology signified other stages of oestrous. This simple, quick, non-invasive measure of receptivity was accurate and easily adopted and, when applied prospectively, will avoid unnecessary surgery and subsequent culling of non-suitable recipients, while maximizing the implantation potential of each recipient female.

Sex-Specific and Estrous Cycle-Dependent Antidepressant-Like Effects and Hippocampal Akt Signaling of Leptin.

Sex differences in the incidence of depression and antidepressant treatment responses are well documented. Depression is twice as common in women as in men. Recent studies indicate that low levels of leptin, an adipocyte-derived hormone, are associated with increased symptoms of depression in women. Leptin has been shown to produce antidepressant-like effects in male rodents. In the present study, we examined sex differences and estrous cycle variations in antidepressant-like responses to leptin. Leptin administration significantly reduced immobility, a putative measure of behavioral despair, in the forced swim test in intact female mice in the proestrus phase but not in the diestrus phase of the estrous cycle. Moreover, leptin administration stimulated Akt phosphorylation in the hippocampus of female mice in proestrus but not in diestrus, in correlation with its differential behavioral effects in these two phases of the cycle. Leptin-induced behavioral responses and stimulation of hippocampal Akt phosphorylation in female mice were abolished by ovariectomy. By contrast, the antidepressant-like effect of leptin in male mice was not affected by gonadectomy (castration). Pretreatment with 17ß-estradiol restored sensitivity to the effects of leptin on behavior and hippocampal Akt phosphorylation in ovariectomized female mice. These results suggest leptin regulates depression-like behavior and hippocampal Akt signaling in a sex-specific and estrous cycle-dependent manner.

The Receptive Endometrial Transcriptomic Signature Indicates an Earlier Shift from Proliferation to Metabolism at Early Diestrus in the Cow.

This study aimed to characterize the endometrial transcriptome and functional pathways overrepresented in the endometrium of cows treated to ovulate larger (≥13 mm) versus smaller (≤12 mm) follicles. Nelore cows were presynchronized prior to receiving cloprostenol (large follicle [LF] group) or not (small follicle [SF] group), along with a progesterone (P4) device on Day (D) -10. Devices were withdrawn and cloprostenol administered 42-60 h (LF) or 30-36 h (SF) before GnRH agonist treatment (D0). Tissues were collected on D4 (experiment [Exp.] 1; n = 24) or D7 (Exp. 2; n = 60). Endometrial transcriptome was obtained by RNA-Seq, whereas proliferation and apoptosis were assessed by immunohistochemistry. Overall, LF cows developed larger follicles and corpora lutea, and produced greater amounts of estradiol (D-1, Exp. 1, SF: 0.7 ± 0.2; LF: 2.4 ± 0.2 pg/ml; D-1, Exp. 2, SF: 0.5 ± 0.1; LF: 2.3 ± 0.6 pg/ml) and P4 (D4, Exp. 1, SF: 0.8 ± 0.1; LF: 1.4 ± 0.2 ng/ml; D7, Exp. 2, SF: 2.5 ± 0.4; LF: 3.7 ± 0.4 ng/ml). Functional enrichment indicated that biosynthetic and metabolic processes were enriched in LF endometrium, whereas SF endometrium transcriptome was biased toward cell proliferation. Data also suggested reorganization of the extracellular matrix toward a proliferation-permissive phenotype in SF endometrium. LF endometrium showed an earlier onset of proliferative activity, whereas SF endometrium expressed a delayed increase in glandular epithelium proliferation. In conclusion, the periovulatory endocrine milieu regulates bovine endometrial transcriptome and seems to determine the transition from a proliferation-permissive to a biosynthetic and metabolically active endometrial phenotype, which may be associated with the preparation of an optimally receptive uterine environment.

Sex-related neurogenesis decrease in hippocampal dentate gyrus with depressive-like behaviors in sigma-1 receptor knockout mice.

Male sigma-1 receptor knockout (σ1R(-/-)) mice showed depressive-like phenotype with deficit in the survival of newly generated neuronal cells in the hippocampal dentate gyrus (DG), but female σ1R(-/-) mice did not. The level of serum estradiol (E2) at proestrus or diestrus did not differ between female σ1R(-/-) mice and wild-type (WT) mice. Ovariectomized (OVX) female σ1R(-/-) mice, but not WT mice, presented the same depressive-like behaviors and neurogenesis decrease as male σ1R(-/-) mice. Treatment of male σ1R(-/-) mice with E2 could alleviate the depressive-like behaviors and rescue the neurogenesis decrease. In addition, E2 could correct the decline in the density of NMDA-activated current (INMDA) in granular cells of DG and the phosphorylation of NMDA receptor (NMDAr) subtype 2B (NR2B) in male σ1R(-/-) mice, which was associated with the elevation of Src phosphorylation. The neuroprotection and antidepressant effects of E2 in male σ1R(-/-) mice were blocked by the inhibitor of Src or NR2B. The NMDAr agonist showed also the neuroprotection and antidepressant effects in male σ1R(-/-) mice, which were insensitive to the Src inhibitor. On the other hand, either the deprivation of E2 or the inhibition of Src in female σ1R(-/-) mice rather than WT mice led to a distinct decline in INMDA and NR2B phosphorylation. Similarly, the Src inhibitor could cause neurogenesis decrease and depressive-like behaviors in female σ1R(-/-) mice, but not in WT mice. These results indicate that the σ1R deficiency impairs neurogenesis leading to a depressive-like phenotype, which is alleviated by the neuroprotection of E2.

Expression of proliferating cell nuclear antigen in the endometrium of mares during estrus and at early diestrus / Expressão do antígeno núcleo celular proliferante no endométrio de éguas durante o estro e início do diestro

Immunohistochemical expression of proliferating cell nuclear antigen (PCNA) was evaluated in the endometrium of mares during estrus and at early diestrus. Three samples were collected by endometrial biopsy from 10 mares, on estrus/ second day, in the ovulation day and seven days after the ovulation day. PCNA expression was high in luminal epithelium and low in endometrial glands on samples taken on estrus/second day and on the ovulation day (p 0.05). For samples collected on the seventh day following ovulation, the averaged PCNA immunostaining was higher in glandular epithelium (p 0.05). The study revealed that luminal epithelial cells exhibit higher proliferation during estrus and glandular epithelial cells exhibited higher proliferation during diestrus...

A expressão do antígeno núcleo celular proliferante (ANCP) foi avaliada no endométrio de éguas durante o estro e início do diestro. Em cada uma de dez éguas foram efetuadas biópsias do endométrio em três momentos dos respectivos ciclos reprodutivos: segundo dia do estro, dia da ovulação e sete dias após a ovulação. Nas amostras colhidas no segundo dia do estro e no dia da ovulação, a expressão do ANCP foi elevada no epitélio luminal e baixa nas glândulas endometriais (p 0,05). Nas amostras colhidas no sétimo dia após a ovulação, a média de ANCP imunologicamente corado foi maior no epitélio glandular (p 0,05). O estudo revelou que as células do epitélio luminal apresentaram a maior proliferação durante o estro e que as células epiteliais glandulares apresentaram a maior proliferação durante o diestro...

Regulation of the mouse medial prefrontal cortical synapses by endogenous estradiol.

Recent studies suggest that low endogenous estradiol might be a susceptibility factor for anxiety and trauma-related disorders in women. Consistently, fear extinction, a form of inhibitory learning critical for the management of anxiety symptoms, is positively correlated with endogenous estradiol levels. To understand the synaptic basis of the effect of endogenous estradiol on fear extinction, we studied glutamatergic transmission and plasticity in the infralimbic medial prefrontal cortex (IL-mPFC), a brain region crucial for the regulation of fear extinction. Diestrus mice (low estradiol) exhibited a higher basal glutamatergic transmission compared with proestrus mice (high estradiol). Synaptic plasticity was also regulated by endogenous estradiol, which favored synaptic potentiation in a GluN2B-dependent manner. Activation of estrogen receptor ß (ERß) but not ERα rescued synaptic potentiation in diestrus mice by enhancing GluN2B-mediated NMDA receptor transmission. Our results suggest that both endogenous estradiol and ERß activation facilitate the ability of the IL-mPFC synapses to undergo potentiation, a mechanism necessary for the regulation of fear extinction.

Vaginal cytology after induction of ovulation in the queen: comparison of postoestrus and dioestrus.

OBJECTIVE: To compare the vaginal cytology of ovulating and non-ovulating queens. PROCEDURE: The study group comprised 15 queens showing behavioural oestrus. Ovulation was induced in 7 (dioestrus group) and 8 were left untreated (postoestrus group). Vaginal smears were collected from all animals prior to ovariohysterectomy on day 7. Epithelial cells were classified as basal-parabasal, intermediate, superficial, or anucleated superficial cells and counted using computer-assisted image analysis. From each smear, 50 representative vaginal epithelial cells were chosen. Digital images of cells were taken and cell area, cytoplasm area, nucleus area, cell diameter, cell perimeter, nucleus/cytoplasm ratio and red-green-blue (RGB) values were measured using image analysis software. Measurement data were compared between groups. RESULTS: Ovulation induction was successful in all animals. The swabbing procedure in oestrus did not induce ovulation in any postoestrus queens. Mean duration of oestrus was 6.65 ± 0.44 and 4.71 ± 0.32 days (P > 0.05) in the postoestrus and dioestrus queens, respectively. Intermediate cell count averaged 21.43% in dioestrus cats and 10.76% in postoestrus cats (P < 0.05). Epithelial cells in the postoestrus group had higher cell area, cytoplasm area, cell diameter and cell perimeter measurements (P < 0.01). Red (90.9 ± 1.6), green (76.1 ± 1.3) and blue (83.6 ± 1.4) channel values in postoestrus were higher than the values (81.3 ± 0.8, 65.8 ± 0.9 and 74.0 ± 0.7, respectively) in dioestrus (P < 0.01). CONCLUSION: Induction of ovulation in oestrus queens results in a significant increase in the number of intermediate cells and a significant decrease in both the dimensions and RGB values of vaginal epithelial cells on day 7.

Effect of the season on some aspects of the estrous cycle in Martina Franca donkey.

The Martina Franca (MF) donkey breed, with 48 jackasses and 515 jennies, is considered an endangered breed according to the data from the Monitoring Institute for Rare Breeds and Seeds in Europe. The knowledge of the estrous cycle characteristics has a great impact for assisted reproduction, especially in endangered species. In this study, the estrous cycle characteristics were investigated in 12 MF jennies throughout the year. Estrous cycle, estrous and diestrous lengths, follicular growth and ovulation, and estradiol-17ß (E2) and progesterone (P4) plasma concentrations were monitored in MF jennies and compared in different seasons. In all jennies (100%) estrous cycle was detected during the whole year, with no differences in the estrous cycle length among seasons. However, a significant increase of estrous length in spring and summer compared with autumn and winter was found. Diestrus was shorter in summer than in the other seasons. Estrous behavior was always shown and characterized by rhythmic eversion of the vulvar labia (winking) with exhibition of the clitoris, urination, male receptivity and clapping, with sialorrhoea, neck and head extension, and back ears. Estrus was characterized by the ovulation of a larger follicle in spring and summer than in autumn and winter. The pattern of E2 and P4 plasma concentrations during the estrous cycle were similar to that reported for the mare, but without differences among the four seasons, so that a negligible effect of environmental conditions on ovarian E2 and P4 secretion was hypothesized, despite the larger diameter of the ovulating follicle in spring and summer.