Artificial lactation by exogenous hormone treatment in non-pregnant sows.

This study aimed to determine if lactation can be induced by exogenous hormonal treatment in non-pregnant sows. In experiment 1, pseudopregnant animals were divided into four groups and given: 1) 5 mg of estradiol dipropionate (EDP) 5 days before (n = 4), 2) 5 mg of EDP 10 days before (n = 3), 3) 10 mg of EDP 5 days before (n = 3) or 4) 10 mg of EDP 10 days (n = 3) before PGF2α treatment. Artificial lactation was induced in seven pseudopregnant sows (53.8%) by exogenous hormonal treatment. There was no significant effect of either an increased EDP dosage or interval from the EDP treatment to PGF2α treatment on the induction rate of artificial lactation. In experiment 2, milk samples were collected from artificial lactating and natural lactating sows (n = 6). IgG and IgA levels in the milk collected from both groups were significantly associated with time during the experimental period. Milk IgG levels 24 h after PGF2α treatment in artificial lactating sows were higher than those in the colostrum of lactating sows. In experiment 3, hormonal profiles in pseudopregnant sows with (n = 3) or without (n = 3) EDP treatment were determined. There was a significant difference in estradiol-17ß levels on days 8, 7 and 5 before PGF2α treatment between groups. Progesterone and prolactin concentrations did not differ between groups. The present study revealed for the first time that lactation could be induced by exogenous hormonal treatment in non-pregnant sows and that the milk collected from these sows contained high immunoglobulin levels.

Efficient and scheduled production of pseudopregnant female mice for embryo transfer by estrous cycle synchronization.

In embryo transfer experiments in mice, pseudopregnant females as recipients are prepared by sterile mating with vasectomized males. Because only females at the proestrus stage accept males, such females are selected from a stock of animals based on the appearance of their external genital tract. Therefore, the efficiency of preparing pseudopregnant females largely depends on the size of female colonies and the skill of the operators who select females for sterile mating. In this study, we examined whether the efficiency of preparing pseudopregnant females could be improved by applying an estrous cycle synchronization method by progesterone (P4) pretreatment, which significantly enhances the superovulation outcome in mice. We confirmed that after two daily injections of P4 (designated Days 1 and 2) in randomly selected females, the estrous cycles of most females (about 85%) were synchronized at metestrus on Day 3. When P4-treated females were paired with vasectomized males for 4 days (Days 4-8), a vaginal plug was found in 63% (20/32) of the females on Day 7. After the transfer of vitrified-warmed embryos into their oviducts, 52% (73/140) of the embryos successfully developed into offspring, the rate being comparable to that of the conventional embryo transfer procedure. Similarly, 77% (24/31) of females became pregnant by fertile mating with intact males for 3 days, which allowed the scheduled preparation of foster mothers. Thus, our estrous cycle synchronization method may omit the conventional experience-based process of visually observing the vagina to choose females for embryo transfer. Furthermore, it is expected that the size of female stocks for recipients can be reduced to less than 20%, which could be a great advantage for facilities/laboratories undertaking mouse-assisted reproductive technology.

Reversible estrous cycle suppression in prepubertal female rabbits treated with slow-release deslorelin implants.

The aim of this study was to examine the long-term effect of a 4.7-mg deslorelin GnRH analog implant on ovarian function in the prepubertal female rabbit. Seven female rabbits (group 1) were treated with the implant at the age of 60 days. The implant was inserted subcutaneously in the umbilical region. Two animals (group 2) were not treated and served as a control group. The vulva of all 9 animals was examined for the presence of typical cyclical changes, additionally the occurrence of mounting behavior was recorded. Ovarian function was checked by administration of a short-acting GnRH agonist to induce ovulation and pseudopregnancy (0.8 µg of buserelin per animal intramuscularly). Ten days after each treatment with buserelin, blood was collected for progesterone measurement to confirm pseudopregnancy. After implant insertion, the first blood collection (Day 10) was done without preceding induction of ovulation to screen for implant induced ovulation and pseudopregnancy. The implant was in situ for 273 days, and during this time span, 12 attempts of induction of ovulation were carried out in intervals of 21 days, beginning at the age of 81 days. Afterward, it was removed under local anesthesia and 3 further inductions of ovulation by the same scheme were conducted. The insertion of the implant led to the establishment of a pseudopregnancy in 2 of 7 animals; the remaining 5 animals did not show elevated progesterone values. Attempts to induce ovulation by administration of the short-acting GnRH analog while the slow-release GnRH analog implant was in place were not successful in treated animals, and progesterone concentrations were basal. The effect was reversible as ovulation could be induced in 2 subsequent cycles in all animals by the third induction of ovulation after implant removal. Induction of ovulation in control animals at the age of 110 and 131 days resulted in elevated progesterone levels after 10 days. No adverse side effects could be observed in implant-treated animals. The typical red coloration of the vulva could be seen in group 2 and after implant removal in group 1. The results suggest that in 5 of 7 rabbits, puberty was delayed by the treatment with the 4.7-mg deslorelin slow-release analog until the implant had been removed. In the other animals, the treatment induced an initial flare-up phenomenon. Afterward, the treatment could reversibly suppress ovarian function in all 7 treated animals.

Administration of luteinizing hormone releasing hormone agonist for synchronization of estrus and generation of pseudopregnancy for embryo transfer in rats.

In the past decade, the use of genetically engineered rats has increased exponentially; therefore, the ability to perform embryo transfer (ET) in rats to rederive, reanimate, or create mutant rat lines is increasingly important. However, the successful generation of pseudopregnant female rats for ET represents a limiting factor. We here evaluated the subcutaneous administration of 40 µg luteinizing hormone releasing hormone agonist (LHRHa) for estrus synchronization during the development and implementation of a rat ET program. Our first experiment assessed endogenous estrus cycling patterns by examining vaginal cytology without administration of LHRHa in 5-wk-old peripubertal Sprague-Dawley female rats. These rats then received LHRHa at approximately 7 wk of age; 57% of the rats were synchronized in proestrus or estrus as assessed by vaginal cytology 96 h later. In a second experiment, 8-wk-old virgin, unmanipulated Sprague-Dawley female rats received LHRHa; 55% were synchronized in proestrus or estrus 96 h later. Copulatory plugs were confirmed in 28% and 82% of the rats that had been synchronized in the first and second experiments, respectively, and mated with vasectomized male rats. Embryo transfer surgery was performed, and live pups were born from both fresh and cryopreserved transgenic rat embryos. Our results indicate that subcutaneous administration of 40 µg LHRHa followed by examination of vaginal cytology 96 h later is an effective technique to generate multiple pseudopregnant recipient rats for use in an ET program.

Cell-specific transcriptional profiling reveals candidate mechanisms regulating development and function of uterine epithelia in mice.

All mammalian uteri have luminal (LE) and glandular epithelia (GE) in their endometrium. The LE mediates uterine receptivity and blastocyst attachment for implantation, and the GE synthesize and secrete or transport bioactive substances involved in blastocyst implantation, uterine receptivity, and stromal cell decidualization. However, the mechanisms governing uterine epithelial development after birth and their function in the adult are not fully understood. Here, comprehensive microarray analysis was conducted on LE and GE isolated by laser capture microdissection from uteri on Postnatal Day 10 (PD 10) and day of pseudopregnancy (DOPP) 2.5 and 3.5. This data was integrated with analysis of uteri from gland-containing control and aglandular progesterone-induced uterine gland knockout mice from PD 10 and DOPP 3.5. Many genes were expressed in both epithelia, but there was greater expression of genes in the LE than in the GE. In the neonate, GE-expressed genes were enriched for morphogenesis, development, migration, and retinoic acid signaling. In the adult, LE-expressed genes were enriched for metabolic processes and steroid biosynthesis, whereas retinoid signaling, tight junction, extracellular matrix, and regulation of kinase activity were enriched in the GE. The transcriptome differences in the epithelia support the idea that each cell type has a distinct and complementary function in the uterus. The candidate genes and regulatory networks identified here provide a framework to discover new mechanisms regulating development of epithelia in the postnatal uterus and their functions in early pregnancy.

Reproductive hormone profiles in sows on estrus synchronization using estradiol dipropionate and prostaglandin F(2α)-analogue and the reproductive performance in female pigs on commercial farms.

Changes in ovarian structures and hormonal profiles in estradiol dipropionate (EDP)-induced pseudopregnant sows following PGF2α-analogue (PGF2α-A) administration and practicality of the estrus synchronization protocol using EDP and PGF2α-A on estrus expression and reproductive performance in commercial conditions were investigated. Pseudopregnancy was defined as absence of estrus maintained for at least 20 days after EDP treatment in this study. When 4 pseudopregnant sows induced by 20 mg EDP were treated with PGF2α-A as 0.175 mg cloprostenol twice at a 24-hr interval between 20 and 28 days after EDP treatment, plasma progesterone concentrations rapidly decreased after treatment. The luteinizing hormone surge and ovulation were detected in all sows. The number of ovulated follicles was 17.3 ± 1.1 (SEM). On commercial farms, 94.2% of 52 gilts and 95.2% of 21 sows received EDP became pseudopregnant. When these pseudopregnant females (48 gilts and 20 sows) were treated with PGF2α-A as described above, estrus was detected in all females at 6.1 ± 0.3 days for gilts and 5.5 ± 0.2 days for sows after the first PGF2α-A treatment. There were no significant differences in farrowing rate (85.0 - 100%), average total litter size (10.0 - 11.4), average born alive litter size (9.4 - 10.3) and average piglet birth weight (1.56 - 1.71 kg) between PGF2α-A treated pseudopregnant female pigs that were inseminated during synchronized estrus and females inseminated during spontaneous estrus. This study indicates that estrus synchronization programs using EDP and PGF2α-A are available as practical and convenient procedures for commercial pig farms.

Induction of a local pseudo-pregnancy via levonorgestrel-loaded microspheres for the treatment of endometriosis in a rabbit model.

BACKGROUND: Endometriosis is a chronic disease that responds to systemic pseudo-pregnancy therapy. However, side effects limit their long-term use, and recurrence often occurs after cessation of medication. Reducing side effects whereas improving therapeutic efficacy of pseudo-pregnancy therapy seems contradictory, but appealing. In order to address this dilemma, the efficacy and side effects of local pseudo-pregnancy therapy were investigated for the first time in an endometriosis animal model. METHODS AND RESULTS: Levonorgestrel-loaded polylactic acid microspheres (LNG-microspheres) were prepared by using an oil-in-water emulsification-solvent evaporation method. Rabbits with experimental endometriosis were randomized to treatment with local pseudo-pregnancy therapy, local blank microspheres, systemic pseudo-pregnancy therapy, ovariectomy or the control. Local pseudo-pregnancy was induced by injection of LNG-microspheres directly into endometrial cysts. Compared with the systemic pseudo-pregnancy group, significantly higher intra-cystic drug levels were maintained for at least 6 months with much lower serum levels in the local pseudo-pregnancy group (P < 0.01). The high intra-cystic levonorgestrel simulated a state of potent pregnancy, which induced size reductions and endometrial atrophy comparable to those of ovariectomy. Moreover, major metabolic parameters and ovarian function were not disturbed by local pseudo-pregnancy therapy. CONCLUSIONS: Induction of a local pseudo-pregnancy could achieve therapeutic efficacy comparable to that of ovariectomy without provoking any marked side effects in a rabbit endometriosis model. Thus it may be a preferable option for patients with endometriosis.

Adult hippocampal cell proliferation is suppressed with estrogen withdrawal after a hormone-simulated pregnancy.

Estradiol withdrawal after pregnancy is hypothesized to precipitate depressive symptoms in vulnerable women. A hormone-simulated pregnancy was induced in female rats and the effects of a 'postpartum' drop in estradiol on hippocampal cell proliferation were examined. All groups were ovariectomized or given sham surgery prior to treatment. Rats were randomly assigned to 'postpartum', 'postpartum'+EB (estradiol benzoate), 'postpartum'+DPN (diarylpropionitrile; an ERbeta agonist), 'postpartum'+IMI (imipramine; a tricyclic antidepressant), sham, ovariectomized (OVX), sham+IMI or OVX+IMI groups. All 'postpartum' groups received hormone injections (estradiol and progesterone) over 23 days to simulate pregnancy, while IMI groups also received daily imipramine injections. After day 23, 'postpartum' rats were withdrawn from the hormone-simulated pregnancy (mimicking the postpartum drop in gonadal hormones), while other 'postpartum' treatment groups received daily injections of DPN, EB or IMI. On day 3 'postpartum' all rats were injected with bromodeoxyuridine (BrdU; a DNA synthesis marker) and perfused 24 h later to assess cell proliferation and cell death in the dentate gyrus. 'Postpartum' hormone withdrawal decreased hippocampal cell proliferation in the 'postpartum' and 'postpartum'+EB groups only. Chronic imipramine significantly increased hippocampal cell proliferation in sham+IMI, but not OVX+IMI rats suggesting that imipramine's effects to increase hippocampal cell proliferation in female rats is related to reproductive status. Cell death (pyknotic cells) was decreased only in the 'postpartum' group. Together, these results suggest an important, though complex, role for gonadal hormones in the cellular changes accompanying this model of postpartum depression.

Antipsychotic-induced hyperprolactinemia and delusion of pregnancy.

The authors describe 12 patients with antipsychotic-induced hyperprolactinemia. Six patients had erroneous ideas of being pregnant (four delusional and two non-delusional) temporally associated with hyperprolactinemia and resolving as prolactin levels returned to normal. The remaining six patients did not develop such ideas. Contrasting the clinical features of the two groups of patients in the context of existing literature informs on the possible biological and cognitive mechanisms that can be hypothesized to underlie the relationship between hyperprolactinemia due to antipsychotics and the development of inaccurate beliefs and feelings about pregnancy, and the effect of current mental state on the propensity to develop these beliefs.

In vivo infusion of interleukin-1beta and chorionic gonadotropin induces endometrial changes that mimic early pregnancy events in the baboon.

Both human chorionic gonadotropin (hCG) and IL-1beta induce changes in the endometrium that are associated with the establishment of pregnancy. We investigated the synergistic effect of these two embryonic signals on endometrial function using a baboon model of simulated pregnancy. Recombinant hCG (30 IU/d) was infused between d 6 and 10 post ovulation (PO) to mimic blastocyst transit. On the expected day of implantation (d 10 PO), IL-1beta (12 ng/d) or IL-1 receptor antagonist (IL-1Ra; 12 ng/d) was infused for an additional 5 d. Endometria were harvested on d 15 PO. Both hCG and hCG plus IL-1beta induced marked differences in the distribution of alpha-smooth muscle actin, proliferation marker Ki67, decidualization marker IGF-binding protein-1, and cyclooxygenase-1. The most marked effect of IL-1beta was the induction of IGF-binding protein-1 protein in stromal cells close to the apical surface, whereas cyclooxygenase-1 was down-regulated in the glandular epithelium. Protein arrays of uterine flushings showed significant suppression of death receptors, Fas and TNF receptor 1, in the hCG- with or without IL-1beta-treated groups, suggesting an inhibition of apoptosis. Additionally, cytotoxic T lymphocyte antigen-4, matrix metalloproteinase-3, and IL-4 were suppressed in treated animals compared with controls. However, no differences were observed in cytokine profile between hCG-treated and hCG- plus IL-1beta-treated baboons. This study confirms that in preparation for pregnancy, the primate endometrium undergoes both morphological and functional changes, which are modulated by hCG and IL-1beta, that lead to the inhibition of apoptosis and the development of an immunotolerant environment. These changes suggest that infusion of IL-1beta at the time of implantation into the nonpregnant baboon treated with hCG synergizes with hCG and mimics the early endometrial events associated with the presence of an embryo.

Termination of pseudopregnancy in the rat alters the response to progesterone, chlordiazepoxide, and MK-801 in the elevated plus-maze.

RATIONALE: Allopregnanolone, a neurosteroid-reduced metabolite of progesterone, is a well-documented positive modulator of the gamma-aminobutyric type A (GABA(A)) receptor. As has been reported for other positive modulators of the GABA(A) receptor, chronic exposure to neurosteroids is hypothesized to decrease GABA(A) receptor function. Drawing from the literature on chronic exposure to benzodiazepines or alcohol, putative changes in N-methyl-D-aspartate (NMDA) receptor function are also expected after chronic neurosteroid exposure. OBJECTIVES: To assess the sensitivity of the GABA(A) and NMDA receptors after chronic elevation of neurosteroid produced by termination of pseudopregnancy in behavioral tests of anxiety and sensorimotor coordination. METHODS: Female rats ovariectomized on day 10 of pseudopregnancy were tested in the elevated plus-maze and on the rotor rod after an acute injection of progesterone (4 mg/0.2 ml, s.c.), chlordiazepoxide (5 or 15 mg/kg, i.p.), or MK-801 (0.025, 0.05, or 0.1 mg/kg, i.p.). RESULTS: Pseudopregnancy termination produced an anxiogenic-like response in the plus-maze; an acute injection of progesterone restored baseline levels of behavior in this test. Pseudopregnancy termination eliminated the anxiolytic-like, sedative, and ataxic effects of chlordiazepoxide. In contrast, pseudopregnancy termination produced an increased sensitivity to the anxiolytic-like and ataxic effects of MK-801. CONCLUSIONS: The effects of pseudopregnancy termination on the behavioral response to positive modulators of the GABA(A) receptor are consistent with results from studies in which chronic exposure to neurosteroids decreases the response to acute neurosteroid and benzodiazepine administration. However, unlike the enhanced glutamatergic tone resulting from discontinuation of chronic benzodiazepine or alcohol exposure, the termination of pseudopregnancy apparently decreases NMDA receptor function.

Termination of pseudopregnancy in the rat produces an anxiogenic-like response that is associated with an increase in benzodiazepine receptor binding density and a decrease in GABA-stimulated chloride influx in the hippocampus.

The neurosteroid, 3alpha-OH-5alpha-pregnan-20-one (allopregnanolone) is a potent positive modulator of the GABA(A) receptor complex. Its pharmacological spectrum of action is shared by the benzodiazepines and alcohol, and includes anxiolytic, anticonvulsant, ataxic, and hypnotic effects. Discontinuation from chronic exposure to allopregnanolone or other neuroactive steroids has been shown to elicit behavioral effects that are typically seen in benzodiazepine or alcohol withdrawal. In this series of experiments, the effects of an endogenous elevation of ovarian steroids on brain GABA(A) receptor function was examined by inducing pseudopregnancy. In female rats, pseudopregnancy did not affect behavior in the elevated plus-maze, despite a persistent increase in circulating levels of allopregnanolone. Pseudopregnancy was associated with a decrease in the maximal binding density of 3H-flunitrazepam in the cerebral cortex and cerebellum; however, GABA-stimulated chloride influx in cerebral cortical, hippocampal, and cerebellar synaptoneurosomes remained unaffected during pseudopregnancy. Termination of pseudopregnancy by ovariectomy precipitated an anxiogenic-like effect in the elevated plus-maze. The withdrawal from elevated ovarian steroid levels also increased the number of benzodiazepine receptors and decreased GABA-stimulated chloride influx in the hippocampus.

Expressions of VEGF and its receptors in rat corpus luteum during interferon alpha administration in early and pseudopregnancy.

It is accepted that angiogenesis plays an important role in the development of the corpus luteum (CL) and is probably necessary for normal lutein cell function. A number of drugs currently being tested in clinical trials as possible angiogenesis inhibitors were not originally developed with the intention of suppressing tumor angiogenesis. Interferon alpha (IFN-alpha) is one of the notable examples of such 'accidental angiogenesis inhibitors' and daily administration of IFN-alpha is known to suppress tumor growth, tumor vascularization, and down-regulation of various growth factors. We investigated the effects of IFN-alpha treatment on the expression of vascular endothelial growth factor (VEGF), and its receptors KDR and Flt-1, and CD34 in CL during the first week of pseudopregnancy and pregnancy in hormonally induced rat ovaries by immunohistochemistry and Western blot techniques. Basal body temperatures of the drug-treated rats, as an indicator of treatment effect, were determined daily and were increased significantly when compared to controls (38.03 +/- 0.18 vs. 36.6 +/- 0.1 degrees C), respectively. The effect of IFN-alpha treatment was minimal when the entire week was evaluated, however, the expression of VEGF decreased at 3rd, 5th, and 7th days of both pregnancy and pseudopregnancy, when compared to the 1st day, whereas there was not a such alteration in the untreated rats regarding these days. The daily subcutaneous administrations of 672.500 U IFN-alpha2b had minimal effects on the expressions of VEGF, and its two receptors KDR and Flt-1 in either pregnant or pseudopregnant corpora lutea utilizing HSCORE.

Induction of pseudopregnancy in the American Black Bear (Ursus americanus).

The aim of this study was to determine whether American Black Bears (Ursus americanus) can experience a pseudopregnancy of the same duration as pregnancy. To do this, we treated three nonmated, captive female bears with human chorionic gonadotropin (hCG) during one breeding season, and saline during another. Progesterone concentrations were measured in monthly blood samples to determine whether pseudopregnancy had occurred. Elevated progesterone concentrations were observed in two out of three bears treated with hCG. We conclude that 1) Elevated progesterone concentrations can be induced in black bears by injection of 35 U/kg hCG during the mating season. 2) Bears can experience a pseudopregnancy, identical in length to pregnancy, in which progesterone profiles are indistinguishable from those of pregnancy.

Possible role of cyclooxygenase II in the acquisition of ovarian luteal function in rodents.

The development of the corpus luteum (CL), which involves angiogenesis, is essential for the establishment of early pregnancy. We investigated the roles of the prostaglandin synthases cyclooxygenase (COX) I and COX-II in angiogenesis and progesterone production in the newly formed CL, using inhibitors of the COX enzymes and the gonadotropin-induced pseudopregnant rat as a model. Injection of indomethacin, a nonselective COX inhibitor, on the day of ovulation and the following day decreased serum levels of progesterone, as did injection of the selective COX-II inhibitor NS-398. In contrast, a selective COX-I inhibitor, SC-560, had no effect on serum progesterone concentrations. None of the inhibitors had any effect on the weight of the superovulated ovaries or on the synthesis of progesterone by cultured luteal cells. To determine whether changes in angiogenesis are responsible for the decrease in progesterone synthesis, we measured hemoglobin and CD34 levels in luteinized ovaries following injection of COX inhibitors and measured the relative frequency of cells positive for platelet-endothelial cell adhesion molecule as a specific marker for endothelial cells. All of these parameters were reduced by the COX-II inhibitors, suggesting that changes in the vasculature are responsible for the decrease in serum progesterone. Histological examination of ovarian corrosion casts indicated that NS-398 inhibited the establishment of luteal capillary vessels following the injection of hCG. The results are consistent with the hypothesis that the activity of COX-II is associated with the formation of functional CL via its stimulation of angiogenesis.

8-Chloro-cAMP-related changes on mice uteri.

Histopathological effects of cAMP analog (8-Chloro-cAMP), tamoxifen, and medroxyprogesterone, alone or combined, upon BALB/c mice uteri are reported. 8-Chloro-cAMP diminished uterine weight, but did not modify its histopathology or estral cycle significantly. Tamoxifen diminished uterine weight showing cystic hyperplasia and an estral cycle arrested at diestrus. Medroxyprogesterone increased uterine weight, caused a swelling of the endometrium and a pseudopregnancy estrus. When combined with 8-Chloro-cAMP, tamoxifen or medroxyprogesterone always had a predominant effect. We concluded that the effects of 8-Chloro-cAMP on mice uteri did not cause significant changes on its histopathology, but diminished its weight.

Neurosteroid withdrawal model of perimenstrual catamenial epilepsy.

PURPOSE: Perimenstrual catamenial epilepsy, the increase in seizure frequency that some women with epilepsy experience near the time of menstruation, may in part be related to withdrawal of the progesterone metabolite allopregnanolone, an endogenous anticonvulsant neurosteroid that is a potent positive allosteric gamma-aminobutyric acidA (GABA(A)) receptor modulator. The objective of this study was to develop an animal model of perimenstrual catamenial epilepsy for use in evaluating drug-treatment strategies. METHODS: A state of prolonged high serum progesterone (pseudopregnancy) was induced in 26-day-old female rats by sequential injection of pregnant mares' serum gonadotropin and human chorionic gonadotropin. Neurosteroid withdrawal was induced by treatment with finasteride (100 mg/kg, i.p.), a 5alpha-reductase inhibitor that blocks the conversion of progesterone to allopregnanolone. Plasma progesterone and allopregnanolone levels were measured by gas chromatography/electron capture negative chemical ionization mass spectrometry. Seizure susceptibility was evaluated with the convulsant pentylenetetrazol (PTZ). RESULTS: Plasma allopregnanolone levels were markedly increased during pseudopregnancy (peak level, 55.1 vs. control diestrous level, 9.3 ng/mL) and were reduced by 86% 24 h after finasteride treatment (6.4 ng/mL). Progesterone levels were unaffected by finasteride. After finasteride-induced withdrawal, rats showed increased susceptibility to PTZ seizures. There was a significant increase in the number of animals exhibiting clonic seizures when challenged with subcutaneous PTZ (60 mg/kg) compared with control pseudopregnant animals not undergoing withdrawal and nonpseudopregnant diestrous females. The CD50 (50% convulsant dose) was 46 mg/kg, compared with 73 mg/kg in nonwithdrawn pseudopregnant animals and 60 mg/kg in diestrous controls. The threshold doses for induction of various seizure signs, measured by constant intravenous infusion of PTZ, were reduced by 30-35% in neurosteroid-withdrawing animals compared with control diestrous females. No change in threshold was observed in pseudopregnant rats treated from days 7 to 11 with finasteride, demonstrating that high levels of progesterone alone do not alter seizure reactivity. CONCLUSIONS: Neurosteroid withdrawal in pseudopregnant rats results in enhanced seizure susceptibility, providing an animal model of perimenstrual catamenial epilepsy that can be used for the evaluation of new therapeutic approaches.

NMDA-mediated activation of the medial amygdala initiates a downstream neuroendocrine memory responsible for pseudopregnancy in the female rat.

In female rats, genitosensory stimulation received during mating initiates twice-daily prolactin (PRL) surges, a neuroendocrine response that is the hallmark of early pregnancy or pseudopregnancy (P/PSP). Nocturnal and diurnal PRL surges are expressed repeatedly for up to 2 weeks after copulation, suggesting that a neuroendocrine memory for vaginocervical stimulation (VCS) is established at the time of mating. These studies investigated whether the processing and retention of VCS involves acute glutamatergic activation or de novo protein synthesis within the medial nucleus of the amygdala (MEA), a VCS-responsive brain site that is implicated in P/PSP initiation. Pharmacological activation of the MEA with the glutamate agonist, NMDA, initiated nocturnal PRL surges, causing a PSP state in females that had not received VCS. P/PSP initiation by mating was prevented by intra-amygdalar infusion of the NMDA receptor antagonist, 2-amino-5-phosphonopentanoic acid (AP-5), provided that it was administered before mating. AP-5 treatment also disrupted mating-induced c-fos expression in the principle bed nucleus of the stria terminalis and the ventrolateral division of the ventromedial hypothalamic nucleus, but not in the medial or anteroventral periventricular preoptic nuclei. Neither P/PSP nor downstream cellular activation was prevented when a protein synthesis inhibitor, anisomycin, was administered to the MEA. The results indicate that MEA cells are critical to the early processing of VCS through NMDA channel activation, rapidly conveying information to downstream hypothalamic cell groups that modulate neuroendocrine function.

Single daily intramuscular injections of low quantities of recombinant ovine interferon-tau extends luteal life-span in Angora goats.

The objective of this study was to determine whether single, daily intramuscular injections of low amounts of ovine interferon-tau (ovIFN-tau) would extend luteal life-span in nonpregnant Angora goats. Female goats were assigned randomly to receive a single daily injection of 1) PBS (control; n = 11), 2) 125 microg/d ovIFN-tau (n = 11), or 3) 500 microg/d ovIFN-tau (n = 11) from d 14 to 20 after estrus. Luteal life-span was defined as the number of days from the synchronized estrus until serum progesterone (P4) declined (< 0.5 ng/mL) and was of normal duration in controls (19.4 +/- 0.3 d) but was increased (P < 0.05) in goats receiving 125 microg/d (23.2 +/- 1.3 d) and 500 microg/d (25.5 +/- 1.2 d) ovIFN-tau. Injection of either ovIFN-tau dose caused an initial decrease (P < 0.05) in serum P4 concentrations relative to controls but did not differ from controls thereafter. Rectal temperatures increased (P < 0.05) following ovIFN-tau treatment until d 18 for goats given the lower dose and throughout the treatment period for those given 500 microg/d. In summary, injections of as little as 125 microg/d of ovIFN-tau extended luteal life-span in goats. This dose caused a transient reduction in serum P4 concentrations and induced hyperthermia.