Virgin Animals Research Articles

The role of prolactin in the suppression of the response to restraint stress in the lactating mouse.

Suppression of the hypothalamic-pituitary-adrenal (HPA) axis is a well-characterised maternal adaptation that limits the exposure of the offspring to maternally-derived stress hormones. This current study has investigated the possible involvement of the lactogenic hormone, prolactin, in this physiologically important adaptation. As expected, circulating prolactin levels were higher in unstressed lactating mice compared to their virgin counterparts. Interestingly however, the ability of an acute period of restraint stress to further elevate prolactin levels was diminished in the former group. The stress-induced rise in prolactin levels in the virgin animals was concurrent with an increase in prolactin receptor activation within the adrenal cortical cells. This adrenal response was not seen in either the stressed or control lactation group, an observation that may be in part explained by the observed downregulation of prolactin receptor mRNA expression within this tissue. Further evidence of suppression of the HPA axis during lactation was revealed using in situ hybridisation to demonstrate that while acute restraint stress increased corticotrophin releasing hormone (CRH) mRNA expression in the hypothalamic paraventricular nucleus in both virgin and lactating mice, the magnitude of this response was reduced in the latter group. This potentially adaptive response did not, however, appear to result from the altered prolactin profile during lactation because it was not affected by the pharmacological suppression of prolactin secretion from the pituitary. This study therefore suggests that during lactation the response of the HPA axis to stress is suppressed at multiple physiological levels which are mediated by both prolactin-dependent and prolactin-independent mechanisms.

Profile of maternal serum oxytocin in postpartum and non-pregnant rats

Oxytocin is primarly secreted in the brain as a neuromodulator that affects numerous neurophysiological and behavioral processes. It is also produced in the ovaries and uterus to stimulate delivery and lactation. Oxytocin mRNA is found in the endometrial epithelial cells of non-pregnant women during ovulation and menstruation. Until recently, there have been no data on scientific-level oxytocin in virgin female rats. This study aimed to compare the level of oxytocin in different physical biology between postpartum and non-pregnant experimental animals (virgin or had never given birth). This experimental study was conducted on 19 female white rats (Rattus norvegicus) allocated to two groups: T1 and T2. The ten rats in group T1 (nulliparous virgin) and the nine in group T2 (postpartum) were sacrificed on day two, except for group T1, which were sacrificed following vaginal delivery. Blood was collected intracardiacally, and serum oxytocin levels were evaluated using an ELISA assay. The T-test was used for statistical data analysis. The serum oxytocin level in the T2 group (628.06 ± 168.72 pg/mL) was significantly higher than in the T1 group (366.71 ± 185.03 pg/mL; P < 0.05). In conclusion, oxytocin levels were higher in postpartum animals than in virgin animals. Thus, oxytocin plays a greater role in female reproduction than in normal physiological condition.

The beneficial effects of virgin olive oil against oxidative stress induced by hypercholesterolemia in rats

Cardiovascular disease (CVD) remains the major cause of mortality in the world, typically claiming a third of all deaths. The primary cause of CVD is atherosclerosis. Therefore, timely prevention and therapy of atherosclerosis are able to reduce the risk of the development of its clinical manifestations. Anti-atherosclerotic activity of medicinal plants mainly appears in their multiple effects. This study was carried out to evaluate the hypolipidemic activity of virgin olive oil in experimentally induced hyperlipemic Wistar. A total of 24 rats were randomly allocated to 4 equal groups and treated as follows for 50 days: (1) Normal control (NC); that were fed with a standart diet; (2) High Cholesterol Diet Control (HCD); which received high cholesterol diet for 50 days; (3) Animals receiving high cholesterol diet for 50 days, after this period the animals are fed for eight days by the standard food and receiving by gavage virgin olive oil (HCD+VOO) and (4) Animals fed for eight days with the standard food and receiving by gavage olive oil (VOO). High Cholesterol Diet containing yolk egg and coconut oil. Results showed that olive oil caused a significant (p < 0.01) reduction in serum levels of Total Cholesterol (TC), Triglycerides (TG), Low–Density Lipoprotein Cholesterol (LDL) and Atherogenic Index Serum (AIS). The results also demonstrated a significant (p < 0.01) increase in High–Density Lipoprotein Cholesterol (HDL). Moreover, virgin olive oil induced a significant reduction in liver lipid content. On the other hand, a High cholesterol diet induced oxidative stress was measured by estimating reduced glutathione level and amount of thiobarbituric acid reactive substances (TBARS) formed as an index of lipid peroxidation in a liver and a heart. Virgin olive oil supplementation attenuated all these variations. Our observations of the study indicate that the virgin olive oil has a significant antihyperlipidemic potential.

Meta-analytic evidence that animals rarely avoid inbreeding.

Animals are usually expected to avoid mating with relatives (kin avoidance) as incestuous mating can lead to the expression of inbreeding depression. Yet, theoretical models predict that unbiased mating with regards to kinship should be common, and that under some conditions, the inclusive fitness benefits associated with inbreeding can even lead to a preference for mating with kin. This mismatch between empirical and theoretical expectations generates uncertainty as to the prevalence of inbreeding avoidance in animals. Here, we synthesized 677 effect sizes from 139 experimental studies of mate choice for kin versus non-kin in diploid animals, representing 40 years of research, using a meta-analytical approach. Our meta-analysis revealed little support for the widely held view that animals avoid mating with kin, despite clear evidence of publication bias. Instead, unbiased mating with regards to kinship appears widespread across animals and experimental conditions. The significance of a variety of moderators was explored using meta-regressions, revealing that the degree of relatedness and prior experience with kin explained some variation in the effect sizes. Yet, we found no difference in kin avoidance between males and females, choice and no-choice experiments, mated and virgin animals or between humans and animals. Our findings highlight the need to rethink the widely held view that inbreeding avoidance is a given in experimental studies.

Oral, Cloacal, and Hemipenal Actinomycosis in Captive Ball Pythons (Python regius).

Ball pythons (Python regius) are one of the most commonly kept and bred reptiles in captivity. In a large ball python breeding colony, a unique syndrome characterized by granulomatous inflammation of the cloaca and hemipenes (phalli) was observed in 140 of 481 (29.1%) breeding males, but only one of 1,446 breeding females. Lesions were absent in virgin males (n = 201) and virgin females (n = 293). On postmortem examination (n = 13, 12 males, 1 female), numerous well-defined mucosal and submucosal granulomas were present in the hemipenes (males) and cloaca (males and female). Extension into the coelomic cavity and liver was noted in a subset of these animals. An additional small subset of breeder animals (6/2027; 0.3%) presented with oral and mandibular swellings. Postmortem examination (n = 4, all female) showed oral lesions histologically indistinguishable from the cloacal/hemipenal lesions. Aerobic bacterial culture of a hepatic granuloma of one snake resulted in the isolation of filamentous, Gram-positive bacilli; amplification, and sequencing of the 16S rRNA gene and subsequent phylogenetic analysis of the isolate identified the bacterium as a novel species of Actinomyces. Screening of cloacal and oral granulomas using a specific, heminested 16S rRNA PCR assay confirmed the presence of the agent in all 17 snakes, as well as in cloacal swabs taken at the time of necropsy in 11/13 snakes. The Actinomyces sp. was also identified by PCR of cloacal swabs of unaffected snakes (n = 94) from the affected colony and two unrelated, grossly unaffected breeding colonies. In the affected colony, 65.5% of breeding animals (n = 23) but only 11.9% of virgin animals (n = 42) tested PCR positive, with breeding status being a significant predictor of bacterium presence (P < 0.00001). This study characterizes a granulomatous mucosal disease syndrome of breeding male ball pythons associated with a novel Actinomyces. In stark contrast to male snakes, the presence of the bacterium in both breeding and virgin females was very rarely associated with clinical disease. Though additional studies are necessary, these data suggest a role for the novel bacterium in the disease process, a predilection for clinical disease in male snakes, and the potential for sexual transmission of the disease.

Mammogenesis Effect of Hot Aqueous Extract of Mentha spicata Leaves on Mammary Tissue of Ovariectimized Rabbits

Background: Plants are highly rich in phytochemicals being used to treat various conditions, and a richsource of polyphenols is Spearmint (Mentha spicata L). Such polyphenols have demonstrated multiplebioactivities. This study aims to investigate the effects of the intake of hot-aqueous extracts of spearmintleaves on mammary gland development and growthMethod: Thirty six female rabbits were divided into two main groups (18 rabbits/group): (virgin andlactating). Each group was further subdivided into three subgroups (Control, Ovariectomized (OVX) andSpearmint, (6 rabbits/group).All three groups tissues were examined for histological, histochemical andbiochemical enzymatic analysis.Result: Spearmint-treated ovariectimized virgin animals demonstrated an increase in the size of lobules thataffected the alveolar bud. In the ovariectimized lactating group treated with spearmint, it was shown thatthe lobules were enlarged and produced more branching alveoli. The stain (PAS) and ALP showed positivereaction in the spearmint group treated with lactation.Conclusion: The hot methanol extract of the spearmint Mentha spicata leaves have a beneficial effect onmammary gland growth and development.

An animal model of gestational obesity and prediabetes: HISS-dependent insulin resistance induced by a high-sucrose diet in Sprague Dawley rats.

This study developed an animal model of gestational obesity and prediabetes in Sprague Dawley rats using 35% sucrose supplementation (SS). Postprandially, insulin stimulates glucose uptake and nutrient partitioning via insulin-dependent action as well as hepatic insulin sensitizing substance (HISS) - dependent action. HISS is glycogenic in heart, kidney, and skeletal muscle (contrasting insulin's lipogenic actions in liver and adipose tissue) and is responsible for the vasodilatory action of insulin. Postprandial insulin sensitivity was quantified using the rapid insulin sensitivity test (RIST). Animals at 15-day gestation and virgin animals received SS for 8 weeks (with a 2-week recovery), 10 weeks, or 22 weeks. SS in pregnant and virgin rats eliminated HISS-dependent glucose uptake, resulting in compensatory hyperinsulinemia and resultant hypertriglyceridemia and obesity. In groups with SS for 8 weeks followed by a 2-week recovery, there was spontaneous partial recovery of HISS-dependent glucose uptake in virgins and complete recovery in pregnancy. The 10-week SS resulted in complete absence of HISS-dependent glucose uptake and produced a model of gestational obesity and prediabetes. The 22-week SS did not produce hyperglycemia or worsen hyperinsulinemia but did increase hypertriglyceridemia above 10-week SS. This substantiates the use of 10-week SS as a model of gestational obesity and (or) prediabetes, allowing further studies into treatments of gestational obesity and insulin resistance.

Inguinal White Adipocytes Differentiate to Alveolar Epithelial Cells that Constitute Mammary Cells in Pregnant Rats

IntroductionInguinal adipose tissue has been shown to exhibit high plasticity that exceeds its capacity to differentiate to beige or brown adipocytes ( Giordano et al., 2014, Cinti, 2018). This has led to the concept of pinking whereby adipocytes differentiate to develop an alveolar structure that forms part of the mammary gland.MethodsVirgin and pregnant Sprague Dawley rats were used in this study. Food intake for virgin animals (aged 4 weeks) and body weight for virgin and pregnant animals were measured three times a week. Virgin rats were tissue sampled at 10 weeks of age while pregnant rats, mated at 10 weeks of age, were tissue sampled at either 50% and 90% of pregnancy (10 and 19 days of pregnancy, respectively). Gene expression was studied in the interscapular BAT, omental and inguinal adipose tissue using qPCR. Omental and inguinal sections were stained with H&amp;E for examination of histological appearance.ResultsThe histological sections showed differentiation of inguinal adipocytes to show an alveoli appearance composed of epithelial cells in pregnant but not virgin rats. Gene expression analysis revealed a higher expression of whey acidic protein (WAP) and E74‐Like ETS Transcription Factor 5 (ELF5) genes during pregnancy in inguinal adipocytes of pregnant rats compared to virgin rats. These two genes were absent in the interscapular and omental fat depots of virgin rats. Continuous loss of PPARG with pregnancy appeared in the inguinal adipose tissue. At the gross level, the inguinal fat appeared more compact in pregnant compared to virgin rats.ConclusionsInguinal adipocytes appear to exhibit a pronounced ability to form alveoli which comprises part of the mammary cell structure through gestation. Previous studies have confirmed this from measures of histology and molecular analysis. Further studies designed to examine the mechanism will help to determine factors that may accelerate the formation of neoplastic cells in the mammary glands and possibly breast cancer. Inguinal adipose tissue may no longer be considered a true fat depot in pregnancy.Support or Funding InformationThis work was funded by the EU‐CASCADE fellowship scheme funded by the EU’s 7th FP PCOFUND‐GA‐2012‐600181 (ND), LA was the recipient of a doctoral scholarship from Mutah University.

Mass drives mating success in Armadillidium vulgare (Crustacea, Oniscidea)

In the terrestrial crustacean Armadillidium vulgare, a large size range exists in natural populations within which males and females could potentially mate. Because of continuous growth far beyond sexual maturity, the largest individuals can be nearly ten times the live mass of the smallest sexually mature individuals. In this study, we explored the influence of male and female body mass on the mating behaviour and success. Starting with a representative panel of males and females in which females are significantly larger than males in average, we followed the sexual behaviour of 23 groups of 20 mixed-sex virgin animals under conditions comparable with natural field situation during the early breeding season. We found a correlation between paired individuals showing an assortative pairing. During pairing male stimulates female and duration of stimulation is determinant for pairing follow-up: efficient stimulation is correlated with female size and not with male size. In consequence, pairs in mating show a reversed size dimorphism between male and female where female are about 20% smaller. Largest females were not mated. During copulation behaviour, the quantity of sperm transferred is positively correlated with copulation duration. Stored sperm can be used for immediate breeding by the female and stored in the spermatheca for future breeding. The last option allows to largest females in the field to continue breeding without additional mating, avoiding the lack of availability of large males able to stimulate them efficiently.

Enhanced Response to Oxytocin in Myometrium of Proven Breeder Compared to Virgin Rats Does Not Depend on Augmented Expression of Oxytocin Receptors

ObjectiveOur overall hypothesis is that pregnancy's mechanical and hormonal stimuli induce permanent changes in the properties of uterine tissue. We have shown previously that the response to oxytocin of the non‐pregnant (NP) myometrium is more pronounced in proven breeder than in virgin animals. Our objective here was to investigate some of the possible mechanisms that could produce such difference: 1) Altered number of oxytocin receptors (OXTR); 2) Altered production of intracellular prostaglandins; 3) Altered availability of voltage gated calcium channels (VGCC).MethodVirgin (V) and proven breeder (PB) NP female 18 week old rats were staged and euthanized at proestrus. One uterine horn was dissected in strips suspended in a tissue bath containing Krebs solution (in mM, NaCl 117, KCl 4.7, NaHCO3 25, MgCl2 1.2, KH2PO4 1.2, CaCl2 2.5, glucose 11, pH= 7.4) at 37°C and bubbled with 95% O2 and 5% CO2. Dose response curves to oxytocin (10E‐10 to 10E‐5 M) were recorded in the presence of indomethacin or after exposure to a 0 CaCl2 modified Krebs. The other uterine horn was flash frozen in liquid NO2 and later used for ELISA (kit from Wuhan Fine Biotech, Wuhan China) and qRT‐PCR experiments (Taqman® gene expression assays (Life Technologies) and QuantStudio™ 5 real‐time PCR system (Applied Biosystems, Grand Island, NY) were used to examine the gene of interest mRNA expression using the comparative CT method (Schmittgen and Livak, 2008).ResultsIn the ELISA experiments, NP samples showed a barely significant (32±14%, P=0.040) elevation of OXTR in V (n = 8) vs PB myometrium. This is in open contradiction to our previous motility data. To investigate whether this inversion trend in protein level is matched at the mRNA level, we evaluated OXTR gene expression in NP strips (n=5, in quadruplicates). No significant difference was detected between V and PB expression of β‐actin (P= 0.099). Instead, a significant difference was found in the OXTR gene expression (P&lt;0.01) and the 2−ΔΔCt (RQ) was 0.18 (Min RQ=0.12, Max RQ=0.27, indicative of an 8.3 to 3.7 folds decrease in the OXTR mRNA level in PB vs V samples. On the other hand, in the presence of 10 μM indomethacin (COX inhibitor) or in the absence of extracellular calcium the differences in the responses to oxytocin in V and PB myometrial strips were attenuated (−98% and −96% respectively). This suggest important roles of second messengers activated pathways in the more robust effects of oxytocin in NP PB strips.ConclusionsWhile our previous functional experiments suggested that PB myometrium might contain a higher number of OXTR, ELISA and PCR experiments imply that the opposite might be true. The gene expression of the OXTR is frankly stronger in V, while the actual protein expression is not significantly different between V and PB. A better explanation for our pharmacological observations involves differences in the activity of channels and intracellular mechanisms activated by oxytocin, some of which we presented here and are currently under investigation.Support or Funding InformationThis study was funded by an MWU intramural research grant to MP.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Calcium restriction during lactation has minimal effects on post-weaning mineral metabolism and bone recovery.

Dietary calcium (Ca) restriction during lactation in the rat, which induces intra-cortical and endocortical remodeling, has been proposed as a model to study bone matrix maturation in the adult skeleton. The purpose of this study was to assess the effects of dietary Ca restriction during lactation on post-weaning mineral metabolism and bone formation. Mated female Sprague-Dawley rats were randomized into groups receiving either 0.6% Ca (lactation/normal Ca) or 0.01% Ca (lactation/low Ca) diets during lactation. Virgin animals fed normal Ca were used as controls (virgin/normal Ca). At the time of weaning, animals on the low Ca diet were returned to normal Ca and cohorts of all three groups were sacrificed at days 0, 1, 2, 7, and 14 post-weaning. Lactation caused bone loss, particularly at the endocortical surface, but the amount was not affected by dietary Ca. Rats in the lactation/low Ca group had increased cortical porosity compared to the other groups, particularly within the size range of secondary osteons. Dietary Ca restriction during lactation did not affect post-weaning bone formation kinetics or serum Ca and phosphate levels. In both lactation groups, there was a transient increase in phosphate and fibroblast growth factor 23 (FGF23) post-weaning, which trended toward virgin/normal Ca levels over time. Thus, the additional challenge of low dietary Ca during lactation to induce intra-cortical remodeling in the rat has minimal effects on bone formation kinetics and mineral metabolism during the post-weaning period, providing further justification for this model to study matrix maturation in the adult skeleton.

Osteocytes Acidify Their Microenvironment in Response to PTHrP In Vitro and in Lactating Mice In Vivo.

Osteocytes appear to mobilize calcium within minutes in response to PTH injections; we have previously shown that osteocytes remove their perilacunar matrix during lactation through activation of the PTH type 1 receptor. Mechanisms utilized by osteocytes to mobilize calcium are unknown but we hypothesized that the molecular components may be similar to those used by osteoclasts. Here we show, using IDG-SW3 cells that ATP6V0D2, an essential component of vacuolar ATPase in osteoclasts, and other genes associated with osteoclastic bone resorption, increase with osteoblast to osteocyte differentiation. Furthermore, PTHrP increases ATP6V0D2 expression and induces proton generation by primary osteocytes, which is blocked by bafilomycin, a vacuolar ATPase inhibitor. These in vitro proton measurements raised the question of osteocyte viability in an acidic environment. Interestingly, osteocytes, showed enhanced viability at pH as low as 5 compared to osteoblasts and fibroblasts in vitro. To study in vivo acidification by osteocytes, virgin and lactating CD1 mice on a low calcium diet were injected with the pH indicator dye, acridine orange, and their osteocyte lacuno-canalicular system imaged by confocal microscopy. Lower pH was observed in lactating compared to virgin animals. In addition, a novel transgenic mouse line with a topaz variant of green fluorescent protein (GFPtpz)-tagged collagen α2(I) chain was used. Instead of the expected reduction in GFP-fluorescence only in the perilacunar matrix, reduced fluorescence was observed in the entire bone matrix of lactating mice. Based on our experiments showing quenching of GFP in vitro, we propose that the observed reduction in GFP fluorescence in lactating mice is due to quenching of GFP by the acidic pH generated by osteocytes. Together these findings provide novel mechanistic insight into how osteocytes remove calcium from their perilacunar/pericanalicular matrices through active acidification of their microenvironment and show that osteocytes, like osteoclasts, are resistant to the negative effects of acid on viability. © 2017 American Society for Bone and Mineral Research.

Pup exposure facilitates retrieving behavior via the oxytocin neural system in female mice

Parental behavior in mammals is innate, but it is also facilitated by social experience, specifically social interactions between the parent and infant. Social interactions with infants also induce the alloparental behavior of virgin animals. Oxytocin (OT) plays an important role in mediating alloparental behavior. Although parental behavior is modulated by the medial preoptic area (MPOA) and adjacent regions, it is unclear how OT acts in these regions as a control mechanism of alloparental behavior promoted by adult-pup interaction. The aim of this study was to investigate the role of OT for facilitating effects of adult-pup interactions on alloparental behavior via neural activity of preoptic area (POA), including MPOA and adjacent area. For this purpose, we conducted behavioral tests and examined the neural activity of the OT system in POA. Virgin female mice that were repeatedly exposed to pups showed shorter retrieving latencies and higher number of c-Fos expressing neurons in POA, particular in lateral preoptic area (LPO) compared to control animals that were exposed to pups only one time. In addition, repeated pup exposure increased the proportion of OT neurons and OTR neurons expressing c-Fos in POA. The concentration of OT also significantly increased in the POA. Finally, infusion of an OT antagonist into the POA area blocked the facilitating effects of repeated pup exposure on retrieving behavior. These results demonstrated that the facilitating effects of repeated pup exposure on alloparental behavior occurred via an organizational role of the OT system.

GABAergic inhibition is weakened or converted into excitation in the oxytocin and vasopressin neurons of the lactating rat.

BackgroundIncreased secretion of oxytocin and arginine vasopressin (AVP) from hypothalamic magnocellular neurosecretory cells (MNCs) is a key physiological response to lactation. In the current study, we sought to test the hypothesis that the GABAA receptor-mediated inhibition of MNCs is altered in lactating rats.ResultsGramicidin-perforated recordings in the rat supraoptic nucleus (SON) slices revealed that the reversal potential of GABAA receptor-mediated response (EGABA) of MNCs was significantly depolarized in the lactating rats as compared to virgin animals. The depolarizing EGABA shift was much larger in rats in third, than first, lactation such that GABA exerted an excitatory, instead of inhibitory, effect in most of the MNCs of these multiparous rats. Immunohistochemical analyses confirmed that GABAergic excitation was found in both AVP and oxytocin neurons within the MNC population. Pharmacological experiments indicated that the up-regulation of the Cl− importer Na+-K+-2Cl− cotransporter isotype 1 and the down-regulation of the Cl− extruder K+-Cl− cotransporter isotype 2 were responsible for the depolarizing shift of EGABA and the resultant emergence of GABAergic excitation in the MNCs of the multiparous rats.ConclusionWe conclude that, in primiparous rats, the GABAergic inhibition of MNCs is weakened during the period of lactation while, in multiparous females, GABA becomes excitatory in a majority of the cells. This reproductive experience-dependent alteration of GABAergic transmission may help to increase the secretion of oxytocin and AVP during the period of lactation.

Plasticity of the prolactin (PRL) axis: mechanisms underlying regulation of output in female mice.

The output of prolactin (PRL) is highly dynamic with dramatic changes in its secretion from the anterior pituitary gland depending on prevailing physiological status. In adult female mice, there are three distinct phases of output and each of these is related to the functions of PRL at specific stages of reproduction. Recent studies of the changes in the regulation of PRL during its period of maximum output, lactation, have shown alterations at both the level of the anterior pituitary and hypothalamus. The PRL-secreting cells of the anterior pituitary are organised into a homotypic network in virgin animals, facilitating coordinated bouts of activity between interconnected PRL cells. During lactation, coordinated activity increases due to the changes in structural connectivity, and this drives large elevations in PRL secretion. Surprisingly, these changes in connectivity are maintained after weaning, despite reversion of PRL output to that of virgin animals, and result in an augmented output of hormone during a second lactation. At the level of the hypothalamus, tuberoinfundibular dopamine (TIDA) neurons, the major inhibitors of PRL secretion, have unexpectedly been shown to remain responsive to PRL during lactation. However, there is an uncoupling between TIDA neuron firing and dopamine secretion, with a potential switch to enkephalin release. Such a process may reinforce hormone secretion through dual disinhibition and stimulation of PRL cell activity. Thus, integration of signalling along the hypothalamo-pituitary axis is responsible for increased secretory output of PRL cells during lactation, as well as allowing the system to anticipate future demands.

The effects of lactation on impulsive behavior in vasopressin-deficient Brattleboro rats

Vasopressin (AVP)-deficient Brattleboro rats develop a specific behavioral profile, which—among other things—include altered cognitive performance. This profile is markedly affected by alterations in neuroendocrine state of the animal such as during lactation. Given the links between AVP and cognition we hypothesized that AVP deficiency may lead to changes in impulsivity that is under cognitive control and the changes might be altered by lactation. Comparing virgin and lactating AVP-deficient female Brattleboro rats to their respective controls, we assessed the putative lactation-dependent effects of AVP deficiency on impulsivity in the delay discounting paradigm. Furthermore, to investigate the basis of such effects, we assessed possible interactions of AVP deficiency with GABAergic and serotonergic signaling and stress axis activity, systems playing important roles in impulse control. Our results showed that impulsivity was unaltered by AVP deficiency in virgin rats. In contrast a lactation-induced increase in impulsivity was abolished by AVP deficiency in lactating females. We also found that chlordiazepoxide-induced facilitation of GABAergic and imipramine-induced enhancement of serotonergic activity in virgins led to increased and decreased impulsivity, respectively. In contrast, during lactation these effects were visible only in AVP-deficient rats. These rats also exhibited increased stress axis activity compared to virgin animals, an effect that was abolished by AVP deficiency. Taken together, AVP appears to play a role in the regulation of impulsivity exclusively during lactation: it has an impulsivity increasing effect which is potentially mediated via stress axis-dependent mechanisms and fine-tuning of GABAergic and serotonergic function.

Loss of Igfbp7 Causes Precocious Involution in Lactating Mouse Mammary Gland

BackgroundInsulin like growth factors (IGFs) and their binding proteins (IGFBPs) are secreted peptides that play major roles in regulating the normal development and maturation of mammary gland. While Igfbp7 has been shown to decrease breast tumor growth, its role in regulating the normal mammary gland development has not been studied. To this end, we generated Igfbp7-null mice and examined the development and maturation of mammary glands in the virgin, pregnant and lactating animals.ResultsWe report here that loss of Igfbp7 significantly retards mammary gland development in the virgin animals. More significantly, the pregnant Igfpb7-null glands contained fewer alveolar structures and that during lactation these glands exhibit the morphological changes that are associated with involution. The transcriptome profile of the Igfbp7-null glands on the lactation day 3 revealed a distinct involution-related gene signature compared to the lactating WT glands. Interestingly, we found that the lactating Igfbp7-null glands exhibit increased expression of Stat3 and enhanced activation of (phosphorylated) Stat3, combined with decreased expression of Stat5 suggesting that the absence of Igfbp7 accelerates the onset of involution. We also found that in absence of Igfpb7, the lactating glands contain increased Igfbp5 protein along with decreased expression of IGF-1 Receptor and Akt activation. Finally, we show that during the normal course of involution, Igfbp7 expression is significantly decreased in the mammary gland.ConclusionOur data suggest that loss of Igfbp7 induces precocious involution possibly through diminished cell survival signals. Our findings identify Igfbp7 as major regulator of involution in the mammary gland.

Lactation Reduces Stress-Caused Dopaminergic Activity and Enhances GABAergic Activity in the Rat Medial Prefrontal Cortex

We investigated the effect of restraint on the release of dopamine, GABA and glutamate in the medial prefrontal cortex (mPFC) of lactating compared with virgin Wistar female rats; besides the expression of D1, neuropeptide Y Y2, GABA receptors and corticotropin-releasing factor (CRF). Results from microdialysis experiments showed that basal dopamine and GABA, but not glutamate, concentrations were higher in lactating rats. In virgin animals, immobilization caused significant increase in dopamine, whereas GABA was unchanged and glutamate reduced. In lactating animals, restrain significantly decreased dopamine concentrations and, in contrast to virgin animals, GABA and glutamate concentrations increased. We found a higher expression of CRF, as well as the D1 and neuropeptide Y Y2 receptors in the left mPFC of virgin stressed rats; also, only stressed lactating animals showed a significant increase in immunopositive cells to GABA in the left cingulate cortex; meanwhile, a significant decrease was measured in virgin rats after stress in the left prelimbic region. The increased inhibition of the mPFC dopamine cells during stress and the down-regulated expression of the neuropeptide Y Y2 receptor may explain the lower CRF and hyporesponse to stress measured in lactating animals. Interestingly, participation of mPFC in stress regulation seems to be lateralized.

Adaptive Changes in Basal and Stress-Induced HPA Activity in Lactating and Post-Lactating Female Rats

Lactation represents a period of marked adaptation of the hypothalamo–pituitary–adrenal HPA axis. We characterized basal and stress-induced HPA activity during lactation and experimental weaning using dynamic blood sampling in rats. Pulsatile and diurnal corticosterone release occurred at all reproductive stages studied (virgin; day 10 of lactation; 3 and 14 days after experimental weaning on day 10 of lactation). However, in lactating rats the diurnal peak was significantly reduced, resulting in a flattened rhythm, and three days after weaning, basal HPA activity was markedly suppressed: the number of pulses and underlying basal levels of corticosterone were reduced and the diurnal rise phase delayed. Marked changes in the HPA response to 10 min noise stress also occurred at these times: being completely absent in lactating animals, but restored and highly prolonged in early weaned animals. Injection of methylprednisolone (2 mg, iv) was used to determine whether changes in fast glucocorticoid suppression correlated with these adaptive changes. Methylprednisolone induced a rapid suppression of corticosterone in virgin animals, but this effect was markedly attenuated in lactating and early weaned animals and was accompanied by significant changes in relative expression of hippocampal glucocorticoid and mineralocorticoid receptor mRNA. All effects were reversed or partially reversed 14 days after experimental weaning. Thus, the presence of the pups has an important influence on regulation of the HPA axis, and while postpartum adaptations are reversible, acute weaning evokes marked reorganisation of basal and stress-induced HPA activity.

Estudo morfológico da sínfise púbica de ratos e camundongos durante a gravidez

O objetivo desse estudo foi avaliar as diferenças existentes na sínfise púbica de camundongos e ratos fêmeas, grávidas e não grávidas, descrevendo as alterações morfológicas ocorridas na articulação com a finalidade de entender os movimentos apresentados pela articulação ao longo da gestação. Para tal, as sínfises foram coletadas de camundongos fêmeas grávidas no 6º, 12º e 18º dias de gestação, e nas ratas com 18 dias de gestação. Foram fixadas em paraformoldeído e a seguir descalcificadas em solução de Morse. Na sequência, as peças foram incluídas em parafina. Cortes de 7 micrômetros foram realizados e corados em Picrosirius e Resorcina-Fucsina. A coloração com Picrosirius evidenciou em camundongos fêmeas virgens a presença de fibras grossas de colágeno diferente dos outros grupos de camundongos, os quais apresentaram fibras finas. A análise de fibras elásticas mostrou que, com o decorrer da gestação, estas aumentam em espessura e número. Em ratas com 18 dias de gestação foi observado o aparecimento de tecido conjuntivo fibroso no disco de cartilagem hialina, aumentando assim, o espaço inter-púbico e modificando a estrutura de sincondrose encontrada nos animais virgens. Observou-se também aumento no diâmetro e quantidade de fibras elásticas em relação às ratas virgens. Podemos concluir que a articulação de camundongos fêmeas grávidas passam por transformações estruturais qualitativas e quantitativas ao longo da gravidez. Em ratas prenhas, além do aumento de fibras elásticas e da distância entre os ossos do quadril, a articulação diferenciou-se pelo aparecimento de tecido conjuntivo fibroso para facilitar o parto.