Maternal Oxytocin Administration Before Birth Influences the Effects of Birth Anoxia on the Neonatal Rat Brain.

Ineffective contractions and prolonged labor are common birth complications in primiparous women, and oxytocin is the most common agent given for induction or augmentation of labor. Clinical studies in humans suggest oxytocin might adversely affect the CNS response to hypoxia at birth. In this study, we used a rat model of global anoxia during Cesarean section birth to test if administering oxytocin to pregnant dams prior to birth affects the acute neonatal CNS response to birth anoxia. Anoxic pups born from dams pre-treated with intravenous injections or infusions of oxytocin before birth showed significantly increased brain lactate, a metabolic indicator of CNS hypoxia, compared to anoxic pups from dams pre-treated with saline. Anoxic pups born from dams given oxytocin before birth also showed decreased brain ATP compared to anoxic pups from saline dams. Direct injection of oxytocin to postnatal day 2 rat pups followed by exposure to anoxia also resulted in increased brain lactate and decreased brain ATP, compared to anoxia exposure alone. Oxytocin pre-treatment of the dam decreased brain malondialdehyde, a marker of lipid peroxidation, as well as protein kinase C activity, both in anoxic pups and controls, suggesting oxytocin may reduce aspects of oxidative stress. Finally, when dams were pretreated with indomethacin, a cyclooxygenase (COX) inhibitor, maternal oxytocin no longer potentiated effects of anoxia on neonatal brain lactate, suggesting this effect of oxytocin may be mediated via prostaglandin production or other COX-derived products. The results indicate that maternal oxytocin administration may have multiple acute effects on CNS metabolic responses to anoxia at birth.

Preclinical toxicity screening of intrathecal oxytocin in rats and dogs.

BACKGROUND: Anatomic, physiologic, and behavioral studies in animals suggest that spinally released oxytocin should produce analgesia in humans and may also protect from chronic pain after injury. In this article, the authors report preclinical toxicity screening of oxytocin for intrathecal delivery. METHODS: Intrathecal oxytocin, 11 µg (6 U) or vehicle, was injected intrathecally in 24 rats, followed by frequent behavioral assessment and histologic examination of spinal contents 2 or 14 days after injection. In three dogs, a range of intrathecal oxytocin doses (18 to 550 µg in 0.5 ml) was injected followed by physiologic, biochemical, and behavioral assessments. Ten dogs were then randomized to receive five daily injections of intrathecal oxytocin, 550 µg in 0.5 ml, or vehicle with similar assessments and, necropsy and histologic analysis were conducted 2 days later. RESULTS: In rats, intrathecal oxytocin resulted in transient scratching and itching behaviors, without other differences from vehicle. There was no behavioral, gross anatomic, or histologic evidence of neurotoxicity. Dose ranging in dogs suggested mild effects on motor tone, blood pressure, and heart rate at the 550 µg dose. Repeated boluses in dogs did not produce behavioral, biochemical, neurological, gross anatomic, or histologic evidence of neurotoxicity. CONCLUSIONS: Substances, including natural neurotransmitters, may be toxic when administered in pharmacologic doses in the spinal cord. This preclinical toxicity screen in two species suggests that bolus injections of oxytocin in concentrations up to 1,100 µg/ml are unlikely to cause neurotoxicity. The authors also support cautious clinical application of intrathecal oxytocin under regulatory supervision.

The prevention of postpartum hemorrhage in the community.

João Paulo Souza discusses the implications of a study by Cynthia Stanton and colleagues for the prevention and management of postpartum hemorrhage in the community, particularly in low-income countries, and outlines the remaining challenges. Please see later in the article for the Editors' Summary.

Effect on postpartum hemorrhage of prophylactic oxytocin (10 IU) by injection by community health officers in Ghana: a community-based, cluster-randomized trial.

BACKGROUND: Oxytocin (10 IU) is the drug of choice for prevention of postpartum hemorrhage (PPH). Its use has generally been restricted to medically trained staff in health facilities. We assessed the effectiveness, safety, and feasibility of PPH prevention using oxytocin injected by peripheral health care providers without midwifery skills at home births. METHODS AND FINDINGS: This community-based, cluster-randomized trial was conducted in four rural districts in Ghana. We randomly allocated 54 community health officers (stratified on district and catchment area distance to a health facility: ≥10 km versus <10 km) to intervention (one injection of oxytocin [10 IU] one minute after birth) and control (no provision of prophylactic oxytocin) arms. Births attended by a community health officer constituted a cluster. Our primary outcome was PPH, using multiple definitions; (PPH-1) blood loss ≥500 mL; (PPH-2) PPH-1 plus women who received early treatment for PPH; and (PPH-3) PPH-2 plus any other women referred to hospital for postpartum bleeding. Unsafe practice is defined as oxytocin use before delivery of the baby. We enrolled 689 and 897 women, respectively, into oxytocin and control arms of the trial from April 2011 to November 2012. In oxytocin and control arms, respectively, PPH-1 rates were 2.6% versus 5.5% (RR: 0.49; 95% CI: 0.27-0.88); PPH-2 rates were 3.8% versus 10.8% (RR: 0.35; 95% CI: 0.18-0.63), and PPH-3 rates were similar to those of PPH-2. Compared to women in control clusters, those in the intervention clusters lost 45.1 mL (17.7-72.6) less blood. There were no cases of oxytocin use before delivery of the baby and no major adverse events requiring notification of the institutional review boards. Limitations include an unblinded trial and imbalanced numbers of participants, favoring controls. CONCLUSION: Maternal health care planners can consider adapting this model to extend the use of oxytocin into peripheral settings including, in some contexts, home births. TRIAL REGISTRATION: ClinicalTrials.gov NCT01108289 Please see later in the article for the Editors' Summary.

Susceptibility of subregions of prefrontal cortex and corpus callosum to damage by high-dose oxytocin-induced labor in male neonatal mice.

Induction and augmentation of labor is one of the most common obstetrical interventions. However, this intervention is not free of risks and could cause adverse events, such as hyperactive uterine contraction, uterine rupture, and amniotic-fluid embolism. Our previous study using a new animal model showed that labor induced with high-dose oxytocin (OXT) in pregnant mice resulted in massive cell death in selective brain regions, specifically in male offspring. The affected brain regions included the prefrontal cortex (PFC), but a detailed study in the PFC subregions has not been performed. In this study, we induced labor in mice using high-dose OXT and investigated neonatal brain damage in detail in the PFC using light and electron microscopy. We found that TUNEL-positive or pyknotic nuclei and Iba-1-positive microglial cells were detected more abundantly in infralimbic (IL) and prelimbic (PL) cortex of the ventromedial PFC (vmPFC) in male pups delivered by OXT-induced labor than in the control male pups. These Iba-1-positive microglial cells were engulfing dying cells. Additionally, we also noticed that in the forceps minor (FMI) of the corpus callosum (CC), the number of TUNEL-positive or pyknotic nuclei and Iba-1-positive microglial cells were largely increased and Iba-1-positive microglial cells phagocytosed massive dying cells in male pups delivered by high-dose OXT-induced labor. In conclusion, IL and PL of the vmPFC and FMI of the CC, were susceptible to brain damage in male neonates after high-dose OXT-induced labor.

An integrated study of metabolomics and transcriptomics to reveal the anti-primary dysmenorrhea mechanism of Akebiae Fructus.

ETHNOPHARMACOLOGICAL RELEVANCE: Akebiae Fructus, a Tujia minority folk medicine and a well-known traditional Chinese medicine for soothing the liver, regulating Qi, promoting blood circulation and relieving pain, is widely used in the treatment of primary dysmenorrhea. However, little is known about its underlying mechanism. AIM OF THE STUDY: To explore the effect of Akebiae Fructus on primary dysmenorrhea model induced by estradiol benzoate and oxytocin, and to provide better understanding of the mechanism of Akebiae Fructus for primary dysmenorrhea treatment. MATERIALS AND METHODS: The primary dysmenorrhea mouse model was used in this study. Except for the control group and the normal administration group, the mice of other groups were subcutaneously injected with estradiol benzoate (10 mg/kg/d) for 10 consecutive days. From the 5th day of the ten-day model period, the positive control groups were given 0.075 g/kg ibuprofen and 7.5 g/kg Leonurus granule, the drug groups were given 0.2 g/kg, 0.4 g/kg, 0.8 g/kg Akebiae Fructus extract, the normal administration group was given 0.8 g/kg Akebiae Fructus extract, and the same volume saline was given in the control group. On the tenth day, oxytocin (10 U/kg) was peritoneally injected after estradiol benzoate injected 1 h. After the oxytocin injection, writhing behavior was observed for 30 min. Then the uterine tissue was collected to measure the level of PGF2α and PGE2, and for histological analysis and transcriptomics analysis. Meanwhile, plasma and urine samples were collected for metabolomic analysis. RESULTS: Akebiae Fructus inhibited the writhing, decreased the PGF2α level and ameliorated the morphological changes. 32 potential metabolic biomarkers in plasma and 17 in urine were found for primary dysmenorrhea, and after Akebiae Fructus treatment, 25 metabolites in plasma and 14 in urine were restored. These altered metabolites were mainly involved in lipid, amino acid and organic acid metabolism. For the transcriptomic study, a total of 2244 differentially expressed genes (1346 up-regulated and 898 down-regulated) were obtained between the control and model group, and 148 differentially expressed genes (DEGs) were found related with Akebiae Fructus treatment of primary dysmenorrhea. Correlation analysis was carried out based on the transcriptomic and metabolomic data. 5 differentially expressed genes (Plpp3, Sgpp2, Arg1, Adcy8, Ak5) were found related with the enrichment metabolic pathways. The mechanism by which Akebiae Fructus ameliorates primary dysmenorrhea may account for the regulation of the gene expression to control the key enzymes in the sphingolipid metabolism, arginine and proline metabolism, glycerophospholipid metabolism and purine metabolism, inhibiting the abnormal secretion of PGF2α, alleviating the uterine contraction and reducing inflammation and pain. CONCLUSIONS: Akebiae Fructus could effectively alleviate the symptoms of primary dysmenorrhea, regulate metabolic disorders, and control the related gene expression in primary dysmenorrhea. The study may provide clues for further study of Akebiae Fructus treatment on primary dysmenorrhea.

Expression of synaptic proteins in the hippocampus is modulated by neonatal oxytocin treatment.

An alteration of oxytocin signaling during postnatal maturation of the brain could be associated with etiology of neurodevelopmental disorders among them autism. The aim of the present study was to examine the role of oxytocin in the regulation of expression of selected cell-adhesion molecules and scaffolding proteins in the hippocampus in early rat development. Oxytocin treatment (1 mg/ml, i.p., 50 µl/pup) at postnatal days P2-P3 resulted in the reduction of Neuroligin 3 gene expression, and was accompanied by lower SHANK1 and SHANK3 mRNA levels in the hippocampus at P5 day. Immunostaining revealed a clear trend for the lower density of Neuroligin 3 positive cells in the hippocampus and this trend has been significant in the CA3 hippocampal area. The significantly lower Neurexin 2ß mRNA levels were observed in response to oxytocin treatment, with no effect seen in the Neurexin 2α gene expression. No change has been observed in the gene expression of Neuroligin 1 and Neuroligin 2. Oxytocin induced an increase in the mRNA levels of Neuron-Specific Enolase (NSE) and a decrease in the mRNA levels of glial fibrillary acid protein (GFAP) - marker of astrocytes. Incubation of primary neuronal cells with oxytocin (1 µM, 48 h) stimulated a proliferation of NSE-positive cells. These results suggest that synaptic proteins could be under control of oxytocin in early stages of brain development. The changes of cell-adhesion molecule and scaffolding protein levels might be linked to the modulation of number of neuronal cells.

Intracellular expression of cytokines and granzyme B in auricular lymph nodes draining skin exposed to irritants and sensitizers.

The murine local lymph node assay (LLNA) has been extensively utilized to evaluate sensitizing chemicals. However, there have been some concerns that its use to discriminate between classes of chemicals is minimal. It is thus desirable to identify better or alternative immune endpoints with in LLNA itself. Here, we evaluated the protein and/or mRNA levels of cytokines and granzyme B (GzmB), a cytotoxic lymphocyte product, to discriminate between sensitizers and irritants and to characterize the chemical sensitizers when used as supplemental indicators in LLNA endpoints. For this, CBA/N mice were topically treated daily with a well-known chemical sensitizer such as a strong contact sensitizer 1-chloro-2,4-dinitrobenzene (DNCB), a skin contact sensitizer 2-phenyl-4-ethoxymethylene-5-oxazolone (OXA), and a skin or respiratory sensitizer toluene 2,4-diisocyanate (TDI), and the non-sensitizing irritants, croton oil (CRO) and nonanoic acid (NA), for 3 consecutive days. The protein and/or mRNA levels in auricular lymph nodes draining the ear skin were then analyzed by real-time RT-PCR and immunoassay. The sensitizers, but not the irritants, evoked pronounced interleukin (IL)-2, IL-3 and IL-4 or interferon (IFN)-gamma. Significantly, different sensitizers evoked different cytokine patterns of IL-4 and IFN-gamma, as DNCB strongly up-regulated both IFN-gamma and IL-4, OXA up-regulated IFN-gamma strongly but IL-4 weakly, and TDI up-regulated IL-4 strongly but IFN-gamma weakly. The sensitizers also strongly up-regulated GzmB mRNA, while the irritants had a much weaker effect. Thus, these cytokines and GzmB mRNA may be useful as additional endpoints for discriminating between irritants and sensitizers or contact and respiratory sensitizers in the LLNA.

Oxytocin alters cell fate selection of rat neural progenitor cells in vitro.

Synthetic oxytocin (sOT) is widely used during labor, yet little is known about its effects on fetal brain development despite evidence that it reaches the fetal circulation. Here, we tested the hypothesis that sOT would affect early neurodevelopment by investigating its effects on neural progenitor cells (NPC) from embryonic day 14 rat pups. NPCs expressed the oxytocin receptor (OXTR), which was downregulated by 45% upon prolonged treatment with sOT. Next, we examined the effects of sOT on NPC death, apoptosis, proliferation, and differentiation using antibodies to NeuN (neurons), Olig2 (oligodendrocytes), and GFAP (astrocytes). Treated NPCs were analysed with unbiased high-throughput immunocytochemistry. Neither 6 nor 24 h exposure to 100 pM or 100 nM sOT had an effect on viability as assessed by PI or CC-3 immunocytochemistry. Similarly, sOT had negligible effect on NPC proliferation, except that the overall rate of NPC proliferation was higher in the 24 h compared to the 6 h group regardless of sOT exposure. The most significant finding was that sOT exposure caused NPCs to select a predominantly neuronal lineage, along with a concomitant decrease in glial cells. Collectively, our data suggest that perinatal exposure to sOT can have neurodevelopmental consequences for the fetus, and support the need for in vivo anatomical and behavioral studies in offspring exposed to sOT in utero.

The two fold role of oxytocin in social developmental disorders: A cause and a remedy?

Oxytocin is widely used by obstetricians to induce or facilitate labor. The long lasting consequences of oxytocin administration remain however unknown. Here, we discuss recent evidence suggesting a link between oxytocin labor induction and developmental social impairments such as autism spectrum disorders (ASD). Because these associations are methodologically questionable, we provide a review of animal studies investigating the long term effects of neonatal injection of oxytocin to shed light on the biological mechanisms that mediate the contribution of early oxytocin supplementation on the development of social impairments. In contrast to this potential negative impact on development, oxytocin has been shown to ameliorate social skills of ASD patients. However, results of chronic oxytocin administration from animal experiments are contradictory. We also review recent studies looking at chronic oxytocin effects in animal and in humans. Obstetric and psychiatric uses of exogenous oxytocin both impact on oxytocinergic neurotransmission but the effects may be sharply dissimilar.

In vitro cytogenetic analysis of the effects of oxytocin on human peripheral blood lymphocytes.

The purpose of this study was to determine possible genotoxic and cytotoxic (or mitogenic) effects of high concentrations of oxytocin, active component of Syntocinon in cultures of human peripheral blood lymphocytes. Two test systems were used: (1) analysis of numerical and structural chromosome aberrations, and (2) the in vitro sister chromatid exchange (SCE) test. On the basis of the results obtained it can be concluded that oxytocin does not express any genotoxical properties. Furthermore, the mitotic index did not change significantly.

The nature of the sheep chorionic oxytocic substance.

The effects of infusions of fresh sheep placenta in normal saline and the filtrate obtained therefrom after boiling for 15 min were investigated on guinea-pig and rat uteri, other mammalian non-vascular smooth muscles and the cardiovascular system, noting their responses to the infusion/filtrate in the presence or absence of various inhibitors or agonists. Solvent partition, acute toxicity and thin layer chromatography (TLC) studies were also performed. It was found that the infusion/filtrate had oxytocic activity independent of histamine and muscarinic receptors. It had H(1) receptor activity agonist action on the guinea-pig ileum, antagonized adrenaline-induced contractions in the vas but unlike bradykinin did not relax rat duodenum. It induced vasoconstriction in the rat hindquarters, depressed cat blood pressure but had positive inotropic effect on the guinea-pig Langendorff heart. Only the eluent from the least mobile of the five TLC bands on silica gel had oxytocic activity. It was concluded that the sheep chorionic oxytocic substance is not acetylcholine, histamine, 5-hydroxytryptamine, noradrenaline, adrenaline, prostaglandins F or E but is a peptide, which is not bradykinin, vasopressin or oxytocin.

Fetal exposure to synthetic oxytocin and the relationship with prefeeding cues within one hour postbirth.

BACKGROUND: Prefeeding cues are oral-motor neurobehaviors that communicate feeding readiness, and the ability to self-comfort and regulate behavioral state. Intrapartum and newborn procedures have been associated with altered frequency and emergence of prefeeding cues soon after birth. Intrapartum synthetic oxytocin is commonly used for labor induction/augmentation in the US, yet there is little research on potential effects on infant neurobehavioral cues. AIMS: To explore whether fetal exposure to synthetic oxytocin was associated with the infant's level of prefeeding organization shortly after birth. STUDY DESIGN: Cohort. SUBJECTS: A convenience sample of 47 healthy full-term infants (36 exposed and 11 unexposed to intrapartum synthetic oxytocin) was studied. EXCLUSION CRITERIA: Fetal distress, vacuum/forceps, cesarean, and low Apgar. OUTCOME MEASURES: Videotapes of infants (45-50min postbirth) were coded for frequency of eight prefeeding cues, and analyzed by level of prefeeding organization. RESULTS: In general, fewer prefeeding cues were observed in infants exposed versus unexposed to synOT and differences were significant for brief and sustained hand to mouth cues [incidence rate ratio (95% CI)=0.6 (0.4, 0.9) and 0.5 (0.2, 0.9), respectively]. Forty-four percent of exposed infants demonstrated a low level of prefeeding organization, compared to 0% from the unexposed group. In contrast, 25% of exposed versus 64% of unexposed infants demonstrated high prefeeding organization. After adjusting for covariates, exposed infants were at 11.5 times (95% CI=1.8-73.3) the odds of demonstrating low/medium versus high levels of prefeeding organization compared to unexposed infants. CONCLUSIONS: Newborn neurobehavioral cues may be sensitive to intrapartum synthetic oxytocin.

Effect of a single neonatal oxytocin treatment (hormonal imprinting) on the biogenic amine level of the adult rat brain: could oxytocin-induced labor cause pervasive developmental diseases?

Perinatal single-hormone treatment causes hormonal imprinting with lifelong consequences in receptor-binding capacity, hormone production as well as in social and sexual behavior. In the present experiments, newborn rats were treated with a single dose of oxytocin, and the levels of biogenic amines and their metabolites were studied in 8 different brain regions and in the sera when the male and female animals were 4 months old. Both dopaminergic and serotonergic neurotransmission was found to be significantly influenced. The levels of 3,4-dihydroxyphenylacetic acid, homovanillic acid, and 5-hydroxyindole acetic acid metabolites decreased in the hypothalamus and striatum. Dopamine, serotonin, norepinephrine, and 5-hydroxytryptophol levels were hardly altered, and there was no difference in the epinephrine levels. The results show that dopamine and serotonin metabolism of hypothalamus and striatum are deeply and lifelong influenced by a single neonatal oxytocin treatment Oxytocin imprinting resulted in decreased dopamine turnover in the hypothalamus and decreased serotonin turnover in the hypothalamus, medulla oblongata, and striatum of females. As the disturbance of brain dopamine and serotonin system has an important role in the development of pervasive developmental diseases (eg, autism) and neuropsychiatric disorders (eg, schizophrenia), the growing number of oxytocin-induced labor as a causal factor, cannot be omitted.

Anomalies in ovary following oral exposure to oxytocin: mechanistic studies.

Ovarian anomalies following oral oxytocin (OT) (1 and 10 ng/100 µl) exposure of female Wistar rat pups (10-day old) for 25 days was undertaken as OT injections are illegally used for milk let down in cattle thereby causing oral exposure to human population from early age. OT exposure resulted in increased ovarian weight, γ globulin, total number of follicles, and number of corpus luteum (CLs); indicating higher ovulation. The mechanism may involve over-expression of pEGFR followed by downstream pERK1/2 and subsequently increased ovarian PGE-2 along with enhanced COX-2, HAS-2 & TSG-6 (matrix deposition proteins) and GDF-9 (oocyte factor) proteins, suggesting that oral exposure of OT may affect the physiology and function of the ovary. Further, in vitro studies showed increased internalization of OT in IEC-6 cells which further supports that orally administered OT may cause altered manifestations as shown above following internalization in mucosal membrane.

Repeated intranasal oxytocin administration in early life dysregulates the HPA axis and alters social behavior.

Agonistic interactions are a powerful stressor. Conversely, positive social interactions can reduce the adverse effects of social stress. This possibly occurs through the action of oxytocin (OT), a neuropeptide able to reduce activation of the hypothalamo-pituitary-adrenal (HPA) axis. We hypothesized that repeated OT intranasal administration to neonatal pigs could provide long-lasting protective effects against social stress. In each of six litters, two pigs per litter received 0.5 mL of saline containing 24 IU (or 50 µg) of OT intranasally and two control littermates received 0.5 mL of saline as a control at 1, 2 and 3 days of age. Contrary to our predictions, when socially mixed after weaning at 17 days of age, neonatally OT-administered pigs received more aggressive interactions and performed more aggressive interactions in return, showed greater locomotion, spent less time in social contact, and had greater cortisol concentrations than control pigs. When this social mixing was repeated at 8 weeks of age, OT pigs still performed more aggressive interactions and had greater adrenocorticotropic hormone concentrations than control pigs. A dexamethasone suppression test and corticotropic releasing hormone administration challenge at 11 weeks of age revealed that OT pigs were less responsive to dexamethasone than control pigs, suggesting a deficient HPA axis' negative feedback control. Postnatal repeated OT administration altered social behavior and resulted in a long-term dysregulation of the HPA axis. These findings highlight the complex, fine-tuning of the neurobiological mechanisms regulating the development of social behavior and suggest caution in the application of neonatal peptide treatments during early development.

The effect of 1-deamino-2-tyr(ethyl) oxytocin upon peri- and postnatal development of the rat: growth retardation of the offspring.

The effect of 1-deamino-2-tyr(ethyl) oxytocin (dEtOT) upon peri- and postnatal development of the rat was studied in two experiments when administered between day 15 of pregnancy and the day of parturition. The investigation showed that dEtOT did not affect the pups at birth, that dEtOT caused a dose-related growth retardation of the pups, that the growth inhibiting effect was directly correlated to the length of administration and that the growth inhibiting effect was more pronounced if dEtOT was given close to parturition than if it was given earlier in the pregnancy. In addition, the growth retardation was not due to an effect on the pups but to an effect on their mothers, probably related to inhibition of the emptying mechanisms of the mammary glands, meaning that the pups were insufficiently fed by their mothers immediately after birth.