The magnocellular oxytocin system, the fount of maternity: adaptations in pregnancy

Neuropeptide oxytocin facilitates its own brain-to-periphery uptake

The hypothalamo-neurohypophyseal system is a neuroendocrine conduit through which the neurohormones oxytocin and arginine vasopressin are released from the brain into the general circulation, influencing functions like salt balance and reproduction. However, the precise mechanism for rapid neurohormone transport to the periphery remains unclear. We show, using live imaging in zebrafish, that both hyperosmotic physiological challenge and optogenetic stimulation of oxytocin neurons elicit a local increase in neurohypophyseal blood flow velocities and a change in capillary diameter. This response is dictated by the geometry of the hypophyseal vascular microcircuit. Genetic ablation of oxytocin neurons and inhibition of oxytocin receptor signaling attenuate the changes in capillary blood flow and diameter. Both the osmotic challenge and oxytocin neuronal activation elicit a local rise in neurohypophyseal capillary permeability in an oxytocin-signaling-dependent manner. We propose that oxytocin-dependent neurovascular coupling facilitates its efficient uptake into the blood circulation, suggesting a self-perpetuating stimulus-secretion-uptake mechanism for peripheral hormone transfer.

Safety of antenatal breastmilk expression from week 34 of pregnancy: a randomized controlled pilot study (The Express-MOM study)

BACKGROUND

Mother's own milk (MOM) is important as the first nutrition for preterm infants, but mothers often struggle to initiate milk production right after preterm birth. If antenatal breastmilk expression (aBME) does not induce preterm labor when performed before term age, it could promote nutrition with MOM right after preterm birth. In this pilot study, we aimed to investigate whether aBME induces preterm labor among healthy nulliparous women from week 34 of pregnancy, to examine if aBME promotes the availability of MOM right after birth and affects breastfeeding outcomes.

METHODS

Women were randomized to aBME (10 min 2 × daily) from week 34 of pregnancy until birth or to the control group. Both groups had a breastfeeding consultation between week 33 and 34 of pregnancy and were followed until eight weeks after birth. The primary outcome was gestational age (GA) at birth. Secondary outcomes were the availability of MOM and exclusive breastfeeding rates from 24 h to eight weeks after birth. Ranksum test and a posterior plot for the probability of non-inferiority were applied to the primary outcome. The availability of MOM is reported as medians and IQR. Breastfeeding outcomes were analyzed with mixed effects logistic regression.

RESULTS

One hundred forty-four pregnant women were eligible for participation, 51 were excluded, and 33 declined participation/did not answer inclusion phone calls. 60 women were included and randomized. Primary outcome data were available in 55 women (28 in intervention, 27 in control). We found no difference in GA at birth between the two groups: median (IQR), 40 + 1(39 + 5:41 + 2) in intervention vs. 40 + 2 (39 + 4:41 + 1) in control, p = 0.98. Antenatal expressed MOM was available at birth in most women in the intervention group (23/28, 82%), with a median of 52 mL during pregnancy. There was no statistically significant difference in breastfeeding outcomes. No adverse events were reported.

CONCLUSIONS

aBME performed by healthy nulliparous women from gestational week 34 did not induce preterm labor. In most women in the intervention group, MOM was available right after birth. The study results provide the basis for a trial among women at high risk for preterm birth.

TRIAL REGISTRATION

CLINICALTRIALS

gov (NCT05516199).

The interplay of oxytocin and sex hormones

The neuropeptide oxytocin has historically been associated with reproduction and maternal behavior. However, more recent research has uncovered that oxytocin has a much wider range of roles in physiology and behavior. Despite the excitement surrounding potential therapeutical applications of intranasally administered oxytocin, the results of these intervention studies have been inconsistent. Various reasons for these mixed results have been proposed, which tend to focus on methodological issues, such as study design. While methodological issues are certainly important, emerging evidence suggests that the interaction between oxytocin and sex hormones may also account for these varied findings. To better understand the purpose and function of the interaction of oxytocin with sex hormones, with a focus on estrogens, progesterone, and testosterone, we conducted a comprehensive thematic review via four perspectives: evolutionary, developmental, mechanistic, and survival. Altogether, this synergistic approach highlights the critical function of sex hormone activity for accomplishing the diverse roles of oxytocin via the modulation of oxytocin release and oxytocin receptor activity, which is also likely to contribute to the heterogeneity of outcomes after oxytocin administration.

DNA methylation landscape in pregnancy-induced hypertension: progress and challenges

Gestational hypertension (PIH), especially pre-eclampsia (PE), is a common complication of pregnancy. This condition poses significant risks to the health of both the mother and the fetus. Emerging evidence suggests that epigenetic modifications, particularly DNA methylation, may play a role in initiating the earliest pathophysiology of PIH. This article describes the relationship between DNA methylation and placental trophoblast function, genes associated with the placental microenvironment, the placental vascular system, and maternal blood and vascular function, abnormalities of umbilical cord blood and vascular function in the onset and progression of PIH, as well as changes in DNA methylation in the progeny of PIH, in terms of maternal, fetal, and offspring. We also explore the latest research on DNA methylation-based early detection, diagnosis and potential therapeutic strategies for PIH. This will enable the field of DNA methylation research to continue to enhance our understanding of the epigenetic regulation of PIH genes and identify potential therapeutic targets.

Oxytocin Exhibits Neuroprotective Effects on Hippocampal Cultures under Severe Oxygen-Glucose Deprivation Conditions

Perinatal asphyxia (PA) and hypoxic-ischemic encephalopathy can result in severe, long-lasting neurological deficits. In vitro models, such as oxygen-glucose deprivation (OGD), are used experimentally to investigate neuronal response to metabolic stress. However, multiple variables can affect the severity level of OGD/PA and may confound any measured treatment effect. Oxytocin (OXT) has emerged as a potential neuroprotective agent against the deleterious effects of PA. Previous studies have demonstrated OXT's potential to enhance neuronal survival in immature hippocampal cultures exposed to OGD, possibly by modulating gamma-aminobutyric acid-A receptor activity. Moreover, OXT's precise impact on developing hippocampal neurons under different severities of OGD/PA remains uncertain. In this study, we investigated the effects of OXT (0.1 µM and 1 µM) on 7-day-old primary rat hippocampal cultures subjected to 2 h OGD/sham normoxic conditions. Cell culture viability was determined using the resazurin assay. Our results indicate that the efficacy of 1 µM OXT treatment varied according to the severity of the OGD-induced lesion, exhibiting a protective effect (p = 0.022) only when cellular viability dropped below 49.41% in non-treated OGD cultures compared to normoxic ones. Furthermore, administration of 0.1 µM OXT did not yield significant effects, irrespective of lesion severity (p > 0.05). These findings suggest that 1 µM OXT treatment during OGD confers neuroprotection exclusively in severe lesions in hippocampal neurons after 7 days in vitro. Further research is warranted to elucidate the mechanisms involved in OXT-mediated neuroprotection.

Re-wiring of the bonded brain: Gene expression among pair bonded female prairie voles changes as they transition to motherhood

Motherhood is a costly life-history transition accompanied by behavioral and neural plasticity necessary for offspring care. Motherhood in the monogamous prairie vole is associated with decreased pair bond strength, suggesting a trade-off between parental investment and pair bond maintenance. Neural mechanisms governing pair bonds and maternal bonds overlap, creating possible competition between the two. We measured mRNA expression of genes encoding receptors for oxytocin (oxtr), dopamine (d1r and d2r), mu-opioids (oprm1a), and kappa-opioids (oprk1a) within three brain areas processing salience of sociosensory cues (anterior cingulate cortex; ACC), pair bonding (nucleus accumbens; NAc), and maternal care (medial preoptic area; MPOA). We compared gene expression differences between pair bonded prairie voles that were never pregnant, pregnant (~day 16 of pregnancy), and recent mothers (day 3 of lactation). We found greater gene expression in the NAc (oxtr, d2r, oprm1a, and oprk1a) and MPOA (oxtr, d1r, d2r, oprm1a, and oprk1a) following the transition to motherhood. Expression for all five genes in the ACC was greatest for females that had been bonded for longer. Gene expression within each region was highly correlated, indicating that oxytocin, dopamine, and opioids comprise a complimentary gene network for social signaling. ACC-NAc gene expression correlations indicated that being a mother (oxtr and d1r) or maintaining long-term pair bonds (oprm1a) relies on the coordination of different signaling systems within the same circuit. Our study suggests the maternal brain undergoes changes that prepare females to face the trade-off associated with increased emotional investment in offspring, while also maintaining a pair bond.

The neurohypophyseal hormone oxytocin and eating behaviors: a narrative review

BACKGROUND

The neuropeptide oxytocin (OT) is crucial in several conditions, such as lactation, parturition, mother-infant interaction, and psychosocial function. Moreover, OT may be involved in the regulation of eating behaviors.

METHODS

This review briefly summarizes data concerning the role of OT in eating behaviors. Appropriate keywords and medical subject headings were identified and searched for in PubMed/MEDLINE. References of original articles and reviews were screened, examined, and selected.

RESULTS

Hypothalamic OT-secreting neurons project to different cerebral areas controlling eating behaviors, such as the amygdala, area postrema, nucleus of the solitary tract, and dorsal motor nucleus of the vagus nerve. Intracerebral/ventricular OT administration decreases food intake and body weight in wild and genetically obese rats. OT may alter food intake and the quality of meals, especially carbohydrates and sweets, in humans.

DISCUSSION

OT may play a role in the pathophysiology of eating disorders with potential therapeutic perspectives. In obese patients and those with certain eating disorders, such as bulimia nervosa or binge/compulsive eating, OT may reduce appetite and caloric consumption. Conversely, OT administered to patients with anorexia nervosa may paradoxically stimulate appetite, possibly by lowering anxiety which usually complicates the management of these patients. Nevertheless, OT administration (e.g., intranasal route) is not always associated with clinical benefit, probably because intranasally administered OT fails to achieve therapeutic intracerebral levels of the hormone.

CONCLUSION

OT administration could play a therapeutic role in managing eating disorders and disordered eating. However, specific studies are needed to clarify this issue with regard to dose-finding and route and administration time.

The physiology and pharmacology of oxytocin in labor and in the peripartum period

Oxytocin is a reproductive hormone implicated in the process of parturition and widely used during labor. Oxytocin is produced within the supraoptic nucleus and paraventricular nucleus of the hypothalamus and released from the posterior pituitary lobe into the circulation. Oxytocin is released in pulses with increasing frequency and amplitude in the first and second stages of labor, with a few pulses released in the third stage of labor. During labor, the fetus exerts pressure on the cervix of the uterus, which activates a feedforward reflex-the Ferguson reflex-which releases oxytocin. When myometrial contractions activate sympathetic nerves, it decreases oxytocin release. When oxytocin binds to specific myometrial oxytocin receptors, it induces myometrial contractions. High levels of circulating estrogen at term make the receptors more sensitive. In addition, oxytocin stimulates prostaglandin synthesis and release in the decidua and chorioamniotic membranes by activating a specific type of oxytocin receptor. Prostaglandins contribute to cervical ripening and uterine contractility in labor. The oxytocin system in the brain has been implicated in decreasing maternal levels of fear, pain, and stress, and oxytocin release and function during labor are stimulated by a social support. Moreover, studies suggest, but have not yet proven, that labor may be associated with long-term, behavioral and physiological adaptations in the mother and infant, possibly involving epigenetic modulation of oxytocin production and release and the oxytocin receptor. In addition, infusions of synthetic oxytocin are used to induce and augment labor. Oxytocin may be administered according to different dose regimens at increasing rates from 1 to 3 mIU/min to a maximal rate of 36 mIU/min at 15- to 40-minute intervals. The total amount of synthetic oxytocin given during labor can be 5 to 10 IU, but lower and higher amounts of oxytocin may also be given. High-dose infusions of oxytocin may shorten the duration of labor by up to 2 hours compared with no infusion of oxytocin; however, it does not lower the frequency of cesarean delivery. When synthetic oxytocin is administered, the plasma concentration of oxytocin increases in a dose-dependent way: at infusion rates of 20 to 30 mIU/min, plasma oxytocin concentration increases approximately 2- to 3-fold above the basal level. Synthetic oxytocin administered at recommended dose levels is not likely to cross the placenta or maternal blood-brain barrier. Synthetic oxytocin should be administered with caution as high levels may induce tachystole and uterine overstimulation, with potentially negative consequences for the fetus and possibly the mother. Of note, 5 to 10 IU of synthetic oxytocin is often routinely given as an intravenous or intramuscular bolus administration after delivery to induce uterine contractility, which, in turn, induces uterine separation of the placenta and prevents postpartum hemorrhage. Furthermore, it promotes the expulsion of the placenta.

The importance of optimal body condition to maximise reproductive health and perinatal outcomes in pigs

Overnutrition or undernutrition during all or part of the reproductive cycle predisposes sows to metabolic consequences and poor reproductive health which contributes to a decrease in sow longevity and an increase in perinatal mortality. This represents not only an economic problem for the pig industry but also results in poor animal welfare. To maximise profitability and increase sustainability in pig production, it is pivotal to provide researchers and practitioners with synthesised information about the repercussions of maternal obesity or malnutrition on reproductive health and perinatal outcomes, and to pinpoint currently available nutritional managements to keep sows' body condition in an optimal range. Thus, the present review summarises recent work on the consequences of maternal malnutrition and highlights new findings.

Hindbrain Adrenergic/Noradrenergic Control of Integrated Endocrine and Autonomic Stress Responses

Hindbrain adrenergic/noradrenergic nuclei facilitate endocrine and autonomic responses to physical and psychological challenges. Neurons that synthesize adrenaline and noradrenaline target hypothalamic structures to modulate endocrine responses while descending spinal projections regulate sympathetic function. Furthermore, these neurons respond to diverse stress-related metabolic, autonomic, and psychosocial challenges. Accordingly, adrenergic and noradrenergic nuclei are integrative hubs that promote physiological adaptation to maintain homeostasis. However, the precise mechanisms through which adrenaline- and noradrenaline-synthesizing neurons sense interoceptive and exteroceptive cues to coordinate physiological responses have yet to be fully elucidated. Additionally, the regulatory role of these cells in the context of chronic stress has received limited attention. This mini-review consolidates reports from preclinical rodent studies on the organization and function of brainstem adrenaline and noradrenaline cells to provide a framework for how these nuclei coordinate endocrine and autonomic physiology. This includes identification of hindbrain adrenaline- and noradrenaline-producing cell groups and their role in stress responding through neurosecretory and autonomic engagement. Although temporally and mechanistically distinct, the endocrine and autonomic stress axes are complementary and interconnected. Therefore, the interplay between brainstem adrenergic/noradrenergic nuclei and peripheral physiological systems is necessary for integrated stress responses and organismal survival.

Metabolic and feeding adjustments during pregnancy

Eating behaviours are determined by the integration of interoceptive and environmental inputs. During pregnancy, numerous physiological adaptations take place in the maternal organism to provide an adequate environment for embryonic growth. Among them, whole-body physiological remodelling directly influences eating patterns, commonly causing notable taste perception alterations, food aversions and cravings. Recurrent food cravings for and compulsive eating of highly palatable food can contribute to the development and maintenance of gestational overweight and obesity with potential adverse health consequences for the offspring. Although much is known about how maternal eating habits influence offspring health, the mechanisms that underlie changes in taste perception and food preference during pregnancy (which guide and promote feeding) are only just starting to be elucidated. Given the limited and diffuse understanding of the neurobiology of gestational eating patterns, the aim of this Review is to compile, integrate and discuss the research conducted on this topic in both experimental models and humans. This article sheds light on the mechanisms that drive changes in female feeding behaviours during distinct physiological states. Understanding these processes is crucial to improve gestational parent health and decrease the burden of metabolic and food-related diseases in future generations.

Effect of Neurosteroids on Basal and Stress-Induced Oxytocin Secretion in Luteal-Phase and Pregnant Sheep

Oxytocin (OT) is a neuropeptide synthesized in the hypothalamic nuclei that modulates both behavioral and reproductive functions, associated with the increased neurosteroid synthesis in the brain. Therefore, the present study tested the hypothesis that manipulation of central neurosteroid levels could affect oxytocin synthesis and release in non-pregnant and pregnant sheep under both basal and stressful conditions. In Experiment 1, luteal-phase sheep were subjected to a series of intracerebroventricular (icv.) infusions of allopregnanolone (AL, 4 × 15 μg/60 μL/30 min) for 3 days. In Experiment 2, pregnant animals (4th month) received a series of infusions of the neurosteroid synthesis blocker, finasteride (4 × 25 μg/60 μL/30 min), conducted for 3 days. In non-pregnant sheep AL alone was shown to differentially modulate OT synthesis in basal conditions, and strongly inhibit OT response to stress (p < 0.001). In contrast, in pregnant animals, basal and stress-induced OT secretion was significantly (p < 0.001) increased during finasteride infusion compared to controls. In conclusion, we showed that neurosteroids were involved in the control of OT secretion in sheep, particularly under stress and pregnancy conditions and are part of an adaptive mechanism which is responsible for protecting and maintaining pregnancy in harmful situations.

Oxytocin receptors mediate oxytocin potentiation of methylphenidate-induced stimulation of accumbens dopamine in rats

While the illicit use and misuse of stimulants like cocaine and methylphenidate (MP) has increased, there remains no FDA-approved treatments for psychostimulant use disorders (PSUD). Oxytocin (OT) has shown promise as a potential pharmacotherapy for PSUD. Dopamine (DA) neurotransmission plays a significant role in PSUD. We have recently shown that OT blunts the reinforcing effects of MP but, surprisingly, enhanced MP-induced stimulation of DA levels. Such effects have been suggested as a result of activation of OT receptors or, alternatively, could be mediated by direct actions of OT on MP blockade of the DA transporter. Here, we employed fast scan cyclic voltammetry (FSCV) to investigate the effects of systemic OT on MP-induced changes in the dynamics of DA, phasic release and uptake, in the nucleus accumbens shell (NAS) of Sprague-Dawley rats. We also tested the systemic effects of an antagonist of OT receptors, atosiban, to counteract the OT enhancement of dopaminergic effects of MP under microdialysis procedures in the NAS in rats. Administration of OT alone (2 mg/kg; i.p.) did not significantly modify evoked NAS DA dynamics measured by FSCV, and when administered 10 min before MP (0.1, 0.3, 1.0 mg/kg; i.v.), OT did not potentiate MP-induced increases in phasic DA release and did not alter DA clearance rate, suggesting no direct interactions of OT with the MP-induced blockade of DA uptake. Also, OT alone did not elicit significant changes in tonic, extracellular NAS DA levels measured by microdialysis. However, consistent with previous studies, we observed that OT pretreatments (2 mg/kg; i.p.) potentiated MP-induced (0.1, 0.3, 1.0 mg/kg; i.v.) efflux of extracellular NAS DA levels. This effect was abolished when rats were pretreated with atosiban (2 mg/kg; i.p.), suggesting that OT receptors mediate this OT action. Overall, our results suggest that OT receptors mediated OT potentiation of MP-induced stimulation of extracellular NAS DA levels, likely driven by modulation of DA receptor signaling pathways, without affecting MP blockade of DAT.

Oxytocin and orexin systems bidirectionally regulate the ability of opioid cues to bias reward seeking

As opioid-related fatalities continue to rise, the need for novel opioid use disorder (OUD) treatments could not be more urgent. Two separate hypothalamic neuropeptide systems have shown promise in preclinical OUD models. The oxytocin system, originating in the paraventricular nucleus (PVN), may protect against OUD severity. By contrast, the orexin system, originating in the lateral hypothalamus (LH), may exacerbate OUD severity. Thus, activating the oxytocin system or inhibiting the orexin system are potential therapeutic strategies. The specific role of these systems with regard to specific OUD outcomes, however, is not fully understood. Here, we probed the therapeutic efficacy of pharmacological interventions targeting the orexin or oxytocin system on two distinct metrics of OUD severity in rats-heroin choice (versus choice for natural reward, i.e., food) and cued reward seeking. Using a preclinical model that generates approximately equal choice between heroin and food reward, we examined the impact of exogenously administered oxytocin, an oxytocin receptor antagonist (L-368,899), and a dual orexin receptor antagonist (DORA-12) on opioid choice. Whereas these agents did not alter heroin choice when rewards (heroin and food) were available, oxytocin and DORA-12 each significantly reduced heroin seeking in the presence of competing reward cues when no rewards were available. In addition, the number of LH orexin neurons and PVN oxytocin neurons correlated with specific behavioral economic variables indicative of heroin versus food motivation. These data identify a novel bidirectional role of the oxytocin and orexin systems in the ability of opioid-related cues to bias reward seeking.

Oxytocin-a social peptide? Deconstructing the evidence

In this paper, we analyse the claim that oxytocin is a 'social neuropeptide'. This claim originated from evidence that oxytocin was instrumental in the initiation of maternal behaviour and it was extended to become the claim that oxytocin has a key role in promoting social interactions between individuals. We begin by considering the structure of the scientific literature on this topic, identifying closely interconnected clusters of papers on particular themes. We then analyse this claim by considering evidence of four types as generated by these clusters: (i) mechanistic studies in animal models, designed to understand the pathways involved in the behavioural effects of centrally administered oxytocin; (ii) evidence from observational studies indicating an association between oxytocin signalling pathways and social behaviour; (iii) evidence from intervention studies, mainly involving intranasal oxytocin administration; and (iv) evidence from translational studies of patients with disorders of social behaviour. We then critically analyse the most highly cited papers in each segment of the evidence; we conclude that, if these represent the best evidence, then the evidence for the claim is weak. This article is part of the theme issue 'Interplays between oxytocin and other neuromodulators in shaping complex social behaviours'.

Oxytocin Dynamics in the Body and Brain Regulated by the Receptor for Advanced Glycation End-Products, CD38, CD157, and Nicotinamide Riboside

Investigating the neurocircuit and synaptic sites of action of oxytocin (OT) in the brain is critical to the role of OT in social memory and behavior. To the same degree, it is important to understand how OT is transported to the brain from the peripheral circulation. To date, of these, many studies provide evidence that CD38, CD157, and receptor for advanced glycation end-products (RAGE) act as regulators of OT concentrations in the brain and blood. It has been shown that RAGE facilitates the uptake of OT in mother’s milk from the digestive tract to the cell surface of intestinal epithelial cells to the body fluid and subsequently into circulation in male mice. RAGE has been shown to recruit circulatory OT into the brain from blood at the endothelial cell surface of neurovascular units. Therefore, it can be said that extracellular OT concentrations in the brain (hypothalamus) could be determined by the transport of OT by RAGE from the circulation and release of OT from oxytocinergic neurons by CD38 and CD157 in mice. In addition, it has recently been found that gavage application of a precursor of nicotinamide adenine dinucleotide, nicotinamide riboside, for 12 days can increase brain OT in mice. Here, we review the evaluation of the new concept that RAGE is involved in the regulation of OT dynamics at the interface between the brain, blood, and intestine in the living body, mainly by summarizing our recent results due to the limited number of publications on related topics. And we also review other possible routes of OT recruitment to the brain.

Receptor for advanced glycation end-products and child neglect in mice: A possible link to postpartum depression

The receptor for advanced glycation end-products (RAGE), a pattern recognition molecule, has a role in the remodeling of vascular endothelial cells mainly in lungs, kidney and brain under pathological conditions. We recently discovered that RAGE binds oxytocin (OT) and transports it to the brain from circulation on neurovascular endothelial cells. We produced knockout mice of the mouse homologue of the human RAGE gene, Ager, designated RAGE KO mice. In RAGE KO mice, while hyperactivity has been reported in male mice, maternal behavior was impaired in female mice. After an additional stress, deficits in pup care were observed in RAGE KO mother mice. This resulted in pup death within 1–2 days, suggesting that RAGE plays a critical role during the postpartum period. Thus, RAGE seems to be important in the manifestation of normal maternal behavior in dams. In this review, we summarize the significance of brain OT transport by RAGE and propose that RAGE-dependent OT can dampen stress signals during pregnancy, delivery and early postpartum periods. To the best of our knowledge, there have been no previous articles on these RAGE-dependent results. Based on these results in mice, we discuss a potential critical role of RAGE in emotion swings at the puerperium (peripartum) and postpartum periods in women.

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RAGE play a role in oxytocin transport via the blood-brain barrier into the brain.

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RAGE KO dams had maternal behavior impairment after stress exposure that is in line with the two-hit theory. The first hit is RAGE signaling absence, the second hit is a stress event occurred in the postpartum period.

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We can hypothesize that RAGE signaling can affect maternal depression development through oxytocin transportation into the brain.

Controlling the lifetime of cucurbit[8]uril based self-abolishing nanozymes

Nature has evolved a unique mechanism of self-regulatory feedback loops that help in maintaining an internal cellular environment conducive to growth, healing and metabolism. In biology, enzymes display feedback controlled switchable behaviour to upregulate/downregulate the generation of metabolites as per the need of the cells. To mimic the self-inhibitory nature of certain biological enzymes under laboratory settings, herein, we present a cucurbit[8]uril based pH responsive supramolecular peptide amphiphile (SPA) that assembles into hydrolase mimetic vesicular nanozymes upon addition of alkaline TRIS buffer (activator) but disintegrates gradually owing to the catalytic generation of acidic byproducts (deactivator). The lifetime of these nanozymes could be manipulated in multiple ways, either by varying the amount of catalytic groups on the surface of the vesicles, by changing the acid generating substrate, or by changing the ratio between the activator and the substrate. The self-inhibitory nanozymes displayed highly tunable lifetimes ranging from minutes to hours, controlled and in situ generation of deactivating agents and efficient reproducibility across multiple pH cycles.

An epigenomic shift in amygdala marks the transition to maternal behaviors in alloparenting virgin female mice

Adults of many species will care for young offspring that are not their own, a phenomenon called alloparenting. However, in many cases, nonparental adults must be sensitized by repeated or extended exposures to newborns before they will robustly display parental-like behaviors. To capture neurogenomic events underlying the transition to active parental caring behaviors, we analyzed brain gene expression and chromatin profiles of virgin female mice co-housed with pregnant dams during pregnancy and after birth. After an initial display of antagonistic behaviors and a surge of defense-related gene expression, we observed a dramatic shift in the chromatin landscape specifically in amygdala of the pup-exposed virgin females compared to females co-housed with mother before birth, accompanied by a dampening of anxiety-related gene expression. This epigenetic shift coincided with hypothalamic expression of the oxytocin gene and the emergence of behaviors and gene expression patterns classically associated with maternal care. The results outline a neurogenomic program associated with dramatic behavioral changes and suggest molecular networks relevant to human postpartum mental health.

Oxytocin and love: Myths, metaphors and mysteries

Oxytocin is a peptide molecule with a multitude of physiological and behavioral functions. Based on its association with reproduction - including social bonding, sexual behavior, birth and maternal behavior - oxytocin also has been called "the love hormone." This essay specifically examines association and parallels between oxytocin and love. However, many myths and gaps in knowledge remain concerning both. A few of these are described here and we hypothesize that the potential benefits of both love and oxytocin may be better understood in light of interactions with more ancient systems, including specifically vasopressin and the immune system. Oxytocin is anti-inflammatory and is associated with recently evolved, social solutions to a variety of challenges necessary for mammalian survival and reproduction. The shared functions of oxytocin and love have profound implications for health and longevity, including the prevention and treatment of excess inflammation and related disorders, especially those occurring in early life and during periods of chronic threat or disease.

The Importance of Experimental Investigation of the Peripheral Oxytocin System

Oxytocin and oxytocin receptors are synthesized in the periphery where paracrine/autocrine actions have been described alongside endocrine actions effected by central release of oxytocin from the posterior pituitary. In the female reproductive system, classical actions of uterine contraction and milk ejection from mammary glands are accompanied by actions in the ovaries where roles in steroidogenesis, follicle recruitment and ovulation have been described. Steroidogenesis, contractile activity, and gamete health are similarly affected by oxytocin in the male reproductive tract. In the cardiovascular system, a local oxytocinergic system appears to play an important cardio-protective role. This role is likely associated with emerging evidence that peripheral oxytocin is an important hormone in the endocrinology of glucose homeostasis due to its actions in adipose, the pancreas, and the largely ignored oxytocinergic systems of the adrenal glands and liver. Gene polymorphisms are shown to be associated with a number of reported traits, not least factors associated with metabolic syndrome.

Relationship between Oxytocin and Osteoarthritis: Hope or Despair?

Oxytocin (OT) is involved in breastfeeding and childbirth and appears to play a role in regulating the bone matrix. OT is synthesized in the supraoptic and paraventricular nuclei of the hypothalamus and is released in response to numerous stimuli. It also appears to be produced by osteoblasts in the bone marrow, acting as a paracrine–autocrine regulator of bone formation. Osteoarthritis (OA) is a disease of the whole joint. Different tissues involved in OA express OT receptors (OTRs), such as chondrocytes and osteoblasts. This hormone, which levels are reduced in patients with OA, appears to have a stimulatory effect on chondrogenesis. OT involvement in bone biology could occur at both the osteoblast and chondrocyte levels. The relationships between metabolic syndrome, body weight, and OA are well documented, and the possible effects of OT on different parameters of metabolic syndrome, such as diabetes and body weight, are important. In addition, the effects of OT on adipokines and inflammation are also discussed, especially since recent data have shown that low-grade inflammation is also associated with OA. Furthermore, OT also appears to mediate endogenous analgesia in animal and human studies. These observations provide support for the possible interest of OT in OA and its potential therapeutic treatment.

Oxytocin and Food Intake Control: Neural, Behavioral, and Signaling Mechanisms

The neuropeptide oxytocin is produced in the paraventricular hypothalamic nucleus and the supraoptic nucleus of the hypothalamus. In addition to its extensively studied influence on social behavior and reproductive function, central oxytocin signaling potently reduces food intake in both humans and animal models and has potential therapeutic use for obesity treatment. In this review, we highlight rodent model research that illuminates various neural, behavioral, and signaling mechanisms through which oxytocin’s anorexigenic effects occur. The research supports a framework through which oxytocin reduces food intake via amplification of within-meal physiological satiation signals rather than by altering between-meal interoceptive hunger and satiety states. We also emphasize the distributed neural sites of action for oxytocin’s effects on food intake and review evidence supporting the notion that central oxytocin is communicated throughout the brain, at least in part, through humoral-like volume transmission. Finally, we highlight mechanisms through which oxytocin interacts with various energy balance-associated neuropeptide and endocrine systems (e.g., agouti-related peptide, melanin-concentrating hormone, leptin), as well as the behavioral mechanisms through which oxytocin inhibits food intake, including effects on nutrient-specific ingestion, meal size control, food reward-motivated responses, and competing motivations.

Receptor for advanced glycation end-products (RAGE) plays a critical role in retrieval behavior of mother mice at early postpartum

Receptor for advanced glycation end-products (RAGE) is a pattern recognition molecule belonging to the immunoglobulin superfamily, and it plays a role in the remodeling of endothelial cells under pathological conditions. Recently, it was shown that RAGE is a binding protein for oxytocin (OT) and a transporter of OT to the brain on neurovascular endothelial cells via blood circulation. Deletion of the mouse RAGE gene, Ager (RAGE KO), induces hyperactivity in male mice. Impairment of pup care by mother RAGE KO mice after stress exposure results in the death of neonates 1-2 days after pup birth. Therefore, to understand the role of RAGE during the postpartum period, this study aims to examine parental behavior in female RAGE KO mice and ultrasonic vocalizations in pups. RAGE KO mothers without stress before delivery raised their pups and displayed hyperactivity at postpartum day (PPD) 3. KO dams showed impaired retrieval or interaction behavior after additional stress, such as body restraint stress or exposure to a novel environment, but such impaired behavior disappeared at PPD 7. Postnatal day 3 pups emitted ultrasonic vocalizations at >60 kHz as a part of the mother-pup relationship, but the number and category of calls by RAGE KO pups were significantly lower than wild-type pups. The results indicate that RAGE is important in the manifestation of normal parental behavior in dams and for receiving maternal care by mouse pups; moreover, brain OT recruited by RAGE plays a role in damping of signals of additional external stress and endogenous stress during the early postpartum period. Thus, RAGE-dependent OT may be critical for initiating and maintaining the normal mother-child relationship.

Fetal mortality associated with backfat thickness at first mating and first farrowing of the primiparous sows raised in a commercial herd in Thailand

This study aimed to investigate the fetal mortality, including stillborn piglets (SB) and mummified fetuses (MM), in relation to backfat thickness both at first mating (MBF) and at first farrowing (FBF) in 200 primiparous sows accommodated in a commercial breeding herd in Thailand. Backfat thickness of all pigs was measured at P2 position using an A-mode ultrasonography. Based on MBF, the gilts were classified into four groups: MBF1 (≤12.0 mm), MBF2 (>12.0-15.0 mm), MBF3 (>15.0-18.0 mm), and MBF4 (>18.0 mm). According to FBF, the primiparous sows were categorized into four classes: FBF1 (≤15.0 mm), FBF2 (>15.0-18.0 mm), FBF3 (>18.0-21.0 mm), and FBF4 (>21.0 mm). At farrowing, 174 litters were examined for percentage of SB and MM. The results indicated that mean MBF and FBF were 16.7 ± 0.3 mm and 19.6 ± 0.3 mm, respectively. Based on MBF, the pigs in MBF1 significantly possessed higher percentage of MM (13.8 ± 4.5%) than others; meanwhile, SB percentage was not different among groups (P > 0.05). According to FBF, the pigs in FBF4 farrowed the highest percentage of SB (9.1 ± 3.2%) than others, whereas MM percentage was not different among classes (P > 0.05). In summary, backfat thickness of the gilts should be one of the parameters to pay more attention since it is related to fetal mortality of the primiparous sows. The farmers should monitor the backfat thickness not only at the first mating time, but also along the gestation period in order to minimize fetal mortality in the primiparous sows.

Oxytocin Signaling Pathway: From Cell Biology to Clinical Implications

BACKGROUND

In addition to the well-known role played in lactation and parturition, Oxytocin (OT) and OT receptor (OTR) are involved in many other aspects such as the control of maternal and social behavior, the regulation of the growth of the neocortex, the maintenance of blood supply to the cortex, the stimulation of limbic olfactory area to mother-infant recognition bond, and the modulation of the autonomic nervous system via the vagal pathway. Moreover, OT and OTR show antiinflammatory, anti-oxidant, anti-pain, anti-diabetic, anti-dyslipidemic and anti-atherogenic effects.

OBJECTIVE

The aim of this narrative review is to summarize the main data coming from the literature dealing with the role of OT and OTR in physiology and pathologic conditions focusing on the most relevant aspects.

METHODS

Appropriate keywords and MeSH terms were identified and searched in Pubmed. Finally, references of original articles and reviews were examined.

RESULTS

We report the most significant and updated data on the role played by OT and OTR in physiology and different clinical contexts.

CONCLUSION

Emerging evidence indicates the involvement of OT system in several pathophysiological mechanisms influencing brain anatomy, cognition, language, sense of safety and trust and maternal behavior, with the possible use of exogenous administered OT in the treatment of specific neuropsychiatric conditions. Furthermore, it modulates pancreatic β-cell responsiveness and lipid metabolism leading to possible therapeutic use in diabetic and dyslipidemic patients and for limiting and even reversing atherosclerotic lesions.

Oxytocin modulates local topography of human functional connectome in healthy men at rest

Oxytocin has recently received remarkable attention for its role as a modulator of human behaviour. Here, we aimed to expand our knowledge of the neural circuits engaged by oxytocin by investigating the effects of intranasal and intravenous oxytocin on the functional connectome at rest in 16 healthy men. Oxytocin modulates the functional connectome within discrete neural systems, but does not affect the global capacity for information transfer. These local effects encompass key hubs of the oxytocin system (e.g. amygdala) but also regions overlooked in previous hypothesis-driven research (i.e. the visual circuits, temporal lobe and cerebellum). Increases in levels of oxytocin in systemic circulation induce broad effects on the functional connectome, yet we provide indirect evidence supporting the involvement of nose-to-brain pathways in at least some of the observed changes after intranasal oxytocin. Together, our results suggest that oxytocin effects on human behaviour entail modulation of multiple levels of brain processing distributed across different systems.

Oxytocin reverses ethanol consumption and neuroinflammation induced by social defeat in male mice

Oxytocin (OXT) modulates social interactions, attenuates stressful responses and can decrease drug-seeking and taking behaviors. In previous studies, we observed that social defeat (SD) induced a long-lasting increase in ethanol intake and neuroinflammation in male mice. We also know that OXT blocks the increase in cocaine reward induced by SD. Therefore, in the present study we aimed to evaluate the effect of 1 mg/kg of OXT administered 30 min before each episode of SD on ethanol consumption and the neuroinflammatory response in adult male mice. Three weeks after the last SD, mice underwent oral ethanol self-administration (SA) procedure, and striatal levels of the two chemokines CX3CL1 and CXCL12 were measured after the last SD and at the end of the ethanol SA. OXT administration blocked the increase in voluntary ethanol consumption observed in defeated mice, although it did not affect motivation for ethanol. An increase in the striatal levels of CX3CL1 and CXCL12 was observed in defeated animals immediately after the last defeat and after the ethanol SA. However, defeated mice treated with OXT did not show this increase in the neuroinflammatory response. In conclusion, OXT treatment can be a powerful therapeutic target to reduce the negative effects of social stress on ethanol consumption and the neuroinflammatory process.

Effect of intramuscular and intravaginal PGE-2 treatment compared to intramuscular oxytocin treatment in eutocic sows on the farrowing performance in a free farrowing system

A duration of parturition beyond 300 min negatively impacts the health of the sow and the survival of piglets during parturition. Hence, oxytocin is widely used to speed up the parturition. However, oxytocin's negative side effects raise the need of finding alternative treatments such as those already implemented in human medicine. The aim of this study was to evaluate the efficacy of Prostaglandin E2 (PGE2) applied intravaginally (PGE2-V) (1.0 mg) or intramuscularly (PGE2-M) (2.5 mg) to improve the parturition process after expulsion of the fourth piglet compared to a placebo (P-V), which was sterile intravaginal gel or intramuscular oxytocin application (OXY-M) (20 iu) in free farrowing systems.In total, 201 eutocic sows were examined after stratification by parity and random allocation into groups: 54 (P-V), 48 (OXY-M), 50 (PGE2-V), 49 (PGE2-M). Farrowing duration (time between first piglet and last piglet), piglet interval and placenta expulsion duration (time between first and last placenta) were recorded, and each piglet was scored for meconium staining and vitality. Furthermore, stillborn piglets were categorized into ante-partum and intra-partum deaths.Under the present conditions, neither administration of PGE2 nor oxytocin revealed a significant effect on the farrowing process or the vitality of the piglets when compared to untreated sows. Nonetheless, significant differences could be detected between PGE-2 and oxytocin treatments. The duration of farrowing was significantly shorter in oxytocin-treated sows (156 min) compared to sows treated intramuscularly with PGE2 (238 min). Furthermore, the placenta expulsion duration in the OXY-M group (130 min) significantly differed from PGE2-V (198 min) and PGE2-M group (218 min). Although these accelerations of parturition might be considered as a beneficial effect, routine treatment with uterotonic agents after birth of the fourth piglet in free farrowing eutocic sows cannot be recommended, because an overall benefit when compared to untreated sows was not approved.

Social touch promotes interfemale communication via activation of parvocellular oxytocin neurons

Oxytocin (OT) is a great facilitator of social life but, although its effects on socially relevant brain regions have been extensively studied, OT neuron activity during actual social interactions remains unexplored. Most OT neurons are magnocellular neurons, which simultaneously project to the pituitary and forebrain regions involved in social behaviors. In the present study, we show that a much smaller population of OT neurons, parvocellular neurons that do not project to the pituitary but synapse onto magnocellular neurons, is preferentially activated by somatosensory stimuli. This activation is transmitted to the larger population of magnocellular neurons, which consequently show coordinated increases in their activity during social interactions between virgin female rats. Selectively activating these parvocellular neurons promotes social motivation, whereas inhibiting them reduces social interactions. Thus, parvocellular OT neurons receive particular inputs to control social behavior by coordinating the responses of the much larger population of magnocellular OT neurons.

Oxytocin Controls Chondrogenesis and Correlates with Osteoarthritis

This study investigated the relationship of oxytocin (OT) to chondrogenesis and osteoarthritis (OA). Human bone marrow and multipotent adipose-derived stem cells were cultured in vitro in the absence or presence of OT and assayed for mRNA transcript expression along with histological and immunohistochemical analyses. To study the effects of OT in OA in vivo, a rat model and a human cohort of 63 men and 19 women with hand OA and healthy controls, respectively, were used. The baseline circulating OT, interleukin-6, leptin, and oestradiol levels were measured, and hand X-ray examinations were performed for each subject. OT induced increased aggrecan, collagen (Col) X, and cartilage oligomeric matrix protein mRNA transcript levels in vitro, and the immunolabelling experiments revealed a normalization of Sox9 and Col II protein expression levels. No histological differences in lesion severity were observed between rat OA groups. In the clinical study, a multivariate analysis adjusted for age, body mass index, and leptin levels revealed a significant association between OA and lower levels of OT (odds ratio = 0.77; p = 0.012). Serum OT levels are reduced in patients with hand OA, and OT showed a stimulatory effect on chondrogenesis. Thus, OT may contribute to the pathophysiology of OA.

An Allostatic Theory of Oxytocin

Oxytocin has garnered considerable interest for its role in social behavior, as well as for the potential of intranasal administration to treat social difficulties. However, current theoretical models for the role of oxytocin in social behavior pay little consideration to its evolutionary and developmental history. This article aims to broaden our understanding of the role of oxytocin in social behavior by adopting an ethological approach through the lens of Nikolaas Tinbergen's 'four questions' - how does oxytocin work; how does the role of oxytocin change during development; how does oxytocin enhance survival; and how did the oxytocin system evolve? We argue that oxytocin is most accurately described as an allostatic hormone that modulates both social and non-social behavior by maintaining stability through changing environments.

Prenatal resident-intruder stress decreases levels of allopregnanolone in the cortex, hypothalamus, and midbrain of males, and increases levels in the hippocampus and cerebellum of female, juvenile rat offspring

Prenatal stress (PNS) can influence behaviors associated with cognition, reward and emotional regulation, which are controlled by brain areas such as the cortex, hippocampus, hypothalamus, midbrain and cerebellum. Allopregnanolone in these regions modulates behavioral and parasympathetic effects. The current study tested whether exposing pregnant dams to 5 days of resident-intruder stress on prenatal days 15-20 for 10 min altered the levels of allopregnanolone in cortex, hypothalamus, hippocampus, midbrain, and cerebellum of male and female juvenile offspring. In cortex, hypothalamus, and midbrain of male rats exposed to prenatal stress, levels of allopregnanolone were significantly lower compared to all other groups. In the hippocampus and cerebellum, among females exposed to prenatal stress levels were significantly higher compared to all other groups. These differences in allopregnanolone levels varying by prenatal stress, sex and brain regions provide insight in potential mechanism of stress regulation and etiopathophysiology of stress-related disorders.

Effects of route of administration on oxytocin-induced changes in regional cerebral blood flow in humans

Could nose-to-brain pathways mediate the effects of peptides such as oxytocin (OT) on brain physiology when delivered intranasally? We address this question by contrasting two methods of intranasal administration (a standard nasal spray, and a nebulizer expected to improve OT deposition in nasal areas putatively involved in direct nose-to-brain transport) to intravenous administration in terms of effects on regional cerebral blood flow during two hours post-dosing. We demonstrate that OT-induced decreases in amygdala perfusion, a key hub of the OT central circuitry, are explained entirely by OT increases in systemic circulation following both intranasal and intravenous OT administration. Yet we also provide robust evidence confirming the validity of the intranasal route to target specific brain regions. Our work has important translational implications and demonstrates the need to carefully consider the method of administration in our efforts to engage specific central oxytocinergic targets for the treatment of neuropsychiatric disorders.

Glycemia Regulation: From Feedback Loops to Organizational Closure

Endocrinologists apply the idea of feedback loops to explain how hormones regulate certain bodily functions such as glucose metabolism. In particular, feedback loops focus on the maintenance of the plasma concentrations of glucose within a narrow range. Here, we put forward a different, organicist perspective on the endocrine regulation of glycaemia, by relying on the pivotal concept of closure of constraints. From this perspective, biological systems are understood as organized ones, which means that they are constituted of a set of mutually dependent functional structures acting as constraints, whose maintenance depends on their reciprocal interactions. Closure refers specifically to the mutual dependence among functional constraints in an organism. We show that, when compared to feedback loops, organizational closure can generate much richer descriptions of the processes and constraints at play in the metabolism and regulation of glycaemia, by making explicit the different hierarchical orders involved. We expect that the proposed theoretical framework will open the way to the construction of original mathematical models, which would provide a better understanding of endocrine regulation from an organicist perspective.

The role of oxytocin and vasopressin in the pathophysiology of heart failure in pregnancy and in fetal and neonatal life

Pregnancy and early life create specific psychosomatic challenges for the mother and child, such as changes in hemodynamics, resetting of the water-electrolyte balance, hypoxia, pain, and stress, that all play an important role in the regulation of the release of oxytocin and vasopressin. Both of these hormones regulate the water-electrolyte balance and cardiovascular functions, maturation of the cardiovascular system, and cardiovascular responses to stress. These aspects may be of particular importance in a state of emergency, such as hypertension in the mother or severe heart failure in the child. In this review, we draw attention to a broad spectrum of actions exerted by oxytocin and vasopressin in the pregnant mother and the offspring during early life. To this end, we discuss the following topics: 1) regulation of the secretion of oxytocin and vasopressin and expression of their receptors in the pregnant mother and child, 2) direct and indirect effects of oxytocin and vasopressin on the cardiovascular system in the healthy mother and fetus, and 3) positive and negative consequences of altered secretion of oxytocin and vasopressin in the mother with cardiovascular pathology and in the progeny with heart failure. The present survey provides evidence that moderate stimulation of the oxytocin and vasopressin receptors plays a beneficial role in the healthy pregnant mother and fetus; however, under pathophysiological conditions the inappropriate action of these hormones exerts several negative effects on the cardiovascular system of the mother and progeny and may potentially contribute to the pathophysiology of heart failure in early life.

Low Serum Oxytocin Concentrations Are Associated with Painful Menstruation

Oxytocin-dependent mechanisms are hypothesized to contribute to painful menses, but clinical trials of oxytocin antagonists for dysmenorrhea have had divergent outcomes. In contrast, broader studies have shown that increased systemic oxytocin concentrations are associated with increased pain tolerance and improved psychosocial function. We sought to confirm whether increased serum oxytocin concentrations are associated with menstrual pain and other psychosocial factors. Women with a history of primary dysmenorrhea (n = 19), secondary dysmenorrhea (n = 12), and healthy controls (n = 15) completed pain and psychosocial questionnaires, provided a medical history, and rated their pain during the first 48 h of menses. Serum samples were collected during menses to measure oxytocin concentrations. Oxytocin was significantly lower in participants with a history of primary (704 ± 33 pg/mL; p < 0.001) or secondary (711 ± 66 pg/mL; p < 0.01) dysmenorrhea compared to healthy controls (967 ± 53 pg/mL). Menstrual pain over the past 3 months (r = -0.58; p < 0.001) and during the study visit (r = -0.45; p = 0.002) was negatively correlated with oxytocin concentrations. Pain catastrophizing (r = -0.39), pain behavior (r = -0.32), and pain interference (r = -0.31) were also negatively correlated with oxytocin levels (p's < 0.05). Oxytocin was not significantly correlated with psychosocial factors. Contrary to our hypothesis, women with a history of primary or secondary dysmenorrhea had lower oxytocin concentrations during menses when compared to healthy controls. Lower circulating oxytocin concentrations were also associated with worse menstrual pain and pain-related behavior. When considering the existing literature, low circulating oxytocin may be a sign of dysfunctional endogenous pain modulation.

Kisspeptin as a potential biomarker throughout pregnancy

Kisspeptins are a family of neuropeptides that are critical for the puberty initiation and female fertility. Plasma or serum kisspeptin is mainly derived from the placenta during pregnancy and plasma kisspeptin levels significantly increase across pregnancy. Plasma kisspeptin levels could be used as a potential biomarker for the detection of miscarriage, pre-eclampsia, gestational trophoblastic neoplasia (GTN), and fetal development. Kisspeptin may also be involved in the process of parturition by stimulating oxytocin secretion during term pregnancy. This review discussed the potential use of kisspeptin as a marker across pregnancy and highlighted the unresolved problems in this area. Tweetable abstract: Plasma kisspeptin levels could be used as a potential biomarker across pregnancy.

Opioids and the hormone oxytocin

The neuropeptide Oxytocin (ΟΤ) is involved as a neurohormone, a neurotransmitter, or a neuromodulator in an extensive range of central and peripheral effects, complex emotional and social human behaviors, memory and learning processes. It is implicated in homeostatic, neuroadaptive processes associated with stress responses and substance use via interactions with the hypothalamic-pituitary-adrenal (HPA) axis and the dopamine mesolimbic reward stress system. This chapter reviews the preclinical and clinical literature on the complicated relationships between endogenous and exogenous opioids and ΟΤ systems and attempts to highlight key findings to date on the effectiveness of intranasal OT administration to treat opioid use disorders. OΤ seems to attenuate, even inhibit, the development of opioid use disorders in preclinical models but is still under clinical research as a promising pharmacological agent in the treatment of opioid use related behaviors. Evidence suggests a role for OT as an adjunctive or stand-alone treatment of behavioral, cognitive and emotional deficits associated with substance use, which may be responsible for seeking behavior and relapse. The mechanisms by which oxytocin acts to reverse the neural substrates of these deficits, partially due to substance induced alterations of the endogenous OT system, and thus modify the behavioral response to substance use are discussed. Other clinically relevant issues are also discussed.

DNA methylation-reprogrammed oxytocin receptor underlies insensitivity to oxytocin in pre-eclamptic placental vasculature

Pre‐eclampsia is associated with inadequate placental blood flow and placental ischaemia. Placental vascular tone is essential for maintaining adequate placental blood flow. Oxytocin is increased in placental system at late pregnancy and onset of labour, and presented strongly concentration‐dependent contractions in placental vascular, suggesting that oxytocin could be involved in regulating placental vascular tone and circulation. However, information about the reactivity of oxytocin in pre‐eclamptic placental vasculature is limited. This study used a large number of human placentas to reveal the pathophysiological changes and its underlying mechanisms of oxytocin‐induced vasoconstrictions in placental vessels under pre‐eclamptic condition. Present study found that oxytocin‐induced contractions were significantly decreased in human pre‐eclamptic placental vasculature, associated with a deactivated transcription of oxytocin receptor gene. The deactivated oxytocin receptor gene transcription was ascribed to a relatively higher DNA methylation status of CpG islands in oxytocin receptor gene promoter. This study was first to reveal that a hyper‐methylation of CpG islands in oxytocin receptor gene promoter, leading to a relatively low pattern of oxytocin receptor expression, was responsible for the decreased sensitivity of oxytocin in pre‐eclamptic placental vessels.

Giving a good start to a new life via maternal brain allostatic adaptations in pregnancy

Successful pregnancy requires adjustments to multiple maternal homeostatic mechanisms, governed by the maternal brain to support and enable survival of the growing fetus and placenta. Such adjustments fit the concept of allostasis (stability through change) and have a cost: allostatic load. Allostasis is driven by ovarian, anterior pituitary, placental and feto-placental hormones acting on the maternal brain to promote adaptations that support the pregnancy and protect the fetus. Many women carry an existing allostatic load into pregnancy, from socio-economic circumstances, poor mental health and in 'developed' countries, also from obesity. These pregnancies have poorer outcomes indicating negative interactions (failing allostasis) between pre-pregnancy and pregnancy allostatic loads. Use of animal models, such as adult prenatally stressed female offspring with abnormal neuroendocrine, metabolic and behavioural phenotypes, to probe gene expression changes, and epigenetic mechanisms in the maternal brain in adverse pregnancies are discussed, with the prospect of ameliorating poor pregnancy outcomes.

The osmoresponsiveness of oxytocin and vasopressin neurones: Mechanisms, allostasis and evolution

In the rat supraoptic nucleus, every oxytocin cell projects to the posterior pituitary, and is involved both in reflex milk ejection during lactation and in regulating uterine contractions during parturition. All are also osmosensitive, regulating natriuresis. All are also regulated by signals that control appetite, including the neural and hormonal signals that arise from the gut after food intake and from the sites of energy storage. All are also involved in sexual behaviour, anxiety-related behaviours and social behaviours. The challenge is to understand how a single population of neurones can coherently regulate such a diverse set of functions and adapt to changing physiological states. Their multiple functions arise from complex intrinsic properties that confer sensitivity to a wide range of internal and environmental signals. Many of these properties have a distant evolutionary origin in multifunctional, multisensory neurones of Urbilateria, the hypothesised common ancestor of vertebrates, insects and worms. Their properties allow different patterns of oxytocin release into the circulation from their axon terminals in the posterior pituitary into other brain areas from axonal projections, as well as independent release from their dendrites.

The endocrinology of the brain

The brain hosts a vast and diverse repertoire of neuropeptides, a class of signalling molecules often described as neurotransmitters. Here I argue that this description entails a catalogue of misperceptions, misperceptions that feed into a narrative in which information processing in the brain can be understood only through mapping neuronal connectivity and by studying the transmission of electrically conducted signals through chemical synapses. I argue that neuropeptide signalling in the brain involves primarily autocrine, paracrine and neurohormonal mechanisms that do not depend on synaptic connectivity and that it is not solely dependent on electrical activity but on mechanisms analogous to secretion from classical endocrine cells. As in classical endocrine systems, to understand the role of neuropeptides in the brain, we must understand not only how their release is regulated, but also how their synthesis is regulated and how the sensitivity of their targets is regulated. We must also understand the full diversity of effects of neuropeptides on those targets, including their effects on gene expression.

Thalamic integration of social stimuli regulating parental behavior and the oxytocin system

Critically important components of the maternal neural circuit in the preoptic area robustly activated by suckling were recently identified. In turn, suckling also contributes to hormonal adaptations to motherhood, which includes oxytocin release and consequent milk ejection. Other reproductive or social stimuli can also trigger the release of oxytocin centrally, influencing parental or social behaviors. However, the neuronal pathways that transfer suckling and other somatosensory stimuli to the preoptic area and oxytocin neurons have been poorly characterized. Recently, a relay center of suckling was determined and characterized in the posterior intralaminar complex of the thalamus (PIL). Its neurons containing tuberoinfundibular peptide 39 project to both the preoptic area and oxytocin neurons in the hypothalamus. The present review argues that the PIL is a major relay nucleus conveying somatosensory information supporting maternal behavior and oxytocin release in mothers, and may be involved more generally in social cue evoked oxytocin release, too.

Cyclic Peptides that Govern Signal Transduction Pathways: From Prokaryotes to Multi-Cellular Organisms

Cyclic peptide scaffolds are key components of signal transduction pathways in both prokaryotic and eukaryotic organisms since they act as chemical messengers that activate or inhibit specific cognate receptors. In prokaryotic organisms these peptides are utilized in non-essential pathways, such as quorum sensing, that are responsible for virulence and pathogenicity. In the more evolved eukaryotic systems, cyclic peptide hormones play a key role in the regulation of the overall function of multicellular organisms, mainly through the endocrine system. This review will highlight several prokaryote and eukaryote systems that use cyclic peptides as their primary signals and the potential associated with utilizing these scaffolds for the discovery of novel therapeutics for a wide range of diseases and illnesses.

Role of central oxytocin and dopamine systems in nociception and their possible interactions: suggested hypotheses

Central oxytocin and dopamine have an important role in the process of nociception at the spinal level as well as supraspinal structures, e.g. anterior cingulate cortex, insular cortex, amygdala, nucleus accumbens, and hypothalamus. Many studies have pointed out the importance of both systems in the pain descending modulatory system and in pain-related symptoms in some chronic disorders, e.g. Parkinson disease and fibromyalgia. The interaction between oxytocin and dopamine systems has been addressed in some motivational behaviors, e.g. maternal and sexual behaviors, pair bonding, and salience. In this aspect, we propose that an oxytocin-dopamine interaction could be present in nociception, and we also explain the possible hypotheses of such an interaction between these systems.