Negative inotropic and chronotropic effects of oxytocin

Carbetocin Is More Effective in Stabilizing Hemodynamic Parameters Compared to Oxytocin During Cesarean Section

Background/Objectives: First-line uterotonics include carbetocin and oxytocin, which act on the oxytocin receptor with varying potencies. Methods: In 70 pregnant Caucasian women who delivered by cesarean section, the effects of oxytocin and carbetocin on heart rate and blood pressure were compared. The pregnant women were divided into two groups: the OXY group, which received intravenous oxytocin 5 IU on an even day of the month, and the CARBE group, which received intravenous carbetocin 100 µg on an odd day of the month. Blood pressure and heart rate were measured noninvasively every 3 min from the beginning of cesarean section until the lower uterine incision, and then at 1, 2, and 3 min after the fetus and placenta were removed and the uterotonic drugs were discontinued. Subsequent measurements were taken at 3 min intervals until the end of the cesarean procedure. Results: After the administration of uterotonic drugs, a significant decrease in systolic blood pressure was observed only in the group receiving oxytocin at the first (p < 0.0001) and second minute after drug administration (p < 0.0001). Diastolic arterial pressure was significantly different in the study groups at the sixth minute after oxytocin and carbetocin administration (p = 0.004). Mean arterial pressure values were significantly different in the two study groups at the first and sixth minute after drug administration (p = 0.006; p = 0.014). With regard to heart rate, significant differences between the groups were found at 6 min after uterotonic drug administration (p = 0.019). Conclusions: Blood pressure and heart rate variability are significantly higher after oxytocin than after carbetocin administration in women delivering by cesarean section.

A comprehensive review on the effects of sex hormones on chemotherapy-induced cardiotoxicity: are they lucrative or unprofitable?

Chemotherapy is one of the routine treatment for preventing rapid growth of the tumor cells. However, chemotherapeutic agents, especially doxorubicin cause damages to the normal cells especially cardiomyocytes. Cardiotoxicity induced by chemotherapeutic drugs lead to the myocardial cell injury and finally causes left ventricular dysfunction. It seems that there were some differences in the severity of cardiovascular side effects of drugs used in the treatment of cancers. Sex hormones in male and female play crucial roles in cardiovascular development and physiological function of the heart and blood vessels. Gender differences and sex-specific hormones influence various aspects of cardiovascular health, including ventricular function, mitochondrial autophagy, and the development of abdominal aortic aneurysms. The most important gender related hormones are LH, FSH, testosterone, estrogen, progesterone, prolactin and oxytocin. They exert very important cardiovascular effects via different signaling mechanisms. Sex related hormones are also important in the cardiovascular side effects of chemotherapeutic agents, so that chronic cardiotoxicity induced by anthracyclines is more common in women. During different stages of life (before, during, and after sexual life), the levels of these hormones will be changed. This alterations can affect cardiovascular function during physiological conditions and pathological process. Because of the importance of the sex related hormones in the cardiac function, in this review we tried to comprehensively elucidate the role of these physiological hormones in cardiotoxicity induced by chemotherapeutic agents with emphasizing their signaling mechanisms.

Transcriptome Analysis Reveals Enhancement of Cardiogenesis-Related Signaling Pathways by S-Nitroso- N -Pivaloyl- d -Penicillamine: Implications for Improved Diastolic Function and Cardiac Performance

ABSTRACT

We previously reported a novel compound called S-nitroso- N -pivaloyl- d -penicillamine (SNPiP), which was screened from a group of nitric oxide donor compounds with a basic chemical structure of S-nitroso- N -acetylpenicillamine, to activate the nonneuronal acetylcholine system. SNPiP-treated mice exhibited improved cardiac output and enhanced diastolic function, without an increase in heart rate. The nonneuronal acetylcholine-activating effects included increased resilience to ischemia, modulation of energy metabolism preference, and activation of angiogenesis. Here, we performed transcriptome analysis of SNPiP-treated mice ventricles to elucidate how SNPiP exerts beneficial effects on cardiac function. A time-course study (24 and 48 hours after SNPiP administration) revealed that SNPiP initially induced Wnt and cyclic guanosine monophosphate-protein kinase G signaling pathways, along with upregulation of genes involved in cardiac muscle tissue development and oxytocin signaling pathway. We also observed enrichment of glycolysis-related genes in response to SNPiP treatment, resulting in a metabolic shift from oxidative phosphorylation to glycolysis, which was suggested by reduced cardiac glucose contents while maintaining adenosine tri-phosphate levels. In addition, SNPiP significantly upregulated atrial natriuretic peptide and sarcolipin, which play crucial roles in calcium handling and cardiac performance. These findings suggest that SNPiP may have therapeutic potential based on the pleiotropic mechanisms elucidated in this study.

The Role of Central Oxytocin in Autonomic Regulation

Oxytocin (OXT), a neuropeptide originating from the hypothalamus and traditionally associated with peripheral functions in parturition and lactation, has emerged as a pivotal player in the central regulation of the autonomic nervous system (ANS). This comprehensive ANS, comprising sympathetic, parasympathetic, and enteric components, intricately combines sympathetic and parasympathetic influences to provide unified control. The central oversight of sympathetic and parasympathetic outputs involves a network of interconnected regions spanning the neuroaxis, playing a pivotal role in the real-time regulation of visceral function, homeostasis, and adaptation to challenges. This review unveils the significant involvement of the central OXT system in modulating autonomic functions, shedding light on diverse subpopulations of OXT neurons within the paraventricular nucleus of the hypothalamus and their intricate projections. The narrative progresses from the basics of central ANS regulation to a detailed discussion of the central controls of sympathetic and parasympathetic outflows. The subsequent segment focuses specifically on the central OXT system, providing a foundation for exploring the central role of OXT in ANS regulation. This review synthesizes current knowledge, paving the way for future research endeavors to unravel the full scope of autonomic control and understand multifaceted impact of OXT on physiological outcomes.

Cardiovascular effects of oxytocin and carbetocin at cesarean section. A prospective double-blind randomized study using noninvasive pulse wave analysis

BACKGROUND

Oxytocin is routinely administered after delivery for prophylaxis and treatment of postpartum hemorrhage, but it is associated with considerable cardiovascular side-effects. Carbetocin, a synthetic oxytocin analogue, has a myometrial contraction effect of 60 min when given IV, compared with 16 min for oxytocin.

OBJECTIVE

To investigate whether there are differences in cardiovascular effects between oxytocin and carbetocin up to 1 h after treatment.

METHODS

Sixty-one healthy pregnant women undergoing elective cesarean section in spinal anesthesia were randomized to receive an IV bolus of either five units (8.3 µg) of oxytocin or 100 µg of carbetocin after delivery of the baby. Heart rate (HR), mean arterial blood pressure, ECG ST index, oxygen saturation (SaO₂), and photoplethysmographic digital pulse wave analysis variables were recorded before and at 1, 5, 20, and 60 min after drug administration. Vasopressor use, uterine tonus, total bleeding, and need for additional uterotonics were also assessed. Repeated measurement ANOVA was used for statistical analyses.

RESULTS

The drugs had equal vasodilatory and hypotensive effects. Oxytocin, but not carbetocin, caused a decrease in HR at 1 min and a sustained decrease in cardiac left ventricular ejection time. Aggregate vasopressor use was higher in the carbetocin group. Neither drug caused any change in ST index, SaO₂, or subjective cardiac symptoms. Uterine tonus, need for additional uterotonics, or total bleeding did not differ significantly between the groups.

CONCLUSION

Single doses of oxytocin and carbetocin had similar dilatory effects on vascular tonus, where the difference in aggregate vasopressor use can be attributed to a more persistent hypotensive effect of carbetocin. A transient negative chronotropic and sustained negative inotropic effect occurred after oxytocin. Neither drug showed any alarmingly adverse effects. Differences in drug effects may be attributed to differences in oxytocin and vasopressin receptor signaling pathways.

Oxytocin: A Multi-Functional Biomolecule with Potential Actions in Dysfunctional Conditions; From Animal Studies and Beyond

Oxytocin is a hormone secreted from definite neuroendocrine neurons located in specific nuclei in the hypothalamus (mainly from paraventricular and supraoptic nuclei), and its main known function is the contraction of uterine and/or mammary gland cells responsible for parturition and breastfeeding. Among the actions of the peripherally secreted oxytocin is the prevention of different degenerative disorders. These actions have been proven in cell culture and in animal models or have been tested in humans based on hypotheses from previous studies. This review presents the knowledge gained from the previous studies, displays the results from oxytocin intervention and/or treatment and proposes that the well described actions of oxytocin might be connected to other numerous, diverse actions of the biomolecule.

Oxytocin: An Old Hormone, A Novel Psychotropic Drug And Possible Use In Treating Psychiatric Disorders

BACKGROUND

Oxytocin is a nonapeptide synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Historically, this molecule has been involved as a key factor in the formation of infant attachment, maternal behavior and pair bonding and, more generally, in linking social signals with cognition, behaviors and reward. In the last decades, the whole oxytocin system has gained a growing interest as it was proposed to be implicated in etiopathogenesis of several neurodevelopmental and neuropsychiatric disorders.

METHODS

With the main goal of an in-depth understanding of the oxytocin role in the regulation of different functions and complex behaviors as well as its intriguing implications in different neuropsychiatric disorders, we performed a critical review of the current state of art. We carried out this work through PubMed database up to June 2021 with the search terms: 1) "oxytocin and neuropsychiatric disorders"; 2) "oxytocin and neurodevelopmental disorders"; 3) "oxytocin and anorexia"; 4) "oxytocin and eating disorders"; 5) "oxytocin and obsessive-compulsive disorder"; 6) "oxytocin and schizophrenia"; 7) "oxytocin and depression"; 8) "oxytocin and bipolar disorder"; 9) "oxytocin and psychosis"; 10) "oxytocin and anxiety"; 11) "oxytocin and personality disorder"; 12) "oxytocin and PTSD".

RESULTS

Biological, genetic, and epigenetic studies highlighted quality and quantity modifications in the expression of oxytocin peptide or in oxytocin receptor isoforms. These alterations would seem to be correlated with a higher risk of presenting several neuropsychiatric disorders belonging to different psychopathological spectra. Collaterally, the exogenous oxytocin administration has shown to ameliorate many neuropsychiatric clinical conditions.

CONCLUSION

Finally, we briefly analyzed the potential pharmacological use of oxytocin in patient with severe symptomatic SARS-CoV-2 infection due to its anti-inflammatory, anti-oxidative and immunoregulatory properties.

The Gasotransmitter Hydrogen Sulfide and the Neuropeptide Oxytocin as Potential Mediators of Beneficial Cardiovascular Effects through Meditation after Traumatic Events

Trauma and its related psychological and somatic consequences are associated with higher cardiovascular morbidity. The regulation of both the gasotransmitter hydrogen sulfide (H2S) and the neuropeptide oxytocin (OT) have been reported to be affected during physical and psychological trauma. Both mediators are likely molecular correlates of trauma-induced cardiovascular complications, because they share parallel roles and signaling pathways in the cardiovascular system, both locally as well as on the level of central regulation and the vagus nerve. Meditation can alter the structure of specific brain regions and can have beneficial effects on cardiovascular health. This perspective article summarizes the evidence pointing toward the significance of H2S and OT signaling in meditation-mediated cardio-protection.

H2S and Oxytocin Systems in Early Life Stress and Cardiovascular Disease

Today it is well established that early life stress leads to cardiovascular programming that manifests in cardiovascular disease, but the mechanisms by which this occurs, are not fully understood. This perspective review examines the relevant literature that implicates the dysregulation of the gasomediator hydrogen sulfide and the neuroendocrine oxytocin systems in heart disease and their putative mechanistic role in the early life stress developmental origins of cardiovascular disease. Furthermore, interesting hints towards the mutual interaction of the hydrogen sulfide and OT systems are identified, especially with regards to the connection between the central nervous and the cardiovascular system, which support the role of the vagus nerve as a communication link between the brain and the heart in stress-mediated cardiovascular disease.

A functional selective effect of oxytocin secreted under restraint stress in rats

Restraint stress (RS) is an unavoidable stress model that triggers activation of the autonomic nervous system, endocrine activity, and behavioral changes in rodents. Furthermore, RS induces secretion of oxytocin into the bloodstream, indicating a possible physiological role in the stress response in this model. The presence of oxytocin receptors in vessels and heart favors this possible idea. However, the role of oxytocin secreted in RS and effects on the cardiovascular system are still unclear. The aim of this study was to analyze the influence of oxytocin on cardiovascular effects during RS sessions. Rats were subjected to pharmacological (blockade of either oxytocin, vasopressin, or muscarinic receptors) or surgical (hypophysectomy or sinoaortic denervation) approaches to study the functional role of oxytocin and its receptor during RS. Plasma levels of oxytocin and vasopressin were measured after RS. RS increased arterial pressure, heart rate, and plasma oxytocin content, but not vasopressin. Treatment with atosiban (a Gi biased agonist) inhibited restraint-evoked tachycardia without affecting blood pressure. However, this effect was no longer observed after sinoaortic denervation, homatropine (M2 muscarinic antagonist) treatment or hypophysectomy, indicating that parasympathetic activation mediated by oxytocin secreted to the periphery is responsible for blocking the increase in tachycardic responses observed in the atosiban-treated group. Corroborating this, L-368,899 (oxytocin antagonist) treatment showed an opposite effect to atosiban, increasing tachycardic responses to restraint. Thus, this provides evidence that oxytocin secreted to the periphery attenuates tachycardic responses evoked by restraint via increased parasympathetic activity, promoting cardioprotection by reducing the stress-evoked heart rate increase.

Oxytocin Downregulates the CaV1.2 L-Type Ca2+ Channel via Gi/cAMP/PKA/CREB Signaling Pathway in Cardiomyocytes

Oxytocin (OT) and its receptor (OTR) are expressed in the heart and are involved in the physiological cardiovascular functional system. Although it is known that OT/OTR signaling is cardioprotective by reducing the inflammatory response and improving cardiovascular function, the role of OT in the cardiac electrical excitation modulation has not been clarified. This study investigates the molecular mechanism of the action of OT on cardiomyocyte membrane excitation focusing on the L-type Ca²⁺ channel. Our methodology uses molecular biological methods and a patch-clamp technique on rat cardiomyocytes with OT, combined with several signal inhibitors and/or activators. Our results show that long-term treatment of OT significantly decreases the expression of Cav1.2 mRNA, and reduces the L-type Ca²⁺ channel current (I_Ca.L) in cardiomyocytes. OT downregulates the phosphorylated component of a transcription factor adenosine-3′,5′-cyclic monophosphate (cAMP) response element binding protein (CREB), whose action is blocked by OTR antagonist and pertussis toxin, a specific inhibitor of the inhibitory GTP-binding regulators of adenylate cyclase, Gi. On the other hand, the upregulation of Cav1.2 mRNA expression by isoproterenol is halted by OT. Furthermore, inhibition of phospholipase C (PLC) was without effect on the OT action to downregulate Cav1.2 mRNA—which suggests a signal pathway of Gi/protein kinase A (PKA)/CREB mediated by OT/OTR. These findings indicate novel signaling pathways of OT contributing to a downregulation of the Cav1.2-L-type Ca²⁺ channel in cardiomyocytes.

Cardiovascular protective properties of oxytocin against COVID-19

SARS-CoV-2 infection or COVID-19 has become a worldwide pandemic; however, effective treatment for COVID-19 remains to be established. Along with acute respiratory distress syndrome (ARDS), new and old cardiovascular injuries are important causes of significant morbidity and mortality in COVID-19. Exploring new approaches managing cardiovascular complications is essential in controlling the disease progression and preventing long-term complications. Oxytocin (OXT), an immune-regulating neuropeptide, has recently emerged as a strong candidate for treatment and prevention of COVID-19 pandemic. OXT carries special functions in immunologic defense, homeostasis and surveillance. It suppresses neutrophil infiltration and inflammatory cytokine release, activates T-lymphocytes, and antagonizes negative effects of angiotensin II and other key pathological events of COVID-19. Additionally, OXT can promote γ-interferon expression to inhibit cathepsin L and increases superoxide dismutase expression to reduce heparin and heparan sulphate fragmentation. Through these mechanisms, OXT can block viral invasion, suppress cytokine storm, reverse lymphocytopenia, and prevent progression to ARDS and multiple organ failures. Importantly, besides prevention of metabolic disorders associated with atherosclerosis and diabetes mellitus, OXT can protect the heart and vasculature through suppressing hypertension and brain-heart syndrome, and promoting regeneration of injured cardiomyocytes. Unlike other therapeutic agents, exogenous OXT can be used safely without the side-effects seen in remdesivir and corticosteroid. Importantly, OXT can be mobilized endogenously to prevent pathogenesis of COVID-19. This article summarizes our current understandings of cardiovascular pathogenesis caused by COVID-19, explores the protective potentials of OXT against COVID-19-associated cardiovascular diseases, and discusses challenges in applying OXT in treatment and prevention of COVID-19.

Chemical compounds

Angiotensin-converting enzyme 2 (ACE2); atrial natriuretic peptide (ANP); cathepsin L; heparan sulphate proteoglycans (HSPGs); interferon; interleukin; oxytocin; superoxide dismutase; transmembrane serine protease isoform 2 (TMPRSS2).

Effect of oxytocin on lipid accumulation under inflammatory conditions in human macrophages

INTRODUCTION AND AIMS

Oxytocin (OT) is a neuropeptide hormone secreted by the posterior pituitary gland. Deficits in OT action have been observed in patients with behavioral and mood disorders, some of which correlate with an increased risk of cardiovascular disease (CVD). Recent research has revealed a wider systemic role that OT plays in inflammatory modulation and development of atherosclerotic plaques. This study investigated the role that OT plays in cholesterol transport and foam cell formation in LPS-stimulated THP-1 human macrophages.

METHODS

THP-1 differentiated macrophages were treated with media, LPS (100 ng/ml), LPS + OT (10 pM), or LPS + OT (100 pM). Changes in gene expression and protein levels of cholesterol transporters were analyzed by real time quantitative PCR (RT-qPCR) and Western blot, while oxLDL uptake and cholesterol efflux capacity were evaluated with fluorometric assays.

RESULTS

RT-qPCR analysis revealed a significant increase in ABCG1 gene expression upon OT + LPS treatment, compared to LPS alone (p = 0.0081), with Western blotting supporting the increase in expression of the ABCG1 protein. Analysis of oxLDL uptake showed a significantly lower fluorescent value in LPS + OT (100pM) -treated cells when compared to LPS alone (p < 0.0001). While not statistically significant (p = 0.06), cholesterol efflux capacity increased with LPS + OT treatment.

CONCLUSION

We demonstrate here that OT can attenuate LPS-mediated lipid accumulation in THP-1 macrophages. These findings support the hypothesis that OT could be used to reduce pro-inflammatory and potentially atherogenic changes observed in patients with heightened CVD risk. This study suggests further exploration of OT effects on monocyte and macrophage cholesterol handling in vivo.

The Role of Oxytocin in Cardiovascular Protection

The beneficial effects of oxytocin on infarct size and functional recovery of the ischemic reperfused heart are well documented. The mechanisms for this cardioprotection are not well defined. Evidence indicates that oxytocin treatment improves cardiac work, reduces apoptosis and inflammation, and increases scar vascularization. Oxytocin-mediated cytoprotection involves the production of cGMP stimulated by local release of atrial natriuretic peptide and synthesis of nitric oxide. Treatment with oxytocin reduces the expression of proinflammatory cytokines and reduces immune cell infiltration. Oxytocin also stimulates differentiation stem cells to cardiomyocyte lineages as well as generation of endothelial and smooth muscle cells, promoting angiogenesis. The beneficial actions of oxytocin may include the increase in glucose uptake by cardiomyocytes, reduction in cardiomyocyte hypertrophy, decrease in oxidative stress, and mitochondrial protection of several cell types. In cardiac and cellular models of ischemia and reperfusion, acute administration of oxytocin at the onset of reperfusion enhances cardiomyocyte viability and function by activating Pi3K and Akt phosphorylation and downstream cellular signaling. Reperfusion injury salvage kinase and signal transducer and activator of transcription proteins cardioprotective pathways are involved. Oxytocin is cardioprotective by reducing the inflammatory response and improving cardiovascular and metabolic function. Because of its pleiotropic nature, this peptide demonstrates a clear potential for the treatment of cardiovascular pathologies. In this review, we discuss the possible cellular mechanisms of action of oxytocin involved in cardioprotection.

The Interaction of the Endogenous Hydrogen Sulfide and Oxytocin Systems in Fluid Regulation and the Cardiovascular System

The purpose of this review is to explore the parallel roles and interaction of hydrogen sulfide (H2S) and oxytocin (OT) in cardiovascular regulation and fluid homeostasis. Their interaction has been recently reported to be relevant during physical and psychological trauma. However, literature reports on H2S in physical trauma and OT in psychological trauma are abundant, whereas available information regarding H2S in psychological trauma and OT in physical trauma is much more limited. This review summarizes recent direct and indirect evidence of the interaction of the two systems and their convergence in downstream nitric oxide-dependent signaling pathways during various types of trauma, in an effort to better understand biological correlates of psychosomatic interdependencies.

Intranasal oxytocin increases heart-rate variability in men at clinical high risk for psychosis: a proof-of-concept study

Autonomic nervous system (ANS) dysfunction (i.e., increased sympathetic and/or decreased parasympathetic activity) has been proposed to contribute to psychosis vulnerability. Yet, we still lack directed therapeutic strategies that improve ANS regulation in psychosis or at-risk states. The oxytocin system constitutes a potential therapeutic target, given its role in ANS regulation. However, whether intranasal oxytocin ameliorates autonomic regulation during emerging psychosis is currently unknown. We pooled together two datasets, one of 30 men at clinical high risk for psychosis (CHR-P), and another of 17 healthy men, who had participated in two double-blinded, placebo-controlled, randomised, crossover MRI studies with similar protocols. All participants self-administered 40 IU of intranasal oxytocin or placebo using a nasal spray. We recorded pulse plethysmography during a period of 8 min at about 1 h post dosing and estimated heart rate (HR) and high-frequency HR variability (HF-HRV), an index of cardio-parasympathetic activity. CHR-P and healthy men did not differ at resting HR or HF-HRV under placebo. We found a significant condition × treatment effect for HF-HRV, showing that intranasal oxytocin, compared with placebo, increased HF-HRV in CHR-P but not in healthy men. The main effects of treatment and condition were not significant. In this proof-of-concept study, we show that intranasal oxytocin increases cardio-parasympathetic activity in CHR-P men, highlighting its therapeutic potential to improve autonomic regulation in this clinical group. Our findings support the need for further research on the preventive and therapeutic potential of intranasal oxytocin during emerging psychosis, where we lack effective treatments.

Vasopressin & Oxytocin in Control of the Cardiovascular System: An Updated Review

Since the discovery of vasopressin (VP) and oxytocin (OT) in 1953, considerable knowledge has been gathered about their roles in cardiovascular homeostasis. Unraveling VP vasoconstrictor properties and V1a receptors in blood vessels generated powerful hemostatic drugs and drugs effective in the treatment of certain forms of circulatory collapse (shock). Recognition of the key role of VP in water balance via renal V2 receptors gave birth to aquaretic drugs found to be useful in advanced stages of congestive heart failure. There are still unexplored actions of VP and OT on the cardiovascular system, both at the periphery and in the brain that may open new venues in treatment of cardiovascular diseases. After a brief overview on VP, OT and their peripheral action on the cardiovascular system, this review focuses on newly discovered hypothalamic mechanisms involved in neurogenic control of the circulation in stress and disease.

Mechanisms involved in the cardiovascular effects caused by acute osmotic stimulation in conscious rats

Both the autonomic nervous system and the neuroendocrine system are activated by osmotic stimulation (OS) evoking cardiovascular effects. The current study investigated the mechanisms involved in the cardiovascular responses evoked by an acute osmotic stimulus with intraperitoneal (i.p.) injection of either isotonic (0.15 M NaCl) or hypertonic saline (0.6 M NaCl) in conscious rats. Hypertonic saline increased mean arterial pressure (MAP) and heart rate (HR) for 30 min, as well as plasma osmolality and sodium content. Urinary sodium and urinary volume were also increased. Pretreatment with the ganglion blocker pentolinium (i.v.) did not affect the pressor response, but significantly decreased the tachycardic response caused by OS. Pretreatment with the V₁-vasopressin receptor antagonist dTyr(CH₂)₅(Me)AVP (i.v.) reduced the pressor response, without affecting the tachycardic response evoked by the hypertonic OS. Neither the pressor nor the tachycardic response to OS was affected by pretreatment with either the oxytocin receptor antagonist atosiban or the α1-antagonist prazosin. Pretreatment with the β1-antagonist atenolol had no effect on the pressor response, but markedly decreased the tachycardic response evoked by OS. Results indicate that i.p. hypertonic OS-evoked pressor response is mediated by the release of vasopressin, with a minor influence of the vascular sympathetic input.LAY SUMMARYIncreased plasma osmolality, such as that observed during dehydration or salt intake, is a potent stimulus yielding to marked cardiovascular and neuroendocrine responses. The intraperitoneal (i.p.) injection of hypertonic saline solution is a commonly used animal model to cause a sustained increase in plasma osmolality, leading to a cardiovascular response characterized by sustained blood pressure and heart increases, whose systemic mechanisms were presently studied. Our findings indicate that the pressor response to the i.p. osmotic stimulus (OS) is mediated mainly by the release of vasopressin into the blood circulation with a minor or even the noninvolvement of the vascular sympathetic nervous system, whereas activation of the sympathetic-cardiac system mediates the tachycardic response to OS.

Maternal Separation Induces Long-Term Alterations in the Cardiac Oxytocin Receptor and Cystathionine γ-Lyase Expression in Mice

We recently showed that blunt chest trauma reduced the expression of the myocardial oxytocin receptor (Oxtr), which was further aggravated by genetic deletion of the H₂S-producing enzyme cystathionine γ-lyase (CSE). Exogenous H₂S supplementation restored myocardial Oxtr expression under these conditions. Early life stress (ELS) is a risk factor for cardiovascular disease by affecting vascular and heart structures. Therefore, we tested the hypotheses that (i) ELS affects cardiac Oxtr and CSE expressions and (ii) Oxtr and CSE expression patterns depend on the duration of stress exposure. Thus, two stress paradigms were compared: long- and short-term separation stress (LTSS and STSS, respectively). Cardiac Oxtr expression was differentially affected by the two stress paradigms with a significant reduction after LTSS and a significant increase after STSS. CSE expression, which was significantly reduced in Oxtr^−/− knockout hearts, was downregulated and directly related to Oxtr expression in LTSS hearts (r = 0.657, p = 0.012). In contrast, CSE expression was not related to Oxtr upregulation in STSS. Plasma Oxt levels were not affected by either ELS paradigm. The coincidence of LTSS-induced reduction of cardiac Oxtr and reduced CSE expression may suggest a novel pathophysiological link between early life adversities and increased risk for the development of cardiovascular disorders in adulthood.

Therapeutic Potential of Oxytocin in Atherosclerotic Cardiovascular Disease: Mechanisms and Signaling Pathways

Coronary artery disease (CAD) is a major cardiovascular disease responsible for high morbidity and mortality worldwide. The major pathophysiological basis of CAD is atherosclerosis in association with varieties of immunometabolic disorders that can suppress oxytocin (OT) receptor (OTR) signaling in the cardiovascular system (CVS). By contrast, OT not only maintains cardiovascular integrity but also has the potential to suppress and even reverse atherosclerotic alterations and CAD. These protective effects of OT are associated with its protection of the heart and blood vessels from immunometabolic injuries and the resultant inflammation and apoptosis through both peripheral and central approaches. As a result, OT can decelerate the progression of atherosclerosis and facilitate the recovery of CVS from these injuries. At the cellular level, the protective effect of OT on CVS involves a broad array of OTR signaling events. These signals mainly belong to the reperfusion injury salvage kinase pathway that is composed of phosphatidylinositol 3-kinase-Akt-endothelial nitric oxide synthase cascades and extracellular signal-regulated protein kinase 1/2. Additionally, AMP-activated protein kinase, Ca²⁺/calmodulin-dependent protein kinase signaling and many others are also implicated in OTR signaling in the CVS protection. These signaling events interact coordinately at many levels to suppress the production of inflammatory cytokines and the activation of apoptotic pathways. A particular target of these signaling events is endoplasmic reticulum (ER) stress and mitochondrial oxidative stress that interact through mitochondria-associated ER membrane. In contrast to these protective effects and machineries, rare but serious cardiovascular disturbances were also reported in labor induction and animal studies including hypotension, reflexive tachycardia, coronary spasm or thrombosis and allergy. Here, we review our current understanding of the protective effect of OT against varieties of atherosclerotic etiologies as well as the approaches and underlying mechanisms of these effects. Moreover, potential cardiovascular disturbances following OT application are also discussed to avoid unwanted effects in clinical trials of OT usages.

Oxytocin modulates the expression of norepinephrine transporter, β3-adrenoceptors and muscarinic M2 receptors in the hearts of socially isolated rats

Social stress produces behavioral alterations, and autonomic and cardiac dysfunction in animals. In addition to the well-known roles of oxytocin on birth and maternal bonding, recent evidence shows that this neuropeptide possesses cardio-protective properties. However less is known about its role in the regulation of the autonomic nervous system. The direct influence of oxytocin on the cardiac catecholamine synthesizing enzyme, transport beta-adrenoceptors and muscarinic receptors in animals exposed to chronic social isolation stress has not yet been studied. In this study, we examined the influence of peripheral chronic oxytocin treatment on anxiety-related behavior, the morphology and content of epinephrine and norepinephrine, mRNA and protein levels of tyrosine hydroxylase (TH), norepinephrine transporter (NET) and receptors <beta> 3 (β₃-AR) and muscarinic 2 (M₂ MR) in the right and left cardiac atrium and ventricle of chronically socially isolated male rats. Our results show that oxytocin treatment exhibits an anxiolytic effect, decreases the heart/body weight ratio and prevents the hypertrophy of cardiomyocytes in the wall of the left ventricle of stressed rats. Epinephrine and TH protein levels were unchanged after prolonged oxytocin treatment. Peripheral oxytocin administration led to the enhancement of gene expression of β₃-AR in both atria, NET protein in the left ventricle and gene expression of M₂ MR in the right atrium and the left ventricle of chronically socially isolated rats. The study provides evidence that oxytocin treatment in chronically socially isolated animals enhances norepinephrine uptake and expression of cardio-inhibitory receptors in cardiac tissues, which could have a beneficial effect on the cardiovascular system under the increased activity of the sympathoneural system.

Treatment with oestrogen-receptor agonists or oxytocin in conjunction with exercise protects against myocardial infarction in ovariectomized rats

NEW FINDINGS

What is the central question of this study? Could the activation of oxytocin or oestrogen receptors be protective against myocardial injury after ovariectomy? If so, would exercising have an additional ameliorating effect? What is the main finding and its importance? The results revealed that when accompanied by exercise, both oestrogen receptor agonists and oxytocin improved cardiac dysfunction, inhibited the generation of pro-inflammatory cytokines and reduced myocardial injury in ovariectomized female rats, suggesting a new approach for protecting postmenopausal women against ischaemia-induced myocardial injury. To investigate the putative protective effects of oxytocin or oestrogen receptor agonists against myocardial injury of ovariectomized sedentary or exercised rats, female Sprague-Dawley rats assigned to sham-operated control and ovariectomized (OVX) groups were kept sedentary or undertook swimming exercise for 4 weeks and were treated with saline, an oestrogen receptor (ER) β (DPN) or ERα agonist (PPT) or oxytocin. Ovariectomy increased weight gain and anxiety in sedentary rats, whereas exercise prevented weight gain. When accompanied by exercise, both ER agonists and oxytocin inhibited weight gain and anxiety; oxytocin, in the absence or presence of exercise, increased the left ventricular diastolic dimensions and ejection fraction, whereas ER agonists also increased left ventricular diameter when given to exercised rats. Upon the induction of myocardial ischaemia-reperfusion in the OVX rats, plasma creatine kinase-(muscle-brain) was depressed by PPT and oxytocin, whereas DPN, PPT and OT reduced plasminogen activator inhibitor-1 concentrations. The increased tumour necrosis factor-α concentration in OVX rats was also suppressed by exercise or DPN, PPT or oxytocin treatments, whereas the interleukin-6 concentration was diminished by all the treatments when given in conjunction with exercise. Disorganization of cardiac muscle fibres was reduced in all exercised rats. Oestrogen receptor agonists, as well as oxytocin, in conjunction with exercise may be effective new therapeutics to protect against myocardial ischaemia in postmenopausal women.

Echocardiographic and electrocardiographic parameters during the normal postpartum period in toy breeds of dogs

The aim of this study was to evaluate echocardiographic and electrocardiographic parameters during the normal canine postpartum period. Twenty clinically healthy pregnant bitches of toy breeds (11 Miniature poodles, five Yorkshire terriers, two Maltese terriers and two Bichons Frises) were evaluated on days -3, 3, 10, 17, 24, 38, 52 and 80 relative to parturition (day 0). During the first postpartum week, the width of the interventricular septum in systole, the shortening fraction and the left atrium size decreased, while the left ventricle internal diameter in systole and end systolic stress increased. There were progressive decreases in the velocity of circumferential fibre shortening, stroke volume, cardiac output, and mitral E and A wave values. Systolic blood pressure increased markedly during the first postpartum week to gradually increase thereafter. Heart rate and corrected QT interval progressively decreased, while P wave amplitude increased. QRS complex amplitude decreased in the second week after parturition and then increased during the following weeks. In conclusion, there were changes in systolic function and some structural adaptive changes in the bitch during the first 80days postpartum. In addition, maternal heart rate and corrected QT interval decreased, while P wave and QRS amplitudes increased.

Effect of Lactation on myocardial vulnerability to ischemic insult in rats

Background

Cardiovascular diseases are the leading cause of mortality and long-term disability worldwide. Various studies have suggested a protective effect of lactation in reducing the risk of cardiovascular diseases.

Objective

This study was designed to assess the effects of pregnancy and lactation on the vulnerability of the myocardium to an ischemic insult.

Methods

Eighteen female rats were randomly divided into three groups: ischemia-reperfusion (IR), in which the hearts of virgin rats underwent IR (n = 6); lactating, in which the rats nursed their pups for 3 weeks and the maternal hearts were then submitted to IR (n = 6); and non-lactating, in which the pups were separated after birth and the maternal hearts were submitted to IR (n = 6). Outcome measures included heart rate (HR), left ventricular developed pressure (LVDP), rate pressure product (RPP), ratio of the infarct size to the area at risk (IS/AAR %), and ventricular arrhythmias - premature ventricular contraction (PVC) and ventricular tachycardia (VT).

Results

The IS/AAR was markedly decreased in the lactating group when compared with the non-lactating group (13.2 ± 2.5 versus 39.7 ± 3.5, p < 0.001) and the IR group (13.2 ± 2.5 versus 34.0 ± 4.7, p < 0.05). The evaluation of IR-induced ventricular arrhythmias indicated that the number of compound PVCs during ischemia, and the number and duration of VTs during ischemia and in the first 5 minutes of reperfusion in the non-lactating group were significantly (p < 0.05) higher than those in the lactating and IR groups.

Conclusion

Lactation induced early-onset cardioprotective effects, while rats that were not allowed to nurse their pups were more susceptible to myocardial IR injury.

Peripartum cardiomyopathy: a systematic literature review

INTRODUCTION

Peripartum cardiomyopathy (PPCM) is a rare but potentially fatal disease defined by heart failure towards the end of pregnancy or in the months following delivery. We aim to raise awareness of the condition and give the clinician an overview of current knowledge on the mechanisms of pathophysiology, diagnostics and clinical management.

MATERIAL AND METHODS

Systematic literature searches were performed in PubMed and Embase up to June 2016. Cohorts of more than 20 women with PPCM conducted after 2000 were selected to report contemporary outcomes and prognostic data. Guidelines and reviews that provided comprehensive overviews were included, too.

RESULTS

New research on the pathophysiological mechanisms of PPCM points towards a two-hit multifactorial cause involving genetic factors and an antiangiogenic hormonal environment of late gestation with high levels of prolactin and sFlt-1. The prevalence of concomitant preeclampsia is high (often 30-45%) and symptoms can be similar, posing diagnostic difficulties. Most women (71-98%) present postpartum. Echocardiography is essential for diagnosis, and cardiac magnetic resonance imaging may provide new insights to pathophysiology and prognosis. Management is multidisciplinary and involves advanced heart failure therapy. Treatment, timing and mode of delivery in pregnant women depend on disease severity. The risk of relapse in subsequent pregnancies is >20%, and women are often advised against a new pregnancy.

CONCLUSIONS

PPCM has a huge impact on cardiovascular health and reproductive life perspective. New insights into genetics, molecular pathophysiological mechanisms and clinical studies have resulted in potential disease-specific therapies, but many questions remain unanswered.

Effect of different doses of oxytocin on cardiac electrophysiology and arrhythmias induced by ischemia

The onset of acute myocardial ischemia (MI) is accompanied by a rapid increase in electrical instability and often fatal ventricular arrhythmias. This study investigated that whether oxytocin (OT) can modulate ischemia-induced arrhythmias and considered relationships between the severity of arrhythmia and the electrocardiogram parameters during ischemia. OT (0.0001–1 μg) was administrated intraperitoneally 30 min before ischemia. To examine receptor involved, a selective OT-receptor antagonist, atosiban (ATO), was infused 10 min before OT. OT caused a significant and biphasic dose-dependent reduction in ectopic heart activity and arrhythmia score. OT doses that reduced ventricular arrhythmia elicited significant increase in QT interval. OT attenuated the electrophysiological changes associated with MI and there was significant direct relationship between QRS duration and arrhythmia score. ATO treatment reduced beneficial effects of OT on arrhythmogenesis. Nevertheless, ATO failed to alter OT effects on premature ventricular contractions. We assume that the ability of OT to modulate the electrical activity of the heart may play an important role in the antiarrhythmic actions of OT.

Changes in blood pressure, heart rate, and blood profile in mares during the last 3 months of gestation and the peripartum period

In this study, peripartum changes in complete blood count, plasma electrolyte concentrations, blood pressure, heart rate, and heart rate variability (HRV) were determined in pregnant Warmblood mares (n = 10). Blood was collected from Days 245 to 330 of gestation (phase A), 2Days 3 to 1 before foaling (phase B), repeatedly within 12 hours after foaling (phase C), and on Days 1 to 3 postpartum (phase D). On the same days as blood collection, blood pressure and cardiac beat-to-beat intervals were measured and time domain HRV variables were calculated. Blood pressure decreased during the past 3 months of gestation, reached a nadir at foaling and increased rapidly thereafter (P < 0.001). Heart rate increased in phase A, reached a maximum in phase B, and decreased directly after foaling (P < 0.001) while HRV increased transiently after foaling (P < 0.001). The number of polymorphonuclear granulocytes was higher during phases B, C, and D than that during phase A (P < 0.001) and total leukocyte numbers peaked in phase C (P < 0.001). Erythrocyte counts and hematocrit increased immediately after foaling with a rapid decrease thereafter (P < 0.001), while plasma total protein was highest 1 hour after foaling (P < 0.001). Sodium and chloride concentrations increased from phases A to C and decreased in phase D (P < 0.001). Calcium concentrations were lowest immediately after foaling. In conclusion, changes in cardiovascular function and a transient hemoconcentration occur in peripartum mares. These changes may favor adequate uterine perfusion.

Oxytocin and cardioprotection in diabetes and obesity

Oxytocin (OT) emerges as a drug for the treatment of diabetes and obesity. The entire OT system is synthesized in the rat and human heart. The direct myocardial infusion with OT into an ischemic or failing heart has the potential to elicit a variety of cardioprotective effects. OT treatment attenuates cardiomyocyte (CMs) death induced by ischemia-reperfusion by activating pro-survival pathways within injured CMs in vivo and in isolated cells. OT treatment reduces cardiac apoptosis, fibrosis, and hypertrophy. The OT/OT receptor (OTR) system is downregulated in the db/db mouse model of type 2 diabetes which develops genetic diabetic cardiomyopathy (DC) similar to human disease. We have shown that chronic OT treatment prevents the development of DC in the db/db mouse. In addition, OT stimulates glucose uptake in both cardiac stem cells and CMs, and increases cell resistance to diabetic conditions. OT may help replace lost CMs by stimulating the in situ differentiation of cardiac stem cells into functional mature CMs. Lastly, adult stem cells amenable for transplantation such as MSCs could be preconditioned with OT ex vivo and implanted into the injured heart to aid in tissue regeneration through direct differentiation, secretion of protective and cardiomyogenic factors and/or their fusion with injured CMs.

Pulse wave analysis by digital photoplethysmography to record maternal hemodynamic effects of spinal anesthesia, delivery of the baby, and intravenous oxytocin during cesarean section

OBJECTIVE

To investigate changes in maternal ECG ST index, blood pressure (BP), cardiac left ventricular (LV) ejection function and vascular tone/stiffness in large and small arteries occurring during elective cesarean section (CS) in spinal anesthesia.

MATERIAL AND METHODS

Twenty-six women were monitored with photoplethysmographic digital pulse wave (PW) analysis (DPA) before and after spinal anesthesia, after delivery of the baby, after 5 IU oxytocin bolus IV, and 5 min later. Statistics with Wilcoxon matched-pairs signed-rank and Friedman tests at a p < 0.05 were performed.

RESULTS

Spinal anesthesia resulted in significantly decreased BP, increased ST index and LV ejection time, and small-artery vasodilation. Delivery of the baby resulted in global vasoconstriction and increases in systolic BP and heart rate (HR). Oxytocin lowered BP, HR and ST index, increased LV ejection power and caused both large- and small-artery vasodilation. ST index and BP recovered after 5 min, but low HR and low vascular tone persisted.

CONCLUSIONS

Spinal anesthesia and oxytocin caused arterial vasodilation and cardiac affection. Oxytocin caused a decrease in HR despite a fall in BP, indicating a direct negative chronotropic effect. Delivery of the baby caused momentous cardiovascular changes, possibly due to maternal emotions and auto-transfusion of blood from the uterus.

The effects of oxytocin and atosiban on the modulation of heart rate in pregnant women

OBJECTIVE

To evaluate autonomic modulation of heart rate in pregnant women treated with oxytocin to induce labor and with atosiban (an oxytocin antagonist) to arrest preterm labor.

METHODS

A prospective study with two cohorts: 14 pregnant women treated with atosiban for premature uterine contractions, and 28 women undergoing induction of labor with oxytocin. Computerized analyses of the electrocardiogram were performed with spectral and nonlinear dynamic analyses.

RESULTS

Atosiban did not alter any of the variables associated with heart rate variability, whereas oxytocin showed a dose-dependent decrease in heart rate (p < 0.05) and a significant increase in all spectral variables studied (p < 0.01).

CONCLUSIONS

Atosiban has no adverse effects on the cardiovascular system or the modulation of heart rate. Oxytocin, on the other hand, can cause a dose-dependent bradycardic effect and an increase in the spectral power, thus should be used with caution in certain pregnant women.

Oxytocin decreases diurnal and nocturnal arterial blood pressure in the conscious unrestrained spontaneously hypertensive rat

In this study, we assessed the effects of oxytocin (OT) on mean arterial blood pressure (MAP), heart rate (HR), and locomotor activity (LA) in male spontaneous hypertensive rats (SHR) and Sprague-Dawley (SDR) controls using telemetry. OT was given by intravenous injections of 0.1, 0.2 or 0.4mg/kg to assess short term acute effects or by daily subcutaneous injections of 0.5 or 1.0mg/kg for 5 days. Compared to the saline infusion, (i) intravenous OT, regardless of concentration, increased MAP in SHR and SDR, (ii) HR increased, but was periodically lower in both strains with 0.2 or 0.4mg/kg, and (iii) no effects of OT on LA were observed. Subcutaneous injections demonstrated that (i) 1.0mg/kg for 5days lowered diurnal MAP and HR in SDR and SHR, persisting for 6 days, (ii) 1.0mg/kg decreased nocturnal HR in SDR, (iii) 0.5 and 1.0mg/kg decreased MAP with minor effects on HR in the SHR, and lastly (iv) OT decreased LA mainly during the diurnal cycle in both strains. Our main results show that OT induces significant beneficial effects on cardiovascular function over several diurnal and nocturnal cycles in the SHR, with the most prominent effect being a robust decrease in MAP.

Prolonged Subcutaneous Administration of Oxytocin Accelerates Angiotensin II-Induced Hypertension and Renal Damage in Male Rats

Oxytocin and its receptor are synthesised in the heart and blood vessels but effects of chronic activation of this peripheral oxytocinergic system on cardiovascular function are not known. In acute studies, systemic administration of low dose oxytocin exerted a protective, preconditioning effect in experimental models of myocardial ischemia and infarction. In this study, we investigated the effects of chronic administration of low dose oxytocin following angiotensin II-induced hypertension, cardiac hypertrophy and renal damage. Angiotensin II (40 μg/Kg/h) only, oxytocin only (20 or 100 ng/Kg/h), or angiotensin II combined with oxytocin (20 or 100 ng/Kg/h) were infused subcutaneously in adult male Sprague-Dawley rats for 28 days. At day 7, oxytocin or angiotensin-II only did not change hemodynamic parameters, but animals that received a combination of oxytocin and angiotensin-II had significantly elevated systolic, diastolic and mean arterial pressure compared to controls (P < 0.01). Hemodynamic changes were accompanied by significant left ventricular cardiac hypertrophy and renal damage at day 28 in animals treated with angiotensin II (P < 0.05) or both oxytocin and angiotensin II, compared to controls (P < 0.01). Prolonged oxytocin administration did not affect plasma concentrations of renin and atrial natriuretic peptide, but was associated with the activation of calcium-dependent protein phosphatase calcineurin, a canonical signalling mechanism in pressure overload-induced cardiovascular disease. These data demonstrate that oxytocin accelerated angiotensin-II induced hypertension and end-organ renal damage, suggesting caution should be exercised in the chronic use of oxytocin in individuals with hypertension.

Molecular mechanisms underlying oxytocin-induced cardiomyocyte protection from simulated ischemia-reperfusion

Oxytocin (OT) stimulates cardioprotection. Here we investigated heart-derived H9c2 cells in simulated ischemia-reperfusion (I-R) experiments in order to examine the mechanism of OT protection. I-R was induced in an anoxic chamber for 2 hours and followed by 2 h of reperfusion. In comparison to normoxia, I-R resulted in decrease of formazan production by H9c2 cells to 63.5 ± 1.7% (MTT assay) and in enhanced apoptosis from 1.7 ± 0.3% to 2.8 ± 0.4% (Tunel test). Using these assays it was observed that treatment with OT (1-500 nM) exerted significant protection during I-R, especially when OT was added at the time of ischemia or reperfusion. Using the CM-H2DCFDA probe we found that OT triggers a short-lived burst in reactive oxygen species (ROS) production in cells but reduces ROS production evoked by I-R. In cells treated with OT, Western-blot revealed the phosphorylation of Akt (Thr 308, p-Akt), eNOS and ERK 1/2. Microscopy showed translocation of p-Akt and eNOS into the nuclear and perinuclear area and NO production in cells treated with OT. The OT-induced protection against I-R was abrogated by an OT antagonist, the Pi3K inhibitor Wortmannin, the cGMP-dependent protein kinase (PKG) inhibitor, KT5823, as well as soluble guanylate cyclase (GC) inhibitor, ODQ, and particulate GC antagonist, A71915. In conditions of I-R, the cells with siRNA-mediated reduction in OT receptor (OTR) expression responded to OT treatment by enhanced apoptosis. In conclusion, the OTR protected H9c2 cells against I-R, especially if activated at the onset of ischemia or reperfusion. The OTR-transduced signals include pro-survival kinases, such as Akt and PKG.

Oxytocin: recent developments

Oxytocin is a neurohypophyseal hormone that is produced centrally by neurons in the paraventricular nucleus and supraoptic nucleus of the hypothalamus. It is released directly into higher brain centres and into the peripheral circulation where it produces a multitude of effects. Classically, oxytocin is known for inducing uterine contractions at parturition and milk ejection during suckling. Oxytocin also acts in a species and gender specific manner as an important neuromodulator. It can affect behaviours associated with stress and anxiety, as well social behaviours including sexual and relationship behaviours, and maternal care. Additionally, oxytocin has been shown to have a variety of physiological roles in peripheral tissues, many of which appear to be modulated largely by locally produced oxytocin, dispelling the notion that oxytocin is a purely neurohypophyseal hormone. Oxytocin levels are altered in several diseases and the use of oxytocin or its antagonists have been identified as a possible clinical intervention in the treatment of mood disorders and pain conditions, some cancers, benign prostatic disease and osteoporosis. Indeed, oxytocin has already been successful in clinical trials to treat autism and schizophrenia. This review will report briefly on the known functions of oxytocin, it will discuss in depth the data from recent clinical trials and highlight future targets for oxytocinergic modulation.

Oxytocin does not directly alter cardiac repolarization in rabbit or human cardiac myocytes

Oxytocin, a nine amino acid peptide, is highly conserved in placental mammals, including humans. Oxytocin has a physiological role in parturition and parenteral administration of the synthetic peptide is used to induce labor and control postpartum hemorrhage. Endogenous levels of oxytocin before labor are ∼20 pg/mL, but pharmacological administration of the peptide can achieve levels of 110 pg/mL (0.1 nmol/L) following intravenous administration. Cardiac arrhythmia and premature ventricular contractions have been associated with oxytocin administration in addition to QTc interval prolongation. In the conscious rabbit model, intravenous oxytocin produced QT and QTc prolongation. The mechanism of oxytocin-induced QTc prolongation is uncertain but could be the result of indirect changes in autonomic nervous tone, or a direct effect on the duration of cardiomyocyte repolarization. The purpose of this study was to examine the ability of oxytocin to alter cardiac repolarization directly. Two conventional models were used: QTc interval evaluation in the isolated rabbit heart (IRH) and assessment of action potential duration (APD) in human ventricular myocytes (HVM). Oxytocin did not prolong QTc intervals in IRH or APD in HVM when tested at suprapharmacological concentrations, for example, up to 1 μmol/L. The results indicate that oxytocin has very low risk for eliciting QTc and APD prolongation directly, and infer that the QTc changes observed in vivo may be attributed to an indirect mechanism.

Oxytocin ameliorates the immediate myocardial injury in heart transplant through down regulation of the neutrophil dependent myocardial apoptosis

Cardiac oxytocin (OT) is structurally identical to that found in the hypothalamus, which thereby indicates that cardiac OT is derived from the same gene and is an active form of OT. The abundance of OT and OT receptors in atrial myocytes shows that, directly and/or via the release of the cardiac hormone atrial natriuretic peptide, OT can regulate the force of cardiac contractions. Previous studies have demonstrated the role of OT in the myocardial inflammatory response. The mechanism by which OT elicits protective myocardial effects in the immediate post-transplantation period is not yet clear, and the role of the early phase inflammatory elements in this mechanism has not yet been studied. As a result, in this study, we have investigated the anti-inflammatory effects of OT on myocardial protection in the immediate post-transplantation period.

The effect of intranasal oxytocin administration on acute cold pressor pain: a placebo-controlled, double-blind, within-participants crossover investigation

BACKGROUND

This study examined the effect of synthetic oxytocin delivered intranasally on acute pain sensitivity using a placebo-controlled, double-blind, within-participant crossover design.

METHODS

Thirty-seven (18 were male) pain-free young adults underwent two laboratory sessions separated by 1 week. Each session consisted of baseline, administration, second baseline, pain, and recovery phases, completed in a fixed order. Participants were given an intransal administration of 40 IU oxytocin or placebo. Blood pressure and heart rate (HR) were measured at 1-minute intervals throughout each phase. Pain was induced by submersing the nondominant hand in cold (2°C) water. Pain threshold, intensity, unpleasantness, and Short-Form McGill Pain Questionnaire-2 pain descriptors were rated immediately after pain testing. Mood was assessed using visual analog scales after baseline, second baseline, and pain phases. The second laboratory session was identical to the first, with the exception that a different nasal spray was administered.

RESULTS

Participants reported lower pain intensity (50.57 [20.94] versus 56.73 [20.12], p = .047), pain unpleasantness (47.00 [27.24] versus 55.78 [22.46], p = .033), and Short-Form McGill Pain Questionnaire-2 pain descriptors (53.38 [31.18] versus 60.92 [31.17], p = .031) and higher pain threshold (45.70 [59.55] versus 38.35 [59.12], p = .040) after oxytocin administration relative to placebo. There was a nasal spray by phase interaction on HR (p = .006). Pain-related increase in HR was attenuated by oxytocin nasal spray. Systolic and diastolic blood pressure increased during pain testing but were unaffected by nasal spray.

CONCLUSIONS

These results suggest that oxytocin can lead to decreased acute pain sensitivity.

Oxytocin ameliorates the immediate myocardial injury in rat heart transplant through downregulation of neutrophil-dependent myocardial apoptosis

BACKGROUND

Cardiac oxytocin (OT) is structurally identical to that found in the hypothalamus, indicating that this active form of OT is derived from the same gene. The abundance of OT and its receptors in atrial myocytes suggests that, directly and/or via the release of the cardiac hormone atrial natriuretic peptide, this hormone regulates the force of cardiac contractions. Previous studies have demonstrated a role of OT in myocardial inflammatory responses. We sought to study protective myocardial and anti-inflammatory effects of OT in the immediate post-transplant period.

METHODS

We grouped adult male Albino rats into sham, control, and OT-treated groups. Control and treated groups underwent heterotopic cervical heart transplantation. Myocardial injury was assessed by measuring plasma cardiac troponin I, and myocardial proinflammatory cytokines as well as by performing histopathologic assessments injury score, and of apoptotic degree. Myocardial myeloperoxidase, neutrophil infiltration, neutrophil chemotactic mediators as well as formation of reactive oxygen and reactive nitrogen species were measured in the myocardium at 3 hours after reperfusion to assess neutrophil-dependent myocardial injury.

RESULTS

OT downregulates neutrophil chemotactic molecules--KC/CXCL1 and MIP-2/CXCL2. The decrement in myocardial PMN infiltration was associated with reduced reactive oxygen and reactive nitrogen species formation in the myocardium at 3 hours after reperfusion following global ischemia. OT reduced postmyocardial ischemia/reperfusion apoptotic processed.

CONCLUSION

OT ameliorated immediate myocardial injury in heart grafts, through downregulation of the inflammatory response, of reactive oxygen species, and of neutrophil dependent apoptosis.

The role of oxytocin in cardiovascular regulation

Studies of body volume expansion have indicated that lesions of the anteroventral third ventricle and median eminence block the release of atrial natriuretic peptide (ANP) into the circulation. Detailed analysis of the lesions showed that activation of oxytocin (OT)-ergic neurons is responsible for ANP release, and it has become clear that activation of neuronal circuitry elicits OT secretion into the circulation, activating atrial OT receptors and ANP release from the heart. Subsequently, we have uncovered the entire functional OT system in the rat and the human heart. An abundance of OT has been observed in the early development of the fetal heart, and the capacity of OT to generate cardiomyocytes (CMs) has been demonstrated in various types of stem cells. OT treatment of mesenchymal stem cells stimulates paracrine factors beneficial for cardioprotection. Cardiovascular actions of OT include: i) lowering blood pressure, ii) negative inotropic and chronotropic effects, iii) parasympathetic neuromodulation, iv) vasodilatation, v) anti-inflammatory activity, vi) antioxidant activity, and vii) metabolic effects. OT actions are mediated by nitric oxide and ANP. The beneficial actions of OT may include the increase in glucose uptake by CMs and stem cells, reduction in CM hypertrophy, oxidative stress, and mitochondrial protection of several cell types. In experimentally induced myocardial infarction in rats, continuous in vivo OT delivery improves cardiac healing and cardiac work, reduces inflammation, and stimulates angiogenesis. Because OT plays anti-inflammatory and cardioprotective roles and improves vascular and metabolic functions, it demonstrates potential for therapeutic use in various pathologic conditions.

Oxytocin-Gly-Lys-Arg stimulates cardiomyogenesis by targeting cardiac side population cells

The functional oxytocin (OT) system is expressed in the human and rodent hearts. OT stimulates differentiation of cardiac stem cells into contracting cardiomyocytes (CM). In this study, we investigated OT receptors (OTR) expressed in the cells of cardiac side population (SP) and the abilities of these cells to differentiate into CM in response to the treatment with OT-Gly-Lys-Arg (OT-GKR), a dominant and biologically active form of OT, in the fetal rodent heart. Immunocytochemistry of whole rat embryo at mid gestation (E11) revealed parallel staining in the heart of OTR and the ATP-binding cassette sub-family G member 2 (brcp1) antigen the marker of the SP phenotype. Using flow cytometry, the SP cells were selected from the newborn CM stained with Höechst 33342: 5.32%±0.06% of SP and 15.2%±1.10 of main population expressed OTR on the cell surface. The OTR was detected in CD29 (6.6%) and then in CD31 (4.7%) but less frequently in CD45 (0.7%) positive SP cell subpopulations. Specifically, the phenotype of SP CD31- cell, but not SP CD31+ cells, proliferates in the presence of OT-GKR and develops large cell aggregates. Then, OT-GKR treatment induced the apparition of beating cell colonies after 11 days (10±2.78%), which increased until day 16 (52±1.21%). The cells in contractile colonies expressed the markers of a CM phenotype, such as troponin, cardiac myosin light chain-2, and actinin. Finally, SP cells stimulated by OT-GKR induced endothelial phenotype. These results suggest that the C-terminally extended OT molecule stimulates cardiac differentiation of SP CD31- cells and is involved in heart growth.

A role for autonomic cardiac control in the effects of oxytocin on social behavior and psychiatric illness

Cumulative evidence over the last decade indicates that intranasally administered oxytocin (OT) has a major impact on social behavior and cognition. In parallel, researchers have also highlighted the effects of OT on cardiovascular (CV) and autonomic nervous system (ANS) regulation. Taken at face value, these two streams of research appear largely unrelated. However, another line of evidence highlights a key role for autonomic cardiac control in social behavior and cognition. In this review, we suggest that autonomic cardiac control may moderate the relationship between OT and social behavior. We also highlight the importance of autonomic cardiac control in psychiatric disorders of social dysfunction and suggest that heart rate variability (HRV)-an index of autonomic cardiac control-may play a key role in patient response in treatment trials of OT.

Oxytocin revisited: its role in cardiovascular regulation

Traditionally associated with female reproduction, oxytocin (OT) was revisited recently and was revealed to have several new roles in the cardiovascular system. Functional OT receptors have been discovered in the rat and human heart, as well as in vascular beds. The cardiovascular activities of OT include: (i) lowering blood pressure; (ii) negative cardiac inotropy and chronotropy; (iii) parasympathetic neuromodulation; (iv) vasodilatation; (v) anti-inflammatory; (vi) antioxidative; and (vii) metabolic effects. These outcomes are mediated, at least in part, by stimulating cardioprotective mediators, such as nitric oxide and atrial natriuretic peptide. OT and its extended form OT-Gly-Lys-Arg have been shown to be abundant in the foetal mouse heart. OT has the capacity to generate cardiomyocytes from various types of stem cells, including the cardiac side population. Mesenchymal cells transfected with OT-Gly-Lys-Arg, or preconditioned with OT, are resistant to apoptosis and express endothelial cell markers. OT increases glucose uptake in cultured cardiomyocytes from newborn and adult rats, in normal, hypoxic and even insulin resistance conditions. In rats with experimentally-induced myocardial infarction, continuous in vivo OT delivery improves the cardiac healing process, as well as cardiac work, reduces inflammation and stimulates angiogenesis. Therefore, in pathological conditions, OT exerts anti-inflammatory and cardioprotective properties, and improves vascular and metabolic functions. Thus, OT has potential for therapeutic use.

Oxytocin for labour and caesarean delivery: implications for the anaesthesiologist

PURPOSE OF REVIEW

The implications of the obstetric use of oxytocin for obstetric anaesthesia practice are summarised. The review focuses on recent research on the uterotonic effects of oxytocin for prophylaxis and management of uterine atony during caesarean delivery.

RECENT FINDINGS

Oxytocin remains the first-line agent in the prevention and management of uterine atony. In-vitro and in-vivo studies show that prior exposure to oxytocin induces uterine muscle oxytocin receptor desensitization. This may influence oxytocin dosing for adequate uterine tone following delivery. Oxytocin has important cardiovascular side-effects (hypotension, tachycardia and myocardial ischaemia). Recent studies suggest that the effective dose of oxytocin for prophylaxis against uterine atony during caesarean delivery is significantly lower than the 5-10 IU historically used by anaesthesiologists. Slow administration of small bolus doses of oxytocin minimises maternal haemodynamic disturbance. Continuous oxytocin infusions are recommended for maintaining uterine tone after bolus administration, although ideal infusion rates are still to be established. The efficacy of the long-acting oxytocin analogue carbetocin requires further investigation. Recommendations are presented for oxytocin dosing during caesarean delivery.

SUMMARY

Oxytocin remains the first-line uterotonic after vaginal and caesarean delivery. Recent research elucidates the therapeutic range of oxytocin during caesarean delivery, as well as receptor desensitization. Evidenced-based protocols for the prevention and treatment of uterine atony during caesarean delivery are recommended.

Plasma oxytocin is related to lower cardiovascular and sympathetic reactivity to stress

In addition to known reproductive and social affiliation functions, oxytocin (OT) has been identified as a cardiovascular hormone. OT synthesis and receptors are found in cardiac and vascular tissue. Animal studies suggest that OT activates an 'anti-stress' response that reduces cardiovascular and neuroendocrine stress reactivity. We tested 28 early postpartum mothers, obtaining multiple blood samples for OT, the sympathetic marker, norepinephrine (NE), and the lactation hormone, prolactin, while monitoring their cardiovascular responses to two stressors: public speaking and forehead cold pressor. Although plasma OT did not increase reliably from pre-stress levels during stressors, greater overall OT level was related to greater vasodilation and cardiac stroke volume responses to both tasks, to reduction in heart rate to the cold pressor, as well as to lower plasma NE and higher prolactin levels. In contrast, higher NE was linked to increases in heart rate and decreases in stroke volume. These data support a cardioprotective role for OT, which may influence the magnitude and hemodynamic determinants of cardiovascular stress responses.