Magnesium inhibits norepinephrine release by blocking N-type calcium channels at peripheral sympathetic nerve endings

Standardizing a method for functional assessment of neural networks in brain organoids

During the last decade brain organoids have emerged as an attractive model system, allowing stem cells to be differentiated into complex 3D models, recapitulating many aspects of human brain development. Whilst many studies have analysed anatomical and cytoarchitectural characteristics of organoids, their functional characterisation has been limited, and highly variable between studies. Standardised, consistent methods for recording functional activity are critical to providing a functional understanding of neuronal networks at the synaptic and network level that can yield useful information about functional network phenotypes in disease and healthy states. In this study we outline a detailed methodology for calcium imaging and Multi-Electrode Array (MEA) recordings in brain organoids. To illustrate the utility of these functional interrogation techniques in uncovering induced differences in neural network activity we applied various stimulating media protocols. We demonstrate overlapping information from the two modalities, with comparable numbers of active cells in the four treatment groups and an increase in synchronous behaviour in BrainPhys treated groups. Further development of analysis pipelines to reveal network level changes in brain organoids will enrich our understanding of network formation and perturbation in these structures, and aid in the future development of drugs that target neurological disorders at the network level.

Magnesium in hypertension: mechanisms and clinical implications

Hypertension is associated with increased risk of cardiovascular disease and death. Evidence suggests that Mg2+ depletion contributes to hypertension. It is estimated that 25% or more of the United States population experiences chronic, latent Mg2+ depletion. This review explores mechanisms by which Mg2+ influences blood pressure, modifying risk of hypertension and complicating its treatment. Mechanisms addressed include effects upon i) sympathetic tone, via the modulation of N-methyl-D-aspartate (NMDA) receptor and N-type Ca2+ channel activity, influencing catecholamine release from sympathetic nerve endings; ii) vascular tone, via alteration of L-type Ca2+ and endothelial nitric oxide synthase (eNOS) activity and prostacyclin release; iii) renal K+ handling, influencing systemic K+ balance and potentially indirectly influencing blood pressure; iv) aldosterone secretion from the adrenal cortex; and v) modulation of pro-hypertensive inflammatory processes in dendritic cells and macrophages, including activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome and stimulation of isolevuglandin (IsoLG) production. Discovery of these mechanisms has furthered our understanding of the pathogenesis of hypertension, with implications for treatment and has highlighted the role of Mg2+ balance in hypertension and cardiovascular disease.

Nitric oxide, endothelium-derived hyperpolarizing factor, and smooth muscle-dependent mechanisms contribute to magnesium-dependent vascular relaxation in mouse arteries

AIM

Magnesium (Mg2+ ) is a vasorelaxant. The underlying physiological mechanisms driving this vasorelaxation remain unclear. Studies were designed to test the hypothesis that multiple signaling pathways including nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) in endothelial cells as well as Ca2+ antagonization and TRPM7 channels in vascular smooth muscle cells mediate Mg2+ -dependent vessel relaxation.

METHODS

To uncover these mechanisms, force development was measured ex vivo in aorta rings from mice using isometric wire myography. Concentration responses to Mg2+ were studied in intact and endothelium-denuded aortas. Key findings were confirmed in second-order mesenteric resistance arteries perfused ex vivo using pressure myography. Effects of Mg2+ on NO formation were measured in Chinese Hamster Ovary (CHO) cells, isolated mesenteric vessels, and mouse urine.

RESULTS

Mg2+ caused a significant concentration-dependent relaxation of aorta rings. This relaxation was attenuated significantly in endothelium-denuded aortas. The endothelium-dependent portion was inhibited by NO and cGMP blockade but not by cyclooxygenase inhibition. Mg2+ stimulated local NO formation in CHO cells and isolated mesenteric vessels without changing urinary NOx levels. High extracellular Mg2+ augmented acetylcholine-induced relaxation. SKCa and IKCa channel blockers apamin and TRAM34 inhibited Mg2+ -dependent relaxation. The endothelium-independent relaxation in aorta rings was inhibited by high extracellular Ca2+ . Combined blockade of NO, SKCa , and IKCa channels significantly reduced Mg2+ -dependent dilatation in mesenteric resistance vessels.

CONCLUSIONS

In mouse conductance and resistance arteries Mg2+ -induced relaxation is contributed by endothelial NO formation, EDHF pathways, antagonism of Ca2+ in smooth muscle cells, and additional unidentified mechanisms.

Magnesium and Liver Metabolism Through the Lifespan

Within the organism, the liver is the main organ responsible for metabolic homeostasis and xenobiotic transformation. To maintain an adequate liver weight-to-bodyweight ratio, this organ has an extraordinary regenerative capacity and is able to respond to an acute insult or partial hepatectomy. Maintenance of hepatic homeostasis is crucial for the proper functioning of the liver, and in this context, adequate nutrition with macro- and micronutrient intake is mandatory. Among all known macro-minerals, magnesium has a key role in energy metabolism and in metabolic and signaling pathways that maintain liver function and physiology throughout its life span. In the present review, the cation is reported as a potential key molecule during embryogenesis, liver regeneration, and aging. The exact role of the cation during liver formation and regeneration is not fully understood due to its unclear role in the activation and inhibition of those processes, and further research in a developmental context is needed. As individuals age, they may develop hypomagnesemia, a condition that aggravates the characteristic alterations. Additionally, risk of developing liver pathologies increases with age, and hypomagnesemia may be a contributing factor. Therefore, magnesium loss must be prevented by adequate intake of magnesium-rich foods such as seeds, nuts, spinach, or rice to prevent age-related hepatic alterations and contribute to the maintenance of hepatic homeostasis. Since magnesium-rich sources include a variety of foods, a varied and balanced diet can meet both macronutrient and micronutrient needs.

Magnesium Deficiency and Cardiometabolic Disease

Magnesium (Mg²⁺) has many physiological functions within the body. These include important roles in maintaining cardiovascular functioning, where it contributes to the regulation of cardiac excitation-contraction coupling, endothelial functioning and haemostasis. The haemostatic roles of Mg²⁺ impact upon both the protein and cellular arms of coagulation. In this review, we examine how Mg²⁺ homeostasis is maintained within the body and highlight the various molecular roles attributed to Mg²⁺ in the cardiovascular system. In addition, we describe how nutritional and/or disease-associated magnesium deficiency, seen in some metabolic conditions, has the potential to influence cardiac and vascular outcomes. Finally, we also examine the potential for magnesium supplements to be employed in the prevention and treatment of cardiovascular disorders and in the management of cardiometabolic health.

Radiation Therapy Exacerbates Tumor-Promoting Innervation and Nerve Signaling in Rectal Cancer

PURPOSE

Many solid tumors present with perineural invasion (PNI), and innervation correlates with worsened prognosis. The effects that commonly administered therapies such as radiation therapy (RT) have on PNI status remain unknown. We investigated the contribution of RT on the nervous system and elucidated the implications that increased nerve signaling can have on tumor burden using our previously developed orthotopic murine model of rectal cancer (RC) and our targeted and clinically relevant short-course RT (SCRT) regimen.

METHODS

Medical charts for patients with RC treated at the Wilmot Cancer Institute were obtained and PNI status was analyzed. Human data were accompanied by an orthotopic murine model of RC. Briefly, luciferase-expressing murine colon-38 (MC38-luc) tumor cells were injected orthotopically into the rectal wall of C57BL6 mice. Targeted SCRT (5 gray (Gy) per fraction for 5 consecutive fractions) was administered to the tumor. Intratumoral innervation was determined by immunohistochemistry (IHC), local norepinephrine (NE) concentration was quantified by enzyme-linked immunosorbent assay (ELISA), and β2-adrenergic receptor (B2AR) expression was assessed by flow cytometry. Chronic NE signaling was mirrored by daily isoproterenol treatment, and the effect on tumor burden was determined by overall survival, presence of metastatic lesions, and tumor size. Isoproterenol signaling was inhibited by administration of propranolol.

RESULTS

Human RC patients with PNI have decreased overall survival compared with patients without PNI. In our mouse model, SCRT induced the expression of genes involved in neurogenesis, increased local NE secretion, and upregulated B2AR expression. Treating mice with isoproterenol resulted in decreased overall survival, increased rate of metastasis, and reduced SCRT efficacy. Interestingly, the isoproterenol-induced decrease in SCRT efficacy could be abrogated by blocking the BAR through the use of propranolol, suggesting a direct role of BAR stimulation on impairing SCRT responses.

CONCLUSIONS

Our results indicate that while SCRT is a valuable treatment, it is accompanied by adverse effects on the nervous system that may impede the efficacy of therapy and promote tumor burden. Therefore, we could speculate that therapies aimed at targeting this signaling cascade or impairing nerve growth in combination with SCRT may prove beneficial in future cancer treatment.

Magnesium Sulfate Reduces Carrageenan-Induced Rat Paw Inflammatory Edema Via Nitric Oxide Production

Background

Magnesium is an antagonist of the N-methyl-D-aspartate receptor. This study aimed to investigate the anti-edematous effect of magnesium sulfate (MS) in different protocols of use and the possible mechanism of its action.

Methods

In a rat model of carrageenan-induced paw inflammation, the anti-edematous activity of MS was assessed with a plethysmometer. The effects of the nonselective inhibitor (L-NAME), selective inhibitor of neuronal (L-NPA) and inducible (SMT) nitric oxide synthase on the effects of MS were evaluated.

Results

MS administered systemically before or after inflammation reduced edema by 30% (5 mg/kg, P < .05) and 55% (30 mg/kg, P < .05). MS administered locally (.5 mg/paw, P < .05) significantly prevented the development of inflammatory edema by 60%. L-NAME, intraperitoneally administered before MS, potentiated (5 mg/kg, P < .05) or reduced (3 mg/kg, P < .05), while in the highest tested dose L-NPA (2 mg/kg, P < .01) and SMT (.015 mg/kg, P < .01) reduced the anti-edematous effect of MS.

Conclusions

Magnesium is a more effective anti-edematous drug in therapy than for preventing inflammatory edema. The effect of MS is achieved after systemic and local peripheral administration and when MS is administered as a single drug in a single dose. This effect is mediated at least in part via the production of nitric oxide.

The Significance of Low Magnesium Levels in COVID-19 Patients

Magnesium is the fourth most common mineral in the human body and the second richest intracellular cation. This element is necessary for many physiological reactions, especially in the cardiovascular and respiratory systems. COVID-19 is an infectious disease caused by SARS-CoV-2. The majority of people who become ill as a result of COVID-19 have mild-to-moderate symptoms and recover without specific treatment. Moreover, there are people who develop severe forms of COVID-19, which require highly specialized medical assistance. Magnesium deficiency may play a role in the pathophysiology of infection with SARS-CoV-2. The primary manifestation of COVID-19 remains respiratory, but the virus can spread to other organs and tissues, complicating the clinical picture and culminating in multiorgan failure. The key mechanisms involved in the disease include direct viral cytotoxicity, endothelial dysfunction, and exaggerated release of inflammatory cytokines. The aim of this review was to summarize the available data regarding the role of magnesium in COVID-19 patients and its particularities in different clinical settings.

Roles and Sources of Calcium in Synaptic Exocytosis

Calcium ions (Ca2+) play a critical role in triggering neurotransmitter release. The rate of release is directly related to the concentration of Ca2+ at the presynaptic site, with a supralinear relationship. There are two main sources of Ca2+ that trigger synaptic vesicle fusion: influx through voltage-gated Ca2+ channels in the plasma membrane and release from the endoplasmic reticulum via ryanodine receptors. This chapter will cover the sources of Ca2+ at the presynaptic nerve terminal, the relationship between neurotransmitter release rate and Ca2+ concentration, and the mechanisms that achieve the necessary Ca2+ concentrations for triggering synaptic exocytosis at the presynaptic site.

The Mutual Relationship among Cardiovascular Diseases and COVID-19: Focus on Micronutrients Imbalance

Micronutrients are ions and vitamins humbly required by the human body. They play a main role in several physiological mechanisms and their imbalance is strongly associated with potentially-fatal complications. Micronutrient imbalance is associated with many cardiovascular diseases, such as arrythmias, heart failure, and ischemic heart disease. It has been also observed in coronavirus disease 2019 (COVID-19), particularly in most severe patients. The relationship between cardiovascular diseases and COVID-19 is mutual: the latter triggers cardiovascular disease onset and worsening while patients with previous cardiovascular disease may develop a more severe form of COVID-19. In addition to the well-known pathophysiological mechanisms binding COVID-19 and cardiovascular diseases together, increasing importance is being given to the impact of micronutrient alterations, often present during COVID-19 and able to affect the balance responsible for a good functioning of the cardiovascular system. In particular, hypokalemia, hypomagnesemia, hyponatremia, and hypocalcemia are strongly associated with worse outcome, while vitamin A and D deficiency are associated with thromboembolic events in COVID-19. Thus, considering how frequent the cardiovascular involvement is in patients with COVID-19, and how it majorly affects their prognosis, this manuscript provides a comprehensive review on the role of micronutrient imbalance in the interconnection between COVID-19 and cardiovascular diseases.

Immunomodulatory Role of Nutrients: How Can Pulmonary Dysfunctions Improve?

Nutrition is an important tool that can be used to modulate the immune response during infectious diseases. In addition, through diet, important substrates are acquired for the biosynthesis of regulatory molecules in the immune response, influencing the progression and treatment of chronic lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD). In this way, nutrition can promote lung health status. A range of nutrients, such as vitamins (A, C, D, and E), minerals (zinc, selenium, iron, and magnesium), flavonoids and fatty acids, play important roles in reducing the risk of pulmonary chronic diseases and viral infections. Through their antioxidant and anti-inflammatory effects, nutrients are associated with better lung function and a lower risk of complications since they can decrease the harmful effects from the immune system during the inflammatory response. In addition, bioactive compounds can even contribute to epigenetic changes, including histone deacetylase (HDAC) modifications that inhibit the transcription of proinflammatory cytokines, which can contribute to the maintenance of homeostasis in the context of infections and chronic inflammatory diseases. These nutrients also play an important role in activating immune responses against pathogens, which can help the immune system during infections. Here, we provide an updated overview of the roles played by dietary factors and how they can affect respiratory health. Therefore, we will show the anti-inflammatory role of flavonoids, fatty acids, vitamins and microbiota, important for the control of chronic inflammatory diseases and allergies, in addition to the antiviral role of vitamins, flavonoids, and minerals during pulmonary viral infections, addressing the mechanisms involved in each function. These mechanisms are interesting in the discussion of perspectives associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and its pulmonary complications since patients with severe disease have vitamins deficiency, especially vitamin D. In addition, researches with the use of flavonoids have been shown to decrease viral replication in vitro. This way, a full understanding of dietary influences can improve the lung health of patients.

Effects of intravenous magnesium sulfate on serum calcium-regulating hormones and plasma and urinary electrolytes in healthy horses

Intravenous magnesium sulfate (MgSO₄) is used in equine practice to treat hypomagnesemia, dysrhythmias, neurological disorders, and calcium dysregulation. MgSO₄ is also used as a calming agent in equestrian events. Hypercalcemia affects calcium-regulating hormones, as well as plasma and urinary electrolytes; however, the effect of hypermagnesemia on these variables is unknown. The goal of this study was to investigate the effect of hypermagnesemia on blood parathyroid hormone (PTH), calcitonin (CT), ionized calcium (Ca²⁺), ionized magnesium (Mg²⁺), sodium (Na⁺), potassium (K⁺), chloride (Cl^-) and their urinary fractional excretion (F) after intravenous administration of MgSO₄ in healthy horses. Twelve healthy female horses of 4–18 years of age and 432–600 kg of body weight received a single intravenous dose of MgSO₄ (60 mg/kg) over 5 minutes, and blood and urine samples were collected at different time points over 360 minutes. Plasma Mg²⁺ concentrations increased 3.7-fold over baseline values at 5 minutes and remained elevated for 120 minutes (P < 0.05), Ca²⁺ concentrations decreased from 30–60 minutes (P < 0.05), but Na⁺, K⁺ and Cl^- concentrations did not change. Serum PTH concentrations dropped initially to rebound and remain elevated from 30 to 60 minutes, while CT concentrations increased at 5 minutes to return to baseline by 10 minutes (P < 0.05). The FMg, FCa, FNa, FK, and FCl increased, while urine osmolality decreased from 30–60 minutes compared baseline (P < 0.05). Short-term experimental hypermagnesemia alters calcium-regulating hormones (PTH, CT), reduces plasma Ca²⁺ concentrations, and increases the urinary excretion of Mg²⁺, Ca²⁺, K⁺, Na⁺ and Cl^- in healthy horses. This information has clinical implications for the short-term effects of hypermagnesemia on calcium-regulation, electrolytes, and neuromuscular activity, in particular with increasing use of Mg salts to treat horses with various acute and chronic conditions as well as a calming agent in equestrian events.

Induced normothermia ameliorates the procoagulant host response in human endotoxaemia

Background

Dysregulation of coagulation occurs commonly in sepsis, ranging from mild coagulopathy with decreased platelets to disseminated intravascular coagulation (DIC). We investigated the effect of induced normothermia on coagulation during lipopolysaccharide (LPS)-induced endotoxaemia in healthy volunteers.

Methods

Twelve volunteers received an infusion of bacterial lipopolysaccharide (Escherichia coli; 2 ng kg⁻¹) and were assigned to either induced normothermia or control. Induced normothermia to maintain core temperature at 37°C consisted of external surface cooling, cold i.v. fluids, and medication to reduce shivering (buspirone, clonidine, and magnesium sulphate). The primary outcome was the DIC score (International Society on Thrombosis and Haemostasis guideline). Prothrombin time (PT), activated partial thromboplastin time (aPTT), D-dimer, plasma von Willebrand factor (vWf), and rotational thromboelastometry (ROTEM) were measured before and 1, 3, 6, and 8 h after LPS infusion. Differences between groups were tested with a mixed effects model.

Results

In control subjects, lipopolysaccharide caused a fever, transiently decreased platelet levels and lowered activated partial thromboplastin time, while prolonging prothrombin time and increasing D-Dimer and vWf levels. Normothermia prevented the DIC-score exceeding 4, which occurred in 50% of control subjects. Normothermia also reduced the fall in platelet count by 67x10⁹ L⁻¹([95%CI:27-107]; p=0.002), aPTT (mean difference:3s [95%CI:1-5]; p=0.005) and lowered vWf levels by 89% ([95%CI:6-172]; p=0.03), compared to the fever group. ROTEM measurements were unaffected by lipopolysaccharide.

Conclusion

In human endotoxaemia, induced normothermia decreases markers of endothelial activation and DIC. Maintaining normothermia may reduce coagulopathy in hyperinflammatory states.

Magnesium and Hypertension in Old Age

Hypertension is a complex condition in which various actors and mechanisms combine, resulting in cardiovascular and cerebrovascular complications that today represent the most frequent causes of mortality, morbidity, disability, and health expenses worldwide. In the last decades, there has been an exceptional amount of experimental, epidemiological, and clinical studies confirming a close relationship between magnesium deficit and high blood pressure. Multiple mechanisms may help to explain the bulk of evidence supporting a protective effect of magnesium against hypertension and its complications. Hypertension increases sharply with advancing age, hence older persons are those most affected by its negative consequences. They are also more frequently at risk of magnesium deficiency by multiple mechanisms, which may, at least in part, explain the higher frequency of hypertension and its long-term complications. The evidence for a favorable effect of magnesium on hypertension risk emphasizes the importance of broadly encouraging the intake of foods such as vegetables, nuts, whole cereals and legumes, optimal dietary sources of magnesium, avoiding processed food, which are very poor in magnesium and other fundamental nutrients, in order to prevent hypertension. In some cases, when diet is not enough to maintain an adequate magnesium status, magnesium supplementation may be of benefit and has been shown to be well tolerated.

Efficacy and safety of low dose aspirin and magnesium sulfate in the treatment of pregnancy induced hypertension: A protocol for systematic review and meta-analysis

BACKGROUND

Magnesium sulfate combined with low-dose aspirin can significantly reduce adverse reactions and effectively lower blood pressure in patients with pregnancy induced hypertension, but the overall efficacy and safety of the combination of drugs are not clear. The purpose of this study was to evaluate the efficacy and safety of magnesium sulfate combined with low-dose aspirin in the treatment of pregnancy induced hypertension.

METHODS

Randomized controlled trials focusing on the administration of magnesium sulfate combined with low-dose aspirin for pregnancy induced hypertension were searched from PubMed, EMbase, Cochrane Library, Web of Science, China National Knowledge Infrastructure (CNKI), WanFang, and the Chongqing VIP Chinese Science and Technology Periodical Database. Two researchers independently screened titles, abstracts, and full texts, and extracted relevant data. The RevMan 5.3 software and Stata 14 software were used for statistical analysis.

RESULTS

The effect and safety of magnesium sulfate combined with low-dose aspirin in the treatment of pregnancy induced hypertension were assessed by summarizing the related randomized controlled trials.

CONCLUSION

This article provides theoretical support for the clinical application of magnesium sulfate combined with low-dose aspirin in the treatment of pregnancy induced hypertension.

OSF REGISTRATION NUMBER

DOI 10.17605/OSF.IO/SZFGB.

Possibility of magnesium supplementation for supportive treatment in patients with COVID-19

Magnesium as an enzymatic activator is essential for various physiological functions such as cell cycle, metabolic regulation, muscle contraction, and vasomotor tone. A growing body of evidence supports that magnesium supplementation (mainly magnesium sulfate and magnesium oxide) prevents or treats various types of disorders or diseases related to respiratory system, reproductive system, nervous system, digestive system, and cardiovascular system as well as kidney injury, diabetes and cancer. The ongoing pandemic coronavirus disease 19 (COVID-19) characterized by respiratory tract symptoms with different degrees of important organ and tissue damages has attracted global attention. Particularly, effective drugs are still lacking in the COVID-19 therapy. In this review, we find and summarize the effectiveness of magnesium supplementation on the disorders or diseases, and provide a reference to the possibility of magnesium supplementation for supportive treatment in patients with COVID-19.

Effect of magnesium sulfate on baroreflex during acute hypoxemia in chronically instrumented fetal sheep

AIM

To investigate the effects of magnesium sulfate on fetal baroreflex in normoxemia or acute fetal hypoxemia.

METHODS

Fetal baroreflex response was elicited using phenylephrine (30 μg) in saline and magnesium sulfate in 8 chronically treated and instrumented fetal sheep. Hypoxemia was induced using nitrogen gas inflow for 30 min. Baroreflex, calculated as the ratio of the fetal heart rate change to the mean arterial pressure, was monitored after magnesium sulfate administration and in rapid and nonrapid eye movement (NREM) sleep states. Baroreflex was assessed in response to hypoxemia in control groups in both the rapid and NREM sleep states.

RESULTS

Baroreflex was not significantly affected by saline, magnesium sulfate and rapid or NREM sleep states in normoxemic sheep. Hypoxemia increased the baroreflex in the saline-treated group (hypoxemic vs normoxemic rapid eye movement sleep: 4.37 ± 2.48 vs 2.72 ± 0.83; P < 0.05; hypoxemic vs normoxemic NREM sleep: 4.30 ± 1.47 vs 3.15 ± 0.83; P < 0.001). Magnesium sulfate decreased the baroreflex in the hypoxemic fetuses (magnesium sulfate hypoxemic vs. control normoxemic fetuses: 1.42 ± 0.92 vs 3.15 ± 0.83, P < 0.05).

CONCLUSION

The hypoxemic fetal sheep, from the ewes that were receiving magnesium sulfate, showed a significantly reduced in the baroreflex response. In clinical practice, baroreflex-related decelerations in hypoxemic fetuses of mothers receiving magnesium sulfate should be carefully interpreted.

Magnesium Sulfate Treatment During Total Knee Arthroplasty Decreases Postoperative Urinary Retention: A Retrospective Propensity Score-Matched Analysis

Postoperative urinary retention (POUR) is a common complication after total knee arthroplasty. Currently, there are no clinical data regarding the effects of magnesium sulfate on POUR. Here, we investigated the effects of intraoperative magnesium sulfate infusion in patients with POUR following total knee arthroplasty. We reviewed the medical records of patients who underwent elective unilateral total knee arthroplasty under spinal anesthesia between June 2016 and May 2018. The patients were grouped based on whether they were treated with magnesium (magnesium group) or not (control group). We investigated the incidence of POUR and the postoperative analgesic requirement. Totally, 483 patients were included in the analysis. After propensity score matching with the control group, the magnesium group showed a lower incidence of POUR (odds ratio, 0.49; 95% CI, 0.29–0.83; p = 0.011) and lesser opioid consumption (p = 0.049) than the control group. Multivariate logistic regression analysis revealed that intraoperative continuous infusion of magnesium (p = 0.008) and age (p = 0.001) were significantly related to the incidence of POUR. This retrospective observational study demonstrated that administration of magnesium sulfate was associated with a lower incidence of POUR following total knee arthroplasty.

Comparison of effects and safety in providing controlled hypotension during surgery between dexmedetomidine and magnesium sulphate: A meta-analysis of randomized controlled trials

Background

Effectiveness of controlled hypotension has been proven in alleviating intraoperative bleeding. Many recent studies emphasized the efficacy of dexmedetomidine and magnesium in providing controlled hypotension during various surgeries. The present meta-analysis of randomized controlled trials (RCTs) was performed to evaluate comprehensively the effects and safety of these two medications.

Methods

Literature search was performed in four databases from inception to April 2019. All RCTs that used dexmedetomidine and magnesium as hypotensive agents were enrolled. The outcomes contained bleeding condition of surgical site, hemodynamic parameters, duration of surgeries, number of patients requiring opioid/analgesia administration, recovery period, and adverse events emerged during surgeries.

Results

Ten studies with 663 patients met with our inclusion criteria. The results indicated that both bleeding score and values of mean arterial pressure (MAP) and heart rate (HR) were significantly lower in patients receiving dexmedetomidine (SMD 1.65 with 95% CI [0.90,2.41], P<0.00001) compared to the patients receiving magnesium. The effect in decreasing the necessity of using opioid/analgesia was affirmative in dexmedetomidine group (29.13% with magnesium vs 10.78% with dexmedetomidine), and the condition was more favorable in magnesium group in reducing recovery period (SMD -1.98 with 95% CI [-4.27,0.30], P = 0.09). Compared with magnesium, using of dexmedetomidine was associated with higher incidence of bradycardia but lower incidence of nausea and vomiting.

Conclusion

Compared with magnesium, dexmedetomidine is more effective to provide promising surgical field condition, favorable controlled hypotension, and less necessity of opioid or analgesia administration. But long recovery period and high-probability bradycardia should be deliberated.

Involvement of serotonergic and opioidergic systems in the antinociceptive effect of ketamine-magnesium sulphate combination in formalin test in rats

BACKGROUND

Ketamine and magnesium sulphate showed synergic interaction in the tail-immersion test and additive interaction in the rat formalin test. Aim of study was to evaluate the influence of serotonergic and opioidergic system of this combination in the formalin test in rats.

METHODS

Antinociceptive activity was assessed by the formalin test in male Wistar rats (200-250 g). Antagonists (naloxone and methysergide) were administrated 5 min before and magnesium sulphate 5 min after ketamine injection. Formalin (2.5%, 100 μL) was injected into the right hind paw surface (intraplantar) of rats 5 min after ketamine/magnesium combination. Data were recorded as the total time spent in pain related behavior after the injection of formalin or vehicle (0.9% NaCl).

RESULTS

In the intermediate phase of the formalin test, methysergide at a dose of 0.2 mg/kg did not have any effect, but at doses of 0.5 and 1 mg/kg it had a pronociceptive effect. Methysergide (0.2, 0.5 and 1 mg/kg) inhibited the antinociceptive effect of ketamine-magnesium sulphate combination. In the intermediate phase, naloxone at a dose of 0.2 mg/kg did not have any effect, but at a dose of 3 mg/kg it produced a pronociceptive effect. Naloxone (0.2 and 3 mg/kg) antagonized the antinociceptive effect of the ketamine (5 mg/kg)-magnesium sulphate (5 mg/kg) combination.

CONCLUSION

The results of the present study suggest that serotonergic and opioidergic systems are involved, at least in part, in the antinociceptive effect of the ketamine-magnesium sulphate combination in the model of inflammatory pain in rats.

Radio-Telemetric Assessment of Cardiac Variables and Locomotion With Experimentally Induced Hypermagnesemia in Horses Using Chronically Implanted Catheters

The objective of this study was to characterize the pharmacokinetics and pharmacodynamics of intravenous administration of magnesium sulfate to horses using a novel radio-telemetry system for physiologic signal capture. Five Horses were surgically implanted with a radio-telemetric carotid catheter. Implants were paired with a non-invasive telemetric unit which acquired a six lead ECG and 3-axis acceleration to assess activity acquired wirelessly in real-time for future analysis. Horses were exposed to a new stall environment before (baseline) and after 60 mg/kg (30 mL) of magnesium sulfate (MgSO₄), or the same volume of 0.9% saline, administered intravenously in a blinded, random crossover design. Blood for pharmacokinetics, telemetric data, and body temperature were recorded serially for 24 h. Data were analyzed across time and between treatments. Significance was set at P < 0.05. Ionized magnesium concentration (Mg²⁺) increased and the Ca²⁺ to Mg²⁺ ratio decreased and persisted for 5 h after MgSO₄ administration. Heart rate (HR) increased and mean arterial blood pressure (MAP) decreased for at least 6 h. Electrocardiogram (ECG) intervals (RR) decreased and (PR and QTc) increased in duration compared to controls indicating an increase in heart rate, and slower myocardial conduction in the MgSO₄ group. Acceleration in all planes was less in the MgSO₄ group compared to controls indicating decreased locomotion. This novel method permitted collection of physiologic signals without interference by handlers or animal restraint. An intravenous bolus of MgSO₄ produced cardiac variable changes associated with the reduction of locomotion in these horses, and in a direction that may be causal. Locomotion was decreased when horses were first introduced into a new environment which reflects the calming effect desired in sport horses. Telemetric monitoring can be used as a model to elucidate the behavior and physiologic effects of other drugs. The administration of MgSO₄ may be detected for regulatory purposes with the monitoring of Mg²⁺ and Ca²⁺ concentrations and their ratio.

Postoperative Management in Patients with Pheochromocytoma and Paraganglioma

Pheochromocytomas and paragangliomas (PPGLs) are rare catecholamine-secreting neuroendocrine tumors of the adrenal medulla and sympathetic/parasympathetic ganglion cells, respectively. Excessive release of catecholamines leads to episodic symptoms and signs of PPGL, which include hypertension, headache, palpitations, and diaphoresis. Intraoperatively, large amounts of catecholamines are released into the bloodstream through handling and manipulation of the tumor(s). In contrast, there could also be an abrupt decline in catecholamine levels after tumor resection. Because of such binary manifestations of PPGL, patients may develop perplexing and substantially devastating cardiovascular complications during the perioperative period. These complications include hypertension, hypotension, arrhythmias, myocardial infarction, heart failure, and cerebrovascular accident. Other complications seen in the postoperative period include fever, hypoglycemia, cortisol deficiency, urinary retention, etc. In the interest of safe patient care, such emergencies require precise diagnosis and treatment. Surgeons, anesthesiologists, and intensivists must be aware of the clinical manifestations and complications associated with a sudden increase or decrease in catecholamine levels and should work closely together to be able to provide appropriate management to minimize morbidity and mortality associated with PPGLs.

Evaluation of Prophylactic and Therapeutic Effects of Tramadol and Tramadol Plus Magnesium Sulfate in an Acute Inflammatory Model of Pain and Edema in Rats

Background: Inflammatory pain is the most commonly treated clinical pain, since it develops following trauma or surgery, and accompanies rheumatic or arthritic diseases. Tramadol is one of the most frequently used opioid analgesics in acute and chronic pain of different origin. Magnesium is a widely used dietary supplement that was recently shown to be a safe analgesic drug in different models of inflammatory pain. Aim: This study aimed to evaluate the effects of systemically or locally injected tramadol with/without systemically injected magnesium sulfate in prophylactic or therapeutic protocols of application in a rat model of somatic inflammation. Methods: Inflammation of the rat hind paw was induced by an intraplantar injection of carrageenan (0.1 ml, 0.5%). The antihyperalgesic/antiedematous effects of tramadol (intraperitoneally or intraplantarly injected), and tramadol-magnesium sulfate (subcutaneously injected) combinations were assessed by measuring the changes in paw withdrawal thresholds or paw volume induced by carrageenan. The drugs were administered before or after inflammation induction. Results: Systemically administered tramadol (1.25-10 mg/kg) before or after induction of inflammation reduced mechanical hyperalgesia and edema with a maximal antihyperalgesic/antiedematous effect of about 40-100%. Locally applied tramadol (0.125 mg/paw) better reduced edema (50-100%) than pain (20-50%) during 24 h. Administration of a fixed dose of tramadol (1.25 mg/kg) with different doses of magnesium led to a dose-dependent enhancement and prolongation of the analgesic effect of tramadol both in prevention and treatment of inflammatory pain. Magnesium increases the antiedematous effect of tramadol in the prevention of inflammatory edema while reducing it in treatment. Conclusion: According to results obtained in this animal model, systemic administration of low doses of tramadol and magnesium sulfate given in combination is a potent, effective and relatively safe therapeutic option for prevention and especially therapy of somatic inflammatory pain. The best result is achieved when tramadol is combined with magnesium sulfate at a dose that is equivalent to the average human recommended daily dose and when the drugs are administered when inflammation is maximally developed.

Changes in calcium channel proteins according to magnesium sulfate administration in placentas from pregnancies with pre-eclampsia or fetal growth restriction

We aimed to evaluate the changes in plasma membrane Ca²⁺-ATPase (PMCA) and sarcoendoplasmic reticulum CA²⁺-ATPase (SERCA-2) according to the antepartal magnesium sulfate (MgSO₄) administration in the placentas from pregnancies with pre-eclampsia (PE) or fetal growth restriction (FGR). Pregnant women were classified as follows: (group 1) pregnancies without PE or FGR (n=16), (group 2) pregnancies with PE or FGR but without MgSO₄ administration (n=14), and (group 3) pregnancies with PE or FGR and with MgSO₄ administration (n=28). We observed the localization of PMCA and SERCA-2 in placentas and compared its expression among 3 groups. And we observed its expression in BeWo cells following treatment with MgSO₄ and CoCl₂. PMCA staining was more observed in the basal membrane, whereas SERCA-2 staining was observed predominantly under the microvillous membrane. SERCA-2 expression was significantly increased in group 3 compared with that in group 1. Considering the gestational age at delivery, PMCA expression was increased in group 2 and group 3 compared with that in group 1 after 36 weeks of gestation. SERCA-2 was increased in group 3, but not in group 2 compared with that in group 1 after 36 weeks of gestation. In BeWo cells, MgSO₄ treatment increased PMCA and SERCA-2 expression. PMCA expression was influenced by gestational age at delivery, and SERCA-2 expression was increased in the presence of PE and antepartal MgSO₄ administration. This indicates that antepartal MgSO₄ administration has a greater influence on SERCA-2 than PMCA.

Comparative Study between Magnesium Sulfate and Lidocaine for Controlled Hypotension during Functional Endoscopic Sinus Surgery: A Randomized Controlled Study

Background:

Intraoperative bleeding impairs surgical field visibility during functional endoscopic sinus surgery (FESS); several methods have been used to decrease blood loss and improve surgical field, one of them is usage of hypotensive anesthetic agents.

Aim:

We intended to compare magnesium sulfate with lidocaine, regarding their efficiency in inducing controlled hypotension and providing a better surgical field exposure during FESS and the influence of their usage on extubation time.

Settings and Design:

This study design was a prospective randomized controlled double-blinded clinical study.

Patients and Methods:

Eighty adult patients with patients' physical status ASA Classes I and II, aged 20–50 years scheduled for FESS were randomly divided into two study groups; each group contains 40 patients: Group L received lidocaine 2 mg/kg/h with maximum of 200 mg/h starting at induction of anesthesia and continuing until the end of surgery and Group M received an iv bolus of magnesium sulfate 50mg/kg in a total of 100ml saline over 10 min followed by infusion of 15mg/kg/h until the end of surgery; patients were observed for the quality of the surgical field, blood loss, and extubation time.

Statistical Analysis Used:

Student's t-test or Mann–Whitney's U, Chi-square, or Fisher's exact tests were used.

Results:

Group L showed a significant decrease in blood loss (P = 0.01), better surgical field clarity (P = 0.002), and shorter extubation time (P = 0.001) than Group M, but there was no statistically significant difference between the two study groups as regards hemodynamics.

Conclusion:

We concluded that both magnesium sulfate and lidocaine successfully induced controlled hypotension in patients undergoing FEES, but lidocaine provided better surgical field clarity and shorter extubation time.

Changes of Blood Pressure and Hemodynamic Parameters after Oral Magnesium Supplementation in Patients with Essential Hypertension-An Intervention Study

The objective of this study was to examine the changes of blood pressure and hemodynamic parameters after oral magnesium supplementation in patients with essential hypertension. The single-arm non-blinded intervention study comprised 48 patients (19 men; 29 women) whose antihypertensive therapy was not changed for at least one month. The participants were asked to consume (daily at home) 300 mg of oral magnesium-oxide supplementation product for one month and to have their blood pressure and hemodynamic parameters (thoracic fluid content, stroke volume, stroke index, cardiac output, cardiac index, acceleration index, left cardiac work index and systemic vascular resistance index, heart rate) measured in the hospital before and after the intervention. Measurements were performed with impedance cardiography. After magnesium supplementation, systolic and diastolic pressures were significantly decreased (mean ± standard deviation (SD)/mmHg/from 139.7 ± 15.0 to 130.8 ± 13.4 and from 88.0 ± 10.4 to 82.2 ± 9.0, respectively; both p < 0.001). The two significant hemodynamic changes were the decrease of systemic vascular resistance index (dyn s m²/cm⁵) and left cardiac work index (kg m/m²)/mean ± SD from 2319.3 ± 753.3 to 2083.0 ± 526.9 and from 4.8 ± 1.4 to 4.4 ± 0.9, respectively; both p < 0.05). The observed hemodynamic changes may explain lowering blood pressure after magnesium supplementation.

Magnesium and Blood Pressure: A Physiology-Based Approach

Hypertension is an important public health challenge because of its high prevalence and strong association with cardiovascular disease and premature death. Hypertension is a major cause of CKD, is present in more than 80% of CKD patients, and contributes to CKD progression. Risk factors for hypertension include, but are not limited to, age, race, family history, obesity, physical inactivity, tobacco use, and inadequate intake of minerals such as calcium, potassium, and magnesium. Magnesium is the second most abundant intracellular cation in the human body and plays an important role in insulin and adenosine triphosphate metabolism. Low dietary magnesium intake has been associated with an increased risk of developing hypertension in prospective cohort studies. Moreover, clinical trials suggest that magnesium supplementation has blood pressure-lowering effects. In addition, emerging data reveal potential mechanisms by which magnesium may influence blood pressure. Here, we will review these mechanisms, using a physiology-based approach, focusing on the effects of magnesium on total peripheral resistance and cardiac output.

Magnesium and Cardiovascular Disease

Magnesium is the most abundant intracellular divalent cation and essential for maintaining normal cellular physiology and metabolism, acting as a cofactor of numerous enzymes, regulating ion channels and energy generation. In the heart, magnesium plays a key role in modulating neuronal excitation, intracardiac conduction, and myocardial contraction by regulating a number of ion transporters, including potassium and calcium channels. Magnesium also has a role in regulating vascular tone, atherogenesis and thrombosis, vascular calcification, and proliferation and migration of endothelial and vascular smooth muscle cells. As such, magnesium potentially has a major influence on the pathogenesis of cardiovascular disease. As the kidney is a major regulator of magnesium homeostasis, kidney disorders can potentially lead to both magnesium depletion and overload, and as such increase the risk of cardiovascular disease. Observational data have shown an association between low serum magnesium concentrations or magnesium intake and increased atherosclerosis, coronary artery disease, arrhythmias, and heart failure. However, major trials of supplementation with magnesium have reported inconsistent benefits and also raised potential adverse effects of magnesium overload. As such, there is currently no firm recommendation for routine magnesium supplementation except when hypomagnesemia has been proven or suspected as a cause for cardiac arrhythmias.

Involvement of serotonergic, noradrenergic and gabaergic systems in the antinociceptive effect of a ketamine-magnesium sulfate combination in acute pain

Ketamine and magnesium can interact in additive, supra-additive and antagonistic manners in analgesia or anesthesia. Ketamine is a non-competitive NMDA receptor antagonist. Magnesium is an endogenous non-competitive NMDA antagonist that causes anion channel blockade in a dose-dependent manner. It has been established that ketamine and magnesium interact synergistically in the tail-immersion test in rats.

To determine the role of serotonergic, GABAergic and noradrenergic systems in analgesia induced by the ketamine-magnesium sulfate combination.

Experiments were performed on male Wistar albino rats (200-250 g). Antinociception was evaluated by the tail-immersion test.

Methysergide (0.5 and 1 mg/kg, sc) administered alone did not affect nociception in rats. Methysergide (0.5 and 1 mg/kg, sc) antagonized the antinociceptive effect of the ketamine (5 mg/kg)-magnesium sulfate (5mg/kg) combination. Bicuculline (0.5 and 1 mg/kg, sc) given alone did not change the threshold to thermal stimuli in rats. Bicuculline (0.5 and 1 mg/kg, sc) antagonized the antinociceptive effect of the ketamine (5 mg/kg)-magnesium sulfate (5 mg/kg) combination. Yohimbine (0.5, 1 and 3 mg/kg, sc) applied alone did not change nociception. Yohimbine at a dose of 0.5 mg/kg did not influence the effect of ketamine (5 mg/kg)-magnesium sulfate (5 mg/kg), while yohimbine at doses of 1 and 3 mg/kg antagonized the antinociceptive effect of this combination.

Serotonergic, noradrenergic and GABAergic systems participate, at least in part, in the antinociceptive effect of the ketamine-magnesium sulfate combination in acute pain in rats.

Controlled Hypotension During Rhinoplasty: A Comparison of Dexmedetomidine with Magnesium Sulfate

Objective

The current study aimed at comparing the efficacy of dexmedetomidine and magnesium sulfate to control blood pressure (BP) during rhinoplasty and the resultant effects on the quality of surgical field in terms of bleeding and visibility.

Methods

The current randomized, prospective, double-blind study was conducted on 60 patients aged 18 to 50 years classified as ASA (American Society of Anesthesiologists) physical status I who were candidates for rhinoplasty. Patients were randomly divided into 2 groups: (1) group Dex, received 1 µg/kg dexmedetomidine in 10 minutes before induction of anesthesia, followed by 0.4 - 0.6 µg/kg/hour during the maintenance of anesthesia, and (2) group Mg, received 40 mg/kg in 10 minutes before anesthesia induction followed by 10 - 15 mg/kg/hour during anesthesia maintenance. In both groups, the goal was to achieve a mean arterial pressure (MAP) of 60 - 70 mmHg. Hemodynamic variables, anesthetic, opioid, muscle relaxant requirements, and surgical field condition were recorded. Sedation score, time to reach modified Aldrete score ≥ 9, and adverse effects including nausea and vomiting (N&V) and shivering were recorded.

Results

Controlled hypotension was achieved in both groups. There was no significant difference in MAP between the groups, but heart rate (HR) was significantly lower in the Dex group (P < 0.001), compared with that of the Mg group. Bleeding score was lower (P < 0.001) and surgeon's satisfaction score was higher (P < 0.001) in the Dex group. More patients required fentanyl (P < 0.001) or nitroglycerin (P < 0.001) and the mean fentanyl (P = 0.005) or nitroglycerin (P < 0.001) required doses were higher in the Mg group. Patients in the Dex group required more frequent administration of cisatracurium (P = 0.004). Five patients in the Dex group versus no patients in the Mg group received atropine (P = 0.023). Ramsay sedation score and time to reach modified Aldrete score ≥ 9 were significantly higher in the Dex group (P < 0.001 and P < 0.001, respectively). The incidence rate of N&V and shivering were similar in both groups.

Conclusion

Dexmedetomidine was more effective than magnesium to achieve controlled hypotension, and provide a favorable surgical field condition. However, dexmedetomidine also heightened the risk of induced bradycardia and prolonged sedation. These are 2 important points to consider when applying this drug as a hypotensive agent during operation.

The effects of dexmedetomidine and magnesium sulphate in adult patients undergoing endoscopic transnasal transsphenoidal resection of pituitary adenoma: A double-blind randomised study

Background and Aim:

Transnasal transsphenoidal resection of pituitary tumours is associated with blood loss and wide fluctuations in haemodynamic parameters. The aim of the present study was to compare the effect of dexmedetomidine and magnesium sulphate during the transsphenoidal resection of pituitary tumours.

Methods:

The study was a double-blind, randomised study and included 152 patients classified randomly into two groups: Group D: Dexmedetomidine was given as a loading dose 1 μg/kg over 10 min before induction followed by an infusion at 0.5 μg/kg/h during the surgery. Group M: Magnesium sulphate was given as loading dose of 50 mg/kg over 10 min followed by an infusion at 15 mg/kg/h during the surgery. The systolic, diastolic and mean arterial blood pressures, in addition to the amount of blood loss were measured at specific timepoints. Data were described in terms of mean ± standard deviation, median, frequencies, 95% confidence of interval of mean and percentages.

Results:

Mean bleeding score was lower in Group D than Group M (1.36 ± 0.48 vs. 3.05 ± 0.65, respectively; P = 0.002). Mean blood loss was lower in Group D (157.43 ± 48.79 ml vs.299.47 ± 77.28 ml in Group M; P < 0.001)Heart rate, mean arterial pressure, fentanyl requirements, end-tidal sevoflurane concentration, and extubation and emergence times were lower, while incidence of bradycardia and hypotension were higher in Group D.

Conclusions:

During transsphenoidal pituitary resection, dexmedetomidine, compared to magnesium, is associated with lower blood loss and better operating conditions but with more hypotension and bradycardia

Update in the Management of Patients with Preeclampsia

Hypertensive disorders of pregnancy complicate approximately 10% of all deliveries in the United States and are a leading cause of maternal and fetal morbidity and mortality. Preeclampsia is defined as hypertension in association with proteinuria, thrombocytopenia, impaired liver function, renal insufficiency, pulmonary edema, or new-onset cerebral or visual disturbances. The greatest risk factor for the development of preeclampsia is a history of preeclampsia. There currently is no effective means for the prevention of preeclampsia. Approximately 39% of patients diagnosed with preeclampsia have hypertension and approximately 20% have proteinuria 3 months postpartum. Preeclampsia increases the risk of patients developing hypertension later in life.

The antinociceptive effects of magnesium sulfate and MK-801 in visceral inflammatory pain model: The role of NO/cGMP/K(+)ATP pathway

CONTEXT

Magnesium and MK-801 (dizocilpine), antagonists of N-methyl-d-aspartate receptors, are involved in the processing of pain.

OBJECTIVE

This study determines whether magnesium sulfate (MS) and MK-801 affects visceral inflammatory pain and determines a possible mechanism of action.

MATERIALS AND METHODS

Analgesic activity was assessed using the acetic acid-induced writhing test in rats. MS (1-45 mg/kg) or MK-801 (0.005-0.03 mg/kg) was administrated subcutaneously (s.c.). To assess possible mechanisms of action, we examined the effects of l-NAME (10 mg/kg, intraperitoneal), methylene blue (0.5 mg/kg, s.c.), and glibenclamide (3 mg/kg, s.c.) on the effect of MS or MK-801.

RESULTS

MS and MK-801 showed biphasic and linear dose-response pattern, respectively. MS reduces the number of writhing on the dose of 1, 5, and 15 mg/kg by 60, 50, and 78%, respectively, while it has no effects on the doses of 30 and 45 mg/kg. MK-801 (0.005-0.03 mg/kg) showed decrease in the number of writhing by 33-79%. The mean effective doses of MS and MK-801 were 6.6 (first phase) and 0.009 mg/kg, respectively. Both drugs did not impair the rotarod performance. l-NAME, methylene blue, and glybenclamide reduced the effect of MK-801 by 100, 43, and 64%, respectively, but not the effect of MS.

CONCLUSIONS

The results suggest that MS and MK-801 may be useful analgesics in the management of visceral inflammatory pain, at doses that do not induce motor impairment. The modulation of NO/cGMP/K+ATP pathway plays an important role in the antinociceptive mechanism of MK-801, but does not contribute to the antinociceptive effect of MS.

Effect of dietary magnesium supplementation in alleviating stress associated with road transportation in weaned lambs

Magnesium (Mg) supplementation has shown to modulate the stress responses to transport in other species. An experiment was designed to evaluate the effect of Mg for alleviating stress associated with road transportation in lambs. Two groups (n = 18 each) of 4-month old male crossbred lambs (24 ± 4.5 kg) were fed a basal diet comprising oaten hay, pellets and barley, that contained 0.17% Mg. One group was supplemented with magnesium oxide, such that dietary Mg was 0.41%. At the end of the 2-week supplementation period, the lambs were transported by road for 8 h. Blood samples were collected before supplementation, 1 h before transport, within 0.5 h post-transport, at 2 h post-transport and 5 days post-transport. Data were analysed using a repeated-measure analysis of variance and linear mixed model with treatment within time interaction. Supplementation with dietary Mg in the form of MgO increased serum Mg concentrations (1.16 mmol/L ± 0.012, compared with 1.09 mmol/L ± 0.013 in the control group; P < 0.05), but had no effect on alleviating stress during transportation. Transport resulted in a significant increase in serum cortisol, which returned to pre-transport levels 2 h after transport. The serum β-hydroxybutyrate was significantly higher 5 days after transport. The post-transport average feed intake and the average daily gain were significantly lower than pre-transport values, suggesting that the stress of transportation resulted in a decrease in feed intake post-transport, which could have implications on liveweight gain of animals after transportation.

Suppression of peripheral sympathetic activity underlies protease-activated receptor 2-mediated hypotension

Protease-activated receptor (PAR)-2 is expressed in endothelial cells and vascular smooth muscle cells. It plays a crucial role in regulating blood pressure via the modulation of peripheral vascular tone. Although some reports have suggested involvement of a neurogenic mechanism in PAR-2-induced hypotension, the accurate mechanism remains to be elucidated. To examine this possibility, we investigated the effect of PAR-2 activation on smooth muscle contraction evoked by electrical field stimulation (EFS) in the superior mesenteric artery. In the present study, PAR-2 agonists suppressed neurogenic contractions evoked by EFS in endothelium-denuded superior mesenteric arterial strips but did not affect contraction elicited by the external application of noradrenaline (NA). However, thrombin, a potent PAR-1 agonist, had no effect on EFS-evoked contraction. Additionally, ω-conotoxin GVIA (CgTx), a selective N-type Ca²⁺ channel (I_Ca-N) blocker, significantly inhibited EFS-evoked contraction, and this blockade almost completely occluded the suppression of EFS-evoked contraction by PAR-2 agonists. Finally, PAR-2 agonists suppressed the EFS-evoked overflow of NA in endothelium-denuded rat superior mesenteric arterial strips and this suppression was nearly completely occluded by ω-CgTx. These results suggest that activation of PAR-2 may suppress peripheral sympathetic outflow by modulating activity of I_Ca-N which are located in peripheral sympathetic nerve terminals, which results in PAR-2-induced hypotension.

Adenosine, lidocaine and Mg2+ improves cardiac and pulmonary function, induces reversible hypotension and exerts anti-inflammatory effects in an endotoxemic porcine model

Introduction

The combination of Adenosine (A), lidocaine (L) and Mg²⁺ (M) (ALM) has demonstrated cardioprotective and resuscitative properties in models of cardiac arrest and hemorrhagic shock. This study evaluates whether ALM also demonstrates organ protective properties in an endotoxemic porcine model.

Methods

Pigs (37 to 42 kg) were randomized into: 1) Control (n = 8) or 2) ALM (n = 8) followed by lipopolysaccharide infusion (1 μg∙kg^-1∙h^-1) for five hours. ALM treatment consisted of 1) a high dose bolus (A (0.82 mg/kg), L (1.76 mg/kg), M (0.92 mg/kg)), 2) one hour continuous infusion (A (300 μg∙kg^-1 ∙min^-1), L (600 μg∙kg^-1 ∙min^-1), M (336 μg∙kg^-1 ∙min^-1)) and three hours at a lower dose (A (240∙kg^-1∙min^-1), L (480 μg∙kg^-1∙min^-1), M (268 μg∙kg^-1 ∙min^-1)); controls received normal saline. Hemodynamic, cardiac, pulmonary, metabolic and renal functions were evaluated.

Results

ALM lowered mean arterial pressure (Mean value during infusion period: ALM: 47 (95% confidence interval (CI): 44 to 50) mmHg versus control: 79 (95% CI: 75 to 85) mmHg, P <0.0001). After cessation of ALM, mean arterial pressure immediately increased (end of study: ALM: 88 (95% CI: 81 to 96) mmHg versus control: 86 (95% CI: 79 to 94) mmHg, P = 0.72). Whole body oxygen consumption was significantly reduced during ALM infusion (ALM: 205 (95% CI: 192 to 217) ml oxygen/min versus control: 231 (95% CI: 219 to 243) ml oxygen/min, P = 0.016). ALM treatment reduced pulmonary injury evaluated by PaO₂/FiO₂ ratio (ALM: 388 (95% CI: 349 to 427) versus control: 260 (95% CI: 221 to 299), P = 0.0005). ALM infusion led to an increase in heart rate while preserving preload recruitable stroke work. Creatinine clearance was significantly lower during ALM infusion but reversed after cessation of infusion. ALM reduced tumor necrosis factor-α peak levels (ALM 7121 (95% CI: 5069 to 10004) pg/ml versus control 11596 (95% CI: 9083 to 14805) pg/ml, P = 0.02).

Conclusion

ALM infusion induces a reversible hypotensive and hypometabolic state, attenuates tumor necrosis factor-α levels and improves cardiac and pulmonary function, and led to a transient drop in renal function that was reversed after the treatment was stopped.

[Comparison between magnesium sulfate and dexmedetomidine in controlled hypotension during functional endoscopic sinus surgery]

BACKGROUND AND OBJECTIVES

It is crucial to decrease bleeding during functional endoscopic sinus surgery. Our primary goal was to investigate the effects of magnesium sulfate and dexmedetomidine used for controlled hypotension on the visibility of the surgical site.

METHODS

60 patients aged between 18 and 65 years were enrolled. In the magnesium sulfate group (Group M), patients were administered 40mg/kg magnesium sulfate in 100mL saline solution over 10min as the intravenous loading dose 10min before induction, with a subsequent 10-15mg/kg/h infusion during surgery. In the dexmedetomidine group (Group D), patients were administered 1μg/kg dexmedetomidine in 100mL saline solution as the loading dose 10min before surgery and 0.5-1μg/kg/h dexmedetomidine during surgery. Deliberate hypotension was defined as a mean arterial pressure of 60-70mmHg.

RESULTS

Bleeding score was significantly decreased in Group D (p=0.002). Mean arterial pressure values were significantly decreased in Group D compared to that in Group M, except for the initial stage, after induction and 5min after intubation (p<0.05). The number of patients who required nitroglycerine was significantly lower in Group D (p=0.01) and surgeon satisfaction was significantly increased in the same group (p=0.001). Aldrete recovery score ≥9 duration was significantly shorter in Group D (p=0.001). There was no difference between the two groups in terms of recovery room verbal numerical rating scale.

CONCLUSIONS

Dexmedetomidine can provide more effective controlled hypotension and thus contribute to improved visibility of the surgical site.

Protease-activated receptor 2 activation inhibits N-type Ca2+ currents in rat peripheral sympathetic neurons

The protease-activated receptor (PAR)-2 is highly expressed in endothelial cells and vascular smooth muscle cells. It plays a crucial role in regulating blood pressure via the modulation of peripheral vascular tone. Although several mechanisms have been suggested to explain PAR-2-induced hypotension, the precise mechanism remains to be elucidated. To investigate this possibility, we investigated the effects of PAR-2 activation on N-type Ca(2+) currents (I(Ca-N)) in isolated neurons of the celiac ganglion (CG), which is involved in the sympathetic regulation of mesenteric artery vascular tone. PAR-2 agonists irreversibly diminished voltage-gated Ca(2+) currents (I(Ca)), measured using the patch-clamp method, in rat CG neurons, whereas thrombin had little effect on I(Ca). This PAR-2-induced inhibition was almost completely prevented by ω-CgTx, a potent N-type Ca(2+) channel blocker, suggesting the involvement of N-type Ca(2+) channels in PAR-2-induced inhibition. In addition, PAR-2 agonists inhibited I(Ca-N) in a voltage-independent manner in rat CG neurons. Moreover, PAR-2 agonists reduced action potential (AP) firing frequency as measured using the current-clamp method in rat CG neurons. This inhibition of AP firing induced by PAR-2 agonists was almost completely prevented by ω-CgTx, indicating that PAR-2 activation may regulate the membrane excitability of peripheral sympathetic neurons through modulation of N-type Ca(2+) channels. In conclusion, the present findings demonstrate that the activation of PAR-2 suppresses peripheral sympathetic outflow by modulating N-type Ca(2+) channel activity, which appears to be involved in PAR-2-induced hypotension, in peripheral sympathetic nerve terminals.

Hypomagnesemia and prehypertension in otherwise healthy individuals

BACKGROUND

Given the potential implications in the policies focused on the prevention of hypertension, we evaluate the relationship between low serum magnesium levels and prehypertension in otherwise healthy subjects.

METHODS

A cross-sectional study that enrolled 175 healthy men and non-pregnant women, 20 to 65 years of age was carried out. Type 2 diabetes, impaired fasting glucose, hypertension, chronic diarrhea, cancer, impaired renal function, as well as the intake of magnesium supplements in the previous six months, were the exclusion criteria. Hypomagnesemia was defined by serum magnesium concentration of <0.7 mmol/L and prehypertension by Systolic (S) and Diastolic (D) blood pressure (BP) of 120 to 139 and 80 to 89 mmHg. A multivariate logistic conditional forward analysis, adjusted by sex, age, alcohol consumption waist circumference, body mass index, fasting glucose and triglyceride levels was conducted to evaluate the association between hypomagnesemia and prehypertension.

RESULTS

Prehypertension was identified in 68 (13.2%) subjects who were compared with 107 (20.8%) control individuals without prehypertension. Individuals with prehypertension showed lower magnesium (0.73±0.20 vs. 0.77±0.21, p<0.001) and higher triglyceride levels (2.8±3.5 vs. 1.8±1.2, p=0.04) as compared with non-prehypertensive individuals. There were no other significant differences between the groups. The adjusted multivariate logistic conditional forward analysis showed a significant association between hypomagnesemia and prehypertension (OR 1.98; 95% CI 1.11-4.20, p=0.04).

CONCLUSIONS

Our finding suggests that low serum magnesium levels could play an important role in the pathophysiology of prehypertension in otherwise healthy subjects.

Effects of serum calcium and magnesium on heart rate variability in adult women

The present study was designed to evaluate the association of serum calcium (Ca) and magnesium (Mg) levels with heart rate variability (HRV). One hundred and sixteen adult women were recruited in this cross-sectional study. Serum Ca and Mg levels were measured, and HRV in each time and frequency domain was recorded for 5 min. Mean heart rate and standard deviation of the normal to normal interval (SDNN) and root mean square of differences of successive RR interval (RMSSD) in time domain and total power (TP), low-frequency power (LF), high-frequency power (HF), and LF/HF ratio in frequency domain were compared according to the tertiles of serum Ca and Mg levels and Ca/Mg ratio. The associations between serum Ca and Mg levels and Ca/Mg ratio with HRV were evaluated using regression analyses. Mean heart rate tended to increase from the lowest to the highest tertile of Ca levels (p = 0.081), whereas it decreased significantly with higher Mg levels (p = 0.026). Increasing SDNN value was observed from the lowest to the highest tertile of Mg levels (p = 0.009). SDNN value decreased significantly from the lowest to the highest tertile of Ca/Mg ratio (p = 0.030). Participants in the lowest tertile of Ca/Mg ratio had significantly higher TP and LF values compared to those in the middle and highest tertiles (p < 0.05). Decreasing SDNN, TP, and LF values were significantly associated with higher Ca/Mg ratios (p < 0.05). Associations of serum Mg level and Ca/Mg ratio with HRV could be one of the mechanisms involved in cardiovascular diseases.

Domain III regulates N-type (CaV2.2) calcium channel closing kinetics

Ca(V)2.2 (N-type) and Ca(V)1.2 (L-type) calcium channels gate differently in response to membrane depolarization, which is critical to the unique physiological functions mediated by these channels. We wondered if the source for these differences could be identified. As a first step, we examined the effect of domain exchange between N-type and L-type channels on activation-deactivation kinetics, which were significantly different between these channels. Kinetic analysis of chimeric channels revealed N-channel-like deactivation for all chimeric channels containing N-channel domain III, while activation appeared to be a more distributed function across domains. This led us to hypothesize that domain III was an important regulator of N-channel closing. This idea was further examined with R-roscovitine, which is a trisubstituted purine that slows N-channel deactivation by exclusively binding to activated N-channels. L-channels lack this response to roscovitine, which allowed us to use N-L chimeras to test the role of domain III in roscovitine modulation of N-channel deactivation. In support of our hypothesis, all chimeric channels containing the N-channel domain III responded to roscovitine with slowed deactivation, while those chimeric channels with L-channel domain III did not. Thus a combination of kinetic and pharmacological evidence supports the hypothesis that domain III is an important regulator of N-channel closing. Our results support specialization of gating functions among calcium channel domains.