alpha2-Adrenoceptor agonists: shedding light on neuroprotection?

Dexmedetomidine directly binds to and inhibits Toll-like receptor 4

BACKGROUND

While a number of anesthetics has been shown potentially associated with neurotoxicity in the developing brain, dexmedetomidine, a drug that was rather recently introduced into the perioperative setting, is considered beneficial from neurological wellbeing. However, the underlying mechanism of how dexmedetomidine affects brain health remains to be determined. Based on our recent study, we hypothesized that dexmedetomidine would directly bind to and inhibit Toll-like receptor 4 (TLR4), a critical receptor largely expressed in microglia and responsible for neurological insult.

METHODS

We used TLR4 reporter assays to test if dexmedetomidine attenuates TLR4 activation. Furthermore, a direct binding of dexmedetomidine on TLR4 was tested using photoactivatable medetomidine. Lastly, the effect of dexmedetomidine on ketamine (anesthetic)-induced neurotoxicity was tested in rat pups (P7).

RESULTS

We showed that dexmedetomidine attenuated TLR4 activation using reporter assay (IC50 = 5.8 µg/mL). Photoactivatable dexmedetomidine delineated its direct binding sites on TLR4. We also showed that dexmedetomidine attenuated microglia activation both in vitro and in vivo.

DISCUSSION

We proposed a novel mechanism of dexmedetomidine-mediated neuroprotection.

Neuroprotective actions of norepinephrine in neurological diseases

Precise control of norepinephrine (NE) levels and NE-receptor interaction is crucial for proper function of the brain. Much evidence for this view comes from experimental studies that indicate an important role for NE in the pathophysiology and treatment of various conditions, including cognitive dysfunction, Alzheimer's disease, Parkinson's disease, multiple sclerosis, and sleep disorders. NE provides neuroprotection against several types of insults in multiple ways. It abrogates oxidative stress, attenuates neuroinflammatory responses in neurons and glial cells, reduces neuronal and glial cell activity, promotes autophagy, and ameliorates apoptotic responses to a variety of insults. It is beneficial for the treatment of neurodegenerative diseases because it improves the generation of neurotrophic factors, promotes neuronal survival, and plays an important role in the regulation of adult neurogenesis. This review aims to present the evidence supporting a principal role for NE in neuroprotection, and molecular mechanisms of neuroprotection.

Intranasal dexmedetomidine reduces pain scores in preterm infants during retinopathy of prematurity screening

Background

This study aimed to investigate the effectiveness of intranasal dexmedetomidine in reducing pain scores during retinopathy of prematurity (ROP) screening examinations in preterm infants.

Methods

Infants born at ≤32 weeks of gestational age, undergoing routine ROP examinations in the neonatal intensive care unit, were included in the study and divided into two groups: the standard protocol group (n = 43) and the dexmedetomidine group (n = 56), over a 1-year period. Both groups received standard procedural preparation including swaddling, oral dextrose, and topical anesthesia with proparacaine. The dexmedetomidine group additionally received intranasal dexmedetomidine at a dose of 1 mcg/kg before the procedure. Pain scores (PIPP score), heart rate, respiratory rate, blood pressure, and oxygen saturation were compared at baseline, 1-min, and 5-min during the procedure.

Results

There were no significant differences between the groups regarding descriptive and pre-procedure characteristics. In the dexmedetomidine group, the median (25-75p) PIPP score, heart rate, systolic blood pressure and mean (±SD) respiratory rate measured at the 1st minute of the procedure were significantly lower than those in the standard group [PIPP score 10 (8-13) vs. 14 (10-16), p < 0.001; heart rate 165 (153-176) beats/min vs. 182 (17-190) beats/min, p < 0.001; respiratory rate 60 (±7) breaths/min vs. 65(±9) breaths/min, p = 0.002; systolic blood pressure 78 (70-92) mmHg vs. 87 (78-96) mmHg, p = 0.024; respectively] whereas the saturation value was significantly higher (88% (81-95) vs. 84% (70-92), p = 0.036; respectively). By the 5th minute of the procedure, the median (25-75p) PIPP score [4 (2-6) vs. 6 (4-10), p < 0.001], heart rate [148 (143-166) beats/min vs. 162 (152-180) beats/min, p = 0.001] and respiratory rate [56 (54-58) breaths/min vs. 58 (54-62) breaths/min, p = 0.034] were significantly lower, and the saturation level was significantly higher [96% (94-97) vs. 93% (91-96), p = 0.003] in the dexmedetomidine group. Additionally, the frequency of adverse effects was significantly lower in the dexmedetomidine group compared to the standard protocol group (11% vs. 47%, p = 0.001).

Conclusion

Administering intranasal dexmedetomidine before ROP screening examinations was associated with a decrease in pain scores among preterm infants. This suggests its potential as an effective and well-tolerated method for pain management during ROP screenings.

A combination treatment based on drug repurposing demonstrates mutation-agnostic efficacy in pre-clinical retinopathy models

Inherited retinopathies are devastating diseases that in most cases lack treatment options. Disease-modifying therapies that mitigate pathophysiology regardless of the underlying genetic lesion are desirable due to the diversity of mutations found in such diseases. We tested a systems pharmacology-based strategy that suppresses intracellular cAMP and Ca2+ activity via G protein-coupled receptor (GPCR) modulation using tamsulosin, metoprolol, and bromocriptine coadministration. The treatment improves cone photoreceptor function and slows degeneration in Pde6βrd10 and RhoP23H/WT retinitis pigmentosa mice. Cone degeneration is modestly mitigated after a 7-month-long drug infusion in PDE6A-/- dogs. The treatment also improves rod pathway function in an Rpe65-/- mouse model of Leber congenital amaurosis but does not protect from cone degeneration. RNA-sequencing analyses indicate improved metabolic function in drug-treated Rpe65-/- and rd10 mice. Our data show that catecholaminergic GPCR drug combinations that modify second messenger levels via multiple receptor actions provide a potential disease-modifying therapy against retinal degeneration.

Methods of prolonging the effect of caudal block in children

Caudal epidural blockade is one of the most frequently administered regional anesthesia techniques in children. It is a supplement during general anesthesia and for providing postoperative analgesia in pediatrics for sub-umbilical surgeries, especially for genitourinary surgeries. However, the duration of the analgesic effect is occasionally unsatisfactory. In this review, we discuss the main advantages and disadvantages of different techniques to prolong postoperative analgesia for single-injection caudal blockade in children. A literature search of the keywords "caudal", "analgesia", "pediatric", and "children" was performed using PubMed and Web of Science databases. We highlight that analgesic quality correlates substantially with the local anesthetic's type, dose, the timing relationship between caudal block and surgery, caudal catheterization, and administration of epidural opioids or other adjuvant drugs.

Adrenoceptors in the Eye - Physiological and Pathophysiological Relevance

The autonomic nervous system plays a crucial role in the innervation of the eye. Consequently, it comes as no surprise that catecholamines and their corresponding receptors have been extensively studied and characterized in numerous ocular structures, including the cornea, conjunctiva, lacrimal gland, trabecular meshwork, uvea, and retina. These investigations have unveiled substantial clinical implications, particularly in the context of treating glaucoma, a progressive neurodegenerative disorder responsible for irreversible vision loss on a global scale. The primary therapeutic approaches for glaucoma frequently involve the modulation of α1-, α2-, and β-adrenoceptors, making them pivotal targets. In this chapter, we offer a comprehensive overview of the expression, distribution, and functional roles of adrenoceptors within various components of the eye and its associated structures. Additionally, we delve into the pivotal role of adrenoceptors in the pathophysiology of glaucoma. Furthermore, we provide a concise historical perspective on adrenoceptor research, examine the distinct contributions of individual adrenoceptor subtypes to the treatment of various ocular conditions, and propose potential future avenues of exploration in this field.

Neurotoxic Impact of Individual Anesthetic Agents on the Developing Brain

Concerns about the safety of anesthetic agents in children arose after animal studies revealed disruptions in neurodevelopment after exposure to commonly used anesthetic drugs. These animal studies revealed that volatile inhalational agents, propofol, ketamine, and thiopental may have detrimental effects on neurodevelopment and cognitive function, but dexmedetomidine and xenon have been shown to have neuroprotective properties. The neurocognitive effects of benzodiazepines have not been extensively studied, so their effects on neurodevelopment are undetermined. However, experimental animal models may not truly represent the pathophysiological processes in children. Multiple landmark studies, including the MASK, PANDA, and GAS studies have provided reassurance that brief exposure to anesthesia is not associated with adverse neurocognitive outcomes in infants and children, regardless of the type of anesthetic agent used.

Propofol and α2-Agonists Attenuate Microglia Activation and Restore Mitochondrial Function in an In Vitro Model of Microglia Hypoxia/Reoxygenation

Cerebrovascular ischemia is a common clinical disease encompassing a series of complex pathophysiological processes in which oxidative stress plays a major role. The present study aimed to evaluate the effects of Dexmedetomidine, Clonidine, and Propofol in a model of hypoxia/reoxygenation injury. Microglial cells were exposed to 1%hypoxia for 3 h and reoxygenated for 3 h, and oxidative stress was measured by ROS formation and the expression of inflammatory process genes. Mitochondrial dysfunction was assessed by membrane potential maintenance and the levels of various metabolites involved in energetic metabolism. The results showed that Propofol and α2-agonists attenuate the formation of ROS during hypoxia and after reoxygenation. Furthermore, the α2-agonists treatment restored membrane potential to values comparable to the normoxic control and were both more effective than Propofol. At the same time, Propofol, but not α2-agonists, reduces proliferation (Untreated Hypoxia = 1.16 ± 0.2, Untreated 3 h Reoxygenation = 1.28 ± 0.01 vs. Propofol hypoxia = 1.01 ± 0.01 vs. Propofol 3 h Reoxygenation = 1.12 ± 0.03) and microglial migration. Interestingly, all of the treatments reduced inflammatory gene and protein expressions and restored energy metabolism following hypoxia/reoxygenation (ATP content in hypoxia/reoxygenation 3 h: Untreated = 3.11 ± 0.8 vs. Propofol = 7.03 ± 0.4 vs. Dexmedetomidine = 5.44 ± 0.8 vs. Clonidine = 7.70 ± 0.1), showing that the drugs resulted in a different neuroprotective profile. In conclusion, our results may provide clinically relevant insights for neuroprotective strategies in intensive care units.

A novel role of FoxO3a in the migration and invasion of trophoblast cells: from metabolic remodeling to transcriptional reprogramming

Background

The forkhead box O3a protein (FoxO3a) has been reported to be involved in the migration and invasion of trophoblast, but its underlying mechanisms unknown. In this study, we aim to explore the transcriptional and metabolic regulations of FoxO3a on the migration and invasion of early placental development.

Methods

Lentiviral vectors were used to knock down the expression of FoxO3a of the HTR8/SVneo cells. Western blot, matrigel invasion assay, wound healing assay, seahorse, gas-chromatography-mass spectrometry (GC–MS) based metabolomics, fluxomics, and RNA-seq transcriptomics were performed.

Results

We found that FoxO3a depletion restrained the migration and invasion of HTR8/SVneo cells. Metabolomics, fluxomics, and seahorse demonstrated that FoxO3a knockdown resulted in a switch from aerobic to anaerobic respiration and increased utilization of aromatic amino acids and long-chain fatty acids from extracellular nutrients. Furthermore, our RNA-seq also demonstrated that the expression of COX-2 and MMP9 decreased after FoxO3a knockdown, and these two genes were closely associated with the migration/invasion progress of trophoblast cells.

Conclusions

Our results suggested novel biological roles of FoxO3a in early placental development. FoxO3a exerts an essential effect on trophoblast migration and invasion owing to the regulations of COX2, MMP9, aromatic amino acids, energy metabolism, and oxidative stress.

Adrenergic receptors control frequency-dependent switching of the exocytosis mode between "full-collapse" and "kiss-and-run" in murine motor nerve terminal

AIMS

Neurotransmitter release from the synaptic vesicles can occur through two modes of exocytosis: "full-collapse" or "kiss-and-run". Here we investigated how increasing the nerve activity and pharmacological stimulation of adrenoceptors can influence the mode of exocytosis in the motor nerve terminal.

METHODS

Recording of endplate potentials with intracellular microelectrodes was used to estimate acetylcholine release. A fluorescent dye FM1-43 and its quenching with sulforhodamine 101 were utilized to visualize synaptic vesicle recycling.

KEY FINDINGS

An increase in the frequency of stimulation led to a decrease in the rate of FM1-43 unloading despite the higher number of quanta released. High frequency activity promoted neurotransmitter release via the kiss-and-run mechanism. This was confirmed by experiments utilizing (I) FM1-43 dye quencher, that is able to pass into the synaptic vesicle via fusion pore, and (II) loading of FM1-43 by compensatory endocytosis. Noradrenaline and specific α2-adrenoreceptors agonist, dexmedetomidine, controlled the mode of synaptic vesicle recycling at high frequency activity. Their applications favored neurotransmitter release via full-collapse exocytosis rather than the kiss-and-run pathway.

SIGNIFICANCE

At the diaphragm neuromuscular junctions, neuronal commands are translated into contractions necessary for respiration. During stress, an increase in discharge rate of the phrenic nerve shifts the exocytosis from the full-collapse to the kiss-and-run mode. The stress-related molecule, noradrenaline, restricts neurotransmitter release in response to a high frequency activity, and prevents the shift in the mode of exocytosis through α2-adrenoceptor activation. This may be a component of the mechanism that limits overstimulation of the respiratory system during stress.

Considerations for Cannabinoids in Perioperative Care by Anesthesiologists

Increased usage of recreational and medically indicated cannabinoid compounds has been an undeniable reality for anesthesiologists in recent years. These compounds’ complicated pharmacology, composition, and biological effects result in challenging issues for anesthesiologists during different phases of perioperative care. Here, we review the existing formulation of cannabinoids and their biological activity to put them into the context of the anesthesia plan execution. Perioperative considerations should include a way to gauge the patient’s intake of cannabinoids, the ability to gain consent properly, and vigilance to the increased risk of pulmonary and airway problems. Intraoperative management in individuals with cannabinoid use is complicated by the effects cannabinoids have on general anesthetics and depth of anesthesia monitoring while simultaneously increasing the potential occurrence of intraoperative hemodynamic instability. Postoperative planning should involve higher vigilance to the risk of postoperative strokes and acute coronary syndromes. However, most of the data are not up to date, rending definite conclusions on the importance of perioperative cannabinoid intake on anesthesia management difficult.

Tailored Therapeutic Doses of Dexmedetomidine in Evolving Neuroinflammation after Traumatic Brain Injury

BACKGROUND

Understanding the secondary damage mechanisms of traumatic brain injury (TBI) is essential for developing new therapeutic approaches. Neuroinflammation has a pivotal role in secondary brain injury after TBI. Activation of NLRP3 inflammasome complexes results in the secretion of proinflammatory mediators and, in addition, later in the response, microglial activation and migration of the peripheral immune cells into the injured brain are observed. Therefore, these components involved in the inflammatory process are becoming a new treatment target in TBI. Dexmedetomidine (Dex) is an effective drug, widely used over the past few years in neurocritical care units and during surgical operations for sedation and analgesia, and has anti-inflammatory effects, which are shown in in vivo studies. The aim of this original research is to discuss the anti-inflammatory effects of different Dex doses over time in TBI.

METHODS

Brain injury was performed by using a weight-drop model. Half an hour after the trauma, intraperitoneal saline was injected into the control groups and 40 and 200 μg/kg of Dex were given to the drug groups. Neurological evaluations were performed with the modified Neurological Severity Score before being killed. Then, the mice were killed on the first or the third day after TBI and histopathologic (hematoxylin-eosin) and immunofluorescent (Iba1, NLRP3, interleukin-1β, and CD3) findings of the brain tissues were examined. Nonparametric data were analyzed by using the Kruskal-Wallis test for multiple comparisons, and the Mann-Whitney U-test was done for comparing two groups. The results are presented as mean ± standard error of mean.

RESULTS

The results showed that low doses of Dex suppress NLRP3 and interleukin-1β in both terms. Additionally, high doses of Dex cause a remarkable decrease in the migration and motility of microglial cells and T cells in the late phase following TBI. Interestingly, the immune cells were influenced by only high-dose Dex in the late phase of TBI and it also improves neurologic outcome in the same period.

CONCLUSIONS

In the mice head trauma model, different doses of Dex attenuate neuroinflammation by suppressing distinct components of the neuroinflammatory process in a different timecourse that contributes to neurologic recovery. These results suggest that Dex may be an appropriate choice for sedation and analgesia in patients with TBI.

Dexmedetomidine and Phosphocreatine Post-treatment Provides Protection against Focal Cerebral Ischemia-reperfusion Injury in Rats

In this study we investigated the neuroprotective efficacy of dexmedetomidine (Dex) and phosphocreatine (PCr) alone or in combination in a rat model of focal cerebral ischemia-reperfusion injury (I/R). I/R was induced by intraluminal middle cerebral artery occlusion (MCAO) and reperfusion. Male Sprague-Dawley rats were randomly allocated to the Sham group and I/R group, and the I/R group was further divided into three subgroups: Dex (9 μg.kg⁻¹ Dex), PCr (180 mg.kg⁻¹ PCr) and Dex + PCr (9 μg.kg⁻¹ Dex + 180 mg.kg⁻¹ PCr). All treatments were given intravenously at the onset of reperfusion. After 24 hr of reperfusion, the neurological deficit score (NDS) was determined and a magnetic resonance imaging (MRI) scan was performed. Serum concentrations of malonaldehyde (MDA) and 4-hydroxynonenal (4-HNE) were measured and cerebral infarct volume was estimated by triphenyl tetrazolium chloride (TTC) staining. Blood brain barrier, neuronal and mitochondrial damage was assessed by optical and electron microscopy. Neuronal injury was further assessed using double cleaved caspase-3 and NeuN immunofluorescent staining. Compared with group I/R, Dex and PCr significantly reduced the neurological deficit score (P < 0.01), infarct volume (P < 0.01), and brain blood barrier, neuronal and mitochondrial damage. The level of oxidative stress (P < 0.001) and neuronal injury (P < 0.001) also decreased and surviving neurons increased (P < 0.001). Compared with Dex or PCr alone, the combination treatment had overall greater effects (P < 0.05). These results indicate that posttreatment with Dex or PCr decreases focal cerebral I/R injury and that these agents in combination have greater protective effects than each alone.

Dexmedetomidine post-conditioning attenuates cerebral ischemia following asphyxia cardiac arrest through down-regulation of apoptosis and neuroinflammation in rats

Background

Neuroprotection strategies after cardiac arrest (CA)/cardiopulmonary resuscitation (CPR) remain key areas of basic and clinical research. This study was designed to investigate the neuroprotective effects of dexmedetomidine following resuscitation and potential mechanisms.

Methods

Anesthetized rats underwent 6-min asphyxia-based cardiac arrest and resuscitation, after which the experimental group received a single intravenous dose of dexmedetomidine (25 μg/kg). Neurological outcomes and ataxia were assessed after the return of spontaneous circulation. The serum levels and brain expression of inflammation markers was examined, and apoptotic cells were quantified by TUNEL staining.

Results

Neuroprotection was enhanced by dexmedetomidine post-conditioning after the return of spontaneous circulation. This enhancement was characterized by the promotion of neurological function scores and coordination. In addition, dexmedetomidine post-conditioning attenuated the serum levels of the pro-inflammatory cytokine tumor necrosis factor (TNF)-α at 2 h, as well as interleukin IL-1β at 2, 24, and 48 h. TUNEL staining showed that the number of apoptotic cells in the dexmedetomidine post-conditioning group was significantly reduced compared with the control group. Further western blot analysis indicated that dexmedetomidine markedly reduced the levels of caspase-3 and nuclear factor-kappa B (NF-κB) in the brain.

Conclusions

Dexmedetomidine post-conditioning had a neuroprotective effect against cerebral injury following asphyxia-induced cardiac arrest. The mechanism was associated with the downregulation of apoptosis and neuroinflammation.

The immunomodulatory mechanism of dexmedetomidine

Dexmedetomidine has been increasingly introduced into the perioperative care of surgical patients. Because a subset of anesthetics/sedatives are immunomodulatory, it is critical to understand the role of dexmedetomidine in our host immune functions. Here we reviewed the role of dexmedetomidine in different immune cells. We also reviewed published clinical articles that described the role of dexmedetomidine in organ injury, cancer surgery, and infection. In animal studies, dexmedetomidine attenuated organ injury. In clinical studies, dexmedetomidine was associated with an improvement in outcomes in cardiac surgery and transplant surgery. However, there is a paucity in research examining how dexmedetomidine is associated with these outcomes. Further studies are needed to understand its clinical application from immunological standpoints.

The Effect of Dexmedetomidine and Esmolol on Early Postoperative Cognitive Dysfunction After Middle Ear Surgery Under Hypotensive Technique: A Comparative, Randomized, Double-blind Study

OBJECTIVES

Postoperative cognitive dysfunction (POCD) is multifactorial, which may be caused by anesthetic and surgical causes or cerebral injury. This study aimed to evaluate the effect of dexmedetomidine as a neuroprotective drug compared to esmolol on the prevalence of POCD in adult patients undergoing middle ear surgeries under hypotensive anesthesia.

METHODS

This study included male and female adult patients, according to American Society of Anesthesiology physical status (ASA) I, the patients who underwent middle ear surgeries under hypotensive anesthesia were randomly assigned to two groups that received esmolol and dexmedetomidine. The demographic data, heart rate, mean arterial blood pressure, duration of the surgery, evaluation of the surgical field, and the Mini-Mental State Examination (MMSE) (preoperatively and at 1, 6 and 24 hours postoperatively) were recorded.

RESULTS

There was a significant difference between the numbers of patients who had POCD in MMSE1: 12 cases in the esmolol group (41.37%) compared to three cases in the dexmedetomidine group (10.34%) (P = 0.016), in MMSE6: 10 cases in the esmolol group (34.48%) compared with two cases in the dexmedetomidine group (6.89%) (P = 0.023) and in MMSE24: seven cases in the esmolol group (24.13%) compared with one case in the dexmedetomidine group (3.44%) (P = 0.022), while the median and range of MMSE score were comparable between the two groups (P > 0.05).

CONCLUSIONS

This study suggests that intraoperative use of dexmedetomidine as an adjuvant to hypotensive anesthesia reduces the incidence of POCD compared to esmolol.

The Role of Adrenoceptors in the Retina

The retina is a part of the central nervous system, a thin multilayer with neuronal lamination, responsible for detecting, preprocessing, and sending visual information to the brain. Many retinal diseases are characterized by hemodynamic perturbations and neurodegeneration leading to vision loss and reduced quality of life. Since catecholamines and respective bindings sites have been characterized in the retina, we systematically reviewed the literature with regard to retinal expression, distribution and function of alpha₁ (α₁)-, alpha₂ (α₂)-, and beta (β)-adrenoceptors (ARs). Moreover, we discuss the role of the individual adrenoceptors as targets for the treatment of retinal diseases.

Efficacy of caudal vs intravenous administration of α2 adrenoceptor agonists to prolong analgesia in pediatric caudal block: A systematic review and meta-analysis

BACKGROUND

α₂ adrenoceptor agonists have been proposed as adjuncts to prolong analgesia in pediatric caudal block. The aim of this meta-analysis was to compare the analgesic efficacy of caudal vs intravenous α₂ adrenoceptor agonists during pediatric caudal block.

METHODS

A systematic search, data extraction, bias risk assessment, and pooled data analysis were performed following the PRISMA guidelines. All randomized controlled trials comparing caudal with intravenous α₂ adrenoceptor agonists in pediatric caudal block were included. Relative risk and weighted mean differences (the corresponding 95% confidence intervals) were calculated for dichotomous and continuous data, respectively. Trial sequential analyses were performed to evaluate the credibility of the meta-analysis.

RESULTS

A total of 244 patients in five trials were identified. Compared with the intravenous group (9.56 ± 4.23 hours), the time to the first rescue analgesia was prolonged in the caudal α₂ adrenoceptor agonists group (12.72 ± 5.99 hours) by a weighted mean difference of 2.98 hours [95% confidence interval: 0.59-5.36 hours; P = .01]. The number of children requiring rescue analgesia in the caudal group (64, 66.67%) was lower than that in the intravenous group (80, 81.63%) [relative risk = 0.82; 95% confidence interval: 0.69-0.97; P = .02]. These findings were also verified by trial sequential analysis. There were no significant differences in the side effects.

CONCLUSION

Caudal α₂ adrenoceptor agonists as adjuncts to local anesthetic during pediatric caudal block are more effective than intravenous injection. However, the results were affected by small sample size and significant heterogeneity.

Mechanisms of ammonium-induced neurotoxicity. Neuroprotective effect of alpha-2 adrenergic agonists

Here we report the effects of ammonium on the main biophysical features of neurons and astrocytes during the first minutes of exposure. We found that ammonium causes the depolarization of neurons, which leads to the generation of high-frequency action potentials (APs). The initial alkalization and subsequent acidification of the intracellular medium in neurons occur along with the generation of calcium oscillations. Moreover, although the kinetics of calcium response of neurons and astrocytes is different, the dynamics of changes in the intracellular pH (pH_i) is similar. The rate of superoxide production and mitochondrial membrane potential do not change in most neurons and astrocytes during ammonium exposure. At the same time, we observed an increased superoxide production and a decrease in the mitochondrial potential in some neurons in response to ammonium application. However, in both cases, the amplitude of the calcium response in these neurons is significantly higher compared to other neurons. Application of UK 14,304, an agonist of alpha-2 adrenergic receptors (A-2ARs), decreased the frequency of APs upon ammonium-induced high-frequency spike activity. Moreover, we also observed periods of hyperpolarization occurred in individual neurons. We suppose that this hyperpolarization contributes to the suppression of activity and can be mediated by astrocytic GABA release, which is stimulated upon activation of A-2ARs. Thus, our findings reveal a new possible mechanism of the protective action of alpha-2 adrenergic agonists against ammonium-induced hyperexcitation and demonstrate the correlation between intracellular calcium concentration, mitochondrial membrane potential, pH_i, the intensity of superoxide production in hippocampal cells under acute hyperammonemia.

Dexmedetomidine in the prevention of postoperative delirium in elderly patients following non-cardiac surgery: A systematic review and meta-analysis

The efficacy of dexmedetomidine in the prevention of postoperative delirium (POD) remains ambiguous, however, it has been used to reduce the incidence of delirium in elderly patients. Here, we conducted a meta-analysis study for assessing the effects of dexmedetomidine on POD among elderly patients following non-cardiac surgery. A systematic literature search was performed against the PubMed, EMBASE, Cochrane Library, and Web of Science databases, and all relevant literature published till November 30, 2019, were considered. Our analysis included 16 randomised controlled trials conducted with 4534 patients for exploring the effects of dexmedetomidine on POD in elderly patients following non-cardiac surgery. It was observed that the overall incidence of POD was significantly lower in the dexmedetomidine group than in the control group (risk ratio [RR] 0.51, 95% confidence interval [CI] 0.43-0.61, P < .01). Similar results were obtained from subgroup analysis upon comparison of the placebo (RR 0.52, 95% CI 0.41-0.66, P < .01, moderate quality of evidence), propofol-treated (RR 0.55, 95% CI 0.38-0.78, P < .01, low quality of evidence), and midazolam-treated (RR 0.38, 95% CI 0.20-0.71, P < .01, low quality of evidence) groups. Trial sequential analysis revealed that the cumulative z-value superseded the monitoring boundary and reached the required information size. However, patients who received dexmedetomidine had a higher incidence of bradycardia and hypotension. In conclusion, the meta-analysis revealed that dexmedetomidine appears to decrease the risk of POD in elderly patients following non-cardiac surgery. However, as some of the studies were heterogeneous and of low quality, high-quality trials are necessary for drawing more definitive conclusions.

Organ-Protective Effects and the Underlying Mechanism of Dexmedetomidine

Dexmedetomidine (DEX) is a highly selective α2 adrenergic receptor (α2AR) agonist currently used in clinical settings. Because DEX has dose-dependent advantages of sedation, analgesia, antianxiety, inhibition of sympathetic nervous system activity, cardiovascular stabilization, and significant reduction of postoperative delirium and agitation, but does not produce respiratory depression and agitation, it is widely used in clinical anesthesia and ICU departments. In recent years, much clinical study and basic research has confirmed that DEX has a protective effect on a variety of organs, including the nervous system, heart, lungs, kidneys, liver, and small intestine. It acts by reducing the inflammatory response in these organs, activating antiapoptotic signaling pathways which protect cells from damage. Therefore, based on wide clinical application and safety, DEX may become a promising clinical multiorgan protection drug in the future. In this article, we review the physiological effects related to organ protection in α2AR agonists along with the organ-protective effects and mechanisms of DEX to understand their combined application value.

Dexmedetomidine Preconditioning Protects Rats from Renal Ischemia-Reperfusion Injury Accompanied with Biphasic Changes of Nuclear Factor-Kappa B Signaling

Acute kidney injury (AKI) is one of the most common and troublesome perioperative complications. Dexmedetomidine (DEX) is a potent α2-adrenoceptor (α2-AR) agonist with anti-inflammatory and renoprotective effects. In this study, a rat renal ischemia–reperfusion injury (IRI) model was induced. At 24 h after reperfusion, the IRI-induced damage and the renoprotection of DEX preconditioning were confirmed both biochemically and histologically. Changes in nuclear factor-kappa B (NF-κB), as well as its downstream anti-inflammatory factor A20 and proinflammatory factor tumor necrosis factor-α (TNF-α), were detected. Atipamezole, a nonselective antagonist, was then added 5 min before the administration of DEX to further analyze DEX's effects on NF-κB, and another anti-inflammatory medicine, methylprednisolone, was used in comparison with DEX, to further analyze DEX's effects on NF-κB. Different concentrations of DEX (0 nM, 0.1 nM, 1 nM, 10 nM, 100 nM, 1 μM, and 10 μM) were applied to preincubated human renal tubular epithelial cell line (HK-2) cells in vitro. After anoxia and reoxygenation, the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium assay and enzyme-linked immunosorbent assay (ELISA) were performed to evaluate the levels of NF-κB downstream anti-inflammatory cytokines. The results showed that, unlike methylprednisolone, DEX preconditioning led to a time-dependent biphasic change (first activation then inhibition) of NF-κB in the rat renal IRI models that were given 25 μg/kg i.p. It was accompanied by a similarly biphasic change of TNF-α and an early and persistent upregulation of A20. In vitro, DEX's cellular protection showed a concentration-dependent biphasic change which was protective within the range of 0 to 100 nM but became opposite when concentrations are greater than 1 μM. The changes in the A20 and NF-κB messenger RNA (mRNA) levels were consistent with the renoprotective ability of DEX. In other words, DEX preconditioning protected the rats from renal IRI via regulation biphasic change of NF-κB signaling.

Anesthesia and brain tumor surgery: technical considerations based on current research evidence

PURPOSE OF REVIEW

Anesthetics may influence cancer recurrence and metastasis following surgery by modulating the neuroendocrine stress response or by directly affecting cancer cell biology. This review summarizes the current evidence on whether commonly used anesthetics potentially affect postoperative outcomes following solid organ cancer surgery with particular focus on neurological malignancies.

RECENT FINDINGS

Despite significant improvement in diagnostic and therapeutic technology over the past decades, mortality rates after cancer surgery (including brain tumor resection) remains high. With regards to brain tumors, interaction between microglia/macrophages and tumor cells by multiple biological factors play an important role in tumor progression and metastasis. Preclinical studies have demonstrated an association between anesthetics and brain tumor cell biology, and a potential effect on tumor progression and metastasis has been revealed. However, in the clinical setting, the current evidence is inadequate to draw firm conclusions on the optimal anesthetic technique for brain tumor surgery.

SUMMARY

Further work at both the basic science and clinical level is urgently needed to evaluate the association between perioperative factors, including anesthetics/technique, and postoperative brain tumor outcomes.

Pre-school attention deficit hyperactivity disorder: 12 weeks prospective study

INTRODUCTION

Extant literature lack studies on behavioural training or pharmacotherapy in Indian preschool children. With adverse long term outcomes, effective, safe and affordable early interventions for ADHD are a priority. Aim of this prospective study is to report on short term outcome of preschool ADHD with specific focus on safety and tolerability of medications.

METHODS

Children with ADHD aged 2.5-6 years were assessed for severity and adverse events at baseline and follow-up using Conner's abbreviated rating scale and Clinical Global Impression-Severity scale. Children with Autism spectrum disorder and those with social quotient less than 50 were excluded. Statistical Analysis included descriptive statistics and Repeated measures ANOVA.

RESULTS

Of 56 children recruited, 33.93 %(N = 19) were on behavioural interventions alone, 66.07 %(N = 37) were on a combination of medication and behavioural intervention. All children received treatment according to standard care. The most prescribed drug was clonidine (44.64%), then risperidone (28.7%), methylphenidate (10.7%) and atomoxetine (10.7%). Medication choice was determined by affordability, availability and comorbidity profile. Sedation occurred in 24 % of children on clonidine. Atomoxetine was not well tolerated in 2 children. Methylphenidate was well tolerated. Irrespective of medication choice, all children showed significant improvement at 12 weeks (p < 0.001).

CONCLUSIONS

Choice of interventions is largely determined by availability and affordability. There is a need for structured parent behavioural training program deliverable in low resource setting. Anti-ADHD medications should be made available under the NMHP, RBSK program and all government settings in India, to address over-prescription of antipsychotics in preschool ADHD.

Anesthesiology and cognitive impairment: a narrative review of current clinical literature

Background

The impact of general anesthesia on cognitive impairment is controversial and complex. A large body of evidence supports the association between exposure to surgery under general anesthesia and development of delayed neurocognitive recovery in a subset of patients. Existing literature continues to debate whether these short-term effects on cognition can be attributed to anesthetic agents themselves, or whether other variables are causative of the observed changes in cognition. Furthermore, there is conflicting data on the relationship between anesthesia exposure and the development of long-term neurocognitive disorders, or development of incident dementia in the patient population with normal preoperative cognitive function. Patients with pre-existing cognitive impairment present a unique set of anesthetic considerations, including potential medication interactions, challenges with cooperation during assessment and non-general anesthesia techniques, and the possibility that pre-existing cognitive impairment may impart a susceptibility to further cognitive dysfunction.

Main body

This review highlights landmark and recent studies in the field, and explores potential mechanisms involved in perioperative cognitive disorders (also known as postoperative cognitive dysfunction, POCD). Specifically, we will review clinical and preclinical evidence which implicates alterations to tau protein, inflammation, calcium dysregulation, and mitochondrial dysfunction. As our population ages and the prevalence of Alzheimer’s disease and other forms of dementia continues to increase, we require a greater understanding of potential modifiable factors that impact perioperative cognitive impairment.

Conclusions

Future research should aim to further characterize the associated risk factors and determine whether certain anesthetic approaches or other interventions may lower the potential risk which may be conferred by anesthesia and/or surgery in susceptible individuals.

Dexmedetomidine protects hippocampal neurons against hypoxia/reoxygenation-induced apoptosis through activation HIF-1α/p53 signaling

PURPOSE

To observe the effect of dexmedetomidine (DEX) on mitochondrial apoptosis of hippocampal neurons in hypoxia/reoxygenation (H/R) brain injury in developing rats, and to investigate its regulatory mechanism on HIF-1α/p53 signaling pathway.

METHODS

Hypoxia/reoxygenation model was used in this study. TUNEL assay was performed to detect cell apoptosis. Immunohistochemical analysis and Western-blotting analysis were conducted to detect Cytochrome-C (Cyt-c), APAF-1, Caspase-3, Neuroglobin (Ngb), HIF-1α and p53 expression. After 28 days, Morris water maze (MWM) was performed.

RESULTS

50 μg/kg DEX improved H/R-induced brain injury and inhibited mitochondrial apoptosis in rats. Western-blotting and Immunohistochemical results demonstrated that DEX could up-regulate Ngb through α₂ receptor to inhibit H/R-induced mitochondrial apoptosis. In addition, by adding inhibitors yohimbine and 2-methoxyestradiol (2ME2), we found that DEX could activate HIF-1α/p53 signaling pathway. MWM test showed that DEX could enhance long-term learning and memory of H/R brain injury rats.

CONCLUSION

DEX alleviates H/R-induced brain injury and mitochondrial apoptosis in developing rats through α₂ receptor, which may be related to activation of HIF-1α/p53 signaling pathway to up-regulate the expression of Ngb.

Anaesthetic management and complications during hypophysectomy in 37 cats with acromegaly

OBJECTIVES

The aim of this study was to describe the anaesthetic management and perianaesthetic complications encountered during hypophysectomy surgery in acromegalic cats. We explored relationships between animal demographic data, the anaesthetic protocol used and presence of perioperative complications.

METHODS

Cats having undergone hypophysectomy surgery for the treatment of feline acromegaly at a single veterinary referral hospital were identified from hospital records. The anaesthesia records and clinical notes of these animals were retrospectively reviewed. Descriptive statistics were produced and binary logistic regression run to assess for any relationship between patient factors, anaesthetic management and complications during the perioperative period.

RESULTS

Perianaesthetic complications identified included hypothermia, hypotension, bradycardia and airway obstruction. Mortality at 24 h post-anaesthesia was 8%. The use of alpha (α)2 agonists was associated with a lower incidence of hypotension. Fentanyl infusion was associated with a higher incidence of airway obstruction compared with remifentanil. Subjectively assessed anaesthetic recovery quality had an association with the number of days spent in the intensive care ward postoperatively.

CONCLUSIONS AND RELEVANCE

The anaesthetic management described seems effective for hypophysectomy surgery in cats. Intraoperative complications were common and, while not apparently associated with 24 h patient outcome, drugs and equipment to manage these complications should be available.

Dexmedetomidine Use in a Tertiary Care NICU: A Descriptive Study

BACKGROUND

Continuous infusions of dexmedetomidine are increasingly used for sedation in critically ill pediatric patients. Emerging data suggest potential benefits when used for sedation in neonates, including reduced sedative requirements and earlier enteral feeds.

OBJECTIVE

To describe the use, adverse effects, and signs of withdrawal in a cohort of neonates receiving dexmedetomidine, the majority of whom were receiving concomitant opioids.

METHODS

This was a retrospective, descriptive review of 38 neonates receiving dexmedetomidine in a medical surgical neonatal intensive care unit, including data on duration of use, dose, adverse effects, weaning, and signs of withdrawal.

RESULTS

Dexmedetomidine was used for a median of 183 hours, at a median maximum dose of 0.5 µg/kg/h. Premature infants were started on dexmedetomidine at a later chronological age than term infants (41 vs 9 days, P = 0.004). Of 18 patients receiving an opioid infusion at the time of dexmedetomidine initiation, 67% had a dose reduction in opioids by 24 hours. The majority (89%) of neonates had at least 1 potentially related adverse effect during the dexmedetomidine infusion, though no discontinuations were needed as a result. In all, 80% of patients had their dexmedetomidine gradually weaned off, and 71% had at least 1 sign of withdrawal.

CONCLUSIONS AND RELEVANCE

In this cohort, dexmedetomidine was often used in a postsurgical setting, with concomitant opioids, over prolonged periods. These factors appear to affect and likely confound the rates of adverse effects and withdrawal signs from dexmedetomidine. Clinicians considering the use of dexmedetomidine in a similar population can draw guidance from our data.

Reduction of Analgesia Duration after Tracheostomy during Neonatal Intensive Care: A Quality Initiative

Introduction

As survival has improved in the Neonatal Intensive Care Unit (NICU), there has been a 10-fold increase in the proportion of infants requiring a tracheostomy. At our institution, we observed a wide variation in the duration of opioid use posttracheostomy from 6 to 148 days. We aimed to decrease the duration of opioid exposure in postoperative tracheostomy patients in the NICU from a baseline average of 24 days to 7 days by December 31, 2017.

Methods

We established a multidisciplinary team to develop change ideas to implement in 3 Plan-Do-Study-Act cycles that focused on enhanced care plan standardization and communication in patient care rounds with subsequent documentation in the medical record and the timely addition of dexmedetomidine to the postoperative care plan.

Results

Baseline population was from October 2014 to December 2016. The mean posttracheostomy opioid duration was 24.6 days (range, 6-148 days); neuromuscular blockade was 2.89 days (range, 0-9 days), and benzodiazepine exposure was 20.9 days (range, 1-114 days). Following our interventions, the mean duration of posttracheostomy opioid duration was 5.4 days (range, 4-21 days); neuromuscular blockade was 3.14 days (range, 1-5 days), benzodiazepine duration was 8.88 days (range, 4-25 days), and dexmedetomidine was 4.6 days (range, 0-32 days).

Conclusions

We utilized quality improvement methodology to standardize posttracheostomy management and demonstrate that we could significantly reduce the duration of opioid and benzodiazepine use after tracheostomy with the timely addition of dexmedetomidine, a structured written daily care plan, and clarification of roles and responsibilities.

Effect of Clonidine on Hemodynamic Responses During Laparoscopic Cholecystectomy: A Systematic Review and Meta-Analysis

BACKGROUND

Clonidine might be beneficial to the patients undergoing laparoscopic cholecystectomy. This meta-analysis focused on the influence of clonidine on hemodynamic responses in patients undergoing laparoscopic cholecystectomy.

METHODS

We searched several databases including PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases. This meta-analysis included randomized controlled trials regarding the influence of clonidine versus placebo on laparoscopic cholecystectomy. The primary outcomes were mean arterial pressure (MAP) and heart rate (HR) at pneumoperitoneum. The random-effect model was applied for this study.

RESULTS

Compared with control intervention, clonidine intervention was found to significantly reduce the MAP at pneumoperitoneum [standard mean difference=-2.58; 95% confidence interval (CI),-4.63 to -0.53; P=0.01), HR at pneumoperitoneum (standard mean difference=-3.67; 95% CI, -6.57 to -0.76; P=0.01), MAP at intubation (standard mean difference=-2.40; 95% CI, -4.75 to -0.06; P=0.04), HR at intubation (standard mean difference=-3.39; 95% CI, -5.75 to -1.02; P=0.005), propofol requirement (standard mean difference=-2.25; 95% CI, -4.01 to -0.48; P=0.01), as well as postoperative nausea and vomiting (risk ratio, 0.35; 95% CI, 0.19-0.63; P=0.0005).

CONCLUSIONS

Compared with control intervention, clonidine intervention was found to significantly reduce MAP and HR at pneumoperitoneum and intubation, propofol requirement, as well as postoperative nausea and vomiting in patients undergoing laparoscopic cholecystectomy.

Differentially expressed genes in response to amitraz treatment suggests a proposed model of resistance to amitraz in R. decoloratus ticks

The widespread geographical distribution of Rhipicephalus decoloratus in southern Africa and its ability to transmit the pathogens causing redwater, gallsickness and spirochaetosis in cattle makes this hematophagous ectoparasite of economic importance. In South Africa, the most commonly used chemical acaricides to control tick populations are pyrethroids and amitraz. The current amitraz resistance mechanism described in R. microplus, from South Africa and Australia, involves mutations in the octopamine receptor, but it is unlikely that this will be the only contributing factor to mediate resistance. Therefore, in this study we aimed to gain insight into the more complex mechanism(s) underlying amitraz resistance in R. decoloratus using RNA-sequencing. Differentially expressed genes (DEGs) were identified when comparing amitraz susceptible and resistant ticks in the presence of amitraz while fed on bovine hosts. The most significant DEGs were further analysed using several annotation tools. The predicted annotations from these genes, as well as KEGG pathways potentially point towards a relationship between the α-adrenergic-like octopamine receptor and ionotropic glutamate receptors in establishing amitraz resistance. All genes with KEGG pathway annotations were further validated using RT-qPCR across all life stages of the tick. In susceptible ticks, the proposed model is that in the presence of amitraz, there is inhibition of Ca²⁺ entry into cells and subsequent membrane hyperpolarization which prevents the release of neurotransmitters. In resistant ticks, we hypothesize that this is overcome by ionotropic glutamate receptors (NMDA and AMPA) to enhance synaptic transmission and plasticity in the presence of neurosteroids. Activation of NMDA receptors initiates long term potentiation (LTP) which may allow the ticks to respond more rapidly and with less stimulus when exposed to amitraz in future. Overactivation of the NMDA receptor and excitotoxicity is attenuated by the estrone, NAD⁺ and ATP hydrolysing enzymes. This proposed pathway paves the way to future studies on understanding amitraz resistance and should be validated using in vivo activity assays (through the use of inhibitors or antagonists) in combination with metabolome analyses.

Hypothalamic ΔFosB prevents age-related metabolic decline and functions via SNS

The ventral hypothalamus (VHT) integrates several physiological cues to maintain glucose homeostasis and energy balance. Aging is associated with increased glucose intolerance but the underlying mechanisms responsible for age-related metabolic decline, including neuronal signaling in the VHT, remain elusive. We have shown that mice with VHT-targeted overexpression of ∆FosB, a splice variant of the AP1 transcription factor FosB, exhibit increased energy expenditure, leading to decreased adiposity. Here, we show that VHT-targeted overexpression of ∆FosB also improves glucose tolerance, increases insulin sensitivity in target organs and thereby suppresses insulin secretion. These effects are also observed by the overexpression of dominant negative JunD, demonstrating that they occur via AP1 antagonism within the VHT. Furthermore, the improved glucose tolerance and insulin sensitivity persisted in aged animals overexpressing ∆FosB in the VHT. These beneficial effects on glucose metabolism were abolished by peripheral sympathectomy and α-adrenergic, but not β-adrenergic, blockade. Taken together, our results show that antagonizing AP1 transcription activity in the VHT leads to a marked improvement in whole body glucose homeostasis via activation of the SNS, conferring protection against age-related impairment in glucose metabolism. These findings may open novel avenues for therapeutic intervention in diabetes and age-related glucose intolerance.

Postoperative benefits of dexmedetomidine combined with flurbiprofen axetil after thyroid surgery

The present study determined the effect of dexmedetomidine (Dex) combined with flurbiprofen axetil (FA) on analgesia, immune response, and preservation of cognitive function in patients subjected to general anesthesia. We recruited 100 patients with thyroid surgery and randomly divided them into four groups: Dex (D), FA (F), Dex combined with FA (DF), and saline control (C). The extubation and recovery times for Groups D and DF were significantly longer than for Groups F and C. After extubation, the heart rate and mean arterial pressure for Groups F, D, and DF were significantly lower than for Group C, and data for Group DF was significantly lower than for Group F. The visual analog scale and Riker sedation agitation scores were significantly lower in Group DF than for the other three groups. T- and B-lymphocytes were significantly higher in Group DF than in the other three groups. Compared with Groups F and C, the levels of TNF-α and IL-6 in Group DF were significantly reduced, while IL-2 markedly increased. The combined use of Dex and FA significantly improved pain after general anesthesia thyroid surgery, reduced restlessness and postoperative cognitive dysfunction, enhanced immune function, and promoted wound repair.

Neuroprotection and neurotoxicity in the developing brain: an update on the effects of dexmedetomidine and xenon

Growing and consistent preclinical evidence, combined with early clinical epidemiological observations, suggest potentially neurotoxic effects of commonly used anesthetic agents in the developing brain. This has prompted the FDA to issue a safety warning for all sedatives and anesthetics approved for use in children under three years of age. Recent studies have identified dexmedetomidine, the potent α2-adrenoceptor agonist, and xenon, the noble gas, as effective anesthetic adjuvants that are both less neurotoxic to the developing brain, and also possess neuroprotective properties in neonatal and other settings of acute ongoing neurologic injury. Dexmedetomidine and xenon are effective anesthetic adjuvants that appear to be less neurotoxic than other existing agents and have the potential to be neuroprotective in the neonatal and pediatric settings. Although results from recent clinical trials and case reports have indicated the neuroprotective potential of xenon and dexmedetomidine, additional randomized clinical trials corroborating these studies are necessary. By reviewing both the existing preclinical and clinical evidence on the neuroprotective effects of dexmedetomidine and xenon, we hope to provide insight into the potential clinical efficacy of these agents in the management of pediatric surgical patients.

Dexmedetomidine mitigates isoflurane-induced neurodegeneration in fetal rats during the second trimester of pregnancy

Dexmedetomidine has significant neuroprotective effects. However, whether its protective effects can reduce neurotoxicity caused by isoflurane in fetal brain during the second trimester of pregnancy remains unclear. In this study, timed-pregnancy rats at gestational day 14 spontaneously inhaled 1.5% isoflurane for 4 hours, and were intraperitoneally injected with dexmedetomidine at dosages of 5, 10, 20, and 20 μg/kg 15 minutes before inhalation and after inhalation for 2 hours. Our results demonstrate that 4 hours after inhaling isoflurane, 20 μg/kg dexmedetomidine visibly mitigated isoflurane-induced neuronal apoptosis, reversed downregulation of brain-derived neurotrophic factor expression, and lessened decreased spatial learning and memory ability in adulthood in the fetal rats. Altogether, these findings indicate that dexmedetomidine can reduce neurodegeneration induced by isoflurane in fetal rats during the second trimester of pregnancy. Further, brain-derived neurotrophic factor participates in this process.

Effect of dexmedetomidine on postoperative cognitive dysfunction in elderly patients after general anaesthesia: A meta-analysis

Objective

We undertook a meta-analysis to investigate the effect of dexmedetomidine on postoperative cognitive dysfunction (POCD).

Methods

We searched PubMed, EMBASE, the Cochrane Library, CNKI and Google Scholar to find randomized controlled trials (RCTs) of the influence of dexmedetomidine on POCD in elderly adults who had undergone general anaesthesia. Two researchers independently screened the literature, extracted data, and evaluated methodologic quality against inclusion and exclusion criteria. We used RevMan 5.2 to undertake our meta-analysis.

Results

Thirteen RCTs were included. Compared with controls, dexmedetomidine: 1) significantly reduced the incidence of POCD (relative risk = 0.59, 95% confidence interval [CI] 0.45–2.95) and improved Mini-Mental State Examination (MMSE) score (mean difference, MD = 1.74, 95% CI 0.43–3.05) on the first postoperative day; and 2) reduced the incidence of POCD after the first postoperative day (MD = 2.73, 95% CI 1.33–4.12).

Conclusion

Dexmedetomidine reduces the incidence of POCD and improves postoperative MMSE score.

Effect of dexmedetomidine priming on convulsion reaction induced by lidocaine

To study the effect of dexmedetomidine priming on convulsion reaction induced by lidocaine.The New Zealand white rabbits were applied for the mechanism study of dexmedetomidine priming for preventing convulsion reaction induced by lidocaine. The influence of dexmedetomidine priming with different doses on the time for convulsion occurrence and the duration time of convulsion induced by lidocaine, as well as contents of excitatory amino acids (aspartate [Asp], glutamate [Glu]) and inhibitory amino acids (glycine [Gly], γ-aminobutyric acid [GABA]) in the brain tissue were investigated.With 3 and 5 μg/kg dexmedetomidine priming, the occurrence times of convulsion were prolonged from 196 seconds to 349 and 414 seconds, respectively. With dexmedetomidine priming, the contents of excitatory amino acids (Asp, Glu) were much reduced at occurrence time of convulsion comparing with that without dexmedetomidine priming, while content of inhibitory amino acids Gly was much enhanced.The application of dexmedetomidine before local anesthetics can improve intoxication dose threshold of the lidocaine, delay occurrence of the convulsion, and helped for the recovery of convulsion induced by lidocaine. The positive effect of dexmedetomidine on preventing convulsion would owe to not only the inhibition of excitatory amino acids (Asp, Glu), but also the promotion of inhibitory amino acids Gly secretion.

Enhanced sympathetic nerve activity induced by neonatal colon inflammation induces gastric hypersensitivity and anxiety-like behavior in adult rats

Gastric hypersensitivity (GHS) and anxiety are prevalent in functional dyspepsia patients; their underlying mechanisms remain unknown largely because of lack of availability of live visceral tissues from human subjects. Recently, we demonstrated in a preclinical model that rats subjected to neonatal colon inflammation show increased basal plasma norepinephrine (NE), which contributes to GHS through the upregulation of nerve growth factor (NGF) expression in the gastric fundus. We tested the hypothesis that neonatal colon inflammation increases anxiety-like behavior and sympathetic nervous system activity, which upregulates the expression of NGF to induce GHS in adult life. Chemical sympathectomy, but not adrenalectomy, suppressed the elevated NGF expression in the fundus muscularis externa and GHS. The measurement of heart rate variability showed a significant increase in the low frequency-to-high frequency ratio in GHS vs. the control rats. Stimulus-evoked release of NE from the fundus muscularis externa strips was significantly greater in GHS than in the control rats. Tyrosine hydroxylase expression was increased in the celiac ganglia of the GHS vs. the control rats. We found an increase in trait but not stress-induced anxiety-like behavior in GHS rats in an elevated plus maze. We concluded that neonatal programming triggered by colon inflammation upregulates tyrosine hydroxylase in the celiac ganglia, which upregulates the release of NE in the gastric fundus muscularis externa. The increase of NE release from the sympathetic nerve terminals concentration dependently upregulates NGF, which proportionately increases the visceromotor response to gastric distention. Neonatal programming concurrently increases anxiety-like behavior in GHS rats.

Roles of catecholamine related polymorphisms in hypertension

The objective of this review is to summarize current data obtained so far in catecholamine-essential hypertension (EH) relationships on a genetic basis. As the major elements driving the sympathetic system’s actions, catecholamines modulate a variety of physiological processes and mutations related to the system. This could generate serious disorders, such as severe mental illnesses, stress-induced disorders, or impaired control of blood pressure or motor pathways. EH is idiopathic, and the genetic basis of its causes and substantial interindividual discrepancies in response to different types of treatments are the focus of interest. Susceptibility to disease or efficacy of treatments are thought to reflect genomic variabilities among individuals. Therefore, outlining the available knowledge in functional genetic polymorphisms linked to EH will make the picture clearer and will help to establish future prospects in the field.

Noradrenergic signaling in the medial prefrontal cortex and amygdala differentially regulates vicarious trial-and-error in a spatial decision-making task

In uncertain choice situations, we deliberately search and evaluate possible options before taking an action. Once we form a preference regarding the current situation, we take an action more automatically and with less deliberation. In rats, the deliberation process can be seen in vicarious trial-and-error behavior (VTE), which is a head-orienting behavior toward options at a choice point. Recent neurophysiological findings suggest that VTE reflects the rat's thinking about future options as deliberation, expectation, and planning when rats feel conflict. VTE occurs depending on the demand: an increase occurs during initial learning, and a decrease occurs with progression in learning. However, the brain circuit underlying the regulation of VTE has not been thoroughly examined. In situations in which VTE often appears, the medial prefrontal cortex (mPFC) and the amygdala (AMY) are crucial for learning and decision making. Our previous study reported that noradrenaline regulates VTE. Here, to investigate whether the mPFC and AMY are involved in regulation of VTE, we examined the effects of local injection of clonidine, an alpha2 adrenergic autoreceptor agonist, into either region in rats during VTE and choice behavior during a T-maze choice task. Injection of clonidine into either region impaired selection of the advantageous choice in the task. Furthermore, clonidine injection into the mPFC suppressed occurrence of VTE in the early phase of the task, whereas injection into the AMY inhibited the decrease in VTE in the later phase and thus maintained a high level of VTE throughout the task. These results suggest that the mPFC and AMY play a role in the increase and decrease in VTE, respectively, and that noradrenergic mechanisms mediate the dynamic regulation of VTE over experiences.

Comparison of caudal bupivacaine alone with bupivacaine plus two doses of dexmedetomidine for postoperative analgesia in pediatric patients undergoing infra-umbilical surgery: a randomized controlled double-blinded study

BACKGROUND

Data are still insufficient about the effects of different concentrations of caudal dexmedetomidine when used to prolong postoperative analgesia in children. The aim of this study was to assess the analgesic efficacy and side effects of two doses of caudal dexmedetomidine (1 and 2 μg·kg(-1)) co-administered with bupivacaine in terms of postoperative pain scores and requirement of postoperative analgesia over 24 h in children undergoing infra-umbilical surgery.

METHODS

Ninety-one children, aged 1-6 years, undergoing infra-umbilical surgery were included and randomly allocated into three groups of caudal block. Group B received 0.25% bupivacaine 2 mg·kg(-1) (0.8 ml·kg(-1)). Groups BD1 and BD2 received dexmedetomidine 1 and 2 μg·kg(-1), respectively along with bupivacaine 2 mg·kg(-1) in a total volume of 0.8 ml·kg(-1). Anesthesia was induced and maintained with sevoflurane in 100% oxygen. Hemodynamic and other routine intraoperative monitoring was carried out in addition to endtidal sevoflurane concentration. Time to spontaneous eye opening and postoperative pain and sedation scores were recorded in addition to time to first analgesia, paracetamol analgesic requirements, and any side effects during the first 24 postoperative hours.

RESULTS

Time to first analgesia requirement was significantly longer in BD1 and BD2 groups compared to B group with mean values (95% CI) of 809 min (652-965), 880 (733-1026), and 396 (343-448), respectively, P < 0.001. Postoperative paracetamol analgesic requirements over 24 h were higher in group B compared to BD1 and BD2 groups (Mean (95% CI): 3.2 (2.9-3.5) doses, 1.9 (1.5-2.3), and 1.6 (1.3-1.9), respectively), P < 0.001. The dexmedetomidine groups had significantly higher postoperative sedation scores compared to plain bupivacaine group that were dose dependent and for longer time in BD2 group. Two patients in BD2 group developed bradycardia and hypotension, and one developed urine retention compared to none in other groups.

CONCLUSION

A 1 μg·kg(-1) dose of caudal dexmedetomidine achieved comparable prolongation of postoperative analgesia to 2 μg·kg(-1) dose, with shorter duration of postoperative sedation and lower incidence of other side effects.

α2-Adrenergic modulation of the glutamate receptor and transporter function in a chronic ocular hypertension model

Excitotoxicity, glutamate-induced toxic effects to retinal ganglion cells (RGCs), is one of several mechanisms of RGC loss suggested in glaucoma. In this study, we focused on the role of glutamate transporter of glial cells as well as N-methyl-d-aspartate (NMDA) receptor with regard to glutamate toxicity in glaucoma. We also investigated whether α2-adrenoceptor activation could modulate glutamate transporters and NMDA receptors in a chronic ocular hypertension model. Brimonidine 0.15% was administered topically to the eyes of experimental glaucoma and control animals twice daily. After 8 weeks of intraocular pressure (IOP) elevation, staining with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) revealed an increase in the ganglion cell layer, and the number of TUNEL-positive cells was reduced by brimonidine treatment (P<0.05). Animals with experimentally induced glaucoma exhibited an increase in retinal stress marker glial fibrillary acidic protein (GFAP) immunoreactivity; brimonidine treatment reduced GFAP. Excitatory amino acid transporter 1(EAAT1) expression remained stable throughout the period of chronic ocular hypertension. α2-Adrenergic treatment upregulated EAAT1 protein levels (P<0.05). NMDA receptor (GluN1) expression was stimulated by chronic elevation of IOP, and GluN1-positive cells in ganglion cell layer were co-localized with TUNEL staining. Brimonidine administration suppressed GluN1 levels (P<0.05). These results indicate that brimonidine decreased RGC apoptosis, upregulating EAAT1 and downregulating NMDA receptors. We suggest that topical brimonidine treatment may decrease the glutamate excitotoxicity through modulation of glutamate transporter and NMDA receptor in glaucoma.