Comparison of the anesthetic effect by the injection route of mixed anesthesia (medetomidine, midazolam and butorphanol) and the effect of this anesthetic agent on the respiratory function

Validation of the anesthetic effect of a mixture of remimazolam, medetomidine, and butorphanol in three mouse strains

Proper administration of anesthesia is indispensable for the ethical treatment of lab animals in biomedical research. Therefore, selecting an effective anesthesia protocol is pivotal for the design and success of experiments. Hence, continuous development and refinement of anesthetic agents are imperative to improve research outcomes and elevate animal welfare. "Balanced anesthesia" involves using multiple drugs to optimize efficacy while minimizing side effects. The medetomidine, midazolam, and butorphanol, called MMB, and medetomidine, alfaxalone, and butorphanol, called MAB, are popular in Japan. However, the drawbacks of midazolam, including its extended recovery time, and the narrow safety margin of MAB, have prompted research for suitable alternatives. This study replaced midazolam in the MMB combination with remimazolam (RMZ), which is noted for its ultra-short half-life. The resulting combination, called MRB, was effective in providing a wider safety margin compared to MAB while maintaining an anesthesia depth equivalent level to that of MMB in mice. Notably, MRB consistently exhibited better recovery scores after antagonist administration in contrast to MMB. Furthermore, the re-sedation phenomenon observed with MMB was not observed with MRB. The rapid metabolism of RMZ enables reliable anesthesia induction, circumventing the complications linked to MAB. Overall, MRB excelled in providing extended surgical anesthesia and swift post-antagonist recovery. These results highlight the potential of RMZ for broader animal research applications.

Cationic-nanogel nasal vaccine containing the ectodomain of RSV-small hydrophobic protein induces protective immunity in rodents

Respiratory syncytial virus (RSV) is a leading cause of upper and lower respiratory tract infection, especially in children and the elderly. Various vaccines containing the major transmembrane surface proteins of RSV (proteins F and G) have been tested; however, they have either afforded inadequate protection or are associated with the risk of vaccine-enhanced disease (VED). Recently, F protein-based maternal immunization and vaccines for elderly patients have shown promising results in phase III clinical trials, however, these vaccines have been administered by injection. Here, we examined the potential of using the ectodomain of small hydrophobic protein (SHe), also an RSV transmembrane surface protein, as a nasal vaccine antigen. A vaccine was formulated using our previously developed cationic cholesteryl-group-bearing pullulan nanogel as the delivery system, and SHe was linked in triplicate to pneumococcal surface protein A as a carrier protein. Nasal immunization of mice and cotton rats induced both SHe-specific serum IgG and mucosal IgA antibodies, preventing viral invasion in both the upper and lower respiratory tracts without inducing VED. Moreover, nasal immunization induced greater protective immunity against RSV in the upper respiratory tract than did systemic immunization, suggesting a critical role for mucosal RSV-specific IgA responses in viral elimination at the airway epithelium. Thus, our nasal vaccine induced effective protection against RSV infection in the airway mucosa and is therefore a promising vaccine candidate for further development.

Influence of toll-like receptor-4 antagonist on bacterial load of asthma in Swiss albino mice: targeting TLR4/MD2 complex pathway

Air pollution and environmental issues significantly impact life, resulting in the emergence and exacerbation of allergic asthma and other chronic respiratory infections. The main objective of this study is to suppress allergic asthma by TAK-242 from lipopolysaccharide-induced airway inflammation primarily stimulating toll-like receptor-4, and also to determine the potential mechanism of asthma eradication. The TAK-242 anti-allergic action was assured through the ovalbumin murine model of asthma via bronchial hyperresponsiveness and inflammation of the respiration tract in a pre-existing allergic inflammation paradigm. Swiss albino mice were sensitized and then challenged by ovalbumin and lipopolysaccharide for 5 days straight. TAK-242 reaction was assessed by inflammatory cytokines, and inflammatory cell count was determined from blood serum and bronchoalveolar lavage fluid, as well as group-wise regular weight assessments. After ovalbumin, lipopolysaccharide infusion, toll-like receptor-4 agonists caused a substantial increase in airway hyperresponsiveness, specific cellular inflammation, histological alterations, and immune mediator synthesis, as well as dose-related body-weight variations. A decrease in lipopolysaccharide-induced leukocyte count and Th1/Th17 related cytokines, TNF-α, and IL-6 expression through the ELISA study was particularly noticeable. Finally in treated groups, TAK-242, a TLR4/MD2 complex inhibitor, reduced airway inflammation and histopathological changes, cytokine expression, and body-weight management. TAK-242 has been found in an ovalbumin allergic asthma model to be a potential inhibitor of lipopolysaccharide-induced respiratory infection.

Effect of TLR3/dsRNA complex inhibitor on Poly(I:C)-induced airway inflammation in Swiss albino mice

Rhinovirus infection frequently causes COPD and asthma exacerbations. Impaired anti-viral signaling and reduced viral clearance have both been seen in sick bronchial epithelium, potentially increasing exacerbations. Polyinosinic:polycytidylic acid (Poly(I:C)), a Toll-like receptor-3 (TLR3) ligand, has been shown to cause a viral exacerbation of severe asthma by detecting double-stranded RNA (dsRNA). The purpose of this work was to determine the effect of a TLR3/dsRNA complex inhibitor-Calbiochem drug in the prevention of Poly(I:C)-induced airway inflammation following TLR3 activation and to uncover a potential pathway for the cure of asthma through TLR3 inhibition. Mice were sensitized with Poly(I:C) as an asthma model before being challenged by PBS and ovalbumin (OVA) chemicals. The mice were administered a TLR3/dsRNA complex inhibitor. Throughout the trial, the mice's body weight was measured after each dosage. Biochemical methods are used to analyze the protein as well as enzyme composition in airway tissues. BALF specimens are stained using Giemsa to identify inflammatory cells and lung histopathology to determine morphological abnormalities in lung tissues. By using the ELISA approach, cytokine levels such as TNF-α, IL-13, IL-6, IL-5, and IgE antibody expression in lung tissue and blood serum were assessed. TLR3/dsRNA complex inhibitor drug significantly lowered the number of cells in BALF and also on Giemsa staining slides. It also downregulated the level of TNF-α and IL-6 in contrast to OVA and Poly(I:C) administered in animals. A TLR3/dsRNA complex inhibitor decreased the fraction of oxidative stress markers (MDA, GSH, GPx, and CAT) in lung tissues while keeping the mice's body weight constant during the treatment period. By decreasing alveoli, bronchial narrowing, smooth muscle hypertrophy, and granulocyte levels, the TLR3/dsRNA complex blocker significantly reduced the histopathological damage caused by OVA and Poly(I:C) compounds. In an animal model utilizing ovalbumin, TLR3/dsRNA complex inhibitors similarly reduced the bronchial damage produced by Poly(I:C). A novel TLR3/dsRNA complex inhibitor is expected to be employed in clinical studies since it suppresses airway inflammation without inducing antiviral approach resistance.

Novel protocol to establish the myocardial infarction model in rats using a combination of medetomidine-midazolam-butorphanol (MMB) and atipamezole

Background

Myocardial infarction (MI) is one of the most common cardiac problems causing deaths in humans. Previously validated anesthetic agents used in MI model establishment are currently controversial with severe restrictions because of ethical concerns. The combination between medetomidine, midazolam, and butorphanol (MMB) is commonly used in different animal models. The possibility of MMB combination to establish the MI model in rats did not study yet which is difficult because of severe respiratory depression and delayed recovery post-surgery, resulting in significant deaths. Atipamezole is used to counter the cardiopulmonary suppressive effect of MMB.

Objectives

The aim of the present study is to establish MI model in rats using a novel anesthetic combination between MMB and Atipamezole.

Materials and methods

Twenty-five Sprague Dawley (SD) rats were included. Rats were prepared for induction of the Myocardial infarction (MI) model through thoracotomy. Anesthesia was initially induced with a mixture of MMB (0.3/5.0/5.0 mg/kg/SC), respectively. After endotracheal intubation, rats were maintained with isoflurane 1% which gradually reduced after chest closing. MI was induced through the left anterior descending (LAD) artery ligation technique. Atipamezole was administered after finishing all surgical procedures at a dose rate of 1.0 mg/kg/SC. Cardiac function parameters were evaluated using ECG (before and after atipamezole administration) and transthoracic echocardiography (before and 1 month after MI induction) to confirm the successful model. The induction time, operation time, and recovery time were calculated. The success rate of the MI model was also calculated.

Results

MI was successfully established with the mentioned anesthetic protocol through the LAD ligation technique and confirmed through changes in ECG and echocardiographic parameters after MI. ECG data was improved after atipamezole administration through a significant increase in heart rate (HR), PR Interval, QRS Interval, and QT correction (QTc) and a significant reduction in RR Interval. Atipamezole enables rats to recover voluntary respiratory movement (VRM), wakefulness, movement, and posture within a very short time after administration. Echocardiographic ally, MI rats showed a significant decrease in the left ventricular wall thickness, EF, FS, and increased left ventricular diastolic and systolic internal diameter. In addition, induction time (3.440 ± 1.044), operation time (29.40 ± 3.663), partial recovery time (10.84 ± 3.313), and complete recovery time (12.36 ± 4.847) were relatively short. Moreover, the success rate of the anesthetic protocol was 100%, and all rats were maintained for 1 month after surgery with a survival rate of 88%.

Conclusion

Our protocol produced a more easy anesthetic effect and time-saving procedures with a highly successful rate in MI rats. Subcutaneous injection of Atipamezole efficiently counters the cardiopulmonary side effect of MMB which is necessary for rapid recovery and subsequently enhancing the survival rate during the creation of the MI model in rats.

Understanding the Effects of Anesthesia on Cortical Electrophysiological Recordings: A Scoping Review

General anesthesia in animal experiments is an ethical must and is required for all the procedures that are likely to cause more than slight or momentary pain. As anesthetics are known to deeply affect experimental findings, including electrophysiological recordings of brain activity, understanding their mechanism of action is of paramount importance. It is widely recognized that the depth and type of anesthesia introduce significant bias in electrophysiological measurements by affecting the shape of both spontaneous and evoked signals, e.g., modifying their latency and relative amplitude. Therefore, for a given experimental protocol, it is relevant to identify the appropriate anesthetic, to minimize the impact on neuronal circuits and related signals under investigation. This review focuses on the effect of different anesthetics on cortical electrical recordings, examining their molecular mechanisms of action, their influence on neuronal microcircuits and, consequently, their impact on cortical measurements.