Doxapram Research Articles

003 Treatment of Sleep Disordered Breathing with Leptin Loaded Exosomes

Abstract Introduction Obstructive sleep apnea (OSA) is characterized by recurrent periods of upper airway obstruction. The prevalence of OSA exceeds 50% in obese individuals and in 10–20% of obese patients OSA coexists with obesity hypoventilation syndrome (OHS) defined as daytime hypercapnia and hypoventilation during sleep attributed to the depressed control of breathing. There is no effective pharmacotherapy for OSA and OHS. Leptin is a potent respiratory stimulant and a potential therapeutic candidate. However, diet-induced obesity (DIO) results in reduced permeability of the blood-brain barrier (BBB) for leptin. Previous studies have shown that the BBB can be penetrated by exosomes, natural nanoparticles that can be used as drug delivery vehicles. In this study, we aimed to determine if exosomes overcome the BBB and treat OSA and OHS in DIO mice. Methods o examine the ability of exosomes to cross the BBB, male, lean (n=5) and DIO (n=5) C57BL/6J mice were injected with fluorescent exosomes or saline into the lateral tail vein. After 4h fluorescent exosomes biodistribution was evaluated by an in vitro imaging system (IVIS). Saline injected mice images were used for background adjustment. A separate subgroup of male, DIO (n=10) and lean (n=10) mice were headmounted with EEG and nuchal EMG leads. Sleep studies were performed in a plethysmography chamber and mice received saline, empty exosomes, free leptin, or leptin-loaded exosomes in a crossover manner. Results Exosomes were successfully delivered to the brain and the transport across the BBB was more efficient in DIO mice with 2-times greater relative fluorescence units measured in DIO when compared to lean mice (p<0.005). In DIO mice, exosomal leptin induced dramatic 1.7-2.2-fold increases in minute ventilation and 1.5-2.0-fold increases in maximal inspiratory flow during both flow-limited (upper airway/sleep apnea) and non-flow limited breathing (control of breathing) (p<0.05). In contrast, free leptin had no effect. Lean mice did not present significant sleep disordered breathing and no differences were observed between groups. Conclusion We demonstrated that exosomes overcome the BBB and that leptin-loaded exosomes treat OSA and OHS in DIO mice. Support (if any) R01HL 128970, R01HL 138932, R61 HL156240, U18 DA052301, FAPESP 2018/08758-3

Intranasal Leptin Prevents Opioid‐induced Deaths in Mice

Introduction Respiratory depression is the primary cause of morbidity and mortality related to opioids. Previous studies showed that leptin acts as respiratory stimulant and improves ventilation and upper airway obstruction induced by opioids without reducing analgesia. Our objective was to examine if the intranasal (IN) route of administration effectively delivers leptin to the brain and if leptin prevents opioid-related deaths. We hypothesized that IN leptin would reduce opioid related mortality in adult mice. Methods To determine leptin delivery to the brain, male, 12 weeks old, C57BL/6J mice, were treated with IN leptin at 1.2 mg/kg in 1% BSA (n=5) or 1% BSA (n=5) and euthanized 20 min later. Brains were harvested, the olfactory bulbs, medullas and hypotalami were isolated and quick frozen. Brain tissue was homogenized, protease inhibitors, protein concentrations were determined and leptin levels were measured by ELISA. To determine the survival probability, male C57BL/6J mice, 12 weeks of age, received IN leptin (n=26) or vehicle (n=25) at 1.2 mg/kg and 30 minutes later received a bolus of intraperitoneal (IP) morphine at 400mg/kg. Mice were monitored for 24 hours and survival time after morphine injection was recorded. Results We observed a significant increase in leptin levels 20 min after IN leptin administration compared to IN vehicle: 7.53 ng/mL vs 0 ng/mL in the olfactory bulb (p = 0.004), 0.107 ng/mL vs 0.008 ng/mL in the medulla (p=0.01), and a trend in the hypothalamus (0.291 ng/mL vs 0.018 ng/mL, p = 0.1). IN leptin improved mortality induced by morphine, 23 out of 25 mice treated with vehicle died vs 18 out 26 mice treated with IN leptin (p = 0.044). The Kaplan-Meyer curve is shown below. Conclusion We demonstrated that the intranasal route effectively delivered leptin to the brain and that IN leptin decreased opioid-induced mortality in C57BL/6J mice. Our translational data suggests that IN leptin may prevent opioid-related deaths.

DREADD Activation of Leptin Receptor Positive Neurons in The Nucleus of the Solitary Tract During Obstructive Sleep Apnea in Obese Mice

Introduction Obstructive sleep apnea (OSA) is periodic obstruction of the upper airway during sleep leading to intermittent hypoxemia, hypercapnia, and sleep fragmentation. OSA is highly prevalent, particularly in obesity. It leads to high neurocognitive and cardiovascular morbidity and mortality. The mechanisms alleviating OSA remain unknown. Previous studies have documented the role of leptin, an adipose tissue produced hormone, as a potent respiratory stimulant. A long functional isoform of leptin receptor, LepRb, was detected widely in the brain, especially in cell bodies within the nucleus of the solitary tract (NTS), an important region of the brainstem that processes afferent visceral information and controls breathing. We hypothesized that leptin acts on LepRb+ neurons in the NTS to increase ventilation and maintain upper airway patency during sleep in obese mice. Methods We selectively expressed AAV8-hSyn-hM3(Gq)-mCherry into the NTS in LepRb-Cre-GFP diet-induced obese (DIO) mice (fed with a high-fat diet for 12 weeks) and examined the effect of DREADD ligand, J60, on genioglossus activity and breathing during sleep. Results J60 did not stimulate breathing or upper airway in comparison with saline in obese mice during NREM and REM sleep. Conclusion We conclude that the mechanisms alleviating OSA in DIO mice are independent of LepRb+ neurons in the NTS.

Randomised controlled trial of high-flow nasal cannula in preterm infants after extubation.

HFNC therapy is increasingly used as ‘non-invasive’ respiratory support for preterm infants. A 2016 Cochrane Review found that HFNC had similar efficacy to NCPAP for preterm infants following extubation,1 but that further studies were needed, particularly in extremely preterm infants born <28 weeks' gestation, who are at highest risk of extubation failure. The trial by Uchiyama et al is the largest randomised trial of HFNC as post-extubation support in preterm infants, and one of only a few to enrol extremely preterm infants (168 infants enrolled; 76 HFNC, 92 NCPAP/NIPPV). This multicentre non-inferiority trial found NCPAP/NIPPV was superior to HFNC (and HFNC did not satisfy non-inferiority criteria) for the primary outcome of treatment failure within 7 days. Reintubation rates were similar; more than 80% of infants who met HFNC treatment failure criteria avoided reintubation due to crossover to NCPAP/NIPPV. Like previous similar trials2-4 the intervention was not blinded, although objective treatment failure criteria were used. In the NCPAP/NIPPV group, 149 infants received NCPAP and 47 received NIPPV at extubation. In both groups, the escalation of respiratory support was at clinician discretion. As the control group could receive either NCPAP or NIPPV, the definition of ‘treatment failure’ is blurred: some infants received NIPPV before ‘treatment failure’ and others did not. It is not reported whether NIPPV inflations were synchronised with the infant's breathing or not, which may be important.5 A non-inferiority trial design is reasonable given the existing evidence, although the sample size calculation assumed a HFNC treatment failure rate 9% higher than that of NCPAP/NIPPV, and the chosen non-inferiority margin was rather large. There is an imbalance in the allocation of infants to HFNC (47%) and NCPAP/NIPPV (53%). A total of 378 infants were ultimately recruited to the study (38 more than required, even with inflation for anticipated dropouts); however this represents only 33% of eligible infants, which has implications for generalisability of the results. The use of respiratory stimulants prior to extubation is not reported. The trial was prospectively registered; however, there are inconsistencies between the registration and the published trial in the stated sample size, comparator and primary outcome. The starting HFNC gas flow was >2 L/min, lower than some previous studies,3, 4 and it is unclear whether infants received the maximal permitted gas flow of 8 L/min prior to treatment failure being determined. As increasing gas flow is associated with increased delivered pressure,6 this may have contributed to decreased efficacy in the HFNC group. Extubation failure in preterm infants is an important concern for neonatal clinicians, and the optimal mode of post-extubation respiratory support remains uncertain. The results of the trial by Uchiyama et al may tip the balance in favour of NCPAP/NIPPV as initial post-extubation support; however, consistent with previous evidence, reintubation rates are similar when HFNC is used with the ‘backup’ of NCPAP/NIPPV. For the most immature infants at highest risk of extubation failure, it seems prudent to avoid using HFNC as initial post-extubation support. The authors have no conflicts of interest to declare. https://ebneo.org/HFNC-after-extubation

History of Respiratory Stimulants.

The interest in substances that stimulate respiration has waxed and waned throughout the years, intensifying following the introduction of a new class of drugs that causes respiratory depression, and diminishing when antidotes or better drug alternatives are found. Examples include the opioids––deaths increasing during overprescribing, diminishing with wider availability of the opioid receptor antagonist naloxone, increasing again during COVID-19; the barbiturates––until largely supplanted by the benzodiazepines; propofol; and other central nervous system depressants. Unfortunately, two new troubling phenomena force a reconsideration of the status-quo: (1) overdoses due to highly potent opioids such as fentanyl, and even more-potent licit and illicit fentanyl analogs, and (2) overdose due to polysubstance use (the combination of an opioid plus one or more non-opioid drug, such as a benzodiazepine, sedating antidepressant, skeletal muscle relaxant, or various other agents). Since these now represent the majority of cases, new solutions are again needed. An interest in respiratory stimulants has been revived. This interest can be informed by a short review of the history of this interesting class of medications. We present a short history of the trajectory of advances toward more selective and safer respiratory stimulants.

Recent Advances on the s‐Triazine Scaffold with Emphasis on Synthesis, Structure‐Activity and Pharmacological Aspects: A Concise Review

AbstractTriazine nuclei have occupied a propitious place in pharmaceutical chemistry due to their diverse biological behaviour. The marketed drugs such as Azacitidine, Melarsoprol, Altretamine and Almitrine display broad pharmacological activities like anti‐cancer, anti‐parasitic, anti‐inflammatory, Respiratory stimulant and many more. Literature studies reveal that the 2, 4, and 6 substitution on s‐triazine is important for varied biological activities. This diversity in pharmacological activities of triazine scaffold has fascinated the various researchers to further investigate its applications in the treatment of several diseases. This review is complementary to earlier reports and aims to review the work reported on various synthetic methods and biological activities of substituted s‐triazine derivatives from 2016 to 2020 with a list of patents. The enriched structure‐activity relationship may open the doors for further rational drug development of s‐triazine containing analogues as good clinical candidates.

Detection And Quantification Of N-Ethyl-3-Chloro Pyrrolidine And Diphenyl Acetonitrile In Doxapram Hydrochloride Drug Substances Using Gas Chromatography Coupled With Mass Spectrometry Technique

Detection And Quantification Of N-Ethyl-3-Chloro Pyrrolidine And Diphenyl Acetonitrile In Doxapram Hydrochloride Drug Substances Using Gas Chromatography Coupled With Mass Spectrometry Technique

Commentary: “Ockham’s Razor” Doesn’t Apply to “Opioid” Overdose Death

Polysubstance Abuse (PSA) greatly complicates an attempt to implicate a single drug as sole cause of an overdose death. Since PSA now occurs in the majority of cases of drug overdoses, many or most overdose deaths are polysubstance overdose deaths. And since many of the substances involved in a polysubstance Overdose Death (POD) are Central Nervous System (CNS) depressants, many of which can cause overdose death themselves, or synergistically with opioids, it is somewhat puzzling that prescription opioids have been singled out as the cause of these deaths—without reference to PSA. This is particularly puzzling in light of the fact that the issues of PSA and POD have been recognized and discussed in the literature since at least the 1960’s and before. We therefore here consider the question: are we facing an “opioid” crisis or, instead, a “polysubstance crisis”? And we wonder if the issue has been over-simplified, to the detriment of the individuals affected, and to society more broadly. There is a need for an “agnostic” respiratory stimulant that can reverse polysubstance-induced respiratory depression.

The effects of doxapram on haematology, serum biochemical parameters and erythrocyte oxidant/ antioxidant status in dogs anaesthetized with propofol.

The present prospective randomized experimental study was designed to determine the effects of doxapram on haematological, serum biochemical and antioxidant status in dogs after propofol anaesthesia. Twenty‐four healthy male mixed breed dogs, aged 1–2 years, weighing 20.4 ± 2.6 kg was studied. Each dog was anaesthetized twice, with at least one week for washout. Animals were sedated with acepromazine (0.1 mg/kg) intramuscularly. Forty minutes later, anaesthesia was induced using intravenous (IV) propofol (4 mg/kg) titration and maintained for 30 min by propofol (0.2 mg kg−1 min−1). After propofol was discontinued, doxapram (2 mg/kg) hydrochloride was administrated IV in PD treatment while an equal volume of saline was administrated in PS treatment. Blood parameters were analysed in four times: immediately before sedation (T1), after treatment (T2), after complete recovery (T3) and 24 hr later (T4). Haematological assessments revealed no significant difference between treatments except in haematocrit which was significantly reduced at T4 (24 hr later) in PD. A decreasing trend of all haematological variables was observed after doxapram administration until recovery, except monocyte, mean corpuscular haemoglobin, red blood cell distribution width and platelet count. Serum urea, creatinine, glucose, cholesterol, direct bilirubin concentration and alanine aminotransferase activity were not changed following doxapram administration compared to the PS treatment. After doxapram administration, Creatinine (T3), Albumin (T2) and Protein (T2 & T3) decreased while Glucose (T2 & T3) and BT (T3) increased. Antioxidant parameters measured showed no difference between treatments or time. Doxapram (2 mg/kg) IV did not induce any major negative effects on haematological, serum biochemical variables and oxidant/antioxidant status in dogs after propofol anaesthesia.

Lung transcriptome of a COVID-19 patient and systems biology predictions suggest impaired surfactant production which may be druggable by surfactant therapy

An incomplete understanding of the molecular mechanisms behind impairment of lung pathobiology by COVID-19 complicates its clinical management. In this study, we analyzed the gene expression pattern of cells obtained from biopsies of COVID-19-affected patient and compared to the effects observed in typical SARS-CoV-2 and SARS-CoV-infected cell-lines. We then compared gene expression patterns of COVID-19-affected lung tissues and SARS-CoV-2-infected cell-lines and mapped those to known lung-related molecular networks, including hypoxia induced responses, lung development, respiratory processes, cholesterol biosynthesis and surfactant metabolism; all of which are suspected to be downregulated following SARS-CoV-2 infection based on the observed symptomatic impairments. Network analyses suggest that SARS-CoV-2 infection might lead to acute lung injury in COVID-19 by affecting surfactant proteins and their regulators SPD, SPC, and TTF1 through NSP5 and NSP12; thrombosis regulators PLAT, and EGR1 by ORF8 and NSP12; and mitochondrial NDUFA10, NDUFAF5, and SAMM50 through NSP12. Furthermore, hypoxia response through HIF-1 signaling might also be targeted by SARS-CoV-2 proteins. Drug enrichment analysis of dysregulated genes has allowed us to propose novel therapies, including lung surfactants, respiratory stimulants, sargramostim, and oseltamivir. Our study presents a distinct mechanism of probable virus induced lung damage apart from cytokine storm.

Almitrine: a possible therapeutic strategy for COVID-19?

Coronavirus disease 2019 (COVID‐19) remains with no specific treatment, despite the efforts of many scientists around the world. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV-2) penetrates human host banknotes through interaction with angiotensin-converting enzyme 2 and transmembrane protease, serine 2 (TMPRSS2) receptors, located at respiratory tract (upper and lower) and the olfactory epithelium (pathway to the Central Nervous System). The virus causes COVID-19 and sometimes a Severe Acute Respiratory Syndrome (SARS). Several neurological manifestations can be associated with the infection. The SARS-COV-2 neurotropism for cardiorespiratory centers, causing autonomic damage, may contribute to respiratory failure. Almitrine is a respiratory stimulant drug, used in chronic hypoxemic diseases. Almitrine acts in peripheral chemoreceptors and could be a potential treatment for the optimization of chemoreceptors, improving the respiratory control affected by the SARS‐CoV‐2 in patients with COVID-19.

Comparison of impact of administration route (oral gavage and continuous infusion) on whole body plethysmography results using a respiratory stimulant in conscious rats

Comparison of impact of administration route (oral gavage and continuous infusion) on whole body plethysmography results using a respiratory stimulant in conscious rats

Use of Continuous Physiological Monitor Data to Evaluate Doxapram Therapy in Preterm Infants

Introduction: Evaluation of pharmacotherapy during intensive care treatment is commonly based on subjective, intermittent interpretations of physiological parameters. Real-time visualization and analysis may improve drug effect evaluation. We aimed to evaluate the effects of the respiratory stimulant doxapram objectively in preterm infants using continuous physiological parameters. Methods: In this longitudinal observational study, preterm infants who received doxapram therapy were eligible for inclusion. Physiological data (1 Hz) were used to assess respiration and to evaluate therapy effects. The oxygen saturation (SpO₂)/fraction of inspired oxygen (FiO₂) ratio and the area under the 89% SpO₂ curve (duration × saturation depth below target) were calculated as measures of hypoxemia. Regression analyses were performed in 1-h timeframes to discriminate therapy failure (intubation or death) from success (no intubation). Results: Monitor data of 61 patients with a median postmenstrual age (PMA) at doxapram initiation of 28.7 (IQR 27.6–30.0) weeks were available. The success rate of doxapram therapy was 56%. Doxapram pharmacodynamics were reflected in an increased SpO₂ and SpO₂/FiO₂ ratio as well as a decrease in episodes with saturations below target (SpO₂ <89%). The SpO₂/FiO₂ ratio, corrected for PMA and mechanical ventilation before therapy start, discriminated best between therapy failure and success (highest AUC ROC of 0.83). Conclusion: The use of continuous physiological monitor data enables objective and detailed interpretation of doxapram in preterm infants. The SpO₂/FiO₂ ratio is the best predictive parameter for therapy failure or success. Further implementation of real-time data analysis and treatment algorithms would provide new opportunities to treat newborns.

Respiratory Rates Derived From Arterial Blood Pressure Waveforms in Telemetered Dogs.

The objective of this study was to extract low frequency respiratory "artifacts" from a standard arterial blood pressure (ABP) waveform to simultaneously derive reliable breathing rates (BR). Arterial blood pressure derived BR values were characterized against respiratory rates simultaneously obtained from the Respiratory Inductive Plethysmography (RIP) system (EMKA). Reference compounds were introduced to evaluate responsiveness of the derived measures to respiratory depressants and stimulants. Male beagle dogs (n = 3) were instrumented with minimally invasive telemetry devices for measurements of ABP and heart rate. The RIP system was utilized simultaneously to collect respiratory rate, tidal volume, and minute volume of each animal following pharmacological challenges. Early results revealed the derived BR's from ABP waveforms did not correlate well with those measured from the RIP system. Post study X-ray visualization revealed suboptimal catheter positioning, causing poor concordance of BR tallied from the ABP waveforms. Follow-up evaluations were conducted using additional animals instrumented with the ABP catheter tip placement advanced proximal to the thoracic diaphragm. Preliminary data from this subset of animals significantly improved the correlation of BR derived from ABP and respiratory rates recorded by the RIP. This proof of concept investigation was intended to evaluate an algorithm designed to extract additional data from routine cardiac waveforms. We clearly demonstrated that with optimal blood pressure catheter placement and acquisition algorithm, a reliable breathing rate can also be extracted from safety studies without the need for additional studies/animals to capture those respiratory end points.

When will we ditch the AHI?

When will we ditch the AHI?

Isolation of chemical constituents and In-Vitro screening of Plectranthus mollis Spreng for anthelmintic activity

The human being are the most affected with diseases than any other animal species. For a long time, almost all the medicines were extracted from plants and, many herbal drugs were used by different civilization and many of them are still used. Tannins and flavonoids are the chemical constituents in the plants that produces the anti-helminthic activity. In traditional medicine, Plectranthus mollis has been used against snakebites, respiratory stimulant and cure for hemorrhage, antimicrobial, treatment of mental retardation and rheumatism. Moreover, Plectranthus mollis is reported to have a high content of tannins and flavonoids. Depending on this, helminthic activity were proposed.Dried aerial parts of the hydroalcoholic extract of Plectranthus mollis are subjected to preliminary tests for the identification of various active constituents present in the extract. Estimation of total phenolic content were determined calorimetrically using Folin-Ciocalteu method and total flavonoid content were determined by aluminum chloride colorimetric technique for the hydroalcoholic extract of Plectranthus mollis. The antioxidant activity of the hydroalcoholic extract of the plantwere carried out by DPPH radical scavenging assay. The anthelmintic activity of dried aerial parts of the hydroalcoholic extract of Plectranthus mollis are evaluated on adult Pheretima Posthuma (Indian earthworm).The chemical compound present in dried aerial parts of hydroalcoholic extract of Plectranthus mollis were isolatedby flash chromatography. The isolated compound were detected by HPTLC technique and confirmed by GC-MS analysis.

Progesterone prevents oxidative stress and respiratory dysfunctions in female rats exposed to intermittent hypoxia.

The occurrence of sleep apnea (SA) increases after menopause in women, which is partly related to the decreased levels of ovarian hormones. Because progesterone (Prog) is a neuroprotective hormone and a potent respiratory stimulant, we tested the hypothesis that Prog reduces the apnea frequency and the oxidative stress induced by IH. We used OVX female rats implanted with an osmotic pump delivering vehicle (OVX‐Veh) or prog (4mg/kg/day). Two weeks following the surgery, rats were exposed to room air (RA), or IH for 7 days (nadir 10% O2, 10 cycles/hour, 8 hours/day). We studied three groups: OVX‐Veh‐RA; OVX‐Veh‐IH; and OVX‐Prog‐IH. At the end of exposure period, we measured the mean arterial pressure (tail cuff) and assessed the frequency of apneas during sleep and the ventilatory responses to hypoxia using whole body plethysmography. The brain was quickly harvested to measure the activity of the pro‐oxidant enzyme NADPH oxidase (NOX), and the antioxidant enzymes (mitochondrial and cytosolic superoxide dismutase ‐ SOD) in the cerebral cortex and brainstem. IH exposure increased the mean arterial blood pressure, the frequency of apneas during sleep, and the hypoxic ventilatory response. Prog did not prevent the elevation of blood pressure, but effectively reduced the frequency of apneas during sleep and prevented the elevation of the hypoxic ventilatory response. In the cerebral cortex, IH increased NOX activity, and decreased the activity of the cytosolic and mitochondrial SOD, these effects were prevented by Prog. None of these enzyme activities were altered by IH or Prog supplementation in the brainstem. We conclude that Prog prevents the respiratory alterations induced by IH, and reduces oxidative stress in the brain cortex. These studies are useful to better understand the responses to IH and sleep apnea in women particularly after menopause.Support or Funding InformationSupported by CIHR.

Intranasal Leptin Prevents Opioid Induced Respiratory Depression in Obesity

IntroductionNorth America is currently facing obesity and opioid epidemics. Respiratory depression is the main cause of morbidity and mortality from opioids. Obese individuals with Obstructive Sleep Apnea have a higher risk of opioid induced respiratory depression (OIRD). Leptin acts as respiratory stimulant augmenting control of breathing and improving upper airway patency. We have previously shown that obesity‐induced leptin resistance can be circumvented by intranasal administration of leptin. In this study, we aimed to examine if intranasal administration of leptin prevents OIRD.MethodsMale diet‐induced obese C57BL/6J mice (n=8) were instrumented with headmount containing EEG and EMG leads under 1–2% isoflurane anesthesia. After recovery period polysomnograms were performed in a crossover manner with 1 week interval between studies. Mice received intranasal (IN) leptin or vehicle (BSA) at 0.4 mg/kg and 30 minutes later received a bolus of intraperitoneal (IP) morphine at 10 mg/kg followed by implantation of a subcutaneous osmotic pump delivering morphine at 2 mg/kg/h for the duration of the study (11am–5pm). The control group received IN vehicle, IP saline and a sham osmotic pump filled with saline. Minute ventilation (VE) was recorded through sleep/wake states and upper airway obstruction was defined by the presence of inspiratory flow limitation (IFL). Apneas were scored when flow was absent for two or more respiratory cycles. Excitatory post‐synaptic currents (EPSCs) were recorded in‐vitro from hypoglossal motor neurons (HGNs) and changes in EPSC amplitude and frequency were examined following application of the μ opioid receptor agonist (DAMGO) and leptin.ResultsMorphine induced severe inspiratory flow limitation and apneas during NREM sleep. Morphine increased IFL breath frequency (from 12% to 57% of all breaths, p&lt;0.001) and apneas (from 13.5±3.5/h to 91.5±20.0/h, p&lt;0.01) and decreased maximal inspiratory flow (VImax) during IFL breaths (from 3.4±0.4 to 2.3±0.4 mL/s, p&lt;0.05) and VE (from 1.1±0.1 to 0.7±0.2 mL/min/g, p&lt;0.05). Leptin attenuated effects of morphine. IN Leptin decreased IFL breath frequency (from 57% to 45%, p&lt;0.005) and reduced the number of apneas (from 91.5±20.0/h to 34.3±7.0/h, p&lt;0.01). Leptin reduced the severity of upper airway obstruction increasing VImax (from 2.3±0.4 to 2.8±0.4, p&lt;0.05) and minute ventilation (from 0.7±0.2 to 1.0±0.2, p&lt;0.05) during IFL breathing. Furthermore, in vitro studies showed that administration of DAMGO reduced EPSC frequency (but not EPSC amplitude) in HGNs that was reversed by application of leptin.ConclusionMorphine caused respiratory suppression and upper airway obstruction during sleep in DIO mice and decreased EPSC frequency in HGNs. Leptin relieved morphine‐induced hypoventilation and Obstructive Sleep Apnea and reversed the opioid induced depression of excitatory synaptic neurotransmission to HGNs. We conclude that intranasal leptin may prevent OIRD in obesity.Support or Funding InformationR01HL 128970, R01HL 138932, FAPESP 2018/08758‐3

Relaxin‐3 receptor (RXFP3) mediated modulation of central respiratory activity

The neuropeptide, relaxin‐3, is expressed by pontine nucleus incertus (NI) neurons. Relaxin‐3 and synthetic agonist peptides modulate arousal and cognitive processes via activation of the rela xin‐ family peptide 3 receptor (RXFP3). We recently demonstrated that a double‐chain RXFP3 peptidomimetic (RXFP3‐A2) in the nucleus of the solitary tract (NTS) triggered a mild stimulation of respiration and augmented the chemoreceptor reflex in an in situ perfused brainstem preparation ( Furuya et al., 2020). In the present study, we assessed the central respiratory effects of systemic application and local microinjection into the NTS, Kölliker‐Fuse nucleus (KF) or NI of a single chain RXFP3 peptidomimetic (B18) in the perfused brainstem preparation.Systemic application of B18 (2 μM) triggered a dose‐dependent increase in respiratory rate by 22 ± 8%. At this concentration of B18, the NaCN‐evoked (0.1% w/v, 100 μl, bolus injection) tachycardia of the arterial chemoreceptor reflex was augmented by 95 ± 14% compared to control (p&lt;0.001, n=4). Local microinjections into the NTS also increased respiratory frequency (28 ± 5%, p&lt;0.05, n=6) and enhanced the NaCN‐evoked tachycardia by 59%. Microinjections into the KF only triggered a mild increase in respiratory frequency (18 ± 7%, p&lt;0.05, n=6) but had no effect on the NaCN‐evoked chemoreceptor reflex. Finally, microinjections into the NI (n=6) had no effect on either stationary breathing activity, or on the chemoreceptor reflex. We conclude that relaxin‐3 neurons target RXFP3 in respiratory control areas and acts as a general respiratory stimulant, causing mild increases in respiratory frequency. Importantly, RXFP3 stimulation significantly enhanced the respiratory response of arterial chemoreceptor reflex, implicating a major neuromodulatory role in this specific reflex pathway.

The Influence of Anaesthetic Drugs on the Laryngeal Motion in Dogs: A Systematic Review.

Simple SummaryLaryngeal paralysis is secondary to a loss of normal function of the larynx. Older dogs are particularly affected, with normal breathing becoming difficult. A successful diagnosis typically relies on the visualisation of either, complete, or partially absent, laryngeal movements. The use of anaesthesia drugs to provide sedation and stress relief is most commonly necessary during the diagnosis of laryngeal paralysis. While, the excessive administration of anaesthesia drugs may result in absent movements, the ideal anaesthesia regime remains unknown, and the use of sedation is questionable, given the potential for absent laryngeal movements, even in healthy dogs. In this systematic review, we found a potential benefit from using sedation during the evaluation of laryngeal function when compared to injectable anaesthetics only. The respiratory stimulant doxapram was effective in differentiating normal dogs from dogs with laryngeal paralysis but has associated safety hazards.Anaesthetic drugs are commonly used during the evaluation of laryngeal function in dogs. The aim of this review was to systematically analyse the literature describing the effects of anaesthetic drugs and doxapram on laryngeal motion in dogs and to determine which drug regime provides the best conditions for laryngeal examination. PubMed, Google Scholar, and EMBASE databases were used for the literature search up to November 2019. Relevant search terms included laryngeal motion, anaesthetic drugs and dogs. Studies were scored based on their level of evidence (LoE), according to the Oxford Centre for Evidence-based Medicine, and the quality was assessed using the risk-of-bias tool and SIGN-checklist. In healthy dogs, premedication before laryngeal examination provided better examination conditions and maintained overall adequate laryngeal motion in 83% of the studies. No difference in laryngeal motion between induction drugs was found in 73% of the studies but the effects in dogs with laryngeal paralysis remain largely unknown. Doxapram increased laryngeal motion in healthy dogs without serious side effects, but intubation was necessary for some dogs with laryngeal paralysis. Methodological characteristics varied considerably between studies, including the technique and timing of evaluation, number of assessors, study design, drug dose, combinations, route and speed of administration.