Expression of p11 and TASK1 Channels in Rat Carotid Body Glomus Cells Subjected to Chronic Intermittent Hypoxia.

Chronic intermittent hypoxia (CIH) has been used as a model to mimic nocturnal apnea, which is associated with hypertension. One of the mechanisms for hypertension in patients with nocturnal apnea is an enhancement of the plasma membrane response to acute hypoxia in carotid body glomus cells. Hypoxia is known to induce depolarization via inhibiting TWIK-related acid-sensitive K+ (TASK) channels, one type of leak K+ channels, in glomus cells. The present experiment was undertaken to immunocytochemically investigate the effects of CIH on the expression and intracellular localization of TASK1 channels and p11 that critically affect the trafficking of TASK1 to the cell surface. The expression levels of TASK1 proteins and p11 and their intracellular localization in rat carotid body glomus cells were not noticeably affected by CIH, suggesting that the enhanced membrane response to acute hypoxia is not due to an increase in surface TASK channels.

Recent Insights into the Measurement of Carbon Dioxide Concentrations for Clinical Practice in Respiratory Medicine.

In the field of respiratory clinical practice, the importance of measuring carbon dioxide (CO2) concentrations cannot be overemphasized. Within the body, assessment of the arterial partial pressure of CO2 (PaCO2) has been the gold standard for many decades. Non-invasive assessments are usually predicated on the measurement of CO2 concentrations in the air, usually using an infrared analyzer, and these data are clearly important regarding climate changes as well as regulations of air quality in buildings to ascertain adequate ventilation. Measurements of CO2 production with oxygen consumption yield important indices such as the respiratory quotient and estimates of energy expenditure, which may be used for further investigation in the various fields of metabolism, obesity, sleep disorders, and lifestyle-related issues. Measures of PaCO2 are nowadays performed using the Severinghaus electrode in arterial blood or in arterialized capillary blood, while the same electrode system has been modified to enable relatively accurate non-invasive monitoring of the transcutaneous partial pressure of CO2 (PtcCO2). PtcCO2 monitoring during sleep can be helpful for evaluating sleep apnea syndrome, particularly in children. End-tidal PCO2 is inferior to PtcCO2 as far as accuracy, but it provides breath-by-breath estimates of respiratory gas exchange, while PtcCO2 reflects temporal trends in alveolar ventilation. The frequency of monitoring end-tidal PCO2 has markedly increased in light of its multiple applications (e.g., verify endotracheal intubation, anesthesia or mechanical ventilation, exercise testing, respiratory patterning during sleep, etc.).

Evaluation of time courses of agreement between minutely obtained transcutaneous blood gas data and the gold standard arterial data from spontaneously breathing Asian adults, and various subgroup analyses.

BACKGROUND: Usual clinical practice for arterial blood gas analysis (BGA) in conscious patients involves a one-time arterial puncture to be performed after a resting period of 20-30 min. The aim of this study was to evaluate the use of transcutaneous BGA for estimating this gold standard arterial BGA. METHODS: Spontaneously breathing Asian adults (healthy volunteers and respiratory patients) were enrolled (n = 295). Transcutaneous PO2 (PtcO2) and PCO2 (PtcCO2) were monitored using a transcutaneous monitor (TCM4, Radiometer Medical AsP, Denmark) with sensors placed on the chest, forearm, earlobe or forehead. Transcutaneous BGA at 1-min intervals was compared with arterial BGA at 30 min. Reasonable steps to find severe hypercapnia with PaCO2 > 50 mmHg were evaluated. RESULTS: Sensors on the chest and forearm were equally preferred and used because of small biases (n = 272). The average PCO2 bias was close to 0 mmHg at 4 min, and was almost constant (4-5 mmHg) with PtcCO2 being higher than PaCO2 at ≥8 min. The limit of agreement for PCO2 narrowed over time: ± 13.6 mmHg at 4 min, ± 7.5 mmHg at 12-13 min, and ± 6.3 mmHg at 30 min. The limit of agreement for PO2 also narrowed over time (± 23.1 mmHg at 30 min). Subgroup analyses showed that the PaCO2 and PaO2 levels, gender, and younger age significantly affected the biases. All hypercapnia subjects with PaCO2 > 50 mmHg (n = 13) showed PtcCO2 ≥ 50 mmHg for until 12 min. CONCLUSIONS: Although PtcCO2 is useful, it cannot completely replace PaCO2 because PCO2 occasionally showed large bias. On the other hand, the prediction of PaO2 using PtcO2 was unrealistic in Asian adults. PtcCO2 ≥ 50 mmHg for until 12 min can be used as a screening tool for severe hypercapnia with PaCO2 > 50 mmHg.

Disharmony between wake- and respiration-promoting activities: effects of modafinil on ventilatory control in rodents.

BACKGROUND: Modafinil is a wake-promoting drug and has been widely used for daytime sleepiness in patients with narcolepsy and other sleep disorders. A recent case series reported that daily oral modafinil alleviated hypercapnic respiratory failure in patients with COPD. However, the precise action of modafinil on respiration such as hypercapnic and/or hypoxic ventilatory responses remains unclear. The aim of this study is to clarify the effect of modafinil on the ventilatory control. METHODS: We investigated the hypothesis that modafinil enhances resting ventilation as well as the stimulatory ventilatory responses to hypercapnia and hypoxia. We addressed the issue by examining minute ventilation, respiratory rate and volume components using plethysmography, combined with a concurrent EEG monitoring of the level of wakefulness before and after administration of modafinil in two doses of 100 mg/kg and 200 mg/kg in unanesthetized mice. In addition, we monitored the effect of the lower dose of modafinil on mice locomotor activity in a freely moving condition by video-recording. RESULTS: Wakefulness, locomotor activity and variability of the breathing pattern in tidal volume were promoted by both doses of modafinil. Neither dose of modafinil increased the absolute values of resting ventilation or promoted the ventilatory responses to hypercapnia and hypoxia. Rather, higher dose of modafinil slightly suppressed respiratory rate in room air condition. CONCLUSIONS: Modafinil is conducive to the state of wakefulness but does not augment resting ventilation or the hyperventilatory responses to chemical stimuli in unanesthetized rodents.

Thermal Sensitivity and Dimethyl Sulfoxide (DMSO).

Dimethyl sulfoxide (DMSO) is commonly used as a solvent for hydrophobic substances, but the compound's innate bioactivity is an area of limited understanding. In this investigation we seek to determine the analgesic potential of DMSO. We addressed the issue by assessing the perception of thermal pain stimulus, using a 55 °C hotplate design, in conscious mice. The latency of withdrawal behaviors over a range of incremental accumulative intraperitoneal DMSO doses (0.5-15.5 g/kg) in the same mouse was taken as a measure of thermal endurance. The findings were that the latency, on average, amounted to 15-30 s and it differed inappreciably between the sequential DMSO conditions. Nor was it different from the pre-DMSO control conditions. Thus, DMSO did not influence the cutaneous thermal pain perception. The findings do not lend support to those literature reports that point to the plausible antinociceptive potential of DMSO as one of a plethora of its innate bioactivities. However, the findings concern the mouse's footpad nociceptors which have specific morphology and stimulus transduction pathways, which cannot exclude DMSO's antinociceptive influence on other types of pain or in other types of skin. Complex and as yet unresolved neural mechanisms of perception of cutaneous noxious heat stimulus should be further explored with alternative experimental designs.

Oxygen Sensing Mechanisms: A Physiological Penumbra.

This review tackles the unresolved issue of the existence of oxygen sensor in the body. The sensor that would respond to changes in tissue oxygen content, possibly along the hypoxia-normoxia-hyperoxia spectrum, rather than to a given level of oxygen, and would translate the response into lung ventilation changes, the major adaptive process. Studies on oxygen sensing, for decades, concentrated around the hypoxic ventilatory response generated mostly by carotid body chemoreceptor cells. Despite gaining a substantial insight into the cellular transduction pathways in carotid chemoreceptors, the exact molecular mechanisms of the chemoreflex have never been conclusively verified. The article briefly sums up the older studies and presents novel theories on oxygen, notably, hypoxia sensing. These theories have to do with the role of transient receptor potential cation TRPA1 channels and brain astrocytes in hypoxia sensing. Although both play a substantial role in shaping the ventilatory response to hypoxia, neither can yet be considered the ultimate sensor of hypoxia. The enigma of oxygen sensing in tissue still remains to be resolved.

Respiratory Toxicity of Dimethyl Sulfoxide.

Dimethyl sulfoxide (DMSO) is one of the most commonly used solvents for hydrophobic substances in biological experiments. In addition, the compound exhibits a plethora of bioactivities, which makes it of potential pharmacological use of its own. The influence on respiration, and thus on arterial blood oxygenation, of DMSO is unclear, contentious, and an area of limited study. Thus, in the present investigation we set out to determine the influence on lung ventilation of cumulated doses of DMSO in the amount of 0.5, 1.5, 3.5, 7.5, and 15.5 g/kg; each dose given intraperitoneally at 1 h interval in conscious mice. Ventilation and its responses to 7 % hypoxia (N(2) balanced) were recorded in a whole body plethsymograph. We demonstrate a dose-dependent inhibitory effect of DMSO on lung ventilation and its hypoxic responsiveness, driven mostly by changes in the tidal component. The maximum safe dose of DMSO devoid of meaningful consequences for respiratory function was 3.5 g/kg. The dose of 7.5 g/kg of DMSO significantly dampened respiration, with yet well preserved hyperventilatory response to hypoxia. The highest dose of 15.5 g/kg severely impaired ventilation and its responses. The study delineates the safety profile of DMSO regarding the respiratory function which is essential for maintaining proper tissue oxygenation. Caution should be exercised concerning dose concentration of DMSO.

Aminophylline increases respiratory muscle activity during hypercapnia in humans.

BACKGROUND: Theophylline is an old drug traditionally used as a bronchodilator, although it was recently shown to possess anti-inflammatory properties, enhance the actions of corticosteroid actions, and stimulate the respiratory neuronal network. Theophylline has been recognized as an important drug for not only asthma but also corticosteroid-insensitive chronic obstructive pulmonary disease (COPD). To clarify the role of theophylline in hypercapnic ventilatory responses in humans, we analyzed the effects of aminophylline administered at the usual clinical therapeutic doses on ventilation and augmentation of respiratory muscle contractility in room air and under 3 conditions of hypercapnia. STUDY DESIGN: We performed electromyography (EMG) of the parasternal intercostal muscle (PARA) and transversus abdominis muscle (TA) in 7 healthy subjects and recorded both ventilatory parameters and EMG data in room air and under 3 conditions of hypercapnia before (control) and during aminophylline administration. RESULTS: Before aminophylline administration (control), hypercapnic stimulation elicited ventilatory augmentation in a hypercapnia intensity-dependent manner. Ventilatory parameters (tidal volume, frequency of respiration, and minute ventilation) showed significant increases from lower PaCO2 levels during aminophylline administration when compared with the corresponding values before aminophylline administration. EMG activity of both PARA and TA increased significantly at each level of hypercapnia, and those augmentations were shown from lower PaCO2 levels during aminophylline administration. CONCLUSION: Aminophylline administered at the usual clinical therapeutic dose increases ventilation and EMG activity of both inspiratory and expiratory muscles during hypercapnia in healthy humans.

Dynamics of upper airways during the Müller maneuver in healthy subjects: a cine MRI study.

The Müller maneuver has been widely applied to mimic the pathophysiological condition of obstructive sleep apnea (OSA) during wakefulness. We applied cine MRI to elucidate dynamics of the upper airway during the Müller maneuver in healthy subjects (n = 7). Three sets of images (during quiet nose breathing, quiet mouth breathing, and Müller maneuver) were recorded on sagittal midline plane together with impedance pneumography. The position of the tongue root changed during a respiratory cycle when subjects breathed quietly. At the early inspiratory phase the tongue root moved forward and upward, the retroglossal airway size increased toward the middle of inspiration, and the airway size became smaller again toward the end of inspiration. During expiration the airway size became further smaller. When the subject performed the Müller maneuver, the movement of the oropharynx and its narrowing were greater than those of the velopharynx. However, the airway was not completely obstructed. A relatively large morphological change was observed in the retropalatal and retroglossal regions with the backward and downward motion of the tongue root and flattening of the tongue shape during the Müller maneuver. Although patterns of upper airway narrowing and tongue shape alterations were variable among subjects, upper airway narrowing was commonly prominent in the retroglossal area. Cine MRI with the Müller maneuver enables to visualize the upper airway dynamics and could be easily applied to evaluate upper airway collapsibility during wakefulness.

Cell Responses of the Ventrolateral Medulla to PAR1 Activation and Changes in Respiratory Rhythm in Newborn Rat En Bloc Brainstem-Spinal Cord Preparations.

Proteinase-activated receptor-1 (PAR1) is expressed in astrocytes of various brain regions, and its activation is involved in the modulation of neuronal activity. Here, we report effects of PAR1 selective agonist TFLLR on respiratory rhythm generation in brainstem-spinal cord preparations. Preparations were isolated from newborn rats (P0-P4) under deep isoflurane anesthesia and were transversely cut at the rostral medulla. Preparations were superfused with artificial cerebrospinal fluid (25-26 °C), and inspiratory C4 ventral root activity was monitored. The responses to TFLLR of cells close to the cut surface were detected by calcium imaging or membrane potential recordings. Application of 10 µM TFLLR (4 min) induced a rapid and transient increase of calcium signal in cells of the ventrolateral respiratory regions of the medulla. More than 88% of responding cells (223/254 cells from 13 preparations) were also activated by low (0.2 mM) K+ solution, suggesting that they were astrocytes. Immunohistochemical examination demonstrated that PAR1 was expressed on many astrocytes. Respiratory-related neurons in the medulla were transiently hyperpolarized (-1.8 mV) during 10 µM TFLLR application, followed by weak membrane depolarization after washout. C4 burst rate decreased transiently in response to application of TFLLR, followed by a slight increase. The inhibitory effect was partially blocked by 50 µM theophylline. In conclusion, activation of astrocytes via PAR1 resulted in a decrease of inspiratory C4 burst rate in association with transient hyperpolarization of respiratory-related neurons. After washout, slow and weak excitatory responses appeared. Adenosine may be partially involved in the inhibitory effect of PAR1 activation.

Minocycline prevents hypoxia-induced seizures.

Severe hypoxia induces seizures, which reduces ventilation and worsens the ictal state. It is a health threat to patients, particularly those with underlying hypoxic respiratory pathologies, which may be conducive to a sudden unexpected death in epilepsy (SUDEP). Recent studies provide evidence that brain microglia are involved with both respiratory and ictal processes. Here, we investigated the hypothesis that microglia could interact with hypoxia-induced seizures. To this end, we recorded electroencephalogram (EEG) and acute ventilatory responses to hypoxia (5% O2 in N2) in conscious, spontaneously breathing adult mice. We compared control vehicle pre-treated animals with those pre-treated with minocycline, an inhibitory modulator of microglial activation. First, we histologically confirmed that hypoxia activates microglia and that pre-treatment with minocycline blocks hypoxia-induced microglial activation. Then, we analyzed the effects of minocycline pre-treatment on ventilatory responses to hypoxia by plethysmography. Minocycline alone failed to affect respiratory variables in room air or the initial respiratory augmentation in hypoxia. The comparative results showed that hypoxia caused seizures, which were accompanied by the late phase ventilatory suppression in all but one minocycline pre-treated mouse. Compared to the vehicle pre-treated, the minocycline pre-treated mice showed a delayed occurrence of seizures. Further, minocycline pre-treated mice tended to resist post-ictal respiratory arrest. These results suggest that microglia are conducive to seizure activity in severe hypoxia. Thus, inhibition of microglial activation may help suppress or prevent hypoxia-induced ictal episodes.

Real-world effects of once-daily inhaled steroid (fluticasone furoate) combined with long-acting beta-2 agonist (vilanterol) and long-acting muscarinic antagonist (umeclidinium) on lung function tests of asthma patients in Japan.

Background: The Japanese drug use system allowed the once-daily use of inhaled corticosteroid fluticasone furoate (FF) combined with a long-acting beta-2 agonist vilanterol (VI) and a long-acting muscarinic antagonist umeclidinium (UMEC) against asthma on 18 February 2021. We investigated the real-world effects of these drugs (FF/UMEC/VI) mainly on lung function tests. Methods: This was an open-label, uncontrolled, within-group time-series (before-after) study. Prior asthma treatment (inhaled corticosteroid with/without a long-acting beta-2 agonist with/without a long-acting muscarinic antagonist) was switched to FF/UMEC/VI 200/62.5/25 µg. Subjects were evaluated by lung function tests prior to, and 1-2 months after, initiation of FF/UMEC/VI 200/62.5/25 µg. Patients were asked questions regarding the asthma control test and preference for drugs. Results: Overall, 114 asthma outpatients (97% Japanese) were enrolled from February 2021 to April 2022: 104 subjects completed the study. Forced expiratory volume in 1 s, peak flow, and asthma control test score of FF/UMEC/VI 200/62.5/25 µg-treated subjects were significantly increased (p < 0.001, p < 0.001, and p < 0.01, respectively). In contrast with FF/VI 200/25 µg, instantaneous flow at 25% of the forced vital capacity and expiratory reserve volume were significantly increased by FF/UMEC/VI 200/62.5/25 µg (p < 0.01, p < 0.05, respectively). Sixty-six percent of subjects declared they wanted to continue FF/UMEC/VI 200/62.5/25 µg in the future. Adverse effects, mainly local, were seen in 30% of patients, but no serious adverse effects were seen. Conclusion: Once-daily FF/UMEC/VI 200/62.5/25 µg was effective against asthma without serious adverse events. This is the first report that demonstrated FF/UMEC/VI dilated peripheral airways using lung function tests. This evidence on drug effects may improve our understanding of pulmonary physiology and the pathophysiology of asthma.

Preinspiratory calcium rise in putative pre-Botzinger complex astrocytes.

The neural inspiratory activity originates from a ventrolateral medullary region called the pre-Bötzinger complex (preBötC), yet the mechanism underlying respiratory rhythmogenesis is not completely understood. Recently, the role of not only neurons but astrocytes in the central respiratory control has attracted considerable attention. Here we report our discovery that an intracellular calcium rise in a subset of putative astrocytes precedes inspiratory neuronal firing in rhythmically active slices. Functional calcium imaging from hundreds of preBötC cells revealed that a subset of putative astrocytes exhibited rhythmic calcium elevations preceding inspiratory neuronal activity with a time lag of approximately 2 s. These preinspiratory putative astrocytes maintained their rhythmic activities even during the blockade of neuronal activity with tetrodotoxin, whereas the rhythm frequency was lowered and the intercellular phases of these rhythms were decoupled. In addition, optogenetic stimulation of preBötC putative astrocytes induced firing of inspiratory neurons. These findings raise the possibility that astrocytes in the preBötC are actively involved in respiratory rhythm generation in rhythmically active slices.

Time-course of ventilation, arterial and pulmonary CO(2) tension during CO (2) increase in humans.

A change of ventilation (VE), PaCO( 2 ) (arterial CO( 2 ) tension) and PvCO( 2 ) (pulmonary arterial CO( 2 ) tension) with time was not evaluated precisely during exercise or CO( 2 ) rebreathing in humans. In this study, changes of these variables with time were fitted to exponential curves {y = Exp ( x/ T + A ) + k} and compared. When exercise pulmonary hemodynamics was examined in 15 cardiac patients to decide therapies, we asked the patients to undergo CO( 2 ) rebreathing using air with supplementation of consumed O( 2 ). Arterial and pulmonary blood was drawn every minute. During exercise, T was 28.2 ± 8.4 and 26.8 ± 12.4, and A was 0.80 ± 0.50 and 0.50 ± 0.90 in VE and PvCO( 2 ), respectively, with no statistical differences. During CO( 2 ) rebreathing, T was 18.6 ± 5.8, 41.8 ± 38.0 and 21.6 ± 9.7 and A was 0.39 ± 0.67, 1.64 ± 1.35 and 0.17 ± 0.83 in VE, PaCO( 2 ) and PvCO( 2 ), respectively, with statistical difference of PaCO( 2 ) from other variables, suggesting that VE and PvCO( 2 ) showed same mode of change according to time but PaCO( 2 ) did not.

Coherence analysis of the calcium activity of putative astrocytic and neuronal cells on the L5 ventral horn and neural output in activated lumbar CPG networks.

Astrocytes are thought to play a crucial role in providing structure to the spinal cord and maintaining efficient synaptic function and metabolism because their fine processes envelop the synapses of neurons and form many neuronal networks within the central nervous system (CNS). To investigate whether putative astrocytes and putative neurons distributed on the ventral horn play a role in the modulation of lumbar locomotor central pattern generator (CPG) networks, we used extracellular recording and optical imaging techniques and recorded the neural output from the left L5 ventral root and the calcium activity of putative astrocytes and neurons in the L5 ventral horn at the same time when activating an isolated L1-L5 spinal cord preparation from rats aged 0-2 days. Optical measurements detected cells that showed a fluorescence intensity change under all experimental conditions, namely, (1) 5-HT + NMDA, (2) TTX, and (3) TTX + Low K+. These cells were semiautomatically identified using an in-house MATLAB-based program, as putative astrocytes and neurons according to the cell classification, i.e., increased or decreased fluorescence intensity change (ΔF/F0), and subjective judgment based on their soma size. Coherence and its phase were calculated according to the calcium activity of the putative astrocytes and putative neurons, and neural output was calculated during fictive locomotion with in-house MATLAB-based programs. We found that the number of putative astrocytes activated by applying low K+ tends not to differ from that activated by applying the protease-activated receptor 1 (PAR1) selective agonist TFLLR-NH2 (TFLLR). Moreover, the calcium activity of several putative astrocytes and neurons synchronized with locomotor-like activity at a frequency range below 0.5 Hz and the time lag between peaks of cellular calcium activity and locomotor-like activity ranged from -1000 to + 1000 ms. These findings presumably indicates that these putative astrocytes and neurons in the left L5 ventral horn require -1000 to + 1000 ms to communicate with lumbar CPG networks and maintain efficient synaptic function and metabolism in activated lumbar CPG networks. This finding suggests the possibility that putative astrocytic and neuronal cells in the L5 ventral horn contribute to generating the rhythms and patterns of locomotor-like activity by activated CPG networks in the first to fifth lumbar spinal cord.

Effects of smoking cessation using varenicline on the serum concentrations of oxidized high-density lipoprotein: Comparison with high-density lipoprotein cholesterol.

BACKGROUND: The oxidized high-density lipoprotein (oxHDL) is a possible marker for cardiovascular diseases. This study investigated the effects of smoking cessation with varenicline (a partial agonist of nicotinic acetylcholine receptors) on the levels of oxHDL in the serum of subjects compared with those of high-density lipoprotein cholesterol (HDL-C). METHODS: Data of 99 nicotine-dependent adult subjects who visited the smoking cessation outpatient services at International University of Health and Welfare Shioya Hospital were reviewed. Each subject was treated with varenicline titrated up to 1.0 mg twice daily for 12 weeks. Serum levels of oxHDL and HDL-C were repeatedly measured by enzyme-linked immunosorbent assay and enzymatic method, respectively. RESULTS: The serum levels of oxHDL were significantly decreased from 163.2 ± 96.6 to 148.3 ± 80.7 U/mL (p = 0.034, n = 99). This effect was more prominent when the data of subjects in whom the treatment was objectively unsuccessful (exhaled carbon monoxide at 3 months ≥ 10 ppm) were omitted (from 166.6 ± 98.4 to 147.4 ± 80.6 U/mL; p = 0.0063, n = 93). In contrast, the serum levels of HDL-C were significantly increased (p = 0.0044, n = 99). There was a close relationship between the baseline levels of oxHDL and HDL-C (R = 0.45, p < 0.0001, n = 99). Changes in the levels of oxHDL were closely associated with changes in the levels of exhaled carbon monoxide in subjects in whom smoking cessation with varenicline was very effective (decrease in exhaled carbon monoxide by ≥ 15 ppm after treatment with varenicline; R = 0.42, p = 0.0052, n = 43). CONCLUSIONS: Although there was a close relationship between the baseline serum concentrations of oxHDL and HDL-C, smoking cessation decreased oxHDL and increased HDL-C. This effect on oxHDL may be associated with the effectiveness of smoking cessation.

Role of microglia in blood pressure and respiratory responses to acute hypoxic exposure in rats.

Microglia modulate cardiorespiratory activities during chronic hypoxia. It has not been clarified whether microglia are involved in the cardiorespiratory responses to acute hypoxia. Here we investigated this issue by comparing cardiorespiratory responses to two levels of acute hypoxia (13% O2 for 4 min and 7% O2 for 5 min) in conscious unrestrained rats before and after systemic injection of minocycline (MINO), an inhibitor of microglia activation. MINO increased blood pressure but not lung ventilation in the control normoxic condition. Acute hypoxia stimulated cardiorespiratory responses in MINO-untreated rats. MINO failed to significantly affect the magnitude of hypoxia-induced blood pressure elevation. In contrast, MINO tended to suppress the ventilatory responses to hypoxia. We conclude that microglia differentially affect cardiorespiratory regulation depending on the level of blood oxygenation. Microglia suppressively contribute to blood pressure regulation in normoxia but help maintain ventilatory augmentation in hypoxia, which underscores the dichotomy of central regulatory pathways for both systems.

Dual orexin receptor blocker suvorexant attenuates hypercapnic ventilatory augmentation in mice.

Suvorexant (Belsomra(R)), a dual orexin receptor antagonist widely used in the treatment of insomnia, inhibits the arousal system in the brain. However, the drug's ventilatory effects have not been fully explored. This study aims to investigate the expression of orexin receptors in respiratory neurons and the effects of suvorexant on ventilation. Immunohistology of brainstem orexin receptor OX2R expression was performed in adult mice (n = 4) in (1) rostral ventral respiratory group (rVRG) neurons projecting to the phrenic nucleus (PhN) retrogradely labeled by Fluoro-Gold (FG) tracer, (2) neurons immunoreactive for paired like homeobox 2b (Phox2b) in the parafacial respiratory group/retrotrapezoid nucleus (pFRG/RTN), and (3) neurons immunoreactive for neurokinin 1 receptor (NK1R) and somatostatin (SST) in the preBötzinger complex (preBötC). Additionally, we measured in vivo ventilatory responses to hyperoxic hypercapnia (5% CO2) and hypoxia (10% O2) before and after suvorexant pretreatment (10 and cumulative 100 mg/kg) in unrestrained mice (n = 10) in a body plethysmograph. We found the OX2R immunoreactive materials in pFRG/RTN Phox2b and preBötC NK1R/SST immunoreactive neurons but not in FG-labeled rVRG neurons, which suggests the involvement of orexin in respiratory control. Further, suvorexant expressly suppressed the hypercapnic ventilatory augmentation, otherwise unaffecting ventilation. Central orexin is involved in shaping the hypercapnic ventilatory chemosensitivity. Suppression of hypercapnic ventilatory augmentation by the orexin receptor antagonist suvorexant calls for caution in its use in pathologies that may progress to hypercapnic respiratory failure, or sleep-disordered breathing. Clinical trials are required to explore the role of targeted pharmacological inhibition of orexin in ventilatory pathologies.

Randomized double-blind placebo-controlled multicenter trial for the effects of a polyherbal remedy, Yokukansan (YiganSan), in smokers with depressive tendencies.

BACKGROUND: Smoking and depression are closely related and form a vicious cycle. Yokukansan (YiganSan) is a polyherbal remedy that has the effect of calming neuropsychiatric symptoms such as anger and irritation. To examine the efficacy of Yokukansan during smoking cessation (SC) therapy in smokers with depressive tendencies but without major depressive disorders requiring pharmacotherapy. METHODS: A multicenter, double-blind, randomized, placebo-controlled, parallel-group comparison trial was conducted between June 2016 and May 2020 at 12 centers of the National Hospital Organization, Japan. This trial targeted smokers who first visited the SC outpatient clinics, did not receive any pharmacological treatment at the psychiatric or psychosomatic department, and scored 39 or more on the self-rating depression scale (SDS). Participants (n = 198) were randomly assigned to either the Yokukansan or placebo groups. The trial drug was initiated with the start of the SC treatment and continued for 12 weeks. The primary outcome was the high success rate of the SC treatment, and the secondary outcomes included changes in scores of the SDS and the Profile of Mood States (POMS) instrument. RESULTS: The success rate of the SC treatment was similar between the placebo (63%) and Yokukansan (67%) groups (P = .649). The SDS scores (placebo: mean difference [MD] = -3.5, 95% confidence interval [CI][-5.8, -1.2], d = 0.42; Yokukansan: MD = -4.6, 95%CI[-6.8, -2.3], d = 0.55), and the "tension-anxiety" POMS-subscale scores (placebo: MD = -1.6, 95%CI[-2.5, -0.7], d = 0.52; Yokukansan: MD = -1.6, 95%CI[-2.9, -0.3], d = 0.36) showed significant improvement in both groups after the SC treatment. However, "depression-dejection" improved in the Yokukansan group (MD = -1.9, 95%CI[-3.1, -0.7], d = 0.44) but not in the placebo group (MD = -0.1, 95%CI[-1.0, 0.7], d = 0.04). Significant improvement in "fatigue" was noted in the Yokukansan group (MD = -2.1, 95%CI[-3.4, -0.9], d = 0.47) but not in the placebo group (MD = -0.5, 95%CI[-1.8, 0.8], d = 0.11). The time × group interaction on the improvement in "depression-dejection" was significant (P = .019). CONCLUSIONS: Yokukansan does not increase the SC treatment's success rate but has additional positive effects on the psychological states due to the SC treatment in smokers with depressive tendencies but without apparent mental disorders. TRIAL REGISTRATION: ID: UMIN000027036. Retrospectively registered at UMIN on April 18, 2017.

Novel oxygen sensing mechanism in the spinal cord involved in cardiorespiratory responses to hypoxia.

As blood oxygenation decreases (hypoxemia), mammals mount cardiorespiratory responses, increasing oxygen to vital organs. The carotid bodies are the primary oxygen chemoreceptors for breathing, but sympathetic-mediated cardiovascular responses to hypoxia persist in their absence, suggesting additional high-fidelity oxygen sensors. We show that spinal thoracic sympathetic preganglionic neurons are excited by hypoxia and silenced by hyperoxia, independent of surrounding astrocytes. These spinal oxygen sensors (SOS) enhance sympatho-respiratory activity induced by CNS asphyxia-like stimuli, suggesting they bestow a life-or-death advantage. Our data suggest the SOS use a mechanism involving neuronal nitric oxide synthase 1 (NOS1) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX). We propose NOS1 serves as an oxygen-dependent sink for NADPH in hyperoxia. In hypoxia, NADPH catabolism by NOS1 decreases, increasing availability of NADPH to NOX and launching reactive oxygen species-dependent processes, including transient receptor potential channel activation. Equipped with this mechanism, SOS are likely broadly important for physiological regulation in chronic disease, spinal cord injury, and cardiorespiratory crisis.