Vestibular compensation relies on sensory reweighting, but whether repeated hypergravity training (HT) facilitates recovery after bilateral vestibular lesion (BVL) remains unclear. We investigated the effects of HT on motor function and dorsal root ganglion (DRG) transcriptomes in mice following BVL. Mice underwent sham surgery or BVL and were assigned to either HT (2G, 60min/day for 10 days) or no HT (NHT). Body weight, righting reflex, and rotarod performance were evaluated, and RNA sequencing of L5 DRGs was performed on day 7. HT did not improve body weight loss or vestibular-dependent righting reflex deficits. However, HT resulted in significantly better rotarod performance on Day 7 compared with NHT. RNA sequencing identified 397 candidate genes, with enrichment of muscle-related and myelination-related biological processes. These findings suggest that repeated HT facilitates vestibular compensation by promoting transcriptional changes in DRGs and enhancing peripheral somatosensory plasticity rather than restoring vestibular function itself.
Food-induced anaphylaxis is a life-threatening allergic reaction in which endogenous sympathoadrenal responses play a critical role in maintaining physiological homeostasis. However, the functional status of autonomic pathways regulating adrenal catecholamine output during anaphylaxis remains unclear. Using a mouse model of food allergy-induced anaphylaxis, we examined the vagal afferent–medullary C1 neuron–adrenal sympathetic pathway and adrenal adrenergic function. Ovalbumin challenge induced hypotension, hypothermia, metabolic acidosis, and elevated plasma catecholamines. Despite severe systemic deterioration, vagal afferent stimulation and optogenetic activation of C1 neurons continued to evoke robust adrenal sympathetic responses, indicating preserved autonomic regulation. In contrast, adrenal transcriptomic analysis revealed enrichment of hypoxia-related pathways and selective suppression of phenylethanolamine N-methyltransferase (PNMT), a key enzyme for adrenaline synthesis. Oxygen supplementation partially restored PNMT expression, increased plasma adrenaline levels, and improved physiological outcomes. These findings identify hypoxia-associated adrenal dysfunction as a potential limitation of endogenous adrenergic compensation during anaphylactic shock.
Maternal-fetal calcium (Ca2 +) transport through the placenta is crucial for the development of fetal organs including bones. Although we have reported that the transient receptor potential cation channel, subfamily V, member 6 (TRPV6) was responsible for the maternal-fetal Ca2+ transport, there has been no direct evidence for its channel activity in placental trophoblasts. By using human trophoblast stem cells, we observed biphasic higher intracellular Ca2+ levels compared with undifferentiated cells during the differentiation of syncytiotrophoblasts. Second Ca2+ peak, when the syncytiotrophoblasts might mature with transport function, was found to be a Ca2+ flux through TRPV6. Unexpectedly we observed the first peak, when trophoblasts fuse to form syncytiotrophoblast. We found that it was derived through TRPV4, and blocking TRPV4 suppressed trophoblast cell fusion. Our results might provide the first evidence for TRPV6 channel activities in syncytiotrophoblasts involved in the maternal-fetal Ca2+ transport.
Amphibians exhibit intracardiac shunting, by which oxygen from multiple respiratory surfaces is variably distributed between systemic and pulmonary circulations. Although shunting has been extensively studied in terrestrial species that rely heavily on pulmonary respiration, much less is known about more aquatic, cutaneous-respiring species, in which cutaneously oxygenated blood returns to the right atrium, so the right-left oxygen gradient should vary with context. Moreover, the proposed role of ventricular trabeculation in limiting intraventricular mixing has not been directly demonstrated. We combined phosphorescence lifetime microscopy for in vivo pO2 measurement with microbubble-based contrast-enhanced ultrasound for high-resolution tracer-tracking in aquatic Xenopus laevis. In anesthetized animals, blood pO2 was uniformly low (25-40 mmHg), with little arteriovenous difference. Right-to-left shunting was minimal (8%), whereas a strong intraventricular left-to-right shunt (47%) maintained threefold greater pulmonary than systemic flow. Although its significance remains to be elucidated, these approaches provide a foundation for advancing shunt research.
Asparagine-linked (N-linked) glycosylation has emerged as an essential post-translational modification to control the number of channels embedded in the plasma membrane as well as to regulate their functional gating properties. The aim of this study was to evaluate the exact role of α-mannosidase I-dependent N-linked glycosylation process in Golgi apparatus on the human rapidly activating delayed rectifier potassium channel, hERG channel. In the heterologous expression system in HEK293 cells, kifunensine, a selective inhibitor of class I α-mannosidase, does not significantly reduce hERG channel current (IhERG) when applied for 48 h. However, kifunensine selectively reduced the reactivation current of the hERG channel, while activation, inactivation and deactivation kinetics were not detectably affected by kifunensine. Our results suggest that α-mannosidase I-dependent N-linked glycosylation in the Golgi apparatus plays a key role in regulating hERG functional availability during reactivation.
Electroacupuncture (EA) modulates neuroimmune and metabolic pathways, but acupoint-specific physiological responses remain poorly characterized. This study investigated acupoint-dependent differences in nociceptive behavior, synovial inflammation, and serum metabolomic profiles in rats with complete Freund's adjuvant (CFA)-induced knee arthritis. Animals were assigned to three groups: CFA without EA, CFA with EA at SP6, and CFA with EA at ST36. EA at ST36 significantly improved hindlimb weight-bearing (74.1% vs. 45.3% at post-injection day 8; p < 0.01), whereas EA at SP6 did not reach significance. Both acupoints comparably reduced synovial inflammation scores. Targeted GC-MS/MS serum metabolomics identified 14 significantly altered metabolites; 2-hydroxybutyric acid (2-HBA) showed the largest fold-change and was selectively normalized by EA at ST36. Intra-articular 2-HBA injection did not alter pain behavior, indicating it represents a systemic physiological consequence of inflammatory-metabolic burden rather than a nociceptive mediator. These findings demonstrate acupoint-specific modulation of redox-metabolic homeostasis by EA in inflammatory arthritis.
Basal forebrain cholinergic neurons project widely to the cerebral cortex and participate in cerebrovascular regulation. Although cholinergic axons are distributed around the cerebrovasculature, their functional relationship with arteriolar dynamics remains unclear. In this study, we established an in vivo two-photon imaging approach to simultaneously measure Ca²⁺ signals in cholinergic axonal varicosities and arteriolar diameters in urethane-anesthetized mice. An adeno-associated virus (AAV) vector (rAAV-ChAT-jGCaMP8s) was injected into the nucleus basalis of Meynert. In vivo imaging of the frontal cortex revealed bead-shaped GCaMP signals around the arterioles. Pinch stimulation transiently increased Ca²⁺ signals in periarteriolar varicosities, followed by arteriolar dilation, with an approximately 2-s delay between their peaks. Linear regression analysis disclosed a significant relationship between the magnitudes of these changes. This approach enabled simultaneous evaluation of cholinergic axonal activity and arteriolar dynamics in vivo, providing a tool to investigate the cholinergic regulation of cerebrovasculature.
Vascular smooth muscle cells are constantly subjected to cyclic stretch and hydrostatic pressure in vivo, yet the molecular responses to these stimuli remain incompletely understood. We performed transcriptome and secretome analyses to characterize the responses of human aortic smooth muscle cells (HASMCs) to cyclic stretch (10%; S10) or cyclic hydrostatic pressure corresponding to normotensive (120/60 mmHg; P120) or hypertensive (180/120 mmHg; P180) conditions. Principal component analysis and hierarchical clustering revealed distinct transcriptomic and secretomic profiles in P180 compared with S10 and P120. P180 also exhibited the largest number of differentially expressed genes, including several not previously linked to mechanical stress. Among these, vasoactive intestinal peptide receptor 1 (VIPR1), a regulator of vascular tone, was markedly upregulated. These distinct expression profiles induced by hypertensive hydrostatic pressure may provide insight into physiological and pathological responses in HASMCs.
We examined the inter- and intra-site reliability of pilocarpine-induced forearm sweat rate at three concentrations. Under thermoneutral conditions, 10 males and 4 females received 0.001%, 0.01%, and 1% pilocarpine via iontophoresis at the lateral and medial left forearm and the medial right forearm. Sweat rate was measured for 30 min. Inter-site (right vs. left medial) and intra-site (left lateral vs. medial) comparisons were assessed using intraclass correlation (ICC) and coefficient of variation (CV). Inter-site comparisons showed significant correlations at 0.01% and 1% (both p < 0.001, r ≥ 0.688) with good agreement (ICC ≥ 0.79, CV ≤ 21.5%), whereas 0.001% showed poorer reliability (CV = 47.3%). Intra-site reliability was highest at 1% (ICC = 0.89, CV = 16.5%) and lower at 0.01% and 0.001%. These findings indicate that inter-site comparisons of pilocarpine-induced sweating at 1% and 0.01% concentrations provide reliable responses for sweat mechanism studies (e.g., with and without antagonist administration).
Research on the effects of oral ingestion on extracellular and intracellular water balance is scarce. To measure the postprandial change in extracellular-intracellular water balance, 28 healthy adults (mean age 39 years, 20 women, 8 men) were recruited, and their extracellular-intracellular water distribution was measured at five time points: immediately before lunch (fasting), immediately after lunch (postprandial), and 30, 60, and 120 min after lunch using a BCM® body composition measuring device (Fresenius Medical Care, Germany). The results did not show significant changes in the total water volume, whereas the extracellular-intracellular distribution ratio decreased significantly from 0.7468 ± 0.0496 during fasting to 0.7376 ± 0.0473 during postprandial periods, which gradually increased over the next 120 min (0.7491 ± 0.0569). The estimated mean postprandial loss of extracellular fluid was 132 mL. Overall, oral ingestion promotes the transient transfer of body water from extracellular to intracellular spaces.
Serotonin (5-HT) reuptake in the heart is mediated by the platelet serotonin reuptake transporter (SERT) and the cardiomyocyte plasma membrane monoamine transporter (PMAT). However, the specific roles of these transporters in myocardial cell injury during ischemia/reperfusion remain unclear. Sprague-Dawley rats underwent left coronary artery occlusion followed by reperfusion. Using cardiac microdialysis technique, fluoxetine (SERT inhibitor, 900 μM) or decynium 22 (PMAT inhibitor, 100 μM) was administered locally to the ischemic region. Myoglobin concentrations in the dialysate were measured during ischemia followed by reperfusion. In the fluoxetine-treated group, peak myoglobin concentration (14,889 ± 1364 ng/mL) during 0-15 min of reperfusion was significantly higher compared to both the control group (9800 ± 1627 ng/mL) and the decynium 22-treated group (8172 ± 877 ng/mL) (P < 0.01 for both). Local SERT inhibition exacerbated myocardial cell injury during ischemia/reperfusion. However, co-inhibition of PMAT reduced myocardial cell injury under SERT inhibition to the control level.
Episodic hypoxaemia is associated with muscle dysfunction in respiratory insufficiencies, but its effects depend on the hypoxia/reoxygenation pattern. Sustained Intermittent Hypoxemia (SIH) characterizes a large subgroup of COPD patients, yet muscle adaptations to SIH remain poorly known. We used a mouse model of SIH (FiO₂: 10%, 8 h/day) and analysed myofibre structure, muscle mass regulators, and myogenic markers in fast and slow-twitch hindlimb muscles. SIH induced an increase in haematocrit. At 35 days, Soleus cross-sectional area increased predominantly in slow-twitch fibres, but not in the fast Tibialis Anterior (TA) muscle. HIF1 target gene expression was increased at early timepoints with muscle-type-specific differences. While myostatin plasma levels were decreased, myostatin receptor and atrogene expression differed between muscles at baseline and upon SIH. Myod1 and Myog expression decreased over time in the TA only. In conclusion, SIH induces muscle-type-specific adaptations, promoting hypertrophy in slow-twitch muscle while impairing myogenic regulation in fast-twitch muscle.
To explore the role of polyamine metabolism in muscle-type-specific hypertrophy, we analyzed changes in the expression profiles of polyamine metabolic enzymes and key enzymes for muscle metabolism induced by voluntary wheel running exercise in different muscle types. Effect of the polyamine precursor, putrescine, which was reported to have potential to regulate muscle volume, was also tested. Polyamine synthetic enzymes were upregulated in hypertrophic soleus muscle whereas polyamine catabolic enzymes were upregulated in nonhypertrophic plantar muscle by exercise in correlation with increased mitochondria-related protein expression. The increased catabolic enzymes of polyamines in the plantar muscle were hypothesized to be possibly involved in restriction of hypertrophy in fast-type skeletal muscles correlating with increased aerobic metabolism. Putrescine administration minimally affected polyamine metabolism and muscle volume indicating that it did not effectively regulate muscle hypertrophy. Polyamine oxidase localized in the perinuclear and intermyofibrillar region suggesting a correlation between aerobic metabolism and polyamine catabolism.
Sweet detection involves at least two mechanisms: a G-protein coupled sweet taste receptor (Tas1r2/Tas1r3) and glucose transporters. As in pancreatic β-cells, glucose transport may lead to closure of ATP-sensitive potassium (KATP) channels. Since expression of KATP channels in sweet taste cells has been reported, modulation of KATP channel activity would affect sweet taste sensitivity. Here, we examined the effect of glibenclamide (a KATP channel closer) and diazoxide (an opener) on mouse taste behavior. Glibenclamide selectively reduced taste sensitivity to glucose without affecting responses to sucrose or sucralose compared to insulin, suggesting selective impairment of the transporter-dependent pathway. In contrast, diazoxide broadly suppressed responses to all tested sweeteners, indicating a generalized effect on sweet detection. Neither drug altered responses to non-sweet taste. These findings suggest that pharmacological modulation of KATP channel differently influences sweet taste; closers reduce glucose sensitivity whereas openers attenuate response to multiple sweeteners.
Fast- and slow-twitch skeletal muscle fibers exhibit distinct glycerophospholipid compositions, and slow-twitch transition is accompanied by characteristic changes in glycerophospholipid molecular species. However, whether glycerophospholipid composition is remodeled during fast-twitch fiber transition and skeletal muscle hypertrophy remains unclear. In this study, we examined changes in palmitate- and stearate-containing glycerophospholipids using a mouse model of clenbuterol-induced fast-twitch transition and hypertrophy. Clenbuterol administration increased the proportion of fast-twitch fibers and induced skeletal muscle hypertrophy. Lipidomic analysis revealed a significant increase in palmitate-containing phosphatidylcholine and a decrease in stearatecontaining phosphatidylcholine in the tibialis anterior and soleus muscles. Consistent with these glycerophospholipid alterations, the expression of several acyltransferases, such as glycerol-3-phosphate acyltransferase 3 (GPAT3), involved in glycerophospholipid acyl-chain determination was significantly altered. These findings demonstrate that glycerophospholipid composition is remodeled during fast-twitch fiber transition and muscle hypertrophy, highlighting lipid remodeling as a component of skeletal muscle phenotypic adaptation.
Attention is crucial for motor performance because it enhances task-relevant processing while suppressing distractions. However, physiological markers of attentional engagement during motor activity remain incompletely understood. The present study investigated how attention modulates sensory gating (SG) along with heart rate variability (HRV) and eye blink rate (EBR) during a visual cue-based typing task. Twenty-five participants performed under three conditions: (1) no typing, (2) free typing, (3) precision typing. The results revealed that higher attention led to a consistent increase in SG across distinct modalities. Particularly, this modulation was observed in higher-order components: N1, P2 in auditory evoked potential; P1 in visual evoked potential; P2, P3 in somatosensory evoked potential. Furthermore, task-related HRV modulation was associated with varying attentional and motor demands, while EBR decreased with increased visual attentional engagement. These findings further clarify SG and autonomic changes during attentional modulation in motor tasks, highlighting their potential for assessing attentional engagement.
Sodium-glucose co-transporter 2 (SGLT2) inhibitors, diabetic medicines, induce glucosuria to lower glycemia and energy reserve, initially reducing weight. The weight-reducing capacity substantially differs between individuals, likely due to both social/psychological factors and physical/metabolic states. Exclusively analyzing the contribution of physical/metabolic states is difficult in humans but feasible in mice. To explore whether metabolic states can alter weight outcomes of SGLT2 inhibitor treatment, the impact of canagliflozin was studied comparatively in high-fat-diet-induced obese (DIO) mice and leptin-receptor-deficient db/db mice. Canagliflozin, orally administered, induced rapid reductions in glycemia and weight followed by elevated food intake in both models. The initial weight loss was rebounded in db/db mice, but progressed and sustained in DIO mice accompanied by circadian rises in body temperature and locomotor activity, the effects possibly balancing the elevated food intake. These results reveal that physical/metabolic states, independent of social/psychological factors, influence weight outcome of canagliflozin treatment.
Transient potential melastatin 2 (TRPM2) plays important roles in Ca2+ signaling in tissues and cells, and contributes to various cellular functions. The Ca2+ influx induced by TRPM2 may activate the intermediate conductance Ca2+-activated potassium channel (IKCA1/ KCa3.1/ SK4) and trigger K+ efflux. Here we demonstrate that a functional interaction between TRPM2 and IKCA1 contributes to cell volume changes in HEK293T cells and mouse primary microglia. Ca2+ entering cells through TRPM2 causes K+ efflux, followed by cell shrinkage upon water efflux. In addition, mouse microglia exhibited temperature-dependent movement in vitro that was modulated by the TRPM2-IKCA1 interaction within the physiological body temperature range. This interaction was also found to be involved in cytokine production in microglia. Understanding how the TRPM2-IKCA1 interaction in microglia can promote cell movement and cytokine production could be valuable for developing new strategies for treatments of diseases involving TRPM2.
Mice are nocturnal and normally feed during the night; however, timed daily feeding can markedly alter behavioral and physiological rhythms. A well-known example is food-anticipatory activity (FAA), characterized by increased locomotor activity before feeding. In this study, we examined age-related effects on FAA under temporally restricted feeding (RF). Male C57BL/6 J mice aged 12 weeks and 54 weeks were maintained under a 12:12 light-dark cycle and subjected to a 4-h daily RF schedule. Wheel-running activity, feeding timing, intake, and body weight were monitored. Under ad libitum conditions, both age groups exhibited nocturnal activity and feeding. During RF, FAA emerged significantly earlier in young mice than in middle-aged mice. After returning to ad libitum feeding, daytime activity gradually merged into nocturnal rhythms, although some middle-aged mice showed unstable patterns. These results indicate that FAA reflects a circadian system distinct from the suprachiasmatic nucleus and that aging delays and destabilizes its expression.
Long-term treatment with eicosapentaenoic acid (EPA) has been reported to reduce the risk of atrial fibrillation (AF) in mice fed a high-fat diet (HFD); however, the appropriate dose required to attenuate atrial vulnerability to AF remains unclear. The present study aimed to determine whether different amounts of daily intake of EPA exert preventive effects against AF. We conducted a series of experiments in HFD-fed mice treated with either low-dose EPA (30mg/kg) or high-dose EPA (300mg/kg). Both EPA doses similarly shortened AF duration and improved atrial conduction, as assessed by P-wave duration on surface electrocardiography. Notably, neither low- nor high-dose EPA significantly improved HFD-induced dyslipidemia, and no difference in cholesterol-lowering effects was observed between the two EPA treatment groups. These findings suggest that physiologically relevant dietary intake of EPA is sufficient to prevent atrial arrhythmias and to ameliorate impaired atrial conduction associated with AF, independent of systemic lipid-lowering effects.
