Model-based analysis of the acute effects of transcutaneous magnetic spinal cord stimulation on micturition after spinal cord injury in humans.

AIM: After spinal cord injuries (SCIs), patients may develop either detrusor-sphincter dyssynergia (DSD) or urinary incontinence, depending on the level of the spinal injury. DSD and incontinence reflect the loss of coordinated neural control among the detrusor muscle, which increases bladder pressure to facilitate urination, and urethral sphincters and pelvic floor muscles, which control the bladder outlet to restrict or permit bladder emptying. Transcutaneous magnetic stimulation (TMS) applied to the spinal cord after SCI reduced DSD and incontinence. We defined, within a mathematical model, the minimum neuronal elements necessary to replicate neurogenic dysfunction of the bladder after a SCI and incorporated into this model the minimum additional neurophysiological features sufficient to replicate the improvements in bladder function associated with lumbar TMS of the spine in patients with SCI. METHODS: We created a computational model of the neural circuit of micturition based on Hodgkin-Huxley equations that replicated normal bladder function. We added interneurons and increased network complexity to reproduce dysfunctional micturition after SCI, and we increased the density and complexity of interactions of both inhibitory and excitatory lumbar spinal interneurons responsive to TMS to provide a more diverse set of spinal responses to intrinsic and extrinsic activation of spinal interneurons that remains after SCI. RESULTS: The model reproduced the re-emergence of a spinal voiding reflex after SCI. When we investigated the effect of monophasic and biphasic TMS at two frequencies applied at or below T10, the model replicated the improved coordination between detrusor and external urethral sphincter activity that has been observed clinically: low-frequency TMS (1 Hz) within the model normalized control of voiding after SCI, whereas high-frequency TMS (30 Hz) enhanced urine storage. CONCLUSION: Neuroplasticity and increased complexity of interactions among lumbar interneurons, beyond what is necessary to simulate normal bladder function, must be present in order to replicate the effects of SCI on control of micturition, and both neuronal and network modifications of lumbar interneurons are essential to understand the mechanisms whereby TMS reduced bladder dysfunction after SCI.

Relative Blood Volume Profiles Hours After Loop Diuretic Administration: A Systematic Review and Meta-analysis.

Background: Plasma refill rates can be estimated by combining measurements of urine output with relative blood volume profiles. Change in plasma refill rates could guide decongestive loop diuretic therapy in acute heart failure. The objective of the study was to assess average relative blood volume profiles generated from 2 or 3 follow-up measurements obtained hours after loop diuretic administration in subjects with vs without baseline congestion. Methods: A systematic review was conducted of articles written in English, French, Spanish, and German, using MEDLINE (1964 to 2019), Cochrane Reviews (1996 to 2019), and Embase (1974 to 2019). Search terms included the following: diuretics, hemoconcentration, plasma volume, and blood volume. We included studies of adults given a loop diuretic with at least one baseline and one follow-up measurement. A single author extracted subject- or group-level blood volume measurements, aggregated them when needed, and converted them to relative changes. Results: Across all 16 studies that met the prespecified inclusion criteria, relative blood volume maximally decreased 9.2% (6.6% to 12.0%) and returned to baseline after 3 or more hours. Compared to subjects without congestion, those with congestion experienced smaller decreases in relative blood volume across all follow-up periods (P = 0.001) and returned to baseline within the final follow-up period. Conclusions: Single doses of loop diuretics produce measurable changes in relative blood volume that follow distinct profiles for subjects with vs without congestion. Measured alongside urine output, these profiles may be used to estimate plasma refill rates-potential patient-specific targets for decongestive therapy across serial diuretic doses.

Contexte: Le taux de remplissage plasmatique peut être estimé en combinant les mesures de la diurèse et les profils volémiques relatifs. Chez les personnes atteintes d'insuffisance cardiaque aiguë, une variation du taux de remplissage plasmatique pourrait guider un traitement décongestif par un diurétique de l'anse. L'étude avait pour objectif d'évaluer les profils volémiques relatifs moyens obtenus dans le cadre de deux ou trois mesures de suivi réalisées quelques heures après l'administration d'un diurétique de l'anse à des sujets présentant ou non une congestion initiale. Méthodologie: Une revue systématique d'articles rédigés en anglais, en français, en espagnol et en allemand a été effectuée au moyen des bases de données MEDLINE (1964 à 2019), Cochrane Reviews (1996 à 2019) et Embase (1974 à 2019). Les termes de recherche comprenaient : diurétiques, hémoconcentration, volume plasmatique et volume sanguin. Nous avons inclus des études portant sur des adultes ayant reçu un diurétique de l'anse chez qui au moins une mesure initiale et une mesure de suivi avaient été effectuées. Un seul auteur a recueilli des mesures du volume sanguin individuelles ou de groupe, les a regroupées, au besoin, et converties en variations relatives. Résultats: Parmi les 16 études qui répondaient aux critères d'inclusion prédéfinis, le volume sanguin relatif a diminué de 9,2 % (de 6,6 % à 12,0 %) et est revenu aux valeurs initiales après trois heures ou plus. Les sujets qui présentaient une congestion ont connu des diminutions du volume sanguin relatif inférieures à celles de ceux n'en présentant pas lors de toutes les périodes de suivi (p = 0,001); le volume sanguin relatif est revenu aux valeurs initiales durant la période finale de suivi. Conclusions: Des doses uniques de diurétique de l'anse produisent des changements mesurables du volume sanguin relatif selon des profils distincts chez les sujets présentant une congestion, comparativement à ceux n'en présentant pas. Utilisés en association avec les mesures de la diurèse, ces profils peuvent servir à estimer le taux de remplissage plasmatique, qui constitue potentiellement une cible particulière au patient qui reçoit une série de doses d'un diurétique comme traitement décongestif.

Machine learning classifies predictive kinematic features in a mouse model of neurodegeneration.

Motor deficits are observed in Alzheimer's disease (AD) prior to the appearance of cognitive symptoms. To investigate the role of amyloid proteins in gait disturbances, we characterized locomotion in APP-overexpressing transgenic J20 mice. We used three-dimensional motion capture to characterize quadrupedal locomotion on a treadmill in J20 and wild-type mice. Sixteen J20 mice and fifteen wild-type mice were studied at two ages (4- and 13-month). A random forest (RF) classification algorithm discriminated between the genotypes within each age group using a leave-one-out cross-validation. The balanced accuracy of the RF classification was 92.3 ± 5.2% and 93.3 ± 4.5% as well as False Negative Rate (FNR) of 0.0 ± 0.0% and 0.0 ± 0.0% for the 4-month and 13-month groups, respectively. Feature ranking algorithms identified kinematic features that when considered simultaneously, achieved high genotype classification accuracy. The identified features demonstrated an age-specific kinematic profile of the impact of APP-overexpression. Trunk tilt and unstable hip movement patterns were important in classifying the 4-month J20 mice, whereas patterns of shoulder and iliac crest movement were critical for classifying 13-month J20 mice. Examining multiple kinematic features of gait simultaneously could also be developed to classify motor disorders in humans.

Prenatal intermittent hypoxia sensitizes the laryngeal chemoreflex, blocks serotoninergic shortening of the reflex, and reduces 5-HT3 receptor binding in the NTS in anesthetized rat pups.

We tested the hypothesis that exposure to intermittent hypoxia (IH) during pregnancy would prolong the laryngeal chemoreflex (LCR) and diminish the capacity of serotonin (5-hydroxytryptamine; 5-HT) to terminate the LCR. Prenatal exposure to IH was associated with significant prolongation of the LCR in younger, anesthetized, postnatal day (P) rat pups age P8 to P16 compared to control, room air (RA)-exposed rat pups of the same age. Serotonin microinjected into the NTS shortened the LCR in rat pups exposed to RA during gestation, but 5-HT failed to shorten the LCR in rat pups exposed to prenatal IH. Given these observations, we tested the hypothesis that prenatal hypoxia would decrease binding to 5-HT3 receptors in the nucleus of the solitary tract (NTS) where 5-HT acts to shorten the LCR. Serotonin 3 receptor binding was reduced in younger rat pups exposed to IH compared to control, RA-exposed rat pups in the age range P8 to P12. Serotonin 3 receptor binding was similar in older animals (P18-P24) regardless of gas exposure during gestation. The failure of the 5-HT injected into the NTS to shorten the LCR was correlated with a developmental decrease in 5-HT3 receptor binding in the NTS associated with exposure to prenatal IH. In summary, prenatal IH sensitized reflex apnea and blunted processes that terminate reflex apneas in neonatal rat pups, processes that are essential to prevent death following apneas such as those seen in babies who died of SIDS.

Limited agreement between two noninvasive measurements of blood volume during fluid removal: ultrasound of inferior vena cava and finger-clip spectrophotometry of hemoglobin concentration.

OBJECTIVE: Plots of blood volume measurements over time (profiles) may identify euvolemia during fluid removal for acute heart failure. We assessed agreement between two noninvasive measurements of blood volume profiles during mechanical fluid removal, which exemplifies the interstitial fluid shifts that occur during diuretic-induced fluid removal. APPROACH: During hemodialysis we compared change in maximum diameter of the inferior vena cava by ultrasound ([Formula: see text]) to change in relative blood volume derived from capillary hemoglobin concentration from finger-clip spectrophotometry (RBVSpHb). We grouped profiles of these measurements into three distinct shapes using an unbiased, data-driven modeling technique. METHODS: Fifty patients who were not in acute heart failure underwent a mean of five paired measurements while an average of 1.3 liters of fluid was removed over 2 h during single hemodialysis sessions. [Formula: see text] changed -1.0 mm (95% CI -1.9 to -0.2 mm) and the RBVSpHb changed -1.1% (95% CI -2.7 to +0.5%), but these changes were not correlated (r -0.04, 95% CI -0.32 to +0.24). Nor was there agreement between categorization of profiles of change in the two measurements (kappa -0.1, 95% CI -0.3 to +0.1). SIGNIFICANCE: [Formula: see text] and RBVSpHb estimates of blood volume do not agree during mechanical fluid removal, likely because regional changes in blood flow and pressure modify IVC dimensions as well as changes total blood volume.

A Proof-of-Concept Study of Transcutaneous Magnetic Spinal Cord Stimulation for Neurogenic Bladder.

Patients with chronic spinal cord injury (SCI) cannot urinate at will and must empty the bladder by self-catheterization. We tested the hypothesis that non-invasive, transcutaneous magnetic spinal cord stimulation (TMSCS) would improve bladder function in individuals with SCI. Five individuals with American Spinal Injury Association Impairment Scale A/B, chronic SCI and detrusor sphincter dyssynergia enrolled in this prospective, interventional study. After a two-week assessment to determine effective stimulation characteristics, each patient received sixteen weekly TMSCS treatments and then received "sham" weekly stimulation for six weeks while bladder function was monitored. Bladder function improved in all five subjects, but only during and after repeated weekly sessions of 1 Hz TMSCS. All subjects achieved volitional urination. The volume of urine produced voluntarily increased from 0 cc/day to 1120 cc/day (p = 0.03); self-catheterization frequency decreased from 6.6/day to 2.4/day (p = 0.04); the capacity of the bladder increased from 244 ml to 404 ml (p = 0.02); and the average quality of life ranking increased significantly (p = 0.007). Volitional bladder function was re-enabled in five individuals with SCI following intermittent, non-invasive TMSCS. We conclude that neuromodulation of spinal micturition circuitry by TMSCS may be used to ameliorate bladder function.

Angiotensin 1-7 in the rostro-ventrolateral medulla increases blood pressure and splanchnic sympathetic nerve activity in anesthetized rats.

Angiotensin 1-7 (ANG-(1-7)), a derivative of angiotensin I or II, is involved in the propagation of sympathetic output to the heart and vasculature, and the receptor for ANG-(1-7), the Mas receptor, is expressed on astrocytes in the rostral ventrolateral medulla (RVLM). We recorded blood pressure (BP) and splanchnic sympathetic nerve activity (SSNA) before and after focal injection of ANG-(1-7) into the RVLM of rats. Unilateral injection of ANG-(1-7) into the RVLM, acting through the Mas receptor, increased SSNA and BP, and glutamate receptor antagonists, CNQX and D-AP5, partially reduced the ANG-(1-7) effect. ATP is often co-released with glutamate, and blocking ATP with PPADS also reduced the pressor response to microinjection of ANG-(1-7) within the RVLM. The effects of ANG-(1-7) were blocked by the MAS receptor antagonist, A-779 (which had no consistent effect on blood pressure or sympathetic nerve activity when injected on its own). We conclude that astrocytes in the RVLM participate in central, angiotensin-dependent regulation of blood pressure and sympathetic nerve activity, and the Mas receptor, when activated by ANG-(1-7), elicits the release of the gliotransmitters, glutamate and ATP. These gliotransmitters then cause an increase in sympathetic nerve activity and blood pressure by interacting with AMPA/kainate and P2X receptors in the RVLM.

Reproducibility of point-of-care ultrasonography for central vein diameter measurement: Separating image acquisition from interpretation.

PURPOSE: Central vein point-of-care ultrasonography must be reproducible to detect intravascular volume changes. We sought to determine which measurement step, image acquisition or interpretation, could be more compromising for reproducibility. METHODS: Three investigators each acquired inferior vena cava (IVC) and internal jugular (IJV) vein ultrasonographic sequences (US) from a convenience sample of 21 hospitalized general medicine participants and then interpreted each US three separate times. We partitioned the random errors of acquisition and interpretation, attributing wider dispersions of each to larger reductions in reproducibility. RESULTS: We analyzed 351 interpretations of 39 IVC and 432 interpretations of 48 IJV US. Reproducibility of the maximum (standard error of measurement 3.3 mm [95% confidence interval, CI 2.7-4.2 mm]) and minimum (4.8 mm [3.9-6.3 mm]) IVC diameter measurements were worse than that of the mediolateral (2.5 mm [2.0-3.2 mm]) and anteroposterior (2.5 mm [2.0-3.1 mm]) IJV diameters. The dispersions of random measurement errors were wider among acquisitions than interpretations. CONCLUSIONS: Among our investigators, central vein diameter measurements obtained by point-of-care ultrasonography are not sufficiently reproducible to distinguish clinically meaningful intravascular volume changes from measurement errors. Reproducibility could be most effectively improved by reducing the random measurement errors of acquisition. © 2017 Wiley Periodicals, Inc. J Clin Ultrasound 45:488-496, 2017.

Activation of serotonergic neurons in the medullary caudal raphe shortens the laryngeal chemoreflex in anaesthetized neonatal rats.

NEW FINDINGS: What is the central question of this study? Does activation of serotonergic neurons in the caudal medullary raphe, some of which project to the nucleus of the solitary tract, shorten the laryngeal chemoreflex? What is the main finding and its importance? We found that serotonin originating from neurons in the caudal raphe acts through a 5-HT3 receptor located in the nucleus of the solitary tract to terminate reflex apnoea. Failure or deficiency of this arousal-related process is likely to be relevant to the pathogenesis of sudden infant death syndrome. Failure to terminate apnoea and arouse is likely to contribute to sudden infant death syndrome (SIDS). Serotonin is deficient in the brainstems of babies who have died of SIDS. We tested the hypothesis that activation of serotoninergic neurons in the caudal medullary raphe, some of which project to the nucleus of the solitary tract (NTS), would shorten the laryngeal chemoreflex (LCR). We studied anaesthetized neonatal rat pups between postnatal days 9 and 17. We injected 5-40 µl of water into the larynx to elicit the LCR and measured the duration of respiratory disruption. Microinjection of 50 nl of 100 µm AMPA into the caudal medullary raphe shortened the apnoeas (P < 0.001) and respiratory inhibition (P < 0.005) associated with the LCR. When 50 nl of 30 mm ondansetron, a 5-HT3 antagonist, was microinjected bilaterally into the NTS, AMPA microinjected into the caudal raphe no longer shortened the LCR. After bilateral microinjection of vehicle into the NTS, AMPA microinjection into the caudal raphe significantly shortened the LCR. AMPA, a glutamate receptor agonist, may activate many neurons within the caudal raphe, but blocking the 5-HT3 receptor-dependent responses in the NTS prevented the shortening of the LCR associated with AMPA microinjections into the caudal raphe. Thus, serotonin originating from neurons in the caudal raphe acts through a 5-HT3 receptor located in the NTS to terminate or shorten the LCR. Serotonin is deficient in the brainstems of babies who have died of SIDS, and deficient serotonergic termination of apnoea is likely to be relevant to the pathogenesis of SIDS.

Cerium oxide nanoparticles with antioxidant properties ameliorate strength and prolong life in mouse model of amyotrophic lateral sclerosis.

Cerium oxide nanoparticles (CeNPs) neutralize reactive oxygen and nitrogen species. Since oxidative stress plays a role in amyotrophic lateral sclerosis (ALS) in humans and in the SOD1G93A mouse model of ALS, we tested whether administration of CeNPs would improve survival and reduce disease severity in SOD1G93A transgenic mice. Twice a week intravenous treatment of SOD1G93A mice with CeNPs started at the onset of muscle weakness preserved muscle function and increased longevity in males and females. Median survival after the onset of CeNP treatment was 33.0±3.7days (N=20), and only 22.0±2.5days in mice treated with vehicle, control injections (N=27; P=0.022). Since these citrate-EDTA stabilized CeNPs exhibited catalase and oxidase activity in cell-free systems and in in vitro models of ischemic oxidative stress, we hypothesize that antioxidant activity is the protective mechanism prolonging survival in the SOD1G93A mice.

Interleukin-1ß and interleukin-6 enhance thermal prolongation of the LCR in decerebrate piglets.

Thermal stress and prior upper respiratory tract infection are risk factors for the Sudden Infant Death Syndrome. The adverse effects of prior infection are likely mediated by interleukin-1ß (IL-1ß). Therefore, we examined the single and combined effects of IL-1ß and elevated body temperature on the duration of the Laryngeal Chemoreflex (LCR) in decerebrate neonatal piglets ranging in age from post-natal day (P) 3 to P7. We examined the effects of intraperitoneal (I.P.) injections of 0.3mg/Kg IL-1ß with or without I.P. 10mg/Kg indomethacin pretreatment on the duration of the LCR, and in the same animals we also examined the duration of the LCR when body temperature was elevated approximately 2°C. We found that IL-1ß significantly increased the duration of the LCR even when body temperature was held constant. There was a significant multiplicative effect when elevated body temperature was combined with IL-1ß treatment: prolongation of the LCR was significantly greater than the sum of independent thermal and IL-1ß-induced prolongations of the LCR. The effects of IL-1ß, but not elevated body temperature, were blocked by pretreatment with indomethacin alone. We also tested the interaction between IL-6 given directly into the nucleus of the solitary tract (NTS) bilaterally in 100ngm microinjections of 50µL and pretreatment with indomethacin. Here again, there was a multiplicative effect of IL-6 treatment and elevated body temperature, which significantly prolonged the LCR. The effect of IL-6 on the LCR, but not elevated body temperature, was blocked by pretreatment with indomethacin. We conclude that cytokines interact with elevated body temperature, probably through direct thermal effects on TRPV1 receptors expressed pre-synaptically in the NTS and through cytokine-dependent sensitization of the TRPV1 receptor. This sensitization is likely initiated by cyclo-oxygenase-2 dependent synthesis of prostaglandin E2, which is stimulated by elevated levels of IL-1ß or IL-6. Inflammatory sensitization of the LCR coupled with thermal prolongation of the LCR may increase the propensity for apnea and Sudden Infant Death Syndrome.

Serotonin in the solitary tract nucleus shortens the laryngeal chemoreflex in anaesthetized neonatal rats.

What is the central question of this study? Failure to terminate apnoea and arouse is likely to contribute to sudden infant death syndrome (SIDS). Serotonin is deficient in the brainstems of babies who died of SIDS. Therefore, we tested the hypothesis that serotonin in the nucleus of the solitary tract (NTS) would shorten reflex apnoea. What is the main finding and its importance? Serotonin microinjected into the NTS shortened the apnoea and respiratory inhibition associated with the laryngeal chemoreflex. Moreover, this effect was achieved through a 5-HT3 receptor. This is a new insight that is likely to be relevant to the pathogenesis of SIDS. The laryngeal chemoreflex (LCR), an airway-protective reflex that causes apnoea and bradycardia, has long been suspected as an initiating event in the sudden infant death syndrome. Serotonin (5-HT) and 5-HT receptors may be deficient in the brainstems of babies who die of sudden infant death syndrome, and 5-HT seems to be important in terminating apnoeas directly or in causing arousals or as part of the process of autoresuscitation. We hypothesized that 5-HT in the brainstem would limit the duration of the LCR. We studied anaesthetized rat pups between 7 and 21 days of age and made microinjections into the cisterna magna or into the nucleus of the solitary tract (NTS). Focal, bilateral microinjections of 5-HT into the caudal NTS significantly shortened the LCR. The 5-HT1a receptor antagonist, WAY 100635, did not affect the LCR consistently, nor did a 5-HT2 receptor antagonist, ketanserin, alter the duration of the LCR. The 5-HT3 specific agonist, 1-(3-chlorophenyl)-biguanide, microinjected bilaterally into the caudal NTS significantly shortened the LCR. Thus, endogenous 5-HT released within the NTS may curtail the respiratory depression that is part of the LCR, and serotonergic shortening of the LCR may be attributed to activation of 5-HT3 receptors within the NTS. 5-HT3 receptors are expressed presynaptically on C fibre afferents of the superior laryngeal nerve, and serotonergic shortening of the LCR may be mediated presynaptically by enhanced activation of inhibitory interneurons within the NTS.

Glutamate oxidase biosensor based on mixed ceria and titania nanoparticles for the detection of glutamate in hypoxic environments.

We report on the design and development of a glutamate oxidase (GmOx) microelectrode for measuring l-glutamic acid (GluA) in oxygen-depleted conditions, which is based on the oxygen storage and release capacity of cerium oxides. To fabricate the biosensor, a nanocomposite of oxygen-rich ceria and titania nanoparticles dispersed within a semi-permeable chitosan membrane was co-immobilized with the enzyme GmOx on the surface of a Pt microelectrode. The oxygen delivery capacity of the ceria nanoparticles embedded in a biocompatible chitosan matrix facilitated enzyme stabilization and operation in oxygen free conditions. GluA was measured by amperometry at a working potential of 0.6 V vs Ag/AgCl. Detection limits of 0.594 µM and 0.493 µM and a sensitivity of 793 pA/µM (RSD 3.49%, n=5) and 395 pA/µM (RSD 2.48%, n=5) were recorded in oxygenated and deoxygenated conditions, with response times of 2s and 5s, respectively. The biosensor had good operational stability and selectivity against common interfering substances. Operation of the biosensor was tested in cerebrospinal fluid. Preliminary in vivo recording in Sprague-Dawley rats to monitor GluA in the cortex during cerebral ischemia and reperfusion demonstrate a potential application of the biosensor in hypoxic conditions. This method provides a solution to ensure functionality of oxidoreductase enzymes in oxygen-free environments.

Modeling the influence of vitamin D deficiency on cigarette smoke-induced emphysema.

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality worldwide. While the primary risk factor for COPD is cigarette smoke exposure, vitamin D deficiency has been epidemiologically implicated as a factor in the progressive development of COPD-associated emphysema. Because of difficulties inherent to studies involving multiple risk factors in the progression of COPD in humans, we developed a murine model in which to study the separate and combined effects of vitamin D deficiency and cigarette smoke exposure. During a 16-week period, mice were exposed to one of four conditions, control diet breathing room air (CD-NS), control diet with cigarette smoke exposure (CD-CSE), vitamin D deficient diet breathing room air (VDD-NS) or vitamin D deficient diet with cigarette smoke exposure (VDD-CSE). At the end of the exposure period, the lungs were examined by a pathologist and separately by morphometric analysis. In parallel experiments, mice were anesthetized for pulmonary function testing followed by sacrifice and analysis. Emphysema (determined by an increase in alveolar mean linear intercept length) was more severe in the VDD-CSE mice compared to control animals and animals exposed to VDD or CSE alone. The VDD-CSE and the CD-CSE mice had increased total lung capacity and increased static lung compliance. There was also a significant increase in the matrix metalloproteinase-9: tissue inhibitor of metalloproteinases-1 (TIMP-1) ratio in VDD-CSE mice compared with all controls. Alpha-1 antitrypsin (A1AT) expression was reduced in VDD-CSE mice as well. In summary, vitamin D deficiency, when combined with cigarette smoke exposure, seemed to accelerate the appearance of emphysemas, perhaps by virtue of an increased protease-antiprotease ratio in the combined VDD-CSE animals. These results support the value of our mouse model in the study of COPD.

Laryngeal reflex apnea in neonates: effects of CO2 and the complex influence of hypoxia.

We have examined influence of hypocapnia, mild hypercapnia and hypoxia on the durations of fictive apnea and respiratory disruption elicited by injection of 0.1ml of water into the laryngeal lumen-the laryngeal chemoreflex (LCR)-in 20 unanesthetized, decerebrate, vagotomized piglets aged 4-10 days that were paralyzed and ventilated with a constant frequency and tidal volume. The LCR was enhanced by hypocapnia and attenuated by hypercapnia as reported by others. The responses to laryngeal stimulation during hypoxia were varied and complex: some animals showed abbreviated responses during the tachypnea of early hypoxia, followed after 10-15min by more prolonged apnea and respiratory disruption accompanying the reduction in ventilatory activity that commonly occurs during sustained hypoxia in neonates. We speculate that this later hypoxic enhancement of the LCR may be due to accumulation of adenosine in the brain stem.

Influence of age, body temperature, GABAA receptor inhibition and caffeine on the Hering-Breuer inflation reflex in unanesthetized rat pups.

We measured the duration of apnea induced by sustained end-inspiratory lung inflation (the Hering Breuer Reflex, HBR) in unanesthetized infant rat pups aged 4 days (P4) to P20 at body temperatures of 32°C and 36°C. The expiratory prolongation elicited by the HBR lasted longer in the younger pups and lasted longer at the higher body temperature. Blockade of adenosine receptors by caffeine following injection into the cisterna magna (ICM) significantly blunted the thermal prolongation of the HBR. Blockade of gama-amino-butyric acid A (GABAA) receptors by pre-treatment with ICM bicuculline had no effect on the HBR duration at either body temperature. To test the hypothesis that developmental maturation of GABAergic inhibition of breathing was modifying the response to bicuculline, we pretreated rat pups with systemically administered bumetanide to lower the intracellular chloride concentration, and repeated the bicuculline studies. Bicuculline still did not alter the HBR at either temperature after bumetanide treatment. We administered PSB-36, a selective adenosine A1 receptor antagonist, and this drug treatment did not modify the HBR. We conclude that caffeine blunts the thermal prolongation of the HBR, probably by blocking adenosine A2a receptors. The thermally sensitive adenosinergic prolongation of the HBR in these intact animals does not seem to depend on GABAA receptors.

Neuroprotective mechanisms of cerium oxide nanoparticles in a mouse hippocampal brain slice model of ischemia.

Cerium oxide nanoparticles (nanoceria) are widely used as catalysts in industrial applications because of their potent free radical-scavenging properties. Given that free radicals play a prominent role in the pathology of many neurological diseases, we explored the use of nanoceria as a potential therapeutic agent for stroke. Using a mouse hippocampal brain slice model of cerebral ischemia, we show here that ceria nanoparticles reduce ischemic cell death by approximately 50%. The neuroprotective effects of nanoceria were due to a modest reduction in reactive oxygen species, in general, and ~15% reductions in the concentrations of superoxide (O(2)(•-)) and nitric oxide, specifically. Moreover, treatment with nanoceria markedly decreased (~70% reduction) the levels of ischemia-induced 3-nitrotyrosine, a modification to tyrosine residues in proteins induced by the peroxynitrite radical. These findings suggest that scavenging of peroxynitrite may be an important mechanism by which cerium oxide nanoparticles mitigate ischemic brain injury. Peroxynitrite plays a pivotal role in the dissemination of oxidative injury in biological tissues. Therefore, nanoceria may be useful as a therapeutic intervention to reduce oxidative and nitrosative damage after a stroke.

TRPV1 channels in the nucleus of the solitary tract mediate thermal prolongation of the LCR in decerebrate piglets.

Elevating body temperature or just the temperature of the dorsal medulla by approximately 2°C prolongs the laryngeal chemoreflex (LCR) in decerebrate neonatal piglets. We tested the hypothesis that transient receptor potential vanilloid 1 (TRPV1) receptors in the nucleus of the solitary tract (NTS) mediate thermal prolongation of the LCR. We studied the effect of a selective TRPV1 receptor antagonist on thermal prolongation of the LCR, and we tested the effect of a TRPV1 agonist on the duration of the LCR under normothermic conditions. We studied 37 decerebrate neonatal piglets between the ages of post-natal days 4 and 7. The TRPV1 receptor antagonist, 5'-iodoresiniferatoxin (65µM/L in 100nL), blocked thermal prolongation of the LCR when injected bilaterally into the region of the NTS. The TRPV1 agonist, resiniferatoxin (0.65-1.0mM/L in 100nL), prolonged the LCR after bilateral injection into the NTS even when the body temperature of each piglet was normal. The effect of the TRPV1 agonists could be blocked by treatment with the GABA(A) receptor antagonist, bicuculline, whether given intravenously (0.3mg/kg) or focally injected bilaterally into the NTS (10mM in 100nL). We conclude that TRPV1 receptors in the NTS mediate thermal prolongation of the LCR.