bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anatomic Intrapulmonary Arteriovenous Anastomoses And Right‐To‐Left Shunt As Evaluated By The Multiple Inert Gas Elimination Technique
Authors: Stickland Michael K , Wagner Peter D , Tedjasaputra Vincent , Fuhr Desi P , Collins Sophie E , Wagner Harrieth , van Diepen Sean , Byers Brad W , Hopkins Susan R 
Published: November 2023

BackgroundPrevious work using agitated saline contrast echocardiography suggests anatomic intrapulmonary arteriovenous anastomoses (IPAVAs) can be recruited during exercise, in hypoxia and when cardiac output is increased pharmacologically. These observations are in contrast to the considerable work using the multiple inert gas elimination technique (MIGET) which has not found significant right‐to‐left intrapulmonary shunt at rest or during exercise. The purpose of the present study was to evaluate anatomical intra‐pulmonary arteriovenous connections using agitated saline contrast echocardiography and 25μm microspheres and compare to right to left gas exchange shunt quantified by MIGET in the dog.MethodsDogs were anaesthetized (I.V. propofol), ventilated (5 cm H2O PEEP) and evaluated during the following conditions: 1) Baseline, 2) 10 μg/kg/min I.V. dobutamine, 3) 2 μg/kg/min I.V. dopamine, 4) hypoxia (FIO2 = 0.125). Within each condition, pulmonary mixed venous blood was obtained via a Swan‐Ganz catheter, and arterial blood via indwelling femoral catheter. Ventilation‐perfusion mismatch (VA/Q.), diffusion limitation and right‐to‐left shunt was quantified by MIGET and cardiac output by direct Fick. Presence of IPAVAs was evaluated by agitated saline contrast echocardiography, as well as contrast echocardiography using 25μm microspheres.ResultsAt baseline, no animal demonstrated a positive contrast echocardiogram suggestive of IPAVAs, and calculated right‐to‐left shunt from MIGET was 0.3±0.1% of cardiac output. Across the three experimental conditions, saline contrast bubbles were detected in the left ventricle 83% of the time, while 25μm microspheres were detected in the left ventricle by echocardiography 67% of the time. No diffusion limitation or low VA/Q. regions (i.e. V.A/Q. ratio of 0.005–0.1) were detected at any point, and right‐to‐left shunt was below 1% during dobutamine, dopamine, and hypoxia (0.6±0.3%, 0.6±0.3%, 0.8±0.6%, respectively).ConclusionAnatomic arteriovenous anastomoses of approximately 25 μm in diameter can be recruited during hypoxia and pharmacologically in the healthy intact lung; however, their functional contribution to right‐to‐left shunt or gas exchange impairment is minimal.Support or Funding InformationNatural Sciences and Engineering Council of Canada (NSERC)
Inhibitory glial modulation of excitatory neurotransmission is reduced in nucleus tractus solitarius (NTS) of rats after short‐term sustained hypoxia
Authors: Accorsi‐Mendonca Daniela , Bonagamba Leni GH , Machado Benedito H. 
Published: November 2023

During hypoxia condition the peripheral chemoreflex is activated and induces autonomic and respiratory responses. In this study we analyzed the effect of short‐term sustained hypoxia [(SH) 24 hours, FIO210%] on the synaptic transmission of NTS. Using brainstem slices and whole‐cell patch clamp we observed that passive properties of NTS astrocytes were not affected by SH [input resistance: control: 44.5 ± 14 MΩ (n=8) vs SH: 31.5 ± 10 MΩ (n=4)][RMP control: −84 ± 3.6 mV (n=10) vs SH: −75 ± 5.2 mV (n=7)]. Since protease‐activated receptors 1 (PAR1) are found only in NTS astrocytes and not in neurons, we also evaluated the glial modulation on neurotransmission by activation of astrocytes with SFLLRN‐NH2 (PAR1 agonist, 20 μM). The SFLLRN‐NH2 decreased the amplitude of evoked excitatory post‐synaptic currents (eEPSCs) in NTS neurons from SH animals to values similar to the control group [control: −51 ± 5 pA (n=3) vs SH: −56 ± 8 pA (n=5)]. SFLLRN‐NH2 did not change the RMP of NTS neurons in both groups [control: aCSF: −65.5 ± 1.5 mV vs aCSF + SFLLRN‐NH2: −61 ± 5 mV, (n=4); SH: aCSF: −63 ± 5 vs aCSF + SFLLRN‐NH2: −56 ± 8 mV, (n=4)]. In addition, using in vivo labeling and multi‐photon microscopy, we observed that SH decreased the cellular density of astrocytes in NTS [control: 0.003 ± 0.0004 (n=5) vs SH: 0.001 ± 0.0001 cells / μm2 (n=5)]. In conclusion, SH decreased the number of astrocytes and their inhibitory modulation on excitatory transmission on the NTS neurons.Support or Funding InformationFinancial support: FAPESP and CNPq.
Bicuculline sensitive tonic current in RVLM neurons
Authors: Gao Hong , Derbenev Andrei V 
Published: November 2023

Neurons in the rostral ventrolateral medulla (RVLM) are best known for controlling arterial blood pressure and sympathetic outflow. It is well accepted that GABAergic inhibition in the RVLM is critical for the control of sympathetic outflow, and our previous study demonstrated that extrasynaptic GABAA receptors tonically inhibit RVLM neurons. In order to identify the subunit composition of GABAA receptors mediating the tonic current, we conducted whole‐cell patch‐clamp recordings from presympathetic RVLM neurons identified with retrograde viral labeling. First, we determined the effect of zolpidem on the amplitude of tonic current. Application of zolpidem (1μM), which activates GABAA receptors containing α1, α2 and/or α3 subunits, failed to modulate the amplitude of tonic current. Second, to determine the contribution of δ subunits containing GABAA receptors to the tonic current, we used THIP (4,5,6,7‐tetrahydroisoxazolo(5,4‐c)pyridin‐3‐ol), an agonist of δ subunits containing GABAA receptors. Application of THIP (10μM) produced no changes in the amplitude of tonic current in RVLM neurons. Then, a non‐selective voltage‐dependent K+‐channels blocker, 4‐aminopyridine (4‐AP), and a voltage‐dependent transient outward K+‐channels blocker, quinidine, was used. 4‐AP and quinidine induced a significant shift in the baseline current, corresponding to a 32.5±3.3pA and 78.5±8.5pA current, respectively. This data demonstrate that the tonic current sensitive to bicuculline methiodide in the RVLM is partially mediated by time‐ and voltage‐dependent transient outward K+‐channels, which may regulate the initial phase of repolarization modulating the voltage‐ and time‐dependence of action potentials in RVLM neurons.Support or Funding InformationThis work was supported by NIH HL122829 for AVD.
Blockade of orexin receptors reduces glutamatergic excitation of adrenal premotor neurons in the rostral ventrolateral medulla
Authors: Korim Willian Seiji , Verberne Tony J 
Published: November 2023

Excitation of adrenal sympathetic premotor neurons in the rostral ventrolateral medulla (RVLM) elicits epinephrine release as part of the glucose counter‐regulatory response to hypoglycemia. It is known that this response is partly mediated by excitatory inputs from hypothalamic orexin neurons. Although some orexin neurons co‐express glutamate, whether orexin and glutamate interact in order to facilitate adrenal sympathetic premotor neurons is unknown. In pentobarbitone‐anesthetized male Sprague‐Dawley rats, we show tested whether glutamatergic activation of adrenal premotor neurons depends on activation of orexin receptors (Ox‐R). Microinjection of glutamate (50 mM/50 nl) into the RVLM, where adrenal premotor neurons are found, increased adrenal sympathetic nerve activity (ASNA). The increase in ASNA was reduced following non‐selective blockade of orexin receptors. RVLM orexin receptors were blocked by microinjecting a combination of SB334867 (Ox1‐R antagonist) and TCS OX2 29 (Ox2‐R antagonist) into the RVLM. The reduction in ASNA in response to glutamate microinjection into the RVLM was dose dependent (0.1–10 mM/50 nl), and the response was abolished with 1 mM of the combined antagonists (P<0.05). The results suggest that the counter‐regulatory release of epinephrine during hypoglycemia depends on the interaction between glutamate and orexin receptors located on the adrenal sympathetic premotor neurons.Support or Funding InformationNHMRC AustraliaAustin Medical Research Foundation
Insulin‐responsive Adrenergic Neurons in Rat Medulla Oblongata
Authors: Llewellyn‐Smith Ida J , Senthilkumaran Manjula , Bobrovskaya Larisa , Verberne Anthony J M 
Published: November 2023

Adrenergic neurons in the brainstem play critical roles in glucose homeostasis. When glucose availability is low, these neurons drive secretion of adrenaline from the adrenal medulla and food intake. Although glucoprivation‐sensitive adrenergic neurons in the brainstem have been mapped, the distribution of adrenergic neurons that respond to insulin has not been reported. To fill this gap in knowledge, we fasted rats overnight and then gave them intraperitoneal injections of either insulin (10 IU/kg) or saline after 10 days of twice‐daily handling. Tail vein blood samples were collected immediately before injection and at 30, 60 and 90 min after injection, at which time the rats were perfused with 4% formaldehyde. Coronal sections of perfused medulla (1:4 series) from the spinomedullary junction to mid‐facial nucleus were immunoperoxidase stained to show Fos‐immunoreactivity (IR) with a black reaction product plus phenylethanolamine N‐methyltransferase (PNMT) or choline acetyltransferase (ChAT)‐immunoreactivity with a brown reaction product. Insulin treatment lowered blood glucose from 4.9+0.3 mmol/L at baseline to 1.7+0.2 mmol/L at 90 min (mean + SEM; n=6) whereas saline treatment had no effect (4.9+0.2 mmol/L at baseline vs 5.2+0.4 at 90 min; n=3). In insulin‐treated rats, many PNMT‐IR C1 neurons had intensely‐stained Fos‐IR nuclei, indicating that they had been activated. The proportion of Fos‐IR C1 neurons was higher in the caudal than in the rostral part of the C1 cell column. Insulin treatment also induced Fos‐IR in almost all of the rostral C2 neurons and in many of the midline C3 neurons. The insulin‐responsive C2 neurons may be catecholaminergic dorsal vagal motor neurons since ChAT‐positive neurons with Fos‐positive nuclei occurred in the same locations and numbers. In saline‐treated rats, many fewer C1 neurons were stained for Fos and the staining was much less intense. Fos‐IR occurred in almost no C2 or C3 neurons in control animals. These observations indicate that all three groups of medullary adrenergic neurons are activated by insulin. The high numbers of PNMT‐positive neurons that strongly express Fos after insulin treatment support the important roles that these neurons play in the central response to a decrease in glucose bioavailability.Support or Funding InformationDiabetes Australia Research Trust; National Health and Medical Research Council of Australia
ENDOCANNABINOID SIGNALING IN THE DORSAL PERIAQUEDUCTAL GRAY INFLUENCES THE DEVELOPMENT OF NEUROPATHIC PAIN
Authors: Dean Caron , Hillard Cecilia , Seagard Jeanne , Hopp Francis , Hogan Quinn 
Published: November 2023

Descending endocannabinoid modulation of sensory pathways from the midbrain dorsal periaqueductal gray (dPAG) contributes to the relief of neuropathic pain. Endocannabinoids also activate the sympathetic nervous system through actions at cannabinoid 1 receptors (CB1Rs) in the dPAG. These studies were designed to determine if endocannabinoid signaling in the dPAG influences the development of pain and autonomic changes following nerve injury. Male Sprague‐Dawley rats (320–340 gm) were implanted with telemetric transducers to monitor blood pressure. After one week, either a neuropathic pain model of spared nerve injury (SNI) or sham surgery was performed. Heart rate (HR) and HR variability were derived from blood pressure recordings taken on days 5–7 following implantation surgery and on days 1,3,7,10,14 and 21 following SNI or sham surgery. On these days, rats were also tested for hyperalgesia responses to noxious mechanical stimulation of the hindpaw. Animals that demonstrated a hyperalgesia response rate >20% on day 21 were considered hyperalgesic. Brains were removed on day 21 post SNI/sham, and the dPAG region was excised and quick‐frozen in liquid nitrogen. Real time RT‐PCR was performed to analyze the tissue samples for mRNA expression of the endocannabinoid metabolic enzymes fatty acid amide hydrolase (FAAH) and for CB1Rs. Transcript levels were plotted against blood pressure, HR, autonomic activity, and hyperalgesia response rate for regression analysis to determine correlations. Over 21 days, a range of hyperalgesia responses from 0–80 % developed in SNI rats and no hyperalgesia developed in sham animals. Hyperalgesia animals had a significantly depressed low frequency/high frequency (LF/HF) ratio of HR variability, an indicator of sympatho‐vagal balance and higher HF power, indicative of vagal tone. The hyperalgesia response rate was correlated, and the LF/HF power was inversely correlated, to amounts of FAAH mRNA. Reduced FAAH expression in non‐hyperalgesia animals would be expected to result in increased concentrations of the endocannabinoid, anandamide. Transcript levels for CB1R were unchanged. Animals with hyperalgesia showed a significantly greater decrease in HR over 21 days than those without, while blood pressure remained unchanged. These data suggest that increased endocannabinoid signaling in the dPAG influences autonomic nerve activity and prevents the development of neuropathic pain.Support or Funding InformationSupported by Veterans Affairs BX001863 (QHH, CD) and the Research and Education Component of the Advancing a Healthier Wisconsin Endowment at MCW (CJH).
Controlled hypotensive Hemorrhage sensitizes angiotensin II‐elicited hypertension
Authors: Xue Baojian , Beltz Terry G. , Guo Fang , Thunhorst Robert L. , Johnson Alan Kim 
Published: November 2023

Hemorrhagic shock is associated with increased renin‐angiotensin system (RAS) activity and elevated levels of proinflammatory cytokines (PICs) in the circulation and in central nervous system (CNS) regions controlling arterial pressure and vasopressin release. Using an Induction‐Delay‐Expression (IND‐DEL‐EXP) experimental paradigm, our previous studies demonstrated that activation of the central RAS and inflammation produced by various challenges sensitizes angiotensin (ANG) II‐elicited hypertension. The present study tested the hypothesis that controlled hypotensive hemorrhage also sensitizes the ANG II‐elicited hypertensive response. Male rats were prepared for telemetry recording of blood pressure (BP). During IND, rats were hemorrhaged (5 ml/rat at 1.5 ml/min) via the jugular vein on two occasions separated by 1 day. The blood was collected in heparin and centrifuged, and the cells re‐suspended in saline for re‐infusion. Hemorrhage lowered BP to ~40 mmHg that was maintained for 30 min after which time the rats were reinfused. After a one‐week DEL, the rats were administrated ANG II (120 ng/kg/min, SC) for 2 weeks (EXP). Hemorrhaged rats had a significantly enhanced hypertensive response to the ANG II infusion when compared to control rats (Δ52.3±3.8 mmHg vs. Δ29.8±2.8 mmHg). RT‐PCR analysis of tissue from the lamina terminalis and the hypothalamic paraventricular nucleus indicated that the ANG II treatment upregulated mRNA expression of several components of the RAS and PICs including angiotensinogen, angiotensin type 1 receptor, angiotensin converting enzyme, TNF‐α, interleukin (IL)‐1β and IL‐6 in both control and hemorrhaged rats. Notably, the increases in PIC expression were greater in hemorrhaged rats than that in control rats. The results indicate that controlled hypotensive hemorrhage sensitizes ANG II‐elicited hypertension and that this is associated with upregulation of the central RAS and of brain PICs.Support or Funding InformationNIH grants HL‐14388, HL‐98207 and MH‐80241
Neuronal expression of prorenin and the (pro)renin receptor in the paraventricular nucleus of the hypothalamus and brainstem in the central nervous system
Authors: Buller Sophie A , Feng Yumei 
Published: November 2023

The renin angiotensin system (RAS) is important in the regulation of blood pressure and body fluid homeostasis. Evidence of a local RAS exists within the brain, with all components being synthesized locally, however, active renin is detected only at very minimal levels. We previously reported that the conversion of angiotensinogen to Ang I and thus to Ang II in the central nervous system, is largely mediated by the renin precursor, prorenin, which undergoes non‐proteolytic activation upon binding the (pro)renin receptor (PRR). Despite evidence of a local RAS system within the brain, it remains unclear as to which cell types express prorenin and the PRR, especially in the cardiovascular regulatory regions of the brain. To address this question, we used an antibody that specifically recognizes prorenin, but not active renin, and PRR for immunofluorescence co‐staining with neuronal (NeuN) and astroglial (glial fibrillary acidic protein, GFAP) cell markers. We found that prorenin and PRR immune‐reactivity is mainly co‐localized with NeuN but not GFAP in the brain hypothalamus and brainstem. More interestingly, prorenin and PRR immune‐reactivity is found in approximately 95% of the vasopressin‐positive and tyrosine hydroxylase‐positive neurons. Finally, using cholera toxin B (CTB) retrograde tracing from the RVLM to PVN, and immune‐labeling of CTB for PVN presympathetic neurons, we found that prorenin and PRR are highly expressed in the presympathetic neurons in the PVN. In summary, prorenin and PRR protein are found majorly in neurons, but not astrocytes in key brain regions involved in the regulation of blood pressure and cardiovascular function. In the PVN, prorenin and the PRR are expressed in the vasopressin‐positive, tyrosine hydroxylase‐positive and presympathetic neurons. These data provide anatomical support to a potential physiological importance of prorenin and PRR in the PVN and brainstem.Support or Funding InformationNIH/NHBL (1R01HL122770) to Y Feng
Adropin Influences the Excitability of Neurons in the Paraventricular Nucleus
Authors: Loewen Spencer P. , Ferguson Alastair V. 
Published: November 2023

Adropin, a peptide hormone encoded by the Energy Homeostasis Associated (Enho) gene, has been observed to have metabolic roles in the periphery but unknown actions within the brain. The hypothalamic paraventricular nucleus (PVN) is an important autonomic control center required for regulating energy balance, and is therefore a potential target for centrally acting adropin. Three subpopulations of neurons exist within the PVN, each of which can be classified based on distinct electrophysiological fingerprints. These populations are the magnocellular (MNC) neurosecretory, parvocellular preautonomic (PA), and parvocellular neuroendocrine (NE) neurons. In the present study, we used whole‐cell current‐clamp techniques to examine the effects of adropin on the excitability of each subpopulation of neurons within the PVN of the rat. Bath application of 10 nM adropin to MNC PVN neurons (n=9) elicited responses in 100% of cells, with 78% depolarizing (mean: 5.9 ± 2.5 mV) and 22% hyperpolarizing (mean: −2.6 ± 0.4 mV). Adropin treatment to PA neurons (n=15) caused 53% to depolarize (mean: 5.1 ± 1.6 mV), 13% to hyperpolarize (mean: −10.4 ± 1.8 mV), and the remaining 34% showing no response. Finally, adropin caused responses in 57% of NE neurons (n=14), with 43% depolarizing (mean: 5.7 ± 2.6 mV) and 14% hyperpolarizing (mean: −3.7 ± 0.7 mV). These results suggest that central adropin may exert its physiological effects through actions on neurons in the PVN.Support or Funding InformationSupported by: the Canadian Institutes of Health Research
The overactive orexin system may play an important role in the poor sleep quality and its associated cardiorespiratory changes in neurogenic hypertension in Spontaneously Hypertensive Rats
Authors: Briggs Logan , Muggler Corey , Li Aihua 
Published: November 2023

Non‐dipper essential hypertensive patients suffer from sleep disturbances marked by many microarousal‐associated increases in blood pressure (BP), and the offspring of non‐dipper hypertension parents also showed a greater number of microarousals compared to the offspring of dipper hypertensive and normotensive control parents. Sleep disorders are closely linked to hypertension, and autonomic dysfunction, specifically altered chemoreflex control of sympathetic activity, may play a prominent role in this relationship. It has been reported that spontaneously hypertensive rats (SHRs) have higher sympathetic activity, elevated central and peripheral chemoreflexes, an impaired baroreflex, and poorer sleep quality. Recent studies have linked the orexin system to neurogenic hypertension in SHRs and showed that: 1) blocking orexin receptors with a dual orexin receptor antagonist can significantly lower BP in SHRs with no effect on BP in normotensive rats, and 2) SHRs have more orexin neurons in the lateral hypothalamus than that of normotensive WKY rats. In this study we ask: 1) are there age‐related sleep disturbances and associated cardiorespiratory changes in wakefulness and sleep in SHRs, and 2) will blocking orexin receptors improve the sleep quality and sleep‐associated cardiorespiratory disturbances in SHRs. SHRs at two ages, young (P28–45), and adult (3‐month), were used in this study. All the rats were instrumented with blood pressure telemeter, EEG and EMG electrodes, and 24hr blood pressure, heart rate and sleep‐wake cycle were recorded and analyzed. The results showed: 1) during the light period, SHRs spent 45% & 46% more time in wakefulness, 27% & 23% less time in NREM and 46% & 48% less time in REM sleep at young and adult age respectively compared to age‐matched normotensive WKY controls rats; 2) SHRs, both young and adult, have significantly decreased circadian‐related sleep‐wake and blood pressure difference; 3) SHRs have more sleep disturbance, microarousals and associated increases in BP than normotensive WKY control rats; 4) young SHRs appeared to spend more time in wakefulness than adult SHR during the light period (P=0.009); 5) blocking orexin receptor with a dual orexin receptor antagonist can significantly increase the time spend in sleep in both light and dark periods. In conclusion, SHRs have poor sleep quality from a very young age, and this may contribute to the progressive of hypertension. We suggest that the poor sleep quality in SHRs is associated with the overactive orexin system, and modulation of orexin system may be beneficial for improving sleep quality and treating hypertension in neurogenic hypertension.Support or Funding InformationDartmouth Undergraduate Research Office/ Howard Hughes Medical Institute for Undergraduate Research; NIH HL 28066.