bluuebunny/crossref_metadata_2025 huggingface dataset:
The Hypoxic Ventilatory Response is Blocked by AMPK Deletion in Catecholaminergic, but not Adrenergic Cells
Authors: MacMillan Sandy , Evans A. Mark
Published: June 2021

During hypoxia, ventilatory adjustments are critical to the maintenance of adequate oxygen (O2) delivery, for example during sleep or ascent to altitude (1). We recently demonstrated that the AMP‐activated protein kinase (AMPK), a ubiquitously expressed metabolic sensor (2), protects against hypoventilation and apnea during hypoxia (3). Here, we further investigated the circuit mechanism by which AMPK deficiency impacts the hypoxic ventilatory response (HVR). Using unrestrained whole‐body plethysmography, we compared the effects on the HVR of mice with dual deletion of the AMPK‐α1/α2 catalytic subunits in all catecholaminergic (TH‐positive) cells with the HVR of mice with AMPK‐α1/α2 deletion targeted to adrenergic cells alone (Phenylethanolamine N‐methyltransferase (PNMT)‐positive). Relative to controls (AMPK‐α1/α2 floxed), mice with TH‐Cre driven AMPK deletion (TH AMPK‐α1/α2 dKO) exhibited hypoventilation, characterized by marked attenuation of minute ventilation (p<0.0001) during each minute of exposures to severe hypoxia (8% O2). By contrast, in mice with PNMT‐Cre driven AMPK deletion (PNMT AMPK‐α1/α2 dKO) the HVR was augmented rather than attenuated, although this only reached significance relative to controls (AMPK‐α1/α2 floxed and PNMT Cre) when taken as averages for the whole 10min period of exposure to severe hypoxia (p<0.001–0.0001). As one might expect given these outcomes, the HVR of PNMT AMPK‐α1/α2 dKO mice was significantly greater than that for TH AMPK‐α1/α2 dKO during each full minute of hypoxia (p<0.0001). Furthermore, the apnea‐duration index (ADI) was significantly augmented in TH AMPK‐α1/α2 dKO mice compared to controls (p<0.01–0.0001). By contrast, PNMT AMPK‐α1/α2 dKO mice exhibited a reduction in the average ADI compared to controls (p<0.05–0.01). This reduction in the ADI for PNMT AMPK‐α1/α2 dKO mice was primarily due to a lower number of apneas during the first 3 to 4 minutes of hypoxic exposure, the ADI being comparable to controls between 4 and 10 min. Accordingly, the ADI of PNMT AMPK‐α1/α2 dKO was attenuated at each time point throughout the 10min exposure to hypoxia when compared to TH AMPK‐α1/α2 dKO mice (p<0.0001). In conclusion, we have uncovered a split in the AMPK‐dependent regulation of the catecholaminergic respiratory network during hypoxia, where the HVR is promoted by AMPK‐dependent modulation of noradrenergic inputs, but opposed by AMPK‐dependent modulation of adrenergic inputs. AMPK may thus protect against hypoventilation and apnea through noradrenergic signaling, and might aid restoration of normal CO2 levels during hypoxic hyperventilation through adrenergic signaling (4).

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Activation of Lysine Demethylases (KDM's) by Intermittent Hypoxia
Authors: Nanduri Jayasri , Wang Ning , Semenza Gregg L , Prabhakar Nanduri R
Published: June 2021

We previously reported that intermittent hypoxia (IH), a hallmark of sleep apnea, increases reactive oxygen species (ROS) in the central and peripheral nervous system. IH‐induced increase in ROS abundance was in part due to hypoxia‐inducible factor (HIF)‐1 dependent transcriptional up regulation of NADPH oxidase (Nox)‐2 and 4. Emerging evidence suggests that lysine demethylases (KDM's) acting as co‐activators contribute to HIF‐1‐dependent transcriptional activation. The aim of the present study is to assess whether KDM proteins contribute to IH‐evoked Nox4 transcriptional activation by HIF‐1. Experiments were performed on rat pheochromocytoma (PC12) cells treated with alternating cycles of 1.5% O2 for 30 sec followed by 20% O2 for 5 min. Protein abundance and activities of KDM2A, KDM4A, 4B, 4C and KDM6B in nuclear extracts were analyzed by immunoblot and colorimetric assays, respectively. Cells treated with 60 cycles of IH (IH60) showed increased protein abundance and activity of KDM6B. Co‐immunoprecipitation assays showed that KDM6B interacts with HIF‐1α and blockade of KDM6B with silencing RNA prevented Nox4 transcriptional activation by HIF‐1. These findings demonstrate that KDM6B functions as a coactivator of HIF‐1 mediated transactivation of Nox4 by IH.

Support or Funding Information

Supported by NIH‐HL‐90554.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Disrupted spatial learning and memory is unaffected by training prior to intermittent hypoxia exposure
Authors: Nwakudu Chinwendu U. , Arias‐Cavieres Alejandra , Khuu Maggie A. , Garcia Alfredo J.
Published: June 2021

Intermittent hypoxia (IH) is a common event occurring with untreated sleep apnea, a clinical condition commonly associated with cognitive deficits in learning and memory. Rodents exposed to IH, as a model for sleep apnea, exhibit impairments in spatial learning and memory. However, performance on spatial learning and memory tasks show individual variance. The objective of this ongoing study is to determine whether training prior to IH exposure influences performance on spatial learning tasks following IH. We hypothesize that while IH impairs spatial learning and memory through an oxidative stress mediated mechanism, training prior to exposure will improve performance on spatial memory tasks following IH. To test this, we developed a Barnes maze protocol to assess spatial learning and memory in mice preceding and after exposure to 10 days of IH (IH10). Before IH10, variance among individual mice was evident during the probe trial in the latency to initial entry into the exit zone. However, during the second maze session (10 days after the first probe trial), the latency in initial entry into the exit zone was increased in IH10 treated mice (n=4). Conversely, mice naive to IH10 exhibited decreased latency in initial entry into the exit zone during the second maze session (n=4). LTP measured in area CA1 was suppressed in hippocampal brain slices from mice exposed to IH (control 162%±12% (n=7) vs. IH 122±7% (n=11)). This suppression of LTP was only partially mitigated by antioxidant treatment during IH10. These results indicate that IH disrupts learning and memory independent of prior training and impaired spatial learning and memory corresponds with suppressed LTP following IH.

Support or Funding Information

This work was supported by NIH R01 NS10742101 (AJG)

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Erythropoietin Secretion to Hypoxia Is Enhanced with an Expanded Plasma Volume after a Bout of Exercise in Warm Environment
Authors: Okazaki Kazunobu , Takeda Ryosuke , Imai Daiki , Kawai Eriko , Ota Akemi , Saho Kosuke , Morita Emiko , Suzuki Yuta , Goto Kazushige , Yokoyama Hisayo
Published: June 2021

BACKGROUND

Erythropoietin (EPO) secretion is a critical determinant for hematological adaptation to hypoxia, which is associated with the level of hypoxemia. Plasma volume (PV) expansion and the resultant hemodilution is observed even after a bout of exercise especially in warm conditions. With these as background, we tested the hypothesis that EPO secretion to hypoxia was enhanced with an expanded PV after a bout of exercise in a warm condition.

METHODS

Eight healthy young men underwent two identical trials which differs only ambient temperature (Ta) during exercise. In a thermoneutral condition, baseline blood sample was taken, then subjects performed a 72‐min intense‐intermittent exercise (8 sets of 4 min at 80% VO2max ‐5 min at 20% VO2max) under cool (Ta, 20°C) and warm (Ta, 30°C) conditions. Twenty‐three hours after exercise, they exposed to hypoxia (14.4%) for 3 hours and blood sample was taken at the middle and the end of exposure. We determined percent change in PV (%ΔPV) from baseline and serum EPO. Also, esophageal (Tes) and mean skin temperature (Tsk) were measured during exercise.

RESULTS

During exercise, Tsk was significantly (p < 0.05) higher in warm than cool trial while Tes was comparable between trials. %ΔPV at 23 hours after excise was significantly higher in warm than cool trial. Serum EPO during exposure significantly increased from baseline in both trials and we found significant effects of interaction (trial x time) in serum EPO, indicating that EPO response to hypoxia was enhanced during warm trial.

CONCLUSIONS

EPO release to hypoxia was enhanced with expanded PV after a bout of exercise especially in a warm condition.

Support or Funding Information

This study was supported in part by a Grant‐in‐Aid for Scientific Research (17H03741) and a Grant‐in‐Aid for challenging Exploratory Research (16K13020), from Japan Society for the Promotion of Science for Kazunobu Okazaki

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Higher metabolic capacity in mice in comparison to rats during acclimation to chronic hypoxia
Authors: Reyes Christian Arias , Losantos Karen , Soliz Jorge , Joseph Vincent
Published: June 2021

The aptitude of mammals to colonize high altitude (HA) environments is limited by their ability to tolerate decreased oxygen availability. While rats are not found under natural conditions above 2500 meters of altitude, mice are common in such habitats. Previous research in our lab showed that rats and mice display divergent physiological and molecular responses after acute (short‐term) exposure to hypoxia. As the response to hypoxia and metabolism control are tightly linked, in this work we aimed to identify the strategies underlying the metabolic response of mice and rats along the process of acclimation to short and long‐term hypoxia.

Male FVB mice and Sprague – Dawley rats were exposed to hypoxia (12% O2) for 0 hours (normoxic controls), 6 hours, 1, 7 and 21 days. During the last hour of the exposure, the whole‐body oxygen consumption (VO2) and CO2 production (VCO2) were measured by indirect calorimetry. In following, samples of brain cortex were collected to evaluate the mitochondrial O2 consumption rate with the high‐resolution respirometer Oxygraph‐2k (Oroboros Inc.).

Our results in mice showed increased VO2 and VCO2 (25% and 41% compared to controls) starting at 7 days of exposure to hypoxia. At the cellular level, mitochondrial O2 consumption in brain cortex increased after one day of hypoxia and then returned to control levels. A mild uncoupling was also observed in the cerebral mitochondria of mice. Contrastingly, no change was observed in rats.

These results show that mice, are able to increase their aerobic metabolism during acclimatization to chronic hypoxia, while rats are not. Given that this phenotype is also present in other rodent species adapted to high altitude, our findings support hypothesis that mice, but not rats, are pre‐adapted to high altitude hypoxia due to early events in their phylogeographic history.

Support or Funding Information

This research is conducted with the funds granted by the Natural Sciences and Engineering Research Council of Canada.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Role of Calcium‐Sensor in bromine‐induced lung hyper‐reactivity
Authors: Lazrak Ahmed , Creighton Judy , Laube Mandy , Yu Zhihong , Matalon Sadis
Published: June 2021

Exposure to bromine causes major injuries to skin and internal organs. In the lung, the exposure to bromine causes symptoms similar to asthma. When mice were exposed to 600 ppm bromine for 30 minutes, they developed lung hyper‐reactivity. 50% of the exposed animals died when treated with 5 mg/kg of L‐type calcium channel inhibitor nifedipine compared to controls. In contrast, treatement with 5mg/kg of diltiazem, a non dihydropyridine L‐type calcium channel blocker, protected animals from the injury induced by bromine. Exposure of human or murine Airway Smooth Muscle Cells (ASMC) to 100 ppm bromine for 10 minutes caused membrane potential (Vm) depolarization from −62±3 mV to −45±5 mV, p <0.001. Nifedipine exacerbated Vm depolarization to −15±10 mV, p<0.001; however diltiazem helped Vm recovery to −55±5 mV, p< 0.001. Using Fura‐2 AM, we found bromine injury to increase intracellular calcium (Cai) in human and murine ASMC. Cai was reduced by diltiazem but not nifedipine. the nifedipine caused Cai increase was dose dependent with an EC50 of 200 nM. Western blot studies showed an increase of Calcium Sensor (CaSR) expression in human and murine ASMC exposed to bromine and to Low Molecular Weight Hyaluronic Acid (LMW‐HA). LMW‐HA is formed by the breakdown of high molecular weight hyaluronic acid by bromine. The knockdown of the CaSR with siRNA significantly reduced nifedipine induced Vm depolarization, and Cai increase in both human and murine ASMC exposed to bromine or LMW‐HA. In conclusion, lung hyper‐reactivity induced by bromine is caused by an increase in CaSR expression in ASMC mediated by LMW‐HA.

Support or Funding Information

Grants: 1U01ES027697‐01, 5U01ES026458‐02, and SAB100322373

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
cAMP‐dependent modulation of Ih underlies the P2Y1 receptor‐mediated excitation of the preBötzinger Complex inspiratory network in vitro
Authors: Zhang Yong , Biancardi Vivian , Tapia Ana Miranda , Jaib Toka Abu , Gourine Alexander , Kasparov Sergey , Funk Gregory Douglas
Published: June 2021

The ventilatory response to hypoxia comprises an initial peripheral chemoreceptor‐mediated increase in ventilation followed by a centrally‐mediated secondary depression that can be life‐threatening in premature infants with apnea. ATP appears to be released from astrocytes in the preBötzinger Complex (preBötC, critical site for inspiratory rhythm generation), during hypoxia where it attenuates the secondary depression via a P2Y1 receptor (R)‐dependent excitation of inspiratory neurons. Here we apply nerve and whole‐cell recording methods to rhythmic medullary slices (700 μM) from neonatal rat to test the hypothesis that the P2Y1R‐mediated excitation of the preBötC network is mediated via cAMP‐dependent modulation of the hyperpolarization‐activated inward current, Ih, in inspiratory neurons. Local application of MRS2365 (P2Y1R agonist, 100 μM) evoked, in a subpopulation of inspiratory neurons (~33%), inward currents that reversed between −40 and −60 mV, consistent with activation of Ih. MRS2365 also potentiated the sag current, characteristic of Ih, that was progressively activated with hyperpolarizing voltage pulses from −50 to −110 mV (10 mV increments; 32 ± 6% potentiation measured at −100 mV). Comparison of Ih activation curves, produced via analysis of tail currents evoked by a series of 10 mV hyperpolarizing steps from −50 mV to −140 mV, in control and MRS2365, revealed a 6.6 mV, MRS2365‐induced depolarizing shift in V1/2 (Vm at which 50% of HCN channels are open). The MRS2365 inward current and its potentiation of Ih were blocked by local pre‐application of ZD 7288 (open channel blocker of Ih, 100 μM). At the network level, pre‐application of ZD 7288 at 100 μM and 25 μM attenuated the MRS2365‐induced frequency increase in inspiratory‐related activity by 94 ± 3% and 70 ± 12%, respectively. 15‐min intracellular dialysis of SQ 22536 (adenylyl cyclase inhibitor, 100 μM) from the whole‐cell pipette significantly attenuated the MRS2365 currents by 60 ± 4%. Similarly, SQ 22536 (1 mM and 100 μM for local and bath application respectively) attenuated the MRS2365‐induced frequency increase by 67 ± 8%. These data suggest that the P2Y1R‐mediated excitation of the preBötC network is produced, at least in part, via a cAMP‐dependent modulation of Ih in a subpopulation of inspiratory neurons.

Support or Funding Information

CIHR, AIHS, NSERC, CFI, and WCHRI

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Sex Hormone Influence on Nesfatin‐1 Signaling in the Pituitary
Authors: Schnell Abigayle L , Samson Willis K , Yosten Gina LC
Published: June 2021

The stress response is intimately connected to appetite regulation; indeed, many peptides that modulate feeding behavior play a role in stress‐related behaviors. Nesfatin‐1 is a potent anorectic peptide that participates in the hypothalamo‐pituitary‐adrenal (HPA) axis. While nesfatin‐1 signaling in the hypothalamus is well‐studied, nesfatin‐1 signaling in the pituitary has yet to be investigated. Furthermore, the receptor through which nesfatin‐1 acts is currently unknown, and identification of that receptor would be a vital step toward establishing the physiological relevance of nesfatin‐1. Experiments were conducted in dispersed rat pituitaries to identify a candidate receptor and downstream signaling events elicited by treatment with nesfatin‐1. Our preliminary data indicate that the action and expression of nesfatin‐1 is influenced by female sex hormones; therefore, downstream signaling was investigated in both male and cycled female dispersed pituitaries. These studies suggest that nesfatin‐1 signals through an orphan GPCR to physiologically induce activation of the HPA axis in a sex‐dependent manner. Gaining a fuller understanding of how sex hormones influence nesfatin‐1 signaling in the pituitary will provide key insight into sex differences in stress‐related disorders.

Support or Funding Information

National Institute of Health

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Possible behavior modulation in Drosophila mediated by the α1T channel
Authors: Iniguez Jorge , Chu Tiarni , Cheung Elwin
Published: June 2021

Voltage gated calcium channels regulate calcium influx and vesicular release of neurotransmitter at chemical synapses. In Drosophila, there are three genes, Dmca1D, 1A, and α1T encoding Cav1, Cav2 and Cav3‐type channels respectively. Studies have shown that the α1T channels are important in regulation of action potential firing in Drosophila at the neuromuscular junction and the central nervous system. The α1T has been shown to be expressed across the adult fly brain. These include sensory neuropils, motor‐associated neuropils, and neuropils associated with learning and memory. We explored the role the α1T gene in adult Drosophila plays in motor‐associated activity using a locomotor assay. Our data suggests that the α1T gene knockout results in a defect in regulating excitability in adult Drosophila that manifests in altered motor activity.

Support or Funding Information

CSUN PODER program

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Synthetic Corticotropin Therapy Reduces Microglial Activation in a Rodent TBI Model
Authors: Siebold Lorraine , Ashwal Stephen , Bartnik‐Olson Brenda , Johnson Rhaya , Tone Beatriz , Figueroa Johnny , Vega‐Torres Julio , Wilson Christopher G.
Published: June 2021

Traumatic brain injury (TBI) is a leading cause of mortality/morbidity and is associated with chronic neuroinflammation. Melanocortin receptor (MCR) agonists (e.g., ACTH or adrenocorticotropic hormone) that target MC3R/4R ameliorate inflammation and provide a novel therapeutic approach. Following TBI, quiescent microglia become activated resulting in anti and pro‐inflammatory responses and morphological changes. We examined the effect of Cosyntropin (synthetic ACTH) administration on microglial activation through quantification of microglia morphology in a rodent TBI model. We hypothesized that Cosyntropin administration would reduce injury‐induced microglia morphological changes following experimental TBI in rats. We used CCI in adult Sprague‐Dawley rats, randomized to 4 groups: sham‐vehicle (N = 2), sham‐Cosyntropin (N = 2), CCI‐vehicle (N = 4), and CCI‐Cosyntropin (N = 4). Subcutaneous injections of Cosyntropin (120U/kg/day; West Therapeutic Development; Grayslake, IL) were given 30 minutes after CCI and every 12 hours for 7 days thereafter. Microglia activation was quantified based on morphology. Sectioned brains were immunostained (Iba1) and visualized with diaminobenzidine. Image processing and quantification were conducted with FIJI and FracLac for ImageJ resulting in 15 morphological values/cell. Parameters included cell area, fractal dimension, circularity, and cell perimeter and density. CCI animals exhibited increased microglia in the lesion site with no difference in cell count between vehicle and treated. Microglia from CCI animals exhibited no change in cell area, decreased cell perimeter and increased density and circularity compared to sham animals. Cosyntropin treatment altered CCI‐induced microglia changes in cell area, cell perimeter, and cell density. Cosyntropin‐treated CCI animals showed reduced morphological changes in microglia suggesting a reduced activation state. Decreased activation may decrease long‐term deleterious neuroinflammatory effects and may be mediated by Cosyntropin effects on melanocortin receptor signaling.

Support or Funding Information

Supported in part by the Pediatric Epilepsy Research Foundation. Cosyntropin was supplied by West Therapeutic Development (Grayslake, IL).

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Postpartum Changes in Microglia Density and Activation in a Rat Model of Superimposed Preeclampsia
Authors: Clayton Ahsia M , Shao Qingmei , Maeda Kenji J , Garrett Michael R , Sasser Jennifer M , Warrington Junie Paula
Published: June 2021

Microglia are the primary immune cells of the central nervous system, surveying the microenvironment and responding to cell injury or tissue damage. The Dahl Salt Sensitive (Dahl‐S) rat model of superimposed preeclampsia (PE) has preexisting hypertension and chronic kidney disease and exhibits characteristic symptoms of PE during pregnancy. Preexisting cardiovascular and renal disease increase the risk of superimposed PE, which further increases risk of maternal complications. Recently, we showed that the rat model of placental ischemia (induced preeclampsia) has increased posterior cortical microglia activation 2 months postpartum. However, whether superimposed PE exacerbates postpartum microglia activation is not known. Because the Dahl‐S rat has increased peripheral inflammation (increased circulating TNFα) during pregnancy and exacerbated hypertension and proteinuria with subsequent pregnancies, we hypothesized that the Dahl‐S model has increased microglia activation after two pregnancies. Dahl‐S rats were randomly assigned to virgin (DSV) or postpartum (DSP) groups (n=3 per group). Postpartum rats were mated twice (3 and 5 months of age) and brains were collected at 8 months of age. Posterior cerebrum was cryo‐sectioned and immuno‐stained using ionized calcium binding adapter molecule (Iba1). Microglia density and morphology were analyzed using ImageJ in 3 images per region and averaged per rat. There was no difference in microglia density (number of Iba1+ microglia per image) in the hippocampus (10±2 in DSV vs. 9±1 in DSP) or cortex (7±1 in DSV vs. 7±2 in DSP). DSP rats had higher proportion of hippocampal Type 3 (78% vs. 62% in DSV) and fewer Type 4 (5% vs. 22% in DSV) microglia (p<0.05). DSP had fewer hippocampal amoeboid (activated) microglia and higher cortical ramified (surveying) microglia compared to DSV (Figure). Taken together, history of superimposed preeclampsia symptoms in DSP rats does not induce exacerbated microglia activation suggesting that pregnancy is either protective to the brain or that following damage, microglia fail to activate, contributing to incomplete repair processes. These hypotheses will be tested in future studies. Future studies will also determine cortical and hippocampal cytokine levels and astrocyte activation in the postpartum Dahl‐S rats.

Support or Funding Information

NIH R00HL129192, R25HL121042, 5T32HL105324‐09, R01HL134711

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Impaired autonomic cardiac regulation due to altered baroreceptor reflex sensitivity in conscious P2rX7 knockout rats
Authors: Kuzmin Vladislav S , Potter D'Anna L , Arkhipov Sergey N , Pavlov Tengis S
Published: June 2021

Introduction

Baroreceptor (BR) reflex is a central mechanism that underlies autonomic control of the circulation due to tight coordination between heart output and peripheral vasculature resistance. Abnormal and/or pathological sensitivity of the BR reflex (BRRS) is associated with many cardiovascular diseases. ATP acting as a co‐transmitter in sympathetic and parasympathetic terminals regulates excitability of the carotid sinus cells and therefore participates in BRR. The goal of the present study was to reveal the role of P2X7 receptors in the autonomic control of the cardiovascular system and BR reflex sensitivity.

Method

We used a constitutive CRISPR/Cas9‐mediated knockout of P2X7 receptor in the PCK rat background. PCK rats are a model of chronic autosomal recessive polycystic kidney disease which associated with cardiovascular complications. As PCK rats were originally derived from the Sprague Dawley strain, the latter was used as control. BRR was studied in vivo in a series of telemetry‐based subchronic experiments. DSI HD‐S11 transmitters were implanted for direct blood pressure collection from carotid artery in addition to lead II electrode placement for electrocardiogram. After a week‐long recovery period standard approach for BRR testing with bolus intravenous sodium nitroprusside (SNP 10μg/kg) injection was used before and after double autonomic blockade (DAB, atropine plus atenolol). Mean arterial pressure (MAP) and heart rate (HR) were collected from free‐moving conscious animals and BRRS was calculated as ΔMAP/ΔHR relation.

Results

No significant difference in resting HR was observed in Sprague‐Dawley (SD) and WT or P2X7 KO PCK rats (378±15, n=6; 359±16, n=6 and 365±8, n=6 respectively). After DAB, HR reduction was similar in WT and KO groups (11.3±2.2% and 10.1±2.3%), but SD demonstrated a more pronounced effect (18.2±3.1%). The KO rats demonstrated significantly reduced BRRS in comparison to WT and SD animals (0.43±0.05 and 0.63±0.07, 0.57±0.06, respectively). Moreover, while SD and WT rats are characterized by negative slope of ΔMAP‐ΔHR relation, ΔHR in KO group demonstrates lack of dependence on ΔMAP. In addition, the time from the beginning to maximal HR elevation in response to SNP application was significantly shorter in KO (13.5±2.5 s) vs SD (32.4±3.6s).

Conclusion

Autonomic control of cardiac function in PCK rats is impaired in comparison to SD rats due to chronic kidney disease. P2X7 deficiency leads to impaired BR reflex sensitivity. P2X7 receptors involved in neurotransmission contribute to the sympathetic/parasympathetic balance of cardiac function control.

Support or Funding Information

NIH R00 DK105160, P30 DK090868 via Baltimore PKD Center P&F Grant and APS Dean Franklin Award

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Impaired Baroreflex Function during Rest and Graded Orthostasis in Women with PTSD
Authors: Yoo Jeung‐Ki , Badrov Mark B , Parker Rosemary S , Anderson Elizabeth H , Dorn Raymond Peter , Suris Alina M , Levine Benjamin D , Fu Qi
Published: June 2021

Post‐traumatic stress disorder (PTSD) is more prevalent in women and associated with significantly higher risk of hypertension and cardiovascular disease. The underlying mechanisms are unclear, but impaired baroreflex function and vasomotor sympathetic neural control may be involved. We hypothesized that women with PTSD would have an impaired baroreflex control of muscle sympathetic nerve activity (MSNA). MSNA and hemodynamics were measured supine and during 30º and 60º head‐up tilt (HUT) in 14 women with PTSD and 14 healthy women (Controls). Sympathetic baroreflex sensitivity(BRS) was quantified using the slope of the linear correlation between MSNA and diastolic pressure during spontaneous breathing. Age and body mass index were not different between groups. Supine resting MSNA was greater in women with PTSD (PTSD vs. Controls: 27±3 vs. 14±3 bursts/min; P=0.002, mean±SEM). Sympathetic BRS was impaired in women with PTSD compared to controls in the supine position (PTSD vs. Controls: −43±7 vs. −64±9 units 100beats−1 mmHg−1, P=0.02). It remained lower in women with PTSD during 30º and 60º HUT (posturexgroup interaction P=0.1, time P=0.003, group P=0.03). MSNA response to the graded HUT was not different between groups but the efficacy of MSNA for vasoconstriction was greater in women with PTSD (HUT 30: 1.8±0.5 vs.0.9±0.4 %TPR/%totalMSNA; P=0.01, HUT60: 1.2±0.4 vs. 0.7±0.3; P=0.04). Our findings demonstrate that women with PTSD have decreased sympathetic BRS and it may contribute to augmented sympathetic activity. The higher efficacy of MSNA for vasoconstriction in PTSD suggests greater sympathetic vascular transduction and/or other nonadrenergic mechanisms responsible for vasoconstriction. These results may explain, in part, the underlying mechanisms for the greater risk of developing hypertension and cardiovascular disease in women with PTSD.

Support or Funding Information

Supported by the Harry S. Moss Heart Trust

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Alpha Intrusion during Rapid Eye Movement (REM) Sleep Increases Blood Pressure
Authors: Greenlund Ian M , Cunningham Hannah A , Tikkanen Anne L , Durocher John J , Smoot Carl A , Carter Jason R
Published: June 2021

Rapid eye movement (REM) sleep is characterized by low voltage, mixed frequency electroencephalography (EEG). A hallmark of REM sleep includes episodic increases of blood pressure and heart rate, and a higher incidence of adverse cardiovascular events such as myocardial infarction and stroke. In pathological conditions such as fibromyalgia and other chronic pain conditions, alpha frequencies (8–13 Hz) are often observed during normal EEG frequencies, a phenomena referred to as alpha intrusion. The impact of alpha intrusion on blood pressure during REM sleep remains unknown. The purpose of this study was to utilize finger plethysmography to determine the impact of alpha intrusion on beat‐to‐beat blood pressure and heart rate during REM sleep. Eleven participants (6 female, 22±1 years, 28±1 kg/m2) were equipped with overnight finger plethysmography (NOVA, Finapres) and standard 10–20 EEG electrode placement for quantification of sleep stage (SleepWorks, Natus). Overnight EEG was scored according to the American Academy of Sleep Medicine (AASM) guidelines by a trained sleep technician and board‐certified sleep physician. EEG signals were filtered with a common low pass (35 Hz), high pass (0.5 Hz), and notch (60 Hz) filter. Occipital EEG was analyzed using an original MATLAB® code, applying a short‐term Fourier transform function (i.e., spectral analysis) with sliding window parameters of 10 seconds by 5 seconds. Alpha frequencies were normalized to the entire overnight EEG to quantify alpha power density. During the final REM episode, a representative 30 second sample of maximum alpha intrusion was selected, and compared to 30 second baseline and recovery periods immediately preceding and following the maximum alpha intrusion. Each EEG sample was free of any scorable arousals, apneic events, or significant limb movements. Continuous recordings of systolic arterial pressure (SAP), diastolic arterial pressure (DAP), and heart rate (HR) were analyzed during these timeframes. Statistical analysis included repeated measures ANOVA (p<0.05). Alpha power density increased during alpha intrusion (0.228 ± 0.02 μV to 0.347 ± 0.04 μV; p<0.001), and returned to baseline levels during recovery (0.205±0.03 μV). Similarly, SAP increased during alpha intrusion (121 ± 5 mmHg to 124 ± 5 mmHg; p=0.038), and returned to baseline during recovery (121 ± 6 mmHg). DAP tended to increase during alpha intrusion (p = 0.08), while HR did not change with alpha intrusion. These results suggest alpha intrusion increases REM blood pressure. These findings have potential clinical relevance given the higher incidence of adverse cardiovascular events during early morning REM sleep.

Support or Funding Information

Support provided by the National Institutes of Health (AA‐024892) and the Portage Health Foundation.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Reduced Baroreflex Function in the STZ‐Induced Rat Model of Alzheimer's Disease
Authors: Ehlen John Christian , Ostrowski Daniela , Ostrowski Tim Daniel
Published: June 2021

Background

Alzheimer's disease (AD) is a progressive neurodegenerative disorder causing multiple autonomic conditions including cardiovascular impairments. The inability to maintain blood pressure via baroreflex regulation is up to 5.6 times more prevalent in AD and patients present most commonly with orthostatic hypotension. This study aimed to assess the influence of AD on autonomic regulation of blood pressure using the streptozotocin (STZ)‐induced AD rat model, which mimics many hallmark symptoms of sporadic AD in humans.

Methods

Male Sprague‐Dawley rats (345 ± 18 g) were randomly divided into two groups and subjected to intracerebroventricular injection of either vehicle (citrate buffer, CTL) or 2 mg/kg STZ in citrate buffer. After two weeks, memory performance (Morris water maze, MWM), baroreflex function (via femoral cannulation), and heart rate variability (HRV) were evaluated.

Results

MWM verified memory impairment in STZ‐treated rats when compared to CTL (p≤0.01). Analysis of baroreflex function in anesthetized rats revealed a significant impairment in the STZ group when compared to CTL. Particularly, STZ‐treated rats were unable to increase compensatory HR at lower blood pressures (at 50 mmHg: CTL, n=5, 369 ± 13 bpm vs. STZ, n=7, 315 ± 14 bpm; p≤0.05). STZ rats also had a lower baroreflex gain indicating reduced sensitivity to blood pressure fluctuations (p≤0.001). Additionally, recordings of splanchnic sympathetic nerve activity (SSNA) in a subset of rats identified reduced nerve activity during low blood pressure in the STZ group (∫SSNA at 50 mmHg: CTL, n=3, 0.3 ± 0.03 mV.s vs. STZ, n=3, 0.17 ± 0.02 mV.s; p≤0.05). There was no difference between groups at higher blood pressures (150 mmHg). Within the STZ group, HRV was significantly increased only during PE infusion (SDNN, p≤0.05; SD1, p≤0.05; SD2, p≤0.05). Interestingly, the change in HR following blockage of sympathetic or parasympathetic input was not different between groups. Also intrinsic HR and the blood pressure change to ganglionic blockage were similar between STZ and CTL rats.

Conclusions

Our study provides the first insight into the pathological influence of AD on baroreflex function. We showed that STZ rats exhibit lower HR and reduced sympathetic output in response to low blood pressure. These results provide the basis for identifying the mechanism behind orthostatic hypotension in AD patients.

Support or Funding Information

ATSU biomedical grant (JCE) and seed money (TDO)

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Prostaglandin EP3 receptor‐expressing neurons in the preoptic area are activated by ambient heat exposure
Authors: Nakamura Yoshiko , Nakamura Kazuhiro
Published: June 2021

The preoptic area (POA) receives cutaneous warm and cold inputs ascending through the lateral parabrachial nucleus, and local neural circuits in the POA function as a center for body temperature regulation. The cutaneous warm inputs to the POA can activate inhibitory neurons therein, which then inhibit the sympathoexcitatory efferent neural pathways that otherwise drive cold‐defensive thermogenesis and cutaneous vasoconstriction. The POA also contains warm‐sensitive neurons that have intrinsic warm sensitivity to monitor body core (local brain tissue) temperature and thereby determine the basal tone of the thermoregulatory efferent signaling, although the histochemical or molecular identity of warm‐sensitive neurons remains unknown. The prostaglandin EP3 receptor, a Gi‐coupled inhibitory receptor of prostaglandin E2, a pyrogenic mediator, is expressed in POA neurons, and an action of prostaglandin E2 on these neurons triggers fever likely by disinhibiting sympathoexcitatory neurons in the dorsomedial hypothalamus and the rostral medullary raphe region. To determine whether EP3 receptor‐expressing POA neurons contribute to thermal homeostasis in warm and cold conditions, in this study, we exposed rats to a heated (36°C), control (24°C) or cold (4°C) environment for two hours and examined activation of EP3 receptor‐expressing POA neurons by double‐immunostaining for EP3 receptors and c‐Fos, a marker for neuronal activation. Heat‐exposed rats exhibited a significant increase in c‐Fos‐positive cells in EP3 receptor‐expressing POA neurons, compared with rats exposed to the control environment. However, cold exposure had no significant effect on the number of c‐Fos‐positive cells in EP3 receptor‐expressing POA neurons, compared with control exposure. These results suggest that EP3 receptor‐expressing POA neurons are activated in hot environments due to its intrinsic warm sensitivity and/or by cutaneous warm inputs and function for heat defense, as well as fever development after infection.

Support or Funding Information

JSPS KAKENHI 17K08568, 23790271 & 26860159 (YN), 16H05128, 15H05932 & 26118508 (KN); AMED JP18gm5010002 (KN); Hori Sciences and Arts Foundation (YN)

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Water deprivation enhances the hypercapnic ventilatory response in rats
Authors: Nakai Larissa Bonassi , Silva Elaine Fernanda , Menani José Vanderlei , Colombari Débora Simões Almeida , Zoccal Daniel Breseghello , Colombari Eduardo
Published: June 2021

Behavioral, neuroendocrine, autonomic and cardiovascular adjustments are triggered during water deprivation. However, the effects of water deprivation on ventilation remain to be determined. Herein, we evaluated the pulmonary ventilation after 48 h of water deprivation in male Holtzman rats (280–300 g) under unanesthetized conditions. Control rats (n=7) had continuous access to tap water and food, whereas water‐deprived (WD, n=6) rats had water, but not food removed for 48 h before the experiments. Rats were placed in whole‐body plethysmographic chamber (5 L) to measure the respiratory frequency (fR), tidal volume (VT) and minute ventilation (VE) under baseline condition (room air) and during hypercapnia (7% CO2 for 5 min). After the experiments, animals were decapitated for blood collection. WD rats had an increase in serum osmolality (307 ± 1 mOsmol/kg of water, vs. control: 297 ± 1 mOsmol/kg of water; p<0.05) and sodium concentration (148 ± 0.6 mmol/L, vs. control: 141 ± 0.5 mmol/L; p<0.05). WD rats exhibited increased VT (9.7 ± 0.5 mL.kg−1, vs. control: 7.7 ± 0.3 mL.kg−1; p<0.05) but reduced fR (76 ± 2 breaths.min−1, vs. control: 103 ± 7 breaths.min−1; p<0.05) compared to controls. As a result, baseline VE (746 ± 54 mL.kg−1.min−1, vs. control: 799 ± 64 mL.kg−1.min−1) were similar between groups. Under hypercapnia, the response of increases in VT were statistically similar between WD and control groups (ΔVT: 60 ± 16%, vs. control: 33 ± 7%). On the other hand, WD rats demonstrated amplified hypercapnia‐induced increases in fR (Δ: 47 ± 5%, vs. control: 19 ± 5%; p<0.05) and VE (Δ: 140 ± 35%, vs. control: 59 ± 9%; p<0.05). The results show that 48 h of water deprivation enhanced the ventilatory responses induced by hypercapnia in unanesthetized rats.

Support or Funding Information

FAPESP; CNPq

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
The amplitudes of miniature excitatory postsynaptic currents in NTS neurons from female rats vary as a function of the estrus cycle
Authors: Jia Shuping W , MIfflin Steve
Published: June 2021

Very little information exists regarding how glutamatergic transmission within the nucleus of the solitary tract (NTS) of females might vary as a function of the estrus cycle. Spontaneous miniature excitatory postsynaptic currents (mEPSCs) were recorded in caudal NTS slices (250μM thick) superfused with TTX (1 um) and gabazine (25 um) under voltage clamp. Female rats were studied at different stages of the estrus cycle determined by vaginal smear and the number of neurons studied at each stage of the estrus cycle is as follows: estrus n=16; metestrus n=14; diestrus n=22. Male rats (n=33) were also studied for comparison. All mEPSCs were blocked by superfusion of the slice with CNQX (10 um). The amplitude of mEPSCs was significantly lower in diestrus (16.53 ± 1.01 pA) compared to estrus (23.30 ± 2.12 pA), metestrus (19.95 ± 1.13 pA), and males (20.49 ± 1.29 pA) (all p<0.035). The frequency of mEPSCs did not vary across the estrus cycle in females however mEPSC frequency was significantly lower in males (2.74 ± 0.28 Hz) compared to estrus (4.23 ± 0.63 Hz, p=.010) and metestrus (4.34 ± 0.61 Hz, p=.005). The frequency of mEPSCs did not differ between males and females in diestrus (3.68 ± 0.54 Hz, p=.085). mEPSC rise time did not differ between the 3 female groups and males (all p>.111). mEPSC decay time was significantly greater in estrus (9.00 ± 0.75 ms) compared to males (7.50 ± 0.39 ms, p=.038) but decay time during estrus did not differ from that in metestrus (7.58 ± 0.61 ms) and diestrus (7.59 ± 0.41 ms) (both p>.088). These results suggest that glutamatergic transmission in NTS neurons in female rats can vary as a function of the estrus cycle. During diestrus plasma estrogen levels are rising and during diestrus we observed mEPSCs with amplitudes lower than during other phases of the estrus cycle or in males. This suggests that estrogen may have a post‐synaptic effect that reduces NTS neuronal responses to glutamatergic inputs. Preliminary whole cell recordings from 3 NTS neurons in a brain slice from estrogen receptor alpha‐td tomato reporter mice lend support to this interpretation as superfusion of the slice with 100 nm 17β‐estradiol reversibly reduced mEPSC amplitude from 19–29%.

Support or Funding Information

This work was supported by HL088052

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Sex‐Dependent Differences in NMDA and GABA Receptor Subunits in the Rat Rostral Ventrolateral Medulla
Authors: Mueller Patrick J , Azar Toni A , Fyk‐Kolodziej Bozena E
Published: June 2021

The cardioprotective effects of female hormones/female sex are well‐described. In particular, several studies demonstrate the importance of female hormones on regulation of sympathetic outflow, a primary contributor to normal blood pressure as well as cardiovascular disease. Protective effects of ovarian hormones may include actions in the rostral ventrolateral medulla (RVLM), a brain region critical to sympathetic outflow and blood pressure. However, the time course and mechanisms by which sex‐differences contribute to excitation and inhibition of RVLM neurons are not fully elucidated; particularly in sexually immature animals, which lack higher levels of reproductive hormones. Therefore, we hypothesized that in the presence of lower levels of reproductive hormones, sexually immature females may exhibit increased glutamate (excitatory) receptors and decreased GABAA (inhibitory) receptors, indicative of an excitatory profile in the RVLM. To test our hypothesis, we obtained brain punches from the RVLM of four week old, male and female Sprague‐Dawley rats (n=3 ea), and processed them for western blotting. The NMDA (NR1) subunit was expressed in the RVLM of both sexes, but was expressed at a higher level in females compared to males (1.10±0.08 vs. 0.65±0.10 protein/GAPDH, respectively). The GABAAα1 subunit was also expressed in the RVLM of both sexes, but was expressed at lower levels in females compared to males (0.61±0.08 vs. 0.79±0.10 protein/GAPDH, respectively). These results suggest that prior to the onset of sexual maturity, a lower level of female hormones may increase the relative excitability of the RVLM and lead to greater sympathoexcitation in females compared to males. These experiments illustrate the importance of studying the time course and level of sexual maturity of animals in studies involving the influence of reproductive hormones. We are currently performing in vivo studies to examine the functional correlates of a greater excitatory profile in the RVLM of female rats, and to what extent sexual maturation influences the RVLM in both sexes.

Support or Funding Information

(HL096787‐07; AHA25810010)

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.