bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cardiovascular Deconditioning Induces Changes in the Excitatory Neurotransmission and Active Properties of Nucleus Tractus Solitarii Neurons
Authors: Silveira Ludmila Lima , Hasser Eileen M , Kline David D 
Published: June 2021

Hindlimb‐unloading (HU) in rats induces cardiovascular deconditioning analogous to that observed in individuals exposed to microgravity or bed rest. Among other physiological changes, HU rats exhibit autonomic imbalance, increased baseline heart rate and altered baroreflex and chemoreflex. Considering that the nucleus tractus solitariis (nTS) is an important central region for autonomic control and integration of cardiovascular reflex function, in this study we aimed to investigate the effects of HU on glutamatergic synaptic transmission and intrinsic properties of nTS neurons. For this purpose, stainless steel wire rings were positioned in the tail of male Sprague‐Dawley rats (3 weeks) and after one week of recovery the rings was connected to a suspension apparatus. HU rats were suspended at an angle of 30–35° for two weeks with free access to food and water, while control animals were maintained under normal postural conditions. After this period, coronal brainstem slices were obtained and the whole‐cell patch clamp technique was performed to evaluate the electrophysiological properties of nTS neurons. The effectiveness of the HU protocol was confirmed by significant hindlimb muscle atrophy. Adrenal weight was comparable between HU and control rats. Resting membrane potential of nTS neurons from HU rats was comparable to neurons from controls. However, HU reduced the percentage of neurons that exhibited spontaneous firing activity (Control: 46% vs HU: 11%). In addition, HU induced a significant increase in the action potential rheobase and A‐type potassium current of nTS neurons, which may contribute to altered basal firing rate. Furthermore, the frequency, but not the amplitude of spontaneous excitatory postsynaptic currents (sEPSC) was significantly higher in the neurons of HU rats in comparison to the control. Taken together the data indicated that HU increases glutamatergic neurotransmission and reduces the excitability of NTS neurons. Therefore, the results suggest that changes in neuronal activity and synaptic transmission in the nTS may contribute to the cardiovascular reflex alterations observed in HU rats.Support or Funding InformationSupport: HL132836This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Functional Topography in the Rat Rostral Ventrolateral Medulla (RVLM): Distribution of C1 Neurons that Respond to Cardiovascular versus Metabolic Stimuli
Authors: Llewellyn‐Smith Ida J , Senthilkumaran Manjula , Spradley Frank , Etelvino Gisele M , Bobrovskaya Larisa , Carrive Pascal , Mueller Patrick J , Verberne Anthony J M 
Published: June 2021

Neurons controlling cardiovascular responses and glucose counter regulation are co‐located within the RVLM, with activated neurons lying almost exclusively caudal to the caudal pole of the facial nucleus (FN). However, it is unclear whether the same neurons are involved in triggering both cardiovascular and metabolic responses. We compared the distributions of RVLM C1 neurons activated by cardiovascular or metabolic stimuli using Fos to identify activated neurons. To conscious male or female rats, we administered insulin (10 U/kg ip) or 2‐deoxyglucose (2DG; 400 mg/kg sc) to induce hypoglycaemia or nitroprusside (NP; 1 mg/ml iv), hydralazine (HDZ; 10 mg/kg iv) or diazoxide (DZX; 50 mg/kg iv) to cause hypotension. Rats were transcardially perfused with formaldehyde 90 or 120 minutes later. Coronal 30‐micrometer thick sections of medulla (1:4 series) from the spinomedullary junction to mid‐FN were immunoperoxidase‐stained to show Fos‐immunoreactivity plus phenylethanolamine N‐methyl transferase (PNMT)‐immunoreactivity to identify C1 neurons. The 6 sections containing the 600 micrometers caudal to the caudal pole of FN (sections FN0 to FN‐5) were each divided into 3 equal segments (medial, middle, lateral) and the total numbers of PNMT neurons with Fos nuclei (Fos+PNMT neurons) were counted. The numbers of Fos+PNMT neurons were greater in the medial and middle thirds than in the lateral third of the C1 cell column in insulin‐ and 2DG‐treated rats. In NP‐, DZX‐or HDZ‐treated rats, the numbers of Fos+PNMT neurons were greater in the middle and lateral two thirds of the C1 cell column. Two‐way ANOVA showed a very strong interaction between stimulus and laterality (p<0.0001), both for number of Fos+PNMT neurons and for percentage of PNMT neurons with Fos nuclei. These results reveal that the extent of Fos expression in PNMT neurons in the medial versus lateral zones depends on the type of stimulus. Post‐hoc analysis confirmed that, in the medial zone, the metabolic stimuli activated more PNMT neurons than cardiovascular stimuli, while it was the opposite in the lateral zone (p<0.0001 in both cases). These results show that hypoglycaemia‐responsive RVLM C1 neurons are concentrated in the medial and middle thirds of the C1 cell column whereas hypotension‐responsive RVLM C1 neurons are concentrated in the middle and lateral two thirds of the column. Hence, within the rat RVLM, C1 neurons are distributed topographically according to their function.Support or Funding InformationNHMRC 1025031; NIH HL096787 & HL130577This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Voluntary Exercise Prevents Hypertensive Response Sensitization (HTRS)
Authors: Xue Baojian , Beltz Terry G , Guo Fang , Johnson Alan Kim 
Published: June 2021

Exercise training has profound effects on the renin‐angiotensin system (RAS), inflammatory mediators and ROS production, all of which influence autonomic nervous system activity and regulates cardiovascular function in both physiological and pathophysiological states. Our previous studies using an Induction‐Delay‐Expression (IND‐DEL‐EXP) paradigm to study HTRS demonstrated that various challenges (stressors) including a subpressor dose of angiotensin (ANG) II given during IND, resulted in HTRS to a subsequent treatment with slow‐pressor dose of ANG II during EXP. The present study tested whether voluntary exercise would protect against subpressor ANG II‐induced HTRS in rats. Adult male rats were given access to either “blocked” (sedentary rats) or functional running (exercised rats) wheels for 10 weeks, and the IND‐DEL‐EXP paradigm was applied for the rats during the last 4 weeks. A subpressor dose of ANG II (10 ng/kg/min) given during IND produced an enhanced hypertensive response to a pressor dose of ANG II (120 ng/kg/min) given during EXP in sedentary rats in comparison to sedentary animals that received saline (vehicle control) during IND. Voluntary exercise did not attenuate the pressor dose of ANG II‐induced hypertension, but prevented the induction of HTRS seen in sedentary animals. Moreover, the subpressor dose of ANG II given during IND induced upregulation of mRNA expression of several RAS pro‐hypertensive components and proinflammatory cytokines in the lamina terminalis (LT), which was attenuated by exercise. Also, RAS antihypertensive components, such as angiotensin type 2 receptor (AT2‐R) and Mas‐R, were upregulated by subpressor dose of ANG II in exercised rats. These results indicate that exercise training plays a beneficial role in preventing HTRS and that this is associated with reduced expression of increased pro‐hypertensive components of the RAS and of inflammatory mediators and by enhanced expression of RAS antihypertensive components in the CNS.Support or Funding InformationThis work is supported by the NIH grants HL‐14388 (AKJ), HL‐98207 (AKJ & BX), HL‐139575 (AKJ & BX).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Evaluation of Respiratory and Cardiovascular Parameters by Ultrasound Echography Following C2 Spinal Cord Hemisection in Rat
Authors: Michel‐Flutot Pauline , Fayssoil Abdallah , Bonay Marcel , Mansart Arnaud , Vinit Stéphane 
Published: June 2021

High cervical spinal cord injuries induce several permanent deficits of vital functions, often leading to the death of the patient. The injury immediately disrupts the bulbospinal pathways innervating phrenic motoneurons that connect to the diaphragm and also causes damages to the sympathetic innervation of the vascular system. The subsequent functional deficits are respiratory failure and cardiovascular dysfunction. In this study, we use a preclinical model of surgical cervical C2 partial section in the rat that mimic these respiratory and cardiovascular impairments. The physiopathology of the injury is assessed by the adaptation of a non‐invasive medical ultrasound echography device (Logic 9, GE, France) to our model.Seven days post‐injury, we observed a live passive displacement of the diaphragm by ultrasound on the injured side in anesthetized animals, corresponding to an absence of hemidiaphragm contraction (−0,37 ± 0,17 mm) compared to contralateral side (3,27 ± 0,44 mm; p<0,01) and to control group (3,79 ± 0,27 mm; p<0,01). These results have been confirmed by in vivo diaphragmatic electromyography, with low electromyographic activity recorded on the ipsilateral side (0,06 ± 0,03 μV.s.s) compared to the contralateral side (0,53 ± 0,08 μV.s.s; p<0,01) and to control group (0,33 ± 0,08 μV.s.s; p = 0,013). We also observed a reduction of the thickness of the rectus abdominis muscle (accessory expiratory muscle) on both sides (injured and non‐injured) at 7 days post‐injury (non‐injured side = 1,78 ± 0,10 mm; injured side = 1,80 ± 0,10 mm) compared to control (2,14 ± 0,08 mm; p = 0,009 and p = 0,013 respectively), suggesting a role for this muscle in active exhalation following the injury.The doppler echocardiography for the cardiovascular evaluation showed a statistical reduction of the left ventricular ejection fraction (LVEF = 59 ± 3%) compared to control (LVEF = 70 ± 2%; p = 0,01), which corresponds to a systolic dysfunction. However, no diastolic dysfunction has been observed. The mean arterial pressure is getting close to non‐injured levels at 7 days post‐injury (68 ± 7 mmHg) compared to control group (84 ± 10 mmHg). These results suggest that the reduction of the sympathetic innervation caused by the spinal cord injury conduct to a cardiovascular dysfunction partly corrected at 7 days post‐injury.Altogether, we demonstrate that medical ultrasound machine could be a reliable non‐invasive method to evaluate chronic respiratory and cardiovascular dysfunction following high cervical spinal cord injury and for studying chronically the evolution of the eventual spontaneous restoration that can occur in this model.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Blockade of Neuropeptide Y Y1 Receptors in the Dorsomedial Hypothalamus Increases Sympathetic Nerve Activity via Projections to the Hypothalamic Paraventricular Nucleus
Authors: Bonillas Alyssa , Shi Zhigang , Padilla Stephanie L. , Brooks Virginia L. 
Published: June 2021

Arcuate Neuropeptide Y (NPY) neurons tonically suppress basal sympathetic nerve activity (SNA) via binding of NPY to NPY Y1 receptors (NPY1R) in the hypothalamic paraventricular nucleus (PVN) and the dorsomedial hypothalamus (DMH). Projection targets of PVN pre‐sympathetic neurons that are inhibited by NPY include the rostral ventrolateral medulla. However, the downstream targets of DMH NPY‐receptive neurons are unknown. Because DMH neurons send a major projection to the PVN, we hypothesized that the PVN is one target. To test this hypothesis, male Npy1r‐cre mice (n=2) received unilateral DMH injections of an adeno‐associated virus, which allows for the cre‐dependent expression of a fluorescent protein (mCherry) in the cell bodies and axon fibers of NPY1R‐containing neurons. After about two weeks, the animals were sacrificed, and their brains were immunohistochemically processed to enhance the mCherry signal. In support of our hypothesis, we identified an abundance of mCherry‐labeled fibers in the PVN. A second prominent projection target was the nucleus raphe pallidus, an important medullary region involved in the regulation of brown adipose tissue thermogenesis. Next, to test the physiological significance of the DMH projection to the PVN, in α‐chloralose anesthetized WT male mice (n=5), we first bilaterally injected the selective NPY1R antagonist, BIBO3304 (30 nl of 10 mM/L), into the DMH, which increased (all P<0.05) splanchnic SNA (SSNA) by 40±12% control, mean arterial pressure (MAP) from 82±5 to 97±6 mmHg, and heart rate (HR) from 449±35 to 554±29 bpm. After 15 min, the inhibitory GABAA agonist, muscimol (30 nL of 1 mM/L), was injected bilaterally into the PVN and reversed the effects of DMH BIBO3304: SSNA decreased to 112±7 % control, MAP to 83±7 mmHg, and HR to 471±25 bpm. In conclusion, NPY tonically inhibits DMH pre‐sympathetic neurons that express NPY1R and project to the PVN.Support or Funding InformationHL128181; APS/Hearst UGSRFThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Intracellular Chloride Regulation of Supraoptic Vasopressin Neurons during Salt Loading
Authors: Balapattabi Kirthikaa , Farmer George E , Little Joel T , Bachelor Martha E , Cunningham J. Thomas 
Published: June 2021

Salt loading (SL) increases intracellular chloride concentration [Cl]i, impairing GABAA inhibition of arginine vasopressin (AVP) neurons in the supraoptic nucleus (SON) of hypothalamus. But the regulatory mechanisms leading to increased [Cl]i is not completely understood. Based on previous studies, we hypothesize that SL activates tyrosine receptor kinase B (TrkB) and downregulates K+/Cl− co‐transporter 2 (KCC2) membrane expression. Downregulation of KCC2 decreases the efflux of chloride ion causing increase in [Cl]i in SON AVP neurons. In this study, we have combined virally mediated ClopHensorN, a relatively new ratiometric chloride imaging technique with capillary based Simple Western technology to record changes in [Cl]i and specifically detect KCC2 protein expression in individual SON AVP neurons.Adult male Sprague Dawley rats were bilaterally injected in the SON with rAAV2‐0VP1‐ClopHensorN. The ClopHensorN (Addgene Plasmid #50758 from Colin Akerman) was packaged in an AAV2 vector with a AVP specific promotor (Addgene Plasmid #40868 from Harold Gainer). After 2 weeks, the rats were given either water or 2% NaCl to drink for 7 days. At the end of the protocol, the rats were anesthetized with inactin and their SONs were dissociated. The cells were plated on coverslips and placed in a perfusion bath on an inverted microscope for ratiometric live cell imaging. ClopHensorN positive neurons were tested for decrease or increase in [Cl]i to focal application of GABAA agonist muscimol (100uM). After imaging, individual neurons were collected by aspirating into a patch pipette to verify KCC2 and ß‐Actin protein expression. The standard matrix (12–230kDa) in Protein Simple Wes was used to identify and quantitate very low concentration of protein from single neuron. Data were analyzed by Chi‐squared test and one‐way ANOVA with Bonferroni comparisons.Muscimol application to SL SONs either significantly increased chloride efflux (p<0.05;13/20) or did not change chloride flux (7/20). TrkB antagonist (AnA,50uM) significantly blocked the chloride effluxes. SONs from euhydrated rats showed muscimol induced chloride influx (p<0.05;11/16). KCC2 antagonist (VU 0240551,10uM) significantly blocked the chloride influxes in euhydrated rats. SON AVP neurons that responded to pharmacological inhibitors during chloride imaging were viable and expressed KCC2 co‐transporter and ß‐Actin. Neurons that did not respond during chloride imaging did not had KCC2 and ß‐Actin protein expression. Salt loading increases [Cl]i in SON AVP neurons through TrKB‐KCC2 dependent mechanism.Support or Funding InformationSupported by R01 HL119458 and 18PRE34060035This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Do Sedentary Conditions Affect the Number of C1 Neurons in Rat Rostral Ventrolateral Medulla?
Authors: Huber Benjamin , Llewellyn‐Smith Ida J , Mueller Patrick J 
Published: June 2021

Cardiovascular disease (CVD) is the leading cause of death in the United States. One of the primary risk factors for CVD is a lack of regular exercise. The brain controls the activity of the autonomic nervous system, which regulates many physiological functions; including blood pressure. The rostral ventrolateral medulla (RVLM) is an important region in the brainstem for blood pressure control because it contains a critical subset of adrenergic (C1) neurons that project to sympathetic preganglionic neurons in the spinal cord. C1 neurons from sedentary rats show more dendritic branching than in active rats, suggesting a novel mechanism by which inactivity could increase sympathetic activity and contribute to hypertension. However, it is also possible that the absolute number of C1 neurons changes along with the number of dendritic branches in sedentary rats. Therefore, the purpose of this study was to test the hypothesis that there are more C1 neurons in the RVLM of rats living under sedentary conditions compared to freely exercising rats. Aiming to understand the mechanisms by which inactivity leads to hypertension, we maintained four‐week old, male Sprague‐Dawley rats for 10–12 weeks under either physically active conditions (running wheels; 410±5.6 km total per rat) or sedentary conditions (no running wheels). Following perfusion and post‐fixation, sections of brainstem were first immunoperoxidase‐stained black for phenylethanolamine N‐methyltransferase (PNMT), a synthetic enzyme and marker of C1 neurons, and then brown for tyrosine hydroxylase (TH), the enzyme that all catecholamine neurons contain. PNMT+TH and TH only neurons in each rat were counted in the 6 sections containing the 600 μm caudal to the caudal pole of the facial nucleus (FN). Sedentary conditions did not produce a difference in the number, or rostrocaudal pattern, of C1 neurons compared to the active group nor an interaction between the two (two way RM ANOVA, p>0.05 ea). Sedentary conditions also did not affect the low number of TH neurons (likely A1 neurons) in the RVLM compared to active rats (2±1 vs. 2±1, respectively). Because the number of RVLM C1 neurons is the same in active and sedentary rats, we can exclude the possibility that an increase in the number of C1 neurons is a cause of increased activation of vasomotor spinal neurons and that structural neuroplasticity in C1 neurons may underlie increased functional excitability of the RVLM in our other studies. Future functional neuroanatomical studies using Fos protein should show whether the overall activation of the population of C1 neurons differs between sedentary and active rats.Support or Funding Information(HL096787‐09)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Protective actions of angiotensin II type 2 receptors in male mice with muscular dystrophy
Authors: Sabharwal Rasna , Yang Liping , Zimmerman Kathy , Weiss Robert 
Published: June 2021

Muscular dystrophies are inherited group of heterogeneous genetic disorders that cause progressive muscle atrophy and dilated cardiomyopathy (DCM). We have identified that the renin‐angiotensin system plays a crucial role in pathogenesis of muscular dystrophy. In particular, we have demonstrated that angiotensin II (Ang II) via type 1 receptors (AT1R) mediate autonomic and skeletal muscle dysfunction at young age (<10 weeks) and predicts onset of DCM at older ages (>45 weeks) in the sarcoglycan delta deficient (Sgcd−/−) mice, an established model of muscular dystrophy [Exp Physiol 2013, 2015]. It is becoming evident that AngII/AT2R can offset the deleterious actions of AngII/AT1R [Curr Opin Nephrol Hypertens 2017; Pharmacol Res 2017]. Therefore, we hypothesized that agonism of AT2R by a non‐peptide small molecule compound 21 (C21; Vicore Pharma) will ameliorate AngII‐induced autonomic and skeletal muscle dysfunction and delay development of DCM in Sgcd−/− mice. Control C57BL6 (n=5–8) and Sgcd−/− (n=6–10) male mice were infused with either vehicle (saline) or C21 (0.03 mg/kg/min, minpump) for eight‐ten weeks, beginning at 3 weeks of age for group 1 (younger‐aged), and at 45 weeks of age for group 2 (older‐aged) experiments. Mean blood pressure (BP), heart rate (HR) and locomotor activity were recorded by telemetry, while cardiac function was assessed by echocardiography. Autonomic indices including baroreflex sensitivity (BRS, sequence technique) and resting cardiac vagal and sympathetic tone (HR responses to atropine and propranolol) were calculated. Group 1: As expected, Sgcd−/− mice exhibit lower BP (105±5 mmHg) and activity (3±1 counts/min), reduced BRS and vagal tone, and increased sympathetic tone (P<0.05 vs. control). C21 improved BRS and restored sympathovagal balance in Sgcd−/− mice; albeit it did not influence these variables in control mice (P<0.05 vs. vehicle). Importantly, C21 normalized locomotor activity and decreased AT1R expression in skeletal muscle of Sgcd−/− mice (P<0.05 vs. vehicle). Group 2: Compared to older‐aged control mice, Sgcd−/− mice exhibit increased left ventricular end‐diastolic and end‐systolic volumes, and reduced ejection fraction (P<0.05). Chronic C21 infusion remarkably improved cardiac function in Sgcd−/− mice (P<0.05 vs. vehicle; NS vs. control). Furthermore, the protective effects of C21 persisted for an additional two weeks after the treatment was discontinued in Sgcd−/− mice. Thus, we conclude that activation of AT2R is a potential novel treatment strategy that alleviates muscular dystrophy phenotype and delays the onset/severity of dilated cardiomyopathy.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.