Perivascular Nerves Research Articles

Perivascular nerve fibres are increased in the epicardium while perivascular adipose tissue is decreased in the myocardium in patients with acute myocardial infarction

Abstract Background Vasospasm is an important etiological factor in the induction of acute myocardial infarction (AMI). PeriVascular Nerve Fibres (PVNF) and PeriVascular Adipose Tissue (PVAT) play an important role in vasoregulation, although detailed information of their role in the heart is missing in AMI patients. In the present study we have analysed PVNF and PVAT in deceased AMI patients. Methods Sections of epicardial coronary arteries were obtained at autopsy from AMI patients (N=16) and controls without heart disease (N=7). Infarct age was between 3 and 6 hours old. Stenosis of epicardial coronary arteries was quantified in a HE stained slide. To analyse the intramyocardial vasculature samples were taken from the left ventricle of the heart (in AMI patients the infarcted area). Nerve fibres were stained using a specific S100 antibody. Putative activation of these nerves was stained using a specific antibody against neuropeptide Y (NPY). S100+ and NPY+ nerve fibres were quantified by light microscopy and were then calculated per square mm of the adventitia surface areas. PVAT was quantified using an Elastica Von Gieson (EvG) staining. Results Stenosis did not correlate with PVNF. AMI patients had a significant increase in PVNF in the epicardium but not in the myocardium. NPY was non-significantly increased in PVNF in the epicardium and myocardium in AMI patients compared with controls. PVAT was significantly decreased in AMI patients compared with controls. Conclusion The increase in PVNF in the epicardium and the decrease of PVAT in the myocardium suggest that they might play a role in AMI induction, independent of the atherosclerotic changed epicardial coronary arteries. Funding Acknowledgement Type of funding sources: None.

Laser renal denervation: A comprehensive evaluation of microstructural renal artery lesions.

Renal artery denervation (RDN) has been proposed for resistant arterial hypertension. Beyond conventional radiofrequency (RF) ablation, there are emerging RDN technologies, including laser catheter ablation. We aimed at evaluamting the local effects of laser ablation on the renal artery and perivascular nerve injury in comparison with radiofrequency ablation. Thirteen pigs (mean weight 36.7 ± 4.7kg, age 3months) were divided into three groups: (1) laser ablation in normotensive pigs (LA; n=3), (2) bipolar RF ablation in normotensive pigs (RF; n=7), and (3) a sham group (SHAM; n=3). Transcatheter laser and RF ablations were performed under general anesthesia. After euthanasia, pathology and immunohistochemical studies were performed. Artery wall and perivascular nerve lesions were found in the LA and RF groups. A lower rate of intimal microdissections was evaluated after laser ablation when compared with RF ablation (0 vs. 1.5 [1;2.75] per artery; p < .05). There was a numerical prevalence of nerves with tyrosine hydroxylase expression loss after laser RDN when compared with RF ablation (16.7 [4; 18] vs. 9.1 [0;18] per specimen). Laser ablation is noninferior to RF ablation regarding perivascular nerve injury and is associated with less intimal layer damage.

The subpopliteal fat body

IntroductionThe knee is likely to get hurt due to its excessive weight-bearing, for which it is surrounded by strongly tensioned ligaments, connectives and muscles. These highly active structures are imbedded in fatty tissue. The Fatty and loose connective tissue of the knee recently gained a renaissance in research. While the Hoffa fat body in the ventral knee attracted attention over the last years, we have investigated a smaller, dorsal fat body, ventral to the popliteus muscle. This fat body has not been described before. Materials and methods11 knees of 11 fresh specimens were investigated. All muscles but the popliteus muscle were removed. The popliteus was released from its tibial origin and dissected towards its tendinous insertion. Thereby, a subpopliteal fat body (SFB) was shown. The related vessels and nerves were evaluated. The size of the body was measured. Examples of histological slices were stained with HE and immunostained against neurofilament. ResultsThe SFB lies ventral of the popliteus muscle at the concave posterior tibia and attaches to the periosteum and the popliteus muscle. It is not attached to the posterior cruciate ligament. It is separated from the subpopliteal recess by a lamella deriving from the fibular head. Arterial and venous vessels are seen entering the SFB, deriving from the popliteal artery or the anterior tibial artery. A subbranch of the tibial nerve was seen to reach the SFB. The SFB could be identified in MRI scans and in plastinations. DiscussionPrimarily, the SFB provides a gliding space for the mobile part of the popliteus muscle over the tibia. The SFB lies within the tibial concavity, ventral to the popliteus muscle. This is exactly where embryologically, the popliteal artery passes through, before its involution in later stages. Therefore, the SFB may show the former perivascular autonomic nerves which encompass the embryologically created arteries, from which we have seen the arterial remnants. The nerves seen here form neurovascular bundles which could be a source of pain, when compressed. This anatomy may explain the autonomic component of pain in the deep lateral region of the knee. The SFB is functional fat, comparable to the Hoffa’s fat pad in the ventral knee.

Sympathetic nervous system hyperactivity results in potent cerebral hypoperfusion in swine.

Cerebral vasospasm is a complex disease resulting in reversible narrowing of blood vessels, stroke, and poor patient outcomes. Sympathetic perivascular nerve fibers originate from the superior cervical ganglion (SCG) to innervate the cerebral vasculature, with activation resulting in vasoconstriction. Sympathetic pathways are thought to be a significant contributor to cerebral vasospasm. We sought to demonstrate that stimulation of SCG in swine can cause ipsilateral cerebral perfusion deficit similar to that of significant human cerebral vasospasm. Furthermore, we aimed to show that inhibition of SCG can block the effects of sympathetic-mediated cerebral hypoperfusion. SCG were surgically identified in 15 swine and were electrically stimulated to achieve sympathetic activation. CT perfusion scans were performed to assess for changes in cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT) and time-to-maximum (TMax). Syngo.via software was used to determine regions of interest and quantify perfusion measures. SCG stimulation resulted in 20-30% reduction in mean ipsilateral CBF compared to its contralateral unaffected side (p<0.001). Similar results of hypoperfusion were seen with CBV, MTT and TMax with SCG stimulation. Prior injection of lidocaine to SCG inhibited the effects of SCG stimulation and restored perfusion comparable to baseline (p>0.05). In swine, SCG stimulation resulted in significant cerebral perfusion deficit, and this was inhibited by prior local anesthetic injection into the SCG. Inhibiting sympathetic activation by targeting the SCG may be an effective treatment for sympathetic mediated cerebral hypoperfusion.

Eukaryotic elongation factor 2 kinase inhibitor, A484954 inhibits perivascular sympathetic nerve stimulation-induced vasoconstriction in isolated renal artery

Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K) repressively regulates protein translation through phosphorylating eEF2. We previously showed that expression and activity of eEF2K are increased in isolated mesenteric arteries from spontaneously hypertensive rats (SHR) contributing to development of essential hypertension. Furthermore, we have recently shown that 7-Amino-1-cyclopropyl-3-ethyl-1,2,3,4-tetrahydro-2,4-dioxopyrido[2,3-d]pyrimidine-6-carboxamide (A484954), a selective eEF2K inhibitor, induces endothelium-dependent relaxation in isolated mesenteric arteries from SHR inducing an antihypertensive effect. In order to test the hypothesis that inhibition of eEF2K activity induces vasodilatation by suppressing sympathetic nerve activity, we examined the effects of A484954 on perivascular sympathetic nerve stimulation-induced contraction in isolated renal artery from normotensive and hypertensive rats. Electrodes were placed near the isolated renal arteries that were applied with transmural nerve stimulation (TNS). Then, contraction of the arteries was isometrically measured. A484954 inhibited TNS-induced contraction. The A484954-mediated inhibition of TNS-induced contraction was significantly prevented by NG-nitro-L-arginine methyl ester. In SHR isolated renal artery, TNS-induced contraction was enhanced compared with normotensive Wistar rats. Furthermore, A484954-mediated inhibition of TNS-induced contraction in SHR was enhanced compared with Wistar rats. In conclusion, this study demonstrates for the first time that A484954 inhibits perivascular sympathetic nerve stimulation-induced vasoconstriction at least in part perhaps through nitric oxide (NO) release from NO-operating nerve.

Distribution and possible function of galanin about headache and immune system in the rat dura mater

Galanin (GAL) is a nociceptive transmitter or modulator in the trigeminal sensory system. In this study, GAL expression was investigated in the rat dura mater to demonstrate its possible function in headache using immunohistochemical techniques. The cerebral falx and cerebellar dura mater received abundant blood and nerve supply, and were significantly thicker compared to other portions in the cerebral dura mater. GAL-immunoreactivity was expressed by cell and nerve fiber profiles. Presumed macrophages and dendritic cells contained GAL-immunoreactivity, and co-expressed with CD11b-immunoreactivity. Many isolated and perivascular nerve fibers also showed GAL-immunoreactivity. In addition, GAL-immunoreactive nerve fibers were present in the vicinity of macrophages and dendritic cells with either GAL- or ED1-immunoreactivity. GAL-immunoreactive cells and nerve fibers were common in the cerebral falx and cerebellar dura mater and infrequent in other portions. And, GAL-immunoreactive nerve fibers usually co-expressed calcitonin gene-related peptide (CGRP)-immunoreactivity. In the trigeminal ganglion, a substantial proportion of sensory neurons innervating the dura mater contained GAL-immunoreactivity (mean ± SD, 3.4 ± 2.2%), and co-expressed CGRP-immunoreactivity (2.7 ± 2.1%). The present study may suggest that GAL is associated with nociceptive transduction or modulation in the dura mater. GAL also possibly plays a role in the immune mechanism of the dura mater.

High Salt Upregulates Ca2+-Sensing Receptor Expression and Ca2+-Induced Relaxation of Contracted Mesenteric Arteries from Dahl Salt-Sensitive Rats.

High Ca2+ lowers blood pressure in hypertension, but the mechanism is not clear. The missing link may be the perivascular sensory nerve Ca2+-sensing receptor (CaSR) that mediates a vasodilator system after activation by interstitial Ca2+ Our results show that high salt increased CaSR expression in mesenteric arteries as well as Ca2+ relaxation of contracted mesenteric arteries from salt-sensitive (SS) rats. The CaSR was expressed as a doublet (≈120-150 kDa) in arteries from animals fed a high-salt diet for 1-4 weeks. The higher molecular weight glycosylated protein increased in arteries from SS animals; however, expression of the low molecular mass high-mannose protein decreased over 4 weeks of feeding the diet. In tissues from salt-resistant (SR) rats, the diet decreased CaSR expression after 4 weeks. Ca2+ relaxation of mesenteric arteries under phenylephrine tone increased in SS rats but decreased in arteries from SR rats fed the high-salt diet. Ca2+-activated K+ channels have a larger role in Ca2+ relaxation of arteries in SR than SS rats. The data suggest that high salt epigenetically regulates the receptor at the translational level in vivo and that the in vitro effect of Ca2+ is on receptor trafficking and signaling. In conclusion, upregulated expression of the CaSR in salt sensitivity increased receptor-mediated vascular relaxation. These findings show that CaSR signaling may compensate for changes in the vasculature in salt-sensitive hypertension. SIGNIFICANCE STATEMENT: The perivascular sensory nerve Ca2+-sensing receptor (CaSR) mediates Ca2+ relaxation of isolated mesenteric arteries under tension. This receptor may therefore play a significant role in relaxation of resistance arteries in vivo, thus explaining the blood pressure-lowering effect of dietary Ca2+. The present studies describe the effect of high salt-induced upregulation of the CaSR in salt-sensitive rats and the roles played by Ca2+-activated K+ channels and nitric oxide in Ca2+ responses.

The osteoarthritis bone score (OABS): a new histological scoring system for the characterisation of bone marrow lesions in osteoarthritis

SummaryObjectivesBone marrow lesions (BMLs) are associated with pain in osteoarthritis (OA), but histological scores for OA focus on cartilage pathology. We developed a new scoring system, the Osteoarthritis Bone Score (OABS), to characterise OA-related BMLs.MethodsBML/non-BML tissues identified by Magnetic Resonance Imaging (MRI) in 10 knee OA subjects were harvested at total knee replacement (TKR). Osteochondral tissue from a further 140 TKR and 23 post-mortem (PM) cases was assessed. Histological features distinguishing MRI-defined BML/non-BML tissues on qualitative analysis were classified as present (0) or absent (1), summated for the OABS, validated by Rasch analysis and sensitivity to distinguish between sample groups. Immunohistochemistry for PGP9.5 assessed innervation.ResultsSubchondral characteristics associated with BML tissues were cysts, fibrosis, hypervascularity, cartilage islands, trabecular thickening, loss of tidemark integrity and inflammatory cell infiltration. PGP9.5 immunoreactive perivascular nerves were associated with BMLs. OABS performed well as a measurement tool, displayed good reliability (Cronbach alpha = 0.68), had a 2-factor structure (trabecular/non-trabecular), with moderate correlation between the two factors (r = 0.56, 95% CI 0.46, 0.65). OABS scores were higher in TKR than PM cases with chondropathy, median difference 1.5 (95% CI -2, 0). OABS and Mankin scores similarly distinguished TKR from non-OA controls, but only OABS was higher in BML than non-BML tissues, median difference −4 (95% CI -5 to −2).ConclusionsOABS identifies and validly quantifies histopathological changes associated with OA BMLs. Histopathology underlying BMLs may represent 2 inter-related pathological processes affecting trabecular/non-trabecular structures. Increased vascularity/perivascular innervation in BMLs might contribute to pain.

Multi-Channel Bioimpedance System for Detecting Vascular Tone in Human Limbs: An Approach.

Vascular tone plays a vital role in regulating blood pressure and coronary circulation, and it determines the peripheral vascular resistance. Vascular tone is dually regulated by the perivascular nerves and the cells in the inside lining of blood vessels (endothelial cells). Only a few methods for measuring vascular tone are available. Because of this, determining vascular tone in different arteries of the human body and monitoring tone changes is a vital challenge. This work presents an approach for determining vascular tone in human extremities based on multi-channel bioimpedance measurements. Detailed steps for processing the bioimpedance signals and extracting the main parameters from them have been presented. A graphical interface has been designed and implemented to display the vascular tone type in all channels with the phase of breathing during each cardiac cycle. This study is a key step towards understanding the way vascular tone changes in the extremities and how the nervous system regulates these changes. Future studies based on records of healthy and diseased people will contribute to increasing the possibility of early diagnosis of cardiovascular diseases.

Prenatal development of sympathetic innervation of the human pancreas

BackgroundThe sympathetic nervous system plays an important role in the regulation of pancreatic exocrine and endocrine secretion. The results of experimental studies also demonstrate the involvement of the sympathetic nervous system in the regulation of endocrine cell differentiation and islet formation during the development of the pancreas. However, the prenatal development of sympathetic innervation of the human pancreas has not yet been studied. Material and methodsPancreatic autopsy samples from 24 human fetuses were examined using immunohistochemistry with antibodies to tyrosine hydroxylase (TH). The density, concentration, and size (width, length, perimeter and area) of the TH-positive sympathetic nerves were compared in four developmental periods: pre-fetal (8–11 weeks post conception (w.p.c.), n = 6), early fetal (13–20 gestational weeks (g.w.), n = 7), middle fetal (21–28 g.w., n = 6) and late fetal (29–40 g.w., n = 5) using morphometric methods and statistical analysis (Multiple Comparisons p values). Double immunofluorescence with antibodies to TH and either insulin or glucagon and confocal microscopy were applied to analyze the interaction between the sympathetic nerves and endocrine cells, and the co-localization of TH with hormones. ResultsTH-positive sympathetic nerves were detected in the fetal pancreas starting from the early stages (8 w.p.c.). The developmental dynamics of sympathetic nerves was follows: from the pre-fetal period, the amount of TH-positive nerves gradually increased and their branching occurred reaching the highest density and concentration in the middle fetal period, followed by a decrease in these parameters in the late fetal period. From the 14th g.w. onwards, thin TH-positive nerve fibers were mainly distributed in the vicinity of blood vessels and around the neurons of intrapancreatic ganglia, which is similar in adults. There were only rare TH-positive nerve fibers adjacent to acini or located at the periphery of some islets. The close interactions between the TH-positive nerve fibers and endocrine cells were observed in the neuro-insular complexes. Additionally, non-neuronal TH-containing cells were found in the pancreas of fetuses from the pre-fetal and early fetal periods. Some of these cells simultaneously contained glucagon. ConclusionsThe results demonstrate that sympathetic innervation of the human pancreas, including the formation of perivascular and intraganglionic nerve plexuses, extensively develops during prenatal period, while some processes, such as the formation of sympathetic innervation of islet capillaries, may occur postnatally. Non-neuronal TH-containing cells, as well as the interactions between the sympathetic terminals and endocrine cells observed in the fetal pancreas may be necessary for endocrine pancreas development in humans.

Perivascular histamine receptors mediate vasosensory reflex responses elicited by thermal nociceptive stimuli in anaesthetised rat models

Objectives: Reflex responses elicited by intra-arterial (i.a) instillation of nociceptive agents are known as vasosensory reflex responses. The present study was designed to demonstrate the vasosensory reflex responses evoked by thermal nociceptive stimuli in anaesthetised rat models and to examine the role of perivascular histamine receptors in mediating these responses. Materials and Methods: In this study, saline at different temperatures (0°C/30°C/55°C) was instilled retrogradely into the femoral artery to stimulate the perivascular nociceptive terminals and the respiratory movements, BP and ECG were recorded for 10 min. Experiments were performed in four groups of rats. Two groups were dedicated to study the temperature-induced reflex cardiorespiratory (CVR) responses after i.a instillation of cold (0°C) and warm saline (55°C). The responses in these groups were compared with the responses after instillation of normal saline at room temperature (30°C) in a separate group of rats that served as time matched control group. Another group of rats was pre-treated with pheniramine and the responses elicited by warm saline were studied. Results: Instillation of warm saline produced immediate (2–6 s) hyperventilatory, hypotensive and bradycardiac responses which were short-lived, while equivolume of normal saline at room temperature did not. Cold saline also elicited the CVR changes of similar quality as that of warm saline but of lesser quantity which were not significantly different from the control group. Pre-treatment with pheniramine significantly attenuated the warm saline-induced reflex responses. Conclusion: Activation of perivascular sensory nerve terminals by thermal nociceptive stimuli elicits vasosensory reflex responses altering CVR parameters. Perivascular histamine receptors play a significant role in mediating the temperature-induced vasosensory reflex responses.

Transcatheter radiofrequency pulmonary artery denervation in swine: the evaluation of lesion degree, hemodynamics and pulmonary hypertension inducibility

BackgroundMechanisms of positive effects of pulmonary artery (PA) denervation (PADN) remain poorly understood. The study aimed to evaluate pulmonary hemodynamic changes after PADN and their association with the extent of PA wall damage in an acute thromboxane A2 (TXA2)-induced pulmonary hypertension (PH) model in swine.MethodsIn this experimental sham-controlled study, 17 normotensive male white Landrace pigs (the mean weight 36.2 ± 4.5 kg) were included and randomly assigned to group I (n = 9)—PH modeling before and after PADN, group II (n = 4)—PADN only, or group III (n = 4)—PH modeling before and after a sham procedure. Radiofrequency (RF) PADN was performed in the PA trunk and at the proximal parts of the right and left PAs. PA wall lesions were characterized at the autopsy study using histological and the immunohistochemical examination.ResultsIn groups I and II, no statistically significant changes in the mean pulmonary arterial pressure nor systemic blood pressure were found after PADN (−0.8 ± 3.4 vs 4.3 ± 8.6 mmHg, P = 0.47; and 6.0 ± 15.9 vs -8.3 ± 7.5 mmHg, P = 0.1; correspondingly). There was a trend towards a lower diastolic pulmonary arterial pressure after PADN in group I when compared with group III during repeat PH induction (34.4 ± 2.9 vs 38.0 ± 0.8; P = 0.06). Despite the presence of severe PA wall damage at the RF application sites, S100 expression was preserved in the majority of PA specimens. The presence of high-grade PA lesions was associated with HR acceleration after PADN (ρ = 0.68, p = 0.03). No significant correlation was found between the grade of PA lesion severity and PA pressure after PADN with or without PH induction.ConclusionsExtended PADN does not affect PH induction using TXA2. Significant PA adventitia damage is associated with HR acceleration after PADN. Possible delayed effects of PADN on perivascular nerves and pulmonary hemodynamics require further research in chronic experiments.

The Role of Perivascular Adipose Tissue in Early Changes in Arterial Function during High-Fat Diet and Its Combination with High-Fructose Intake in Rats

The aim of the current study was to evaluate the influence of a high-fat diet and its combination with high-fructose intake on young normotensive rats, with focus on the modulatory effect of perivascular adipose tissue (PVAT) on the reactivity of isolated arteries. Six-week-old Wistar–Kyoto rats were treated for 8 weeks with a control diet (10% fat), a high-fat diet (HFD; 45% fat), or a combination of the HFD with a 10% solution of fructose. Contractile and relaxant responses of isolated rat arteries, with preserved and removed PVAT for selected vasoactive stimuli, were recorded isometrically by a force displacement transducer. The results demonstrated that, in young rats, eight weeks of the HFD might lead to body fat accumulation and early excitation of the cardiovascular sympathetic nervous system, as shown by increased heart rate and enhanced arterial contractile responses induced by endogenous noradrenaline released from perivascular sympathetic nerves. The addition of high-fructose intake deteriorated this state by impairment of arterial relaxation and resulted in mild elevation of systolic blood pressure; however, the increase in arterial neurogenic contractions was not detected. The diet-induced alterations in isolated arteries were observed only in the presence of PVAT, indicating that this structure is important in initiation of early vascular changes during the development of metabolic syndrome.

Fiber-optic laser energy for pulmonary artery denervation: results of an experimental study

Abstract Background/Introduction Pulmonary artery denervation (PADN) is an interventional procedure aiming to modulate and correct pulmonary artery (PA) pressure. New technologies and energy sources are being tested currently. However, the effects of laser energy on the PA wall are unknown. Purpose To assess the acute effects and impact of laser energy for PADN procedure in normotensive sheep by applying different power settings and session times. Methods A total of 10 normotensive Katumsky sheep were included in the experiment. Percutaneous vascular access was performed under general anesthesia. A fiberoptic open-irrigated non-steerable catheter was introduced via a femoral vein through a steerable sheath. Laser applications were applied in the PA trunk and the proximal areas of the right and left PA under fluoroscopic guidance with a 5mm distance between points in the anterior, posterior and lateral walls. Applications were delivered with power 10–30W, 10–35s in duration; irrigation flow 40ml/min. After the procedure, experimental animals were euthanized and underwent an autopsy. PA samples were obtained regardless of the absence of visible laser-related lesions for histological analysis (hematoxylin staining) and immunohistochemical labelling (S100). Results A total of 108 ablation sessions were performed, 33 in the right PA, 30 in the left PA and 42 in the PA trunk. During macroscopic examination, laser-related lesions described as irregular brown hemorrhage spots and rough defects observed in the PA endothelium were not homogenous in all experimental animals. Thermal injuries either in the left or right lung lobes were identified in 5 (50%) experimental animals when using 30W during 10–20sec. In 5 (50%) sheep no collateral lung injuries were identified when using 10–20W from 20–35s. A total of 64 PA fragments underwent microscopic examination, acute thermal tissue lesions were observed in all experimental animals despite the absence of laser-related lesions in the PA endothelium; dissection, edema, disruption trough tunica layers, hemorrhage and necrosis at different depth walls. The most frequent nerve damage was obtained with 20W ablation: 5/8 PAs vs, 1/6 with 10–15W and 1/14 with 25–30W (P=0.01). At the same time, there was no difference in intima necrosis between the groups (1/6, 2/8 and 4/14 for 10–15, 20 and 25–30W groups, respectively). Conclusion(s) Percutaneous PA laser ablation is feasible, reduction of perivascular nerve expression is seen most frequently, when 20W/20–35 s ablation is performed. PA lesions may differ in depth and characteristics, and perivascular nerve damage might be seen in cases with preserved intima. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Grant of the Ministry of Science and Higher Education of the Russian Federation

Pulmonary artery radiofrequency ablation in an acute porcine model of pulmonary arterial hypertension

Abstract Introduction Pulmonary hemodynamics improvement after pulmonary artery denervation (PADN) was demonstrated in PAH. Questions arise regarding PADN perioperative effectiveness and the accuracy of the target nerves damage. The aim of the study was to evaluate whether PADN decreases pulmonary artery pressure (PAP) in acute thromboxane A2 (U46619)–induced PAH, and damages PA perivascular nerve fibers. Materials and methods 10 male Landrace swine (34.7±5.1 kg). In 6 swine acute reversible target mean PAP of 40 mm Hg was induced with synthetic thromboxane A2 infusion (U46619). Control group: 4 swine with PADN. Hemodynamics was assessed throughout the study, PAH modeling was done before and 20 min after PADN (radiofrequency energy, 40 Watts), followed by pathology and immunohistochemical studies. Results The mean number of RF applications was 17.5±3.6. Pulmonary embolism (PE) was observed after PADN in 3 swine with U46619 infusion, which were excluded. There was no differences in mPAP, PVR and U46619 dosage after PADN in PAH model (12.3±3.5 vs 12.1±1 mm Hg, p=0.2; 150.4±48.7 vs 129.2±64.1 dynes s cm–5; p=0.2; 24.9±3.3 vs 22.4±4.1 mcg; p=0.18; respectively). Similar hemodynamic results were observed in the control group after PADN (mPAP; p=0.3; PVR; p=0.58). S100 expression was evident in the majority of RFA PA species and in some species loss in tyrosine hydroxylase and M1 acetylcholine receptors expression was detected with no hemodynamic correlation. Conclusions PADN using an electrophysiological catheter with unipolar energy does not lead to an acute PA perivascular nerve fibers destruction and detectable mPAP changes in U46619-induced PAH. Delayed nerve damage might be attributable to PADN effects observed in previous studies. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Grant from the Ministry of Science and Higher Education of the Russian Federation (agreement #075-15-2020-800).

Functional nitrergic innervation of smooth muscle structures in the mucosa of pig lower urinary tract.

Neurally released nitric oxide (NO) functions as an inhibitory neurotransmitter of urethral but not detrusor smooth muscles while relaxing bladder vasculature and muscularis mucosae (MM). Here, the distribution of nitrergic nerves was examined in the mucosa of pig lower urinary tract using immunohistochemistry, and their vasodilatory functions were studied by measuring arteriolar diameter changes. Properties of smooth muscle cells in the lamina propria (SMC-LP) of urethra and trigone were also investigated using florescence Ca2+ imaging. In the bladder mucosa, neuronal nitric oxide synthase (nNOS)-immunoreactive nitrergic fibres projected to suburothelial arterioles and venules. Perivascular nitrergic nerves were intermingled with but distinct from tyrosine hydroxylase (TH)-immunoreactive sympathetic or calcitonin gene-related peptide (CGRP)-immunoreactive afferent nerves. MM receive a nitrergic but not sympathetic or afferent innervation. In the mucosa of urethra and trigone, nitrergic nerves were in close apposition with sympathetic or afferent nerves around suburothelial vasculature but did not project to SMC-LP. In suburothelial arterioles of bladder and urethra, N ω-nitro-L-arginine (L-NA, 100μM), an NOS inhibitor, enhanced electrical field stimulation (EFS)-induced sympathetic vasoconstrictions, while tadalafil (10nM), a phosphodiesterase type 5 (PDE5) inhibitor, suppressed the vasoconstrictions. SMC-LP developed asynchronous spontaneous Ca2+ transients without responding to EFS. The spontaneous Ca2+ transients were enhanced by acetylcholine (1μM) and diminished by noradrenaline (1μM) but not SIN-1 (10μM), an NO donor. In the lower urinary tract mucosa, perivascular nitrergic nerves appear to counteract the sympathetic vasoconstriction to maintain the mucosal circulation. Bladder MM but not SMC-LP receive an inhibitory nitrergic innervation.

Role of TRP ion channels in cerebral circulation and neurovascular communication

The dynamic regulation of blood flow is essential for meeting the high metabolic demands of the brain and maintaining brain function. Cerebral blood flow is regulated primarily by 1) the intrinsic mechanisms that determine vascular contractility and 2) signals from neurons and astrocytes that alter vascular contractility. Stimuli from neurons and astrocytes can also initiate a signaling cascade in the brain capillary endothelium to increase regional blood flow. Recent studies provide evidence that TRP channels in endothelial cells, smooth muscle cells, neurons, astrocytes, and perivascular nerves control cerebrovascular contractility and cerebral blood flow. TRP channels exert their functional effects either through cell membrane depolarization or by serving as a Ca2+ influx pathway. Endothelial cells and astrocytes also maintain the integrity of the blood-brain barrier. Both endothelial cells and astrocytes express TRP channels, and an increase in endothelial TRP channel activity has been linked with a disrupted endothelial barrier function. Therefore, TRP channels can play a potentially important role in regulating blood-brain barrier integrity. Here, we review the regulation of cerebrovascular contractility by TRP channels under healthy and disease conditions and their potential roles in maintaining blood-brain barrier function.

Immunoelectron Microscopic Characterization of Vasopressin-Producing Neurons in the Hypothalamo-Pituitary Axis of Non-Human Primates by Use of Formaldehyde-Fixed Tissues Stored at -25 °C for Several Years.

Translational research often requires the testing of experimental therapies in primates, but research in non-human primates is now stringently controlled by law around the world. Tissues fixed in formaldehyde without glutaraldehyde have been thought to be inappropriate for use in electron microscopic analysis, particularly those of the brain. Here we report the immunoelectron microscopic characterization of arginine vasopressin (AVP)-producing neurons in macaque hypothalamo-pituitary axis tissues fixed by perfusion with 4% formaldehyde and stored at −25 °C for several years (4–6 years). The size difference of dense-cored vesicles between magnocellular and parvocellular AVP neurons was detectable in their cell bodies and perivascular nerve endings located, respectively, in the posterior pituitary and median eminence. Furthermore, glutamate and the vesicular glutamate transporter 2 could be colocalized with AVP in perivascular nerve endings of both the posterior pituitary and the external layer of the median eminence, suggesting that both magnocellular and parvocellular AVP neurons are glutamatergic in primates. Both ultrastructure and immunoreactivity can therefore be sufficiently preserved in macaque brain tissues stored long-term, initially for light microscopy. Taken together, these results suggest that this methodology could be applied to the human post-mortem brain and be very useful in translational research.

Zinc drives vasorelaxation by acting in sensory nerves, endothelium and smooth muscle

Zinc, an abundant transition metal, serves as a signalling molecule in several biological systems. Zinc transporters are genetically associated with cardiovascular diseases but the function of zinc in vascular tone regulation is unknown. We found that elevating cytoplasmic zinc using ionophores relaxed rat and human isolated blood vessels and caused hyperpolarization of smooth muscle membrane. Furthermore, zinc ionophores lowered blood pressure in anaesthetized rats and increased blood flow without affecting heart rate. Conversely, intracellular zinc chelation induced contraction of selected vessels from rats and humans and depolarized vascular smooth muscle membrane potential. We demonstrate three mechanisms for zinc-induced vasorelaxation: (1) activation of transient receptor potential ankyrin 1 to increase calcitonin gene-related peptide signalling from perivascular sensory nerves; (2) enhancement of cyclooxygenase-sensitive vasodilatory prostanoid signalling in the endothelium; and (3) inhibition of voltage-gated calcium channels in the smooth muscle. These data introduce zinc as a new target for vascular therapeutics.

The Influence of an Adrenergic Antagonist Guanethidine on the Distribution Pattern and Chemical Coding of Caudal Mesenteric Ganglion Perikarya and Their Axons Supplying the Porcine Bladder.

This study was aimed at disclosing the influence of intravesically instilled guanethidine (GUA) on the distribution, relative frequency and chemical coding of both the urinary bladder intramural sympathetic nerve fibers and their parent cell bodies in the caudal mesenteric ganglion (CaMG) in juvenile female pigs. GUA instillation led to a profound decrease in the number of perivascular nerve terminals. Furthermore, the chemical profile of the perivascular innervation within the treated bladder also distinctly changed, as most of axons became somatostatin-immunoreactive (SOM-IR), while in the control animals they were found to be neuropeptide Y (NPY)-positive. Intravesical treatment with GUA led not only to a significant decrease in the number of bladder-projecting tyrosine hydroxylase (TH) CaMG somata (94.3 ± 1.8% vs. 73.3 ± 1.4%; control vs. GUA-treated pigs), but simultaneously resulted in the rearrangement of their co-transmitters repertoire, causing a distinct decrease in the number of TH+/NPY+ (89.6 ± 0.7% vs. 27.8 ± 0.9%) cell bodies and an increase in the number of SOM-(3.6 ± 0.4% vs. 68.7 ± 1.9%), calbindin-(CB; 2.06 ± 0.2% vs. 9.1 ± 1.2%) or galanin-containing (GAL; 1.6 ± 0.3% vs. 28.2 ± 1.3%) somata. The present study provides evidence that GUA significantly modifies the sympathetic innervation of the porcine urinary bladder wall, and thus may be considered a potential tool for studying the plasticity of this subdivision of the bladder innervation.