Postganglionic Research Articles

Differential effects of sympatholytic agents on the power spectrum of rats during the cooling-induced hemodynamic perturbations.

Cold stress-elicited hemodynamic perturbations (CEHP) its underlying mechanisms still not clear. We examined the difference of two effector arms of sympathetic outflows, the sympathoadrenal system, and postganglionic sympathetic neurons, their role in CEHP genesis by using two sympatholytic agents, fusaric acid (FA, dopamine-β-hydroxylase inhibitor) and guanethidine (GUA, norepinephrine-depleting drug). Adult male Sprague-Dawley rats were divided into three groups (n = 6, each), an intraperitoneal injection of control vehicle saline or FA or GUA and then all rats were subjected to a 10-min CS trial. Systolic blood pressure (SBP), heart rate (HR), dicrotic notch (Dn), power spectrum of blood pressure variability and HR variability (BPV, HRV), and coherence spectrum at very-low, low, and high frequency regions (VLF: 0.02-0.2 Hz, LF: 0.2-0.6 Hz, and HF: 0.6-3.0 Hz) were monitored using telemetry throughout the experiment course. We observed both FA and GUA attenuated SBP and HR and the spectral powers of BPV at VLF, LF, and HF in both baseline (PreCS) and cold stimuli (CS) conditions, but apparently, FA exerted stronger effects than GUA did. Both FA and GUA generally attenuated the responses of CS-induced pressor and tachycardia and the CS-increased VLFBPV, LFBPV, and HFBPV, but different effects between FA and GUA, when compared with control vehicle under CS. FA reduced the CS-reduced VLFHRV and the CS-increased LFBPV and HFBPV more than GUA did. We further observed in both PreCS and CS, GUA but not FA increased HFHRV; FA reduced but apparently, GUA increased the occurrence of Dn. Finally, we observed FA weakened, but GUA strengthened the coherence between BPV and HRV at both LF and HF regions. Taken together, the different effects between FA and GUA on CEHP indicate a role of the sympathoadrenal mechanism in response to CS.

Functional Circuitry of Neuro-Immune Communication in the Mesenteric Lymph Node and Spleen

The peripheral nervous system is an active participant in immune responses capable of blocking aberrant activation of a variety of immune cells. As one of these neuro-immune circuits, the cholinergic anti-inflammatory pathway has been well established to reduce the severity of several immunopathologies. While the activation of this pathway by vagal nerve stimulation requires both sympathetic innervation of the spleen the neuro-immune circuitry remains highly controversial. Neuro-immune pathways in other lymphoid tissues such as mesenteric lymph nodes (MLN) that are critical to the surveillance of the small intestine and proximal colon have not been assessed. Using conditionally expressed Channelrhodopsin, selective stimulation of sympathetic post-ganglionic neurons in the superior mesenteric ganglion prevented LPS-induced TNFα production in the spleen and MLN but not the inguinal LN. Site selective stimulation of the SMG induced norepinephrine that resulted in β2 adrenergic receptors (β2AR) acetylcholine release in MLN and spleen. Using selective optogenetic blockade applied at the SMG, we determined that electrical VNS-evoked release of norepinephrine and acetylcholine in the MLN and spleen could be inhibited and restored LPS induced TNFα production. These studies identify the superior mesenteric ganglion as a critical node in the inhibition of immune function in the MLN and the spleen.

Neural interrelationships of autonomic ganglia from the pelvic region of male rats.

The aims of the present study were to describe, in male rats, the anatomical organization of the major and accessory pelvic ganglia (MPG, AG; respectively), the interrelationship of the pelvic plexus components, and the morphometry of the pelvic postganglionic neurons. Anatomical, histochemical and histological studies were performed in anesthetized adult Wistar male rats. We found that the pelvic plexus consists of intricate neural circuits composed of two MPG, and three pairs of AG (AGI, AGII, AGIII) anatomically interrelated through ipsilateral and contralateral commissural nerves. Around 30 nerves emerge from each MPG and 17 from AGI and AGII. The MPG efferent nerves spread out preganglionic information to several pelvic organs controlling urinary, bowel, reproductive and sexual functions, while AG innervation is more regional, and it is confined to reproductive organs located in the rostral region of the urogenital tract. Both MPG and AG contain nerve fascicles, blood vessels, small intensely fluorescent cells, satellite cells and oval neuronal somata with one to three nucleoli. The soma area of AG neurons is larger than those of MPG neurons (p < 0.005). The MPG contains about 75% of the total pelvic postganglionic neurons. Our findings corroborated previous reports about MPG inputs, and add new information regarding pelvic ganglia efferent branches, AG neurons (number and morphometry), and neural interrelationship between the pelvic plexus components. This information will be useful in designing future studies about the role of pelvic innervation in the physiology and pathophysiology of pelvic functions.

Innervation of the human spleen: A complete hilum-embedding approach

IntroductionThe spleen is hypothesized to play a role in the autonomic nervous system (ANS)-mediated control of host defence, but the neuroanatomical evidence for this assumption rests on a sparse number of studies, which mutually disagree with respect to the existence of cholinergic or vagal innervation. MethodsWe conducted an immuno- and enzyme-histochemical study of the innervation of the human spleen using a complete hilum-embedding approach to ensure that only nerves that entered or left the spleen were studied, and that all splenic nerves were included in the sampled area. Furthermore, a complete embedded spleen was serially sectioned to prepare a 3D reconstruction of the hilar nerve plexus. ResultsAll detected nerves entering the spleen arise from the nerve plexus that surrounds branches of the splenic artery and are catecholaminergic. Inside the spleen these nerves continue within the adventitia of the white pulpal central arteries and red pulpal arterioles. Staining for either choline acetyltransferase or acetylcholinesterase did not reveal any evidence for cholinergic innervation of the human spleen, irrespective of the type of fixation (regularly fixed, fresh-frozen post-fixed or fresh-frozen cryoslides). Furthermore, no positive VIP staining was observed (VIP is often co-expressed in postganglionic parasympathetic nerves). ConclusionOur comprehensive approach did not produce any evidence for a direct cholinergic (or VIP-ergic) innervation of the spleen. This finding does not rule out (indirect) vagal innervation via postganglionic non-cholinergic periarterial fibres.

Temporoparietal frey syndrome: An uncommon variant of a common syndrome.

To describe a previously unreported variant of Frey syndrome. Gustatory sweating is a common complication of parotidectomy and typically directly overlies the surgical site or parotid bed. In some instances, the sweating may occur beyond the parotid bed or involve tissue that was undisturbed during the procedure. Retrospective case series. All cases of temporoparietal Frey syndrome in a single surgeon's experience were reviewed. Seven patients were found to have temporoparietal Frey syndrome. Three patients had concomitant first bite syndrome. Three patients had some form of reconstruction at time of surgery. The mean time to onset of symptoms was 11.5 months, with a range of 7 to 21 months. Four patients did not require any treatment for their symptoms, but two patients required intradermal Botox injections for symptomatic relief. This study describes a previously unreported variant of Frey syndrome with symptoms occurring distal to the parotid gland. This likely develops either by regeneration of severed postganglionic fibers into sympathetic targets distally along the course of the auriculotemporal nerve or by regeneration into fibers of the sympathetic plexus traveling along the superficial temporal artery. Laryngoscope, 129:2071-2075, 2019.

Selective tracking of FFAR3-expressing neurons supports receptor coupling to N-type calcium channels in mouse sympathetic neurons

Activation of short-chain free fatty acid receptors 3 (FFAR3) has been suggested to promote sympathetic outflow in postganglionic sympathetic neurons or hamper it by a negative coupling to N-type calcium (CaV2.2) channels. Heterogeneity of FFAR3 expression in sympathetic neurons, however, renders single neurons studies extremely time-consuming in wild-type mice. Previous studies demonstrated large variability of the degree of CaV2.2 channel inhibition by FFAR3 in a global population of rat sympathetic neurons. Therefore, we focused on a small subpopulation of mouse sympathetic neurons using an FFAR3 antibody and an Ffar3 reporter mouse to perform immunofluorescent and electrophysiological studies. Whole-cell patch-clamp recordings of identified FFAR3-expressing neurons from reporter mice revealed a 2.5-fold decrease in the CaV2.2-FFAR3 inhibitory coupling variability and 1.5-fold increase in the mean ICa2+ inhibition, when compared with unlabeled neurons from wild-type mice. Further, we found that the ablation of Ffar3 gene expression in two knockout mouse models led to a complete loss-of-function. Subpopulations of sympathetic neurons are associated with discrete functional pathways. However, little is known about the neural pathways of the FFAR3-expressing subpopulation. Our data indicate that FFAR3 is expressed primarily in neurons with a vasoconstrictor phenotype. Thus, fine-tuning of chemically-coded neurotransmitters may accomplish an adequate outcome.

Evidence for differential control of muscle sympathetic single units during mild sympathoexcitation in young, healthy humans.

Two subpopulations of muscle sympathetic single units with opposite discharge characteristics have been identified during low-level cardiopulmonary baroreflex loading and unloading in middle-aged adults and patients with heart failure. The present study sought to determine whether similar subpopulations are present in young healthy adults during cardiopulmonary baroreflex unloading ( study 1) and rhythmic handgrip exercise ( study 2). Continuous hemodynamic and multiunit and single unit muscle sympathetic nerve activity (MSNA) data were collected at baseline and during nonhypotensive lower body negative pressure (LBNP; n = 12) and 40% maximal voluntary contraction rhythmic handgrip exercise (RHG; n = 24). Single unit MSNA responses were classified as anticipated or paradoxical based on whether changes were concordant or discordant with the multiunit MSNA response, respectively. LBNP and RHG both increased multiunit MSNA burst frequency (∆5 ± 3 bursts/min, P < 0.001; ∆5 ± 8 bursts/min, P = 0.005), burst amplitude (∆5 ± 7%, P = 0.04; ∆13 ± 14%, P < 0.001), and total MSNA (∆302 ± 191 AU/min, P = 0.001; ∆585 ± 556 AU/min, P < 0.001). During LBNP and RHG, 43 and 64 muscle single units were identified, respectively, which increased spike frequency (∆9 ± 11 spikes/min, P < 0.001; ∆10 ± 19 spikes/min, P < 0.001) and the probability of multiple spike firing (∆10 ± 12%, P < 0.001; ∆11 ± 26%, P = 0.001). During LBNP and RHG, 36 (84%) and 39 (61%) single units possessed anticipated firing responses (∆12 ± 10 spikes/min, P < 0.001; ∆19 ± 19 spikes/min, P < 0.001), whereas 7 (16%) and 25 (39%) single units exhibited paradoxical reductions (∆-3 ± 1 spikes/min, P = 0.003; ∆-4 ± 5 spikes/min, P < 0.001). The observation of divergent subpopulations of muscle sympathetic single units in healthy young humans during two mild sympathoexcitatory stressors supports differential control at the fiber level as a fundamental characteristic of human sympathetic regulation. NEW & NOTEWORTHY The activity of muscle sympathetic single units was recorded during cardiopulmonary baroreceptor unloading and rhythmic handgrip exercise in young healthy humans. During both stressors, the majority of single units (84% and 61%) exhibited anticipated behavior concordant with the integrated muscle sympathetic response, whereas a smaller proportion (16% and 39%) exhibited paradoxical sympathoinhibition. These results support differential control of postganglionic muscle sympathetic fibers as a characteristic of human sympathetic regulation during mild sympathoexcitatory stress. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/differential-control-of-sympathetic-outflow-in-young-humans/ .

Assessing changes in tissue oxygenation by near-infrared spectroscopy following brachial plexus block for arteriovenous fistula surgery: A prospective observational pilot study.

Near-infrared spectroscopy (NIRS) can be used to measure tissue oxygen saturation (StO2) in different sites and in a wide range of clinical scenarios. Peripheral regional anaesthesia induces vascular changes causing increased arterial blood flow and venodilatation, but its effect on StO2 is still under debate. This is especially so for patients undergoing arteriovenous fistula surgery, wherein latest data suggest an improved outcome under brachial plexus block (BPB) compared with local anaesthesia, but no data are available. The aim of this study was to investigate changes in StO2 following BPB prior to arteriovenous fistula surgery using NIRS. A prospective observational study. A secondary teaching hospital from August 2016 to March 2017. Fifteen patients undergoing arteriovenous fistula surgery. Ultrasound-guided BPB in 15 patients undergoing arteriovenous fistula surgery. StO2 at baseline and compared with baseline and the contralateral arm following BPB measured using NIRS of the thenar eminence (NIRSth). Baseline values of StO2 assessed by NIRSth were 42.6 ± 7.7% in the arteriovenous fistula arm and 42.7 ± 9.7% in the contralateral arm. There was no significant difference between the two. Five minutes after BPB, there was a significant increase in StO2 of the blocked arm, compared with the control arm expressed as difference of absolute values (7.1 ± 9.7%). At 60 min, an absolute difference of 21.0 ± 13.5% was reached. The absolute increase in StO2 of the blocked arm compared with baseline reached significance after 5 min (8.8 ± 4.6%) and increased up to 23.2 ± 8.2% after 60 min. NIRSth indicates that BPB significantly increases StO2 of the arteriovenous fistula arm in patients undergoing haemodialysis. Clinicaltrials.gov: NCT03044496.

Monoamines in the enteric nervous system

Recent advances in neurogastroenterology have extended and refined our knowledge on the roles monoamines play in physiology and pathophysiology of the gastrointestinal tract. The catecholamine noradrenaline, as the primary transmitter of postganglionic sympathetic neurons, orchestrates motility and secretory reflexes and controls arterial perfusion as well as immune functions. The catecholamine dopamine is produced by a subpopulation of enteric neurons which possibly use it as transmitter. Serotonin, largely produced by enterochromaffin cells and to a small extent by enteric neurons profoundly affects gut motility, enteric neuron development and is also involved in immunomodulation. However, its mode of action and the relative contribution of non-neuronal versus neuronal serotonin was recently subject to debate again. Histamine, although entirely of non-neuronal origin, is pivotal for gastrointestinal neuroimmunomodulation besides its paracrine effect in gastric HCl production.

\u03b2-Adrenergic signaling blocks murine CD8+ T-cell metabolic reprogramming during activation: a mechanism for immunosuppression by adrenergic stress

Primary and secondary lymphoid organs are heavily innervated by the autonomic nervous system. Norepinephrine, the primary neurotransmitter secreted by post-ganglionic sympathetic neurons, binds to and activates β-adrenergic receptors expressed on the surface of immune cells and regulates the functions of these cells. While it is known that both activated and memory CD8+ T-cells primarily express the β2-adrenergic receptor (β2-AR) and that signaling through this receptor can inhibit CD8+ T-cell effector function, the mechanism(s) underlying this suppression is not understood. Under normal activation conditions, T-cells increase glucose uptake and undergo metabolic reprogramming. In this study, we show that treatment of murine CD8+ T-cells with the pan β-AR agonist isoproterenol (ISO) was associated with a reduced expression of glucose transporter 1 following activation, as well as decreased glucose uptake and glycolysis compared to CD8+ T-cells activated in the absence of ISO. The effect of ISO was specifically dependent upon β2-AR, since it was not seen in adrb2−/− CD8+ T-cells and was blocked by the β-AR antagonist propranolol. In addition, we found that mitochondrial function in CD8+ T-cells was also impaired by β2-AR signaling. This study demonstrates that one mechanism by which β2-AR signaling can inhibit CD8+ T-cell activation is by suppressing the required metabolic reprogramming events which accompany activation of these immune cells and thus reveals a new mechanism by which adrenergic stress can suppress the effector activity of immune cells.

Sudomotor dysfunction is frequent and correlates with disability in Friedreich ataxia

ObjectivesTo evaluate autonomic symptoms and function in Friedreich’s Ataxia (FRDA). MethodsTwenty-eight FRDA patients and 24 controls underwent clinical/electrophysiological testing. We employed the Friedreich’s Ataxia Rating Scale (FARS) and the Scales for Outcomes in Parkinson’s Disease: Autonomic Questionnaire-SCOPA-AUT to estimate the intensity of ataxia and autonomic complaints, respectively. Cardiovagal tests and the quantitative sudomotor axonal reflex, Q-SART, were then assessed in both groups. ResultsIn the patient group, there were 11 men with mean age of 31.5 ± 11.1 years. Mean SCOPA-AUT score was 15.1 ± 8.1. Minimum RR interval at rest was shorter in the FRDA group (Median 831.3 × 724.0 ms, p < 0.001). The 30:15 ratio, Valsalva index, E:I ratio, low and high frequency power presented no differences between patients and controls (p > 0.05). Sweat responses were significantly reduced in patients for all sites tested (forearm 0.389 × 1.309 µL; proximal leg 0.406 × 1.107 µL; distal leg 0.491 × 1.232 µL; foot 0.265 × 0.708 µL; p value < 0.05). Sweat volumes correlated with FARS scores. ConclusionsWe found abnormal sudomotor but normal heart rate variability in FRDA. Small cholinergic post-ganglionic fibers are affected in the disease. SignificanceQuantification of sudomotor function might be a biomarker for FRDA.

The role of the paravertebral ganglia in human sympathetic neural discharge patterns.

The mechanisms affecting recruitment patterns of postganglionic sympathetic nerves remain unclear. The divergent and convergent preganglionic innervation patterns of postganglionic neurons and the presence of differently sized postganglionic nerves suggest that the ganglia may participate in modifying the discharge patterns of single sympathetic postganglionic neurons innervating the skeletal muscle circulation. Whether the ganglia affect the ordered behaviour of varying sized postganglionic sympathetic neurons in humans has not been studied. Trimethaphan infusion produced an ordered pattern of action potential (AP) de-recruitment whereby the firing of larger, low probability APs present at baseline was abolished first, followed by progressive decreased probability of smaller APs. Although integrated sympathetic bursts were no longer detected after several minutes of trimethaphan, firing of the smallest APs was detected. These data suggest the ganglia affect the distribution of firing probabilities exhibited by differently sized sympathetic neurons. The ganglia may contribute to sympathetic neural emission patterns involved in homeostatic regulation. Do the ganglia contribute to the ordered behaviour of postganglionic neuronal discharge within the sympathetic nervous system? To further understand the functional organization of the sympathetic nervous system we employed the microneurographic approach to record muscle sympathetic nerve activity (MSNA) and a continuous wavelet transform to study postganglionic action potential (AP) behaviour during nicotinic blockade at the ganglia (trimethaphan camsylate, 1-7mgmin-1 ) in seven females (37± 5 years). Trimethaphan elicited a progressive reduction in sympathetic outflow characterized by fewer integrated bursts with decaying amplitude. Underlying trimethaphan-mediated attenuations in integrated MSNA were reductions in AP incidence (186± 101 to 29± 31 AP(100 beats)-1 ) and AP content per integrated burst (7± 2 to 3± 1 APsburst-1 ) (both P< 0.01) in the final minute of detectable bursting activity in the trimethaphan condition, compared to baseline. We observed an ordered de-recruitment of larger to smaller AP clusters active at baseline (14± 3 to 8± 2 active AP clusters, P< 0.01). Following cessation of integrated bursts in the trimethaphan condition, the smallest 6± 2 sympathetic AP clusters persisted to fire in an asynchronous pattern (49± 41AP (100 beats)-1 ) in all participants. Valsalva's manoeuvre did not increase the incidence of these persistent APs (60± 42 AP(100 beats)-1 , P= 0.52), or recruit any larger APs in six of seven participants (6± 1 total AP clusters, P= 0.30). These data suggest that the ganglia participate in the ordered recruitment of differently sized postganglionic sympathetic nerves.

FGF21 increases water intake, urine output and blood pressure in rats.

Fibroblast growth factor 21 (FGF21) is a hormone secreted by the liver in response to metabolic stress. In addition to its well-characterized effects on energy homeostasis, FGF21 has been shown to increase water intake in animals. In this study, we sought to further explore the effects of FGF21 on fluid homeostasis in rats. A single dose of a long-acting FGF21 analog, PF-05231023, significantly increased water consumption, which was accompanied by an elevation in urine output that appeared prior to a significant change in water intake. We observed that FGF21 rapidly and significantly increased heart rate and blood pressure in telemeter-implanted rats, before changes in urine output and water intake were observed. Our data suggest that sympathetic activation may contribute to the pathogenesis by which FGF21 increases blood pressure as the baroreceptor unloading induced reflex tachycardia was significantly elevated in FGF21-treated animals. However, FGF21 was still capable of causing hypertension in animals in which approximately 40% of the sympathetic post-ganglionic neurons were ablated. Our data suggest that FGF21-induced water intake is in fact secondary to diuresis, which we propose to be a compensatory mechanism engaged to alleviate the acute hypertension caused by FGF21.

PACAP/PAC1 Regulation of Inflammation via Catecholaminergic Neurons in a Model of Multiple Sclerosis.

The sympathetic nervous system (SNS) serves to maintain homeostasis of vital organ systems throughout the body, and its dysfunction plays a major role in human disease. The SNS also links the central nervous system to the immune system during different types of stress via innervation of the lymph nodes, spleen, thymus, and bone marrow. Previous studies have shown that pituitary adenylate cyclase-activating polypeptide (PACAP, gene name adcyap1) exhibits anti-inflammatory properties in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis. Because PACAP is known to regulate SNS function, we hypothesized that part of the immunoprotective action of PACAP is due to its neuromodulatory effects on sympathetic neurons. To examine this, we used an inducible, targeted approach to conditionally disrupt not only the PACAP-preferring PAC1 receptor gene (adcyap1r1) in dopamine β-hydroxylase-expressing cells, which includes postganglionic sympathetic neurons, but also catecholaminergic neurons in the brain and adrenomedullary chromaffin cells. In contrast to our previous EAE studies using PACAP global knockout mice which developed severe and prolonged EAE, we found that mice with conditional loss of PAC1 receptors in catecholaminergic cells developed a delayed time course of EAE with reduced helper T cell type 1 (Th1) and Th17 and enhanced Th2 cell polarization. At later time points, similar to mice with global PACAP loss, mice with conditional loss of PAC1 exhibited more severe clinical disease than controls. The latter was associated with a reduction in the abundance of thymic regulatory T cells (Tregs). These studies indicate that PAC1 receptor signaling acts in catecholaminergic cells in a time-dependent manner. At early stages of disease development, it enhances the ability of the SNS to polarize the Th response towards a more inflammatory state. Then, after disease is established, it enhances the ability of the SNS to dampen the inflammatory response via Tregs. The lack of concordance in results between global PACAP KO mice and mice with the PAC1 deletion targeted to catecholaminergic cells during early EAE may be explained by the fact that PACAP acts to regulate inflammation via multiple receptor subtypes and multiple targets, including inflammatory cells.

Neuronal Correlation Between Acupoint BL 23 and the Adrenal Gland in Rats

To explore the neuroanatomical basis of acupoint-visceral correlation by studying the distribution of the neurons associated with acupoint "Shenshu" (BL 23) area and adrenal gland in rats. AF 488-CTB and AF 594-CTB were injected into the left side of BL 23 area and adrenal gland in the same rat respectively. Three days after injection, the dorsal root ganglions (DRG), sympathetic chain, and spinal cord were dissected out from the perfused rats. The neuronal labeling with AF 488/594-CTB was directly observed on the sections under a fluorescent microscope or a laser scanning confocal microscope. All neural labeling was observed in the injection side. The sensory neurons associated with both acupoint BL 23 and adrenal gland distributed from thoracic (T) 10 to lumbar (L) 2 DRG with high concentration in T 12-T 13 and T 11-T 12, respectively, in which some of them were simultaneously labeled with both AF 488/594-CTB and located in T 12-L 1 DRG. For the sympathetic innervation, the postganglionic neurons correlated with BL 23 and adrenal gland were labeled with AF 488/594-CTB separately in the sympathetic chain at the lumbar segments, while the labeled preganglionic neurons were only observed at the lateral horn of T 11-T 13 spinal segments in the cases of adrenal gland. In addition, the labeled motor neurons were mainly detected in the spinal ventral horn at cervical (C) 7-C 8 and T 11-L 1 segments. These results indicate that there are segmental correlation between BL 23 and adrenal gland on the sensory and sympathetic innervations, and this correlation might be a neural pathway for modulating the function role of adrenal gland through BL 23 needling.

Baicalin Depresses the Sympathoexcitatory Reflex Induced by Myocardial Ischemia via the Dorsal Root Ganglia

Myocardial ischemia (MI) is one of the major causes of death in cardiac diseases. Purinergic signaling is involved in bidirectional neuronal-glial communication in the primary sensory ganglia. The sensory neuritis of cardiac afferent neurons in cervical dorsal root ganglion (cDRG) interacts with cardiac sympathetic efferent postganglionic neurons, forming feedback loops. The P2Y12 receptor is expressed in satellite glial cells (SGCs) of DRG. Baicalin is a major active ingredient extracted from natural herbal medicines, which has anti-inflammatory and strong anti-oxidation properties. In this study we investigated the effect of baicalin on P2Y12 receptor in the cervical DRG SGC-mediated sympathoexcitatory reflex, which is increased during MI. The results showed that the expression of P2Y12 receptor mRNA and protein in DRG, and the co-localization values of P2Y12 receptor and glial fibrillary acidic protein (GFAP) in cDRG SGCs were increased after MI. The activated SGCs increased IL-1β protein expression and elevated Akt phosphorylation in cDRG. Baicalin treatment inhibited the upregulation of the P2Y12 receptor, GFAP protein and Akt phosphorylation in cDRG neurons/SGCs. The stellate ganglia (SG) affect cardiac sympathetic activity. Baicalin treatment also decreased the upregulation of the P2Y12 receptor, GFAP protein in the SG. The P2Y12 agonist, 2Me-SADP, increased [Ca2+]i in HEK293 cells transfected with the P2Y12 receptor plasmid and SGCs in cDRG. These results indicate that application of baicalin alleviates pathologic sympathetic activity induced by MI via inhibition of afferents in the cDRG.

Comparison of the 3-D patterns of the parasympathetic nervous system in the lung at late developmental stages between mouse and chicken

Although the basic schema of the body plan is similar among different species of amniotes (mammals, birds, and reptiles), the lung is an exception. Here, anatomy and physiology are considerably different, particularly between mammals and birds. In mammals, inhaled and exhaled airs mix in the airways, whereas in birds the inspired air flows unidirectionally without mixing with the expired air. This bird-specific respiration system is enabled by the complex tubular structures called parabronchi where gas exchange takes place, and also by the bellow-like air sacs appended to the main part of the lung. That the lung is predominantly governed by the parasympathetic nervous system has been shown mostly by physiological studies in mammals. However, how the parasympathetic nervous system in the lung is established during late development has largely been unexplored both in mammals and birds. In this study, by combining immunocytochemistry, the tissue-clearing CUBIC method, and ink-injection to airways, we have visualized the 3-D distribution patterns of parasympathetic nerves and ganglia in the lung at late developmental stages of mice and chickens. These patterns were further compared between these species, and three prominent similarities emerged: (1) parasympathetic postganglionic fibers and ganglia are widely distributed in the lung covering the proximal and distal portions, (2) the gas exchange units, alveoli in mice and parabronchi in chickens, are devoid of parasympathetic nerves, (3) parasympathetic nerves are in close association with smooth muscle cells, particularly at the base of the gas exchange units. These observations suggest that despite gross differences in anatomy, the basic mechanisms underlying parasympathetic control of smooth muscles and gas exchange might be conserved between mammals and birds.

Neurotransmitter Switching Coupled to β-Adrenergic Signaling in Sympathetic Neurons in Prehypertensive States.

Single or combinatorial administration of β-blockers is a mainstay treatment strategy for conditions caused by sympathetic overactivity. Conventional wisdom suggests that the main beneficial effect of β-blockers includes resensitization and restoration of β1-adrenergic signaling pathways in the myocardium, improvements in cardiomyocyte contractility, and reversal of ventricular sensitization. However, emerging evidence indicates that another beneficial effect of β-blockers in disease may reside in sympathetic neurons. We investigated whether β-adrenoceptors are present on postganglionic sympathetic neurons and facilitate neurotransmission in a feed-forward manner. Using a combination of immunocytochemistry, RNA sequencing, Förster resonance energy transfer, and intracellular Ca2+ imaging, we demonstrate the presence of β-adrenoceptors on presynaptic sympathetic neurons in both human and rat stellate ganglia. In diseased neurons from the prehypertensive rat, there was enhanced β-adrenoceptor-mediated signaling predominantly via β2-adrenoceptor activation. Moreover, in human and rat neurons, we identified the presence of the epinephrine-synthesizing enzyme PNMT (phenylethanolamine-N-methyltransferase). Using high-pressure liquid chromatography with electrochemical detection, we measured greater epinephrine content and evoked release from the prehypertensive rat cardiac-stellate ganglia. We conclude that neurotransmitter switching resulting in enhanced epinephrine release, may provide presynaptic positive feedback on β-adrenoceptors to promote further release, that leads to greater postsynaptic excitability in disease, before increases in arterial blood pressure. Targeting neuronal β-adrenoceptor downstream signaling could provide therapeutic opportunity to minimize end-organ damage caused by sympathetic overactivity.

F53. Cardiovascular and sudomotor autonomic assessment in Friedreich’s Ataxia

Introduction Little is known about autonomic dysfunction in Friedreichs Ataxia (FRDA). Several important questions on its prevalence and severity remain unanswered. In this study we aim to determine the profile of autonomic manifestations in FRDA, as well as to identify possible sites of damage. Methods We have performed clinical and electrophysiological evaluation of 35 patients with FDRA and 21 healthy controls. We used the Friedreich’s Ataxia Rating Scale (FARS) and the Scales for Outcomes in Parkinson’s Disease: Autonomic Questionnaire-SCOPA-AUT to quantify the severity of ataxia and autonomic complaints, respectively. We also studied heart rate variability at rest, during orthostatic challenge (30:15 ratio), Valsalva maneuver (Valsalva index) and deep breathing (E:I ratio). We evaluated spectral analyses of RR intervals at rest and the quantitative sudomotor axonal reflex, Q-SWEAT test. Groups were compared using non-parametric tests and p values set at 0.05. Results In the FRDA group, there were 14 Men with mean age of 32.4 ± 11.2. SCOPA-AUT score was 15.9 ± 8.9. Mean and minimum RR intervals at rest were different between patients and controls (542 × 539 ms; p = 0.039 and 479 × 601 ms, p = 0,001). The 30:15 ratio, Valsalva index, E:I ratio, low and high frequency power were all similar between the groups (p > 0.05). In contrast, 82% of the patients had abnormal sweat responses in at least one site in the body. The legs were the most frequent sites involved. Conclusion Sudomotor, but not cardiovascular autonomic dysfunction is frequent in FDRA. Small cholinergic post-ganglionic nerve fibers are affected in the disease.

Adrenergic Signaling at the Interface of Allergic Asthma and Viral Infections.

Upper respiratory viral infections are a major etiologic instigator of allergic asthma, and they drive severe exacerbations of allergic inflammation in the lower airways of asthma sufferers. Rhinovirus (RV), in particular, is the main viral instigator of these pathologies. Asthma exacerbations due to RV infections are the most frequent reasons for hospitalization and account for the majority of morbidity and mortality in asthma patients. In both critical care and disease control, long- and short-acting β2-agonists are the first line of therapeutic intervention, which are used to restore airway function by promoting smooth muscle cell relaxation in bronchioles. While prophylactic use of β2-agonists reduces the frequency and pathology of exacerbations, their role in modulating the inflammatory response is only now being appreciated. Adrenergic signaling is a component of the sympathetic nervous system, and the natural ligands, epinephrine and norepinephrine (NE), regulate a multitude of autonomic functions including regulation of both the innate and adaptive immune response. NE is the primary neurotransmitter released by post-ganglionic sympathetic neurons that innervate most all peripheral tissues including lung and secondary lymphoid organs. Thus, the adrenergic signaling pathways are in direct contact with both the central and peripheral immune compartments. We present a perspective on how the adrenergic signaling pathway controls immune function and how β2-agonists may influence inflammation in the context of virus-induced asthma exacerbations.