The baroreflex afferent pathway plays a critical role in H2S-mediated autonomic control of blood pressure regulation under physiological and hypertensive conditions.

Hydrogen sulfide (H2S), which is closely related to various cardiovascular disorders, lowers blood pressure (BP), but whether this action is mediated via the modification of baroreflex afferent function has not been elucidated. Therefore, the current study aimed to investigate the role of the baroreflex afferent pathway in H2S-mediated autonomic control of BP regulation. The results showed that baroreflex sensitivity (BRS) was increased by acute intravenous NaHS (a H2S donor) administration to renovascular hypertensive (RVH) and control rats. Molecular expression data also showed that the expression levels of critical enzymes related to H2S were aberrantly downregulated in the nodose ganglion (NG) and nucleus tractus solitarius (NTS) in RVH rats. A clear reduction in BP by the microinjection of NaHS or L-cysteine into the NG was confirmed in both RVH and control rats, and a less dramatic effect was observed in model rats. Furthermore, the beneficial effects of NaHS administered by chronic intraperitoneal infusion on dysregulated systolic blood pressure (SBP), cardiac parameters, and BRS were verified in RVH rats. Moreover, the increase in BRS was attributed to activation and upregulation of the ATP-sensitive potassium (KATP) channels Kir6.2 and SUR1, which are functionally expressed in the NG and NTS. In summary, H2S plays a crucial role in the autonomic control of BP regulation by improving baroreflex afferent function due at least in part to increased KATP channel expression in the baroreflex afferent pathway under physiological and hypertensive conditions.

Sumoylation of the Tumor Suppressor Promyelocytic Leukemia Protein Regulates Arsenic Trioxide-Induced Collagen Synthesis in Osteoblasts.

BACKGROUND/AIMS: Promyelocytic leukemia (PML) protein is a tumor suppressor that fuses with retinoic acid receptor-α (PML-RARα) to contribute to the initiation of acute promyelocytic leukemia (APL). Arsenic trioxide (ATO) upregulates expression of TGF-ß1, promoting collagen synthesis in osteoblasts, and ATO binds directly to PML to induce oligomerization, sumoylation, and ubiquitination. However, how ATO upregulates TGF-ß1 expression is uncertain. Thus, we suggested that PML sumoylation is responsible for regulation of TGF-ß1 protein expression. METHODS: Kunming mice were treated with ATO, and osteoblasts were counted under scanning electron microscopy. Masson's staining was used to quantify collagen content. hFOB1.19 cells were transfected with siRNA against UBC9 or RNF4, and then treated with ATO or FBS. TGF-ß1, PML expression, and sumoylation were quantified with Western blot, and collagen quantified via immunocytochemistry. RESULTS: ATO enhanced osteoblast accumulation, collagen synthesis, and PML-NB formation in vivo. Knocking down UBC9 in hFOB1.19 cells inhibited ATO- and FBS-induced PML sumoylation, TGF-ß1 expression, and collagen synthesis. Conversely, knocking down RNF4 enhanced ATO- and FBS-induced PML sumoylation, TGF-ß1 expression, and collagen synthesis. CONCLUSION: These data suggest that PML sumoylation is required for ATO-induced collagen synthesis in osteoblasts.

Parkinson-like early autonomic dysfunction induced by vagal application of DOPAL in rats.

AIM: To understand why autonomic failures, a common non-motor symptom of Parkinson's disease (PD), occur earlier than typical motor disorders. METHODS: Vagal application of DOPAL (3,4-dihydroxyphenylacetaldehyde) to simulate PD-like autonomic dysfunction and understand the connection between PD and cardiovascular dysfunction. Molecular and morphological approaches were employed to test the time-dependent alternation of α-synuclein aggregation and the ultrastructure changes in the heart and nodose (NG)/nucleus tractus solitarius (NTS). RESULTS: Blood pressure (BP) and baroreflex sensitivity of DOPAL-treated rats were significantly reduced accompanied with a time-dependent change in orthostatic BP, consistent with altered echocardiography and cardiomyocyte mitochondrial ultrastructure. Notably, time-dependent and collaborated changes in Mon-/Tri-α-synuclein were paralleled with morphological alternation in the NG and NTS. CONCLUSION: These all demonstrate that early autonomic dysfunction mediated by vagal application of DOPAL highly suggests the plausible etiology of PD initiated from peripheral, rather than central site. It will provide a scientific basis for the prevention and early diagnosis of PD.

Functional impact of the hyperpolarization-activated current on the excitability of myelinated A-type vagal afferent neurons in the rat.

1. The hyperpolarization-induced, cation-selective current I(h) is widely observed in peripheral sensory neurons of the vagal and dorsal root ganglia, but the peak magnitude and voltage- and time-dependent properties of this current vary widely across afferent fibre type. 2. Using patch clamp investigations of rat isolated vagal ganglion neurons (VGN) identified as myelinated A-type afferents, we established a compendium of functional correlates between changes in membrane potential and the dynamic discharge properties of these sensory neurons as a result of the controlled recruitment of I(h) using the current clamp technique. 3. Two robust responses were observed in response to hyperpolarizing step currents: (i) upon initiation of the negative step current, there was a rapid hyperpolarization of membrane potential followed by a depolarizing voltage sag (DVS) towards a plateau in membrane potential as a result of steady state recruitment of I(h); and (ii) upon termination of the negative step current, there was a rapid return to the pretest resting membrane potential that often led to spontaneous action potential discharge. These data were strongly correlated (r(2) > 0.9) with a broad compendium of dynamic discharge characteristics in these A-type VGN. 4. In response to depolarizing step currents of increasing magnitude, the discharge frequency of the A-type VGN responded with increases in the rate of sustained repetitive discharge. Upon termination of the depolarizing step current, there was a post-excitatory membrane hyperpolarization of a magnitude that was strongly correlated with action potential discharge rate (r(2) > 0.9). 5. Application of the selective hyperpolarization-activated cyclic nucleotide gated (HCN) channel blockers ZD7288 (10 micromol/L) or CsCl (1.0 mmol/L) abolished I(h) and all of the aforementioned functional correlates. In addition to reducing the excitability of the A-type VGN to step depolarizing currents. 6. Because there is increasing evidence that the HCN channel current may represent a valid target for pharmacological intervention, the quantitative relationships described in the present study could potentially help guide the molecular and/or chemical modification of HCN channel gating properties to effect a particular outcome in VGN discharge properties, ideally well beyond merely selective blockade of a particular HCN channel subtype.

Protective effect of the daming capsule on impaired baroreflexes in STZ-induced diabetic rats with hyperlipoidemia.

BACKGROUND: The Daming capsule (DMC) is a traditional Chinese medicine used to treat hyperlipoidemia. Both clinic trials and studies on animal models have demonstrated that DMC is beneficial against diabetic symptoms. Impairment of the baroreflex can cause life-threatening arrhythmias and sudden cardiac death in patients with diabetes mellitus (DM). This study was designed to elucidate the effects of DMC on baroreflexes in streptozocin (STZ)-induced diabetic rats with hyperlipoidemia. METHODS: Wistar rats were randomly divided into three groups: untreated controls, rats pretreated STZ and high lipids (a diabetes model or DM rats), and DM rats treated with DMC. The baroreflex sensitivity was examined during intravenous injection of phenylephrine (PE) or sodium nitroprusside (SNP) and quantified by the change in heart rate over the change in mean arterial blood pressure (ΔHR/ΔMABP). Morphological remodeling of baroreceptors was analyzed by transmission electron microscopy (TEM). The mRNA levels and expression of GluR2 and a GABAA receptor subunit were measured by quantitative RT-PCR and Western blotting. RESULTS: Compared to untreated DM rats, DMC significantly elevated the ratio of ΔHR/ΔMABP by enhancing the compensatory reduction in HR (-ΔHR) in response to PE-induced hypertension (+ΔMABP) (P < 0.05). In the presence of SNP, DMC increased the ΔMABP (P < 0.05). In addition, DMC markedly shortened the duration of blood pressure changes elicited by PE or SNP in DM rats compared to the untreated DM group (P < 0.05). Electron microscopy revealed disrupted myelin sheaths, swollen ER, and lysed mitochondria in the nucleus ambiguous (NAm) DM rats. These signs of neuropathology were largely prevented by treatment with DMC for 30 days. Treatment with DMC elevated both mRNA and protein level of GluR2 in the NAm of DM rats, but had no effect on GABAA receptor expression. CONCLUSION: The Daming capsule partially reversed the parasympathetic baroreflex impairment observed in STZ-induced diabetic rats with hyperlipoidemia. Treatment with DMC also prevented the degeneration of neurons and myelinated axons in the brain stem NAm and reversed the down-regulation of GluR2 mRNA. Rescue of NAm function may contribute to the medicinal properties of DMC in diabetic rats.

Contribution of Baroreflex Afferent Pathway to NPY-Mediated Regulation of Blood Pressure in Rats.

Neuropeptide Y (NPY), a metabolism-related cardiovascular factor, plays a crucial role in blood pressure (BP) regulation via peripheral and central pathways. The expression of NPY receptors (Y1R/Y2R) specific to baroreflex afferents impacts on the sexually dimorphic neural control of circulation. This study was designed to investigate the expression profiles of NPY receptors in the nodose ganglion (NG) and nucleus tractus solitary (NTS) under hypertensive conditions. To this end, rats with hypertension induced by NG-nitro-L-arginine methylester (L-NAME) or high fructose drinking (HFD), and spontaneously hypertensive rats (SHRs) were used to explore the effects/mechanisms of NPY on BP using functional, molecular, and electrophysiological approaches. The data showed that BP was elevated along with baroreceptor sensitivity dysfunction in model rats; Y1R was up- or down-regulated in the NG or NTS of male and female HFD/L-NAME groups, while Y2R was only down-regulated in the HFD groups as well as in the NG of the male L-NAME group. In SHRs, Y1R and Y2R were both down-regulated in the NTS, and not in the NG. In addition to NPY-mediated energy homeostasis, leptin-melanocortin activation may be essential for metabolic disturbance-related hypertension. We found that leptin and α-melanocyte stimulating hormone (α-MSH) receptors were aberrantly down-regulated in HFD rats. In addition, α-MSH concentrations were reduced and NPY concentrations were elevated in the serum and NTS at 60 and 90 min after acute leptin infusion. Electrophysiological recordings showed that the decay time-constant and area under the curve of excitatory post-synaptic currents were decreased by Y1R activation in A-types, whereas, both were increased by Y2R activation in Ah- or C-types. These results demonstrate that sex- and afferent-specific NPY receptor expression in the baroreflex afferent pathway is likely to be a novel target for the clinical management of metabolism-related and essential hypertension.

Estrogen-dependent MicroRNA-504 Expression and Related Baroreflex Afferent Neuroexcitation via Negative Regulation on KCNMB4 and KCa1.1 ß4-subunit Expression.

Large conductance of Ca2+-activated K+ channel (KCa1.1) plays an inhibitory role in neuroexcitation. However, the expression of KCNMB4/ß4-subunit in the nodose ganglia (NG) and nucleus tractus solitarius (NTS), and its effect and regulation on baroreflex afferent function at post-transcriptional level of female rats remains unknown. Here, we demonstrated that the expression of ß4-subunit encoded by KCNMB4 was significantly lower in females vs. males and ovariectomized (OVX) rats in the NG. Although all baroreceptor neurons (BRNs) expressed ß4-subunit, altered discharge characteristics were only observed in Ah-type neurons after ovariectomy. Notably, the decreased excitability of Ah-types was restored by paxilline and further enhanced by iberiotoxin. The consistent changes were observed in excitatory post-synaptic currents. The level of miR-504 was higher in females, which was predicted to bind to the 3'UTR of KCNMB4. In consistent, an inverse expression pattern between miR-504 and KCNMB4 was observed in baroreflex afferents. The paxilline-sensitive ß4-subunits is less in Ah-types and up-regulated by ovariectomy. These data indicated that KCa1.1 ß4-subunit is the key regulator in neuroexcitation of Ah-types and sexual-dimorphism in baroreflex afferent function through estrogen-dependent inhibition of KCNMB4 expression via miR-504.

FGF-21 ameliorates essential hypertension of SHR via baroreflex afferent function.

Hypertension is a common complication of metabolic abnormalities associated with cardiovascular system and characterized by sexual dimorphism in mammals. Fibroblast growth factor-21 (FGF-21) plays a critical role in metabolic-disorder related hypertension through the afferent loop of baroreflex. However, the gender difference in FGF-21-mediated blood pressure (BP) regulation via sexual dimorphic expression of FGFRs in the nodose (NG) and nucleus tractus solitarius (NTS) were not elucidated in physiological and genomic form of hypertension. The gene and protein expression of FGFRs were tested by qRT-PCR, immunoblotting and immunostaining; the serum level of FGF21 was tested using ELISA; The BP was monitored while FGF21 was nodose microinjected. The results showed that more potent BP reduction was confirmed in female vs. male rats by nodose microinjection of rhFGF-21 along with higher expression of FGFR2 and FGFR4 in the nodose compared with age-match male and ovariectomized (OVX) rats, rather than other receptor subtypes, which is consistent well with immunohistochemical analysis. Additionally, serum FGF-21 was significantly higher in female-WKY, and this level of FGF-21 was dramatically declined in spontaneous hypertensive rats (SHR) with significant down-regulation of FGFR1/R4 for male-SHR and FGFR2/FGFR4 for female-SHR, respectively. Apparently, high BP of SHR of either sex could be reduced by rhFGF-21 nodose microinjection. These data extends our current understanding that sexual-specific distribution/expression of FGF-21/FGFRs is likely to contribute at least partially to sexual dimorphism of baroreflex afferent function on BP regulation in rats. FGF-21-mdiated BP reduction sheds new light on clinical management of primary/genomic form of hypertension.

17Beta-estradiol restores excitability of a sexually dimorphic subset of myelinated vagal afferents in ovariectomized rats.

We recently identified a myelinated vagal afferent subpopulation (Ah type) far more prevalent in female than male rats and showed that this difference extends to functionally specific visceral sensory afferents, baroreceptors of the aortic arch. Excitability of myelinated Ah-type afferents is markedly reduced after ovariectomy (OVX). Here we tested the hypothesis that 17beta-estradiol can selectively restore excitability of these sex-specific vagal afferents. Acutely isolated vagal afferent neurons (VGN) from intact and OVX adult female rats were used with patch-clamp technique and current-clamp protocols to assess the effect of acute application of 17beta-estradiol on neuronal excitability. At over physiologically relevant 17beta-estradiol concentrations for rat (1-10 nM) excitability of myelinated Ah-type vagal afferents is restored to discharge frequencies comparable to those in intact females, albeit with some interesting differences related to burst and sustained patterns of neuronal discharge. Restoration of excitability occurs within 3 min of hormone application and is stereo specific, because 1,000 nM 17alpha-estradiol fails to alter excitability. Furthermore, activation of G protein-coupled estrogen receptor GPR30 with highly selective agonist G-1 similarly restores excitability of Ah-type afferents. The effectiveness of 17beta-estradiol and G-1 is completely eliminated by application of high-affinity estrogen receptor ligand ICI-182,780. 17beta-Estradiol conjugated with BSA is approximately 70% as effective as 17beta-estradiol alone in restoring Ah-type VGN excitability. These data support our conclusions that the cellular mechanisms leading to rapid restoration of neuronal excitability of myelinated Ah-type VGN after OVX occur, at least in part, via membrane-bound estrogen receptors. We contend that recovery of high-frequency discharge at physiologically relevant 17beta-estradiol concentrations implies that this unique subtype of low-threshold myelinated vagal afferent may account for some of the sex-related differences in visceral organ system function. Sex differences in cardiovascular and gastrointestinal function and the potential role of GPR30 in modulation of sex-specific myelinated Ah-type vagal afferents are discussed.

Hypoglycaemic and hypolipidaemic effects of emodin and its effect on L-type calcium channels in dyslipidaemic-diabetic rats.

1. The aim of the present study was to evaluate the hypoglycaemic and hypolipidaemic effects of 20, 40 and 80 mg/kg per day emodin and its potential effects on L-type calcium channels in dyslipidaemic-diabetic rats. 2. Dyslipidaemic-diabetic rats were induced by a single intraperitoneal injection of streptozotocin (55 mg/kg) after intragastric administration of a high-fat diet for 2 weeks. 3. Daily administration of emodin for 2 weeks resulted in a significant dose-dependent reductions in blood glucose, serum total cholesterol, triglycerides, free fatty acids and malonaldehyde (P < 0.05) in dyslipidaemic-diabetic rats compared with vehicle-treated dyslipidaemic-diabetic rats. In addition, emodin caused dose-dependent increases in plasma superoxide dismutase activity in dyslipidaemic-diabetic rats (P < 0.05). Immunofluorescent staining and reverse transcription-polymerase chain reaction showed that the expression of L-type calcium channels in the pancreas and heart was restored, to different extents, by the three doses of emodin treatment. 4. The results of the present study suggest that emodin has antidiabetic and lipid-modulating effects that involve, in part, upregulation of L-type calcium channel expression in the pancreas and heart in dyslipidaemic-diabetic rats.

Anti-Hypertensive Action of Fenofibrate via UCP2 Upregulation Mediated by PPAR Activation in Baroreflex Afferent Pathway.

Fenofibrate, an agonist for peroxisome proliferator-activated receptor alpha (PPAR-α), lowers blood pressure, but whether this action is mediated via baroreflex afferents has not been elucidated. In this study, the distribution of PPAR-α and PPAR-γ was assessed in the nodose ganglion (NG) and the nucleus of the solitary tract (NTS). Hypertension induced by drinking high fructose (HFD) was reduced, along with complete restoration of impaired baroreceptor sensitivity, by chronic treatment with fenofibrate. The molecular data also showed that both PPAR-α and PPAR-γ were dramatically up-regulated in the NG and NTS of the HFD group. Expression of the downstream signaling molecule of PPAR-α, the mitochondrial uncoupling protein 2 (UCP2), was up-regulated in the baroreflex afferent pathway under similar experimental conditions, along with amelioration of reduced superoxide dismutase activity and increased superoxide in HFD rats. These results suggest that chronic treatment with fenofibrate plays a crucial role in the neural control of blood pressure by improving baroreflex afferent function due at least partially to PPAR-mediated up-regulation of UCP2 expression and reduction of oxidative stress.

Direct activation of tachykinin receptors within baroreflex afferent pathway and neurocontrol of blood pressure regulation.

AIM: Substance P (SP) causes vasodilation and blood pressure (BP) reduction. However, the involvement of tachykinin receptors (NKRs) within baroreflex afferent pathway in SP-mediated BP regulation is largely unknown. METHODS: Under control and hypertensive condition, NKRs' expressions were evaluated in nodose (NG) and nucleus of tractus solitary (NTS) of male, female, and ovariectomized (OVX) rats; BP was recorded after microinjection of SP and NKRs agonists into NG; Baroreceptor sensitivity (BRS) was tested as well. RESULTS: Immunostaining and immunoblotting data showed that NK1R and NK2R were estrogen-dependently expressed on myelinated and unmyelinated afferents in NG. A functional study showed that BP was reduced dose-dependently by SP microinjection, which was more dramatic in males and can be mimicked by NK1R and NK2R agonists. Notably, further BP elevation and BRS dysfunction were confirmed in desoxycorticosterone acetate (DOCA)-salt model in OVX compared with DOCA-salt model in intact female rats. Additionally, similar changes in NKRs' expression in NG were also detected using DOCA-salt and SHR. Compared with NG, inversed expression profiles of NKRs were also found in NTS with either gender. CONCLUSION: The estrogen-dependent NKRs' expression in baroreflex afferent pathway participates at least partially in sexual-dimorphic and SP-mediated BP regulation under physiological and hypertensive conditions.

GM1 ganglioside contributes to retain the neuronal conduction and neuronal excitability in visceral and baroreceptor afferents.

GM1 ganglioside has a great impact on the function of nodes of Ranvier on myelinated fiber, suggesting its potential role to maintain the electrical and neuronal excitability of neurons. Here we first demonstrate that visceral afferent conduction velocity of myelinated and unmyelinated fibers are reduced significantly by tetrodotoxin (TTX) or cholera toxin-B subunits (CTX-B), and only the effects mediated by CTX-B are prevented by GM1 pre-treatment. At soma of myelinated A and unmyelinated C-type nodose ganglion neurons (NGNs), the action potential spike frequency reduced by CTX-B is also prevented by GM1. Additionally, the current density of both TTX-sensitive (TTX-S) and TTX-resistant (TTX-R) Na(+) channels were significantly decreased by CTX-B without changing the voltage-dependent property. These data confirm that endogenous GM1 may play a dominant role in maintaining the electrical and neuronal excitability via modulation of sodium (Na(+)) channel around nodes and soma as well, especially TTX-S Na(+) channel, which is also confirmed by the reduction of spike amplitude and depolarization. Similar data are also extended to fluorescently identified and electrophysiologically characterized aortic baroreceptor neurons. These findings suggest that GM1 plays an important role in the neural modulation of electric and neuronal excitability in visceral afferent system.

Spontaneous activities in baroreflex afferent pathway contribute dominant role in parasympathetic neurocontrol of blood pressure regulation.

AIM: To study the dominant role of parasympathetic inputs at cellular level of baroreflex afferent pathway and underlying mechanism in neurocontrol of blood pressure regulation. METHODS: Whole-cell patch-clamp and animal study were conducted. RESULTS: For the first time, we demonstrated the spontaneous activities from resting membrane potential in myelinated A- and Ah-type baroreceptor neurons (BRNs, the 1st-order), but not in unmyelinated C-types, using vagus-nodose slice of adult female rats. These data were further supported by the notion that the spontaneous synaptic currents could only be seen in the pharmacologically and electrophysiologically defined myelinated A- and Ah-type baroreceptive neurons (the 2nd-order) of NTS using brainstem slice of adult female rats. The greater frequency and the larger amplitude of the spontaneous excitatory postsynaptic currents (EPSCs) compared with the inhibitory postsynaptic currents (IPSCs) were only observed in Ah-types. The ratio of EPSCs:IPSCs was estimated at 3:1 and higher. These results confirmed that the afferent-specific spontaneous activities were generated from baroreflex afferent pathway in female-specific subpopulation of myelinated Ah-type BRNs in nodose and baroreceptive neurons in NTS, which provided a novel insight into the dominant role of sex-specific baroreflex-evoked parasympathetic drives in retaining a stable and lower blood pressure status in healthy subjects, particularly in females. CONCLUSION: The data from current investigations establish a new concept for the role of Ah-type baroreceptor/baroreceptive neurons in controlling blood pressure stability and provide a new pathway for pharmacological intervention for hypertension and cardiovascular diseases.

Increasing Intracellular calcium of guinea pig ventricular myocytes induced by platelet activating factor through IP3 pathway.

We used Fluo-3/AM to examine the effect of platelet-activating factor on the intracellular Ca2+([Ca2+]i) levels in isolated myocytes of guinea pig ventricle. Myocytes were isolated with Langendorff perfusion technique and were challenged with platelet-activating factor. Addition of platelet-activating factor (1 pM to 10 nM) significantly increased the [Ca2+]i in the presence and absence of extracellular Ca2+. The notion that increases in intracellular Ca2+ induced by platelet-activating factor is the result of stimulation of intracellular Ca2+ pool rather than increasing Ca2+ influx was further supported by the whole cell patch-clamp experiments in which the platelet-activating factor did not alter the activity of L-type of Ca2+ channels (I(Ca-L)). Treatment of myocytes with ryanodine failed to abolish the stimulatory effect of platelet-activating factor on [Ca2+]i. In contrast, inhibition of IP3-sensitive Ca2+ release pool with 2-aminoethoxydiphenyl borate (2-APB) blocked the effect of platelet-activating factor. We conclude that the platelet-activating factor-induced increase in intracellular Ca2+ is mediated by stimulation of IP3 receptor but not by stimulation of I(Ca-L) and ryanodine-sensitive receptor.

Unique Expression of Angiotensin Type-2 Receptor in Sex-Specific Distribution of Myelinated Ah-Type Baroreceptor Neuron Contributing to Sex-Dimorphic Neurocontrol of Circulation.

This study aims to understand the special expression patterns of angiotensin-II receptor (AT1R and AT2R) in nodose ganglia and nucleus of tractus solitary of baroreflex afferent pathway and their contribution in sex difference of neurocontrol of blood pressure regulation. In this regard, action potentials were recorded in baroreceptor neurons (BRNs) using whole-cell patch techniques; mRNA and protein expression of AT1R and AT2R in nodose ganglia and nucleus of tractus solitary were evaluated using real time-polymerase chain reaction, Western blot, and immunohistochemistry at both tissue and single-cell levels. The in vivo effects of 17ß-estradiol on blood pressure and AT2R expression were also tested. The data showed that AT2R, rather than AT1R, expression was higher in female than age-matched male rats. Moreover, AT2R was downregulated in ovariectomized rats, which was restored by the administration of 17ß-estradiol. Single-cell real time-polymerase chain reaction data indicated that AT2R was uniquely expressed in Ah-type BRNs. Functional study showed that long-term administration of 17ß-estradiol significantly alleviated the blood pressure increase in ovariectomized rats. Electrophysiological recordings showed that angiotensin-II treatment increased the neuroexcitability more in Ah- than C-type BRNs, whereas no such effect was observed in A-types. In addition, angiotensin-II treatment prolonged action potential duration, which was not further changed by iberiotoxin. The density of angiotensin-II-sensitive K(+) currents recorded in Ah-types was equivalent with iberiotoxin-sensitive component. In summary, the unique, sex- and afferent-specific expression of AT2R was identified in Ah-type BRNs, and AT2R-mediated KCa1.1 inhibition in Ah-type BRNs may exert great impacts on baroreflex afferent function and blood pressure regulation in females.

FGF21 ameliorates the neurocontrol of blood pressure in the high fructose-drinking rats.

Fibroblast growth factor-21 (FGF21) is closely related to various metabolic and cardiovascular disorders. However, the direct targets and mechanisms linking FGF21 to blood pressure control and hypertension are still elusive. Here we demonstrated a novel regulatory function of FGF21 in the baroreflex afferent pathway (the nucleus tractus solitarii, NTS; nodose ganglion, NG). As the critical co-receptor of FGF21, ß-klotho (klb) significantly expressed on the NTS and NG. Furthermore, we evaluated the beneficial effects of chronic intraperitoneal infusion of recombinant human FGF21 (rhFGF21) on the dysregulated systolic blood pressure, cardiac parameters, baroreflex sensitivity (BRS) and hyperinsulinemia in the high fructose-drinking (HFD) rats. The BRS up-regulation is associated with Akt-eNOS-NO signaling activation in the NTS and NG induced by acute intravenous rhFGF21 administration in HFD and control rats. Moreover, the expressions of FGF21 receptors were aberrantly down-regulated in HFD rats. In addition, the up-regulated peroxisome proliferator-activated receptor-γ and -α (PPAR-γ/-α) in the NTS and NG in HFD rats were markedly reversed by chronic rhFGF21 infusion. Our study extends the work of the FGF21 actions on the neurocontrol of blood pressure regulations through baroreflex afferent pathway in HFD rats.

Neuropeptide Y-mediated sex- and afferent-specific neurotransmissions contribute to sexual dimorphism of baroreflex afferent function.

BACKGROUND: Molecular and cellular mechanisms of neuropeptide-Y (NPY)-mediated gender-difference in blood pressure (BP) regulation are largely unknown. METHODS: Baroreceptor sensitivity (BRS) was evaluated by measuring the response of BP to phenylephrine/nitroprusside. Serum NPY concentration was determined using ELISA. The mRNA and protein expression of NPY receptors were assessed in tissue and single-cell by RT-PCR, immunoblot, and immunohistochemistry. NPY was injected into the nodose while arterial pressure was monitored. Electrophysiological recordings were performed on nodose neurons from rats by patch-clamp technique. RESULTS: The BRS was higher in female than male and ovariectomized rats, while serum NPY concentration was similar among groups. The sex-difference was detected in Y1R, not Y2R protein expression, however, both were upregulated upon ovariectomy and canceled by estrogen replacement. Immunostaining confirmed Y1R and Y2R expression in myelinated and unmyelinated afferents. Single-cell PCR demonstrated that Y1R expression/distribution was identical between A- and C-types, whereas, expressed level of Y2R was ~15 and ~7 folds higher in Ah- and C-types than A-types despite similar distribution. Activation of Y1R in nodose elevated BP, while activation of Y2R did the opposite. Activation of Y1R did not alter action potential duration (APD) of A-types, but activation of Y2R- and Y1R/Y2R in Ah- and C-types frequency-dependently prolonged APD. N-type ICa was reduced in A-, Ah- and C-types when either Y1R, Y2R, or both were activated. The sex-difference in Y1R expression was also observed in NTS. CONCLUSIONS: Sex- and afferent-specific expression of Neuropeptide-Y receptors in baroreflex afferent pathway may contribute to sexual-dimorphic neurocontrol of BP regulation.

KCa1.1 is potential marker for distinguishing Ah-type baroreceptor neurons in NTS and contributes to sex-specific presynaptic neurotransmission in baroreflex afferent pathway.

Sexual-dimorphic neurocontrol of circulation has been described in baroreflex due largely to the function of myelinated Ah-type baroreceptor neurons (BRNs, 1st-order) in nodose. However, it remains unclear if sex- and afferent-specific neurotransmission could also be observed in the central synapses within nucleus of solitary track (NTS, 2nd-order). According to the principle of no mixed neurotransmission among afferents and differentiation of Ah- and A-types to iberiotoxin (IbTX) observed in nodose, the 2nd-order Ah-type BRNs are highly expected. To test this hypothesis, the excitatory post-synaptic currents (EPSCs) were recorded in identified 2nd-order BRNs before and after IbTX using brain slice and whole-cell patch. These results showed that, in male rats, the dynamics of EPSCs in capsaicin-sensitive C-types were dramatically altered by IbTX, but not in capsaicin-insensitive A-types. Interestingly, near 50% capsaicin-insensitive neurons in females showed similar effects to C-types, suggesting the existence of Ah-types in NTS, which may be the likely reason why the females had lower blood pressure and higher sensitivity to aortic depressor nerve stimulation via KCa1.1-mediated presynaptic glutamate release from Ah-type afferent terminals.