Tonic NMDAR Currents of NR2A-Containing NMDARs Represent Altered Ambient Glutamate Concentration in the Supraoptic Nucleus.

NMDA receptors (NMDARs) modulate glutamatergic excitatory tone in the brain via two complementary modalities: a phasic excitatory postsynaptic current and a tonic extrasynaptic modality. Here, we demonstrated that the tonic NMDAR-current (I NMDA) mediated by NR2A-containing NMDARs is an efficient biosensor detecting the altered ambient glutamate level in the supraoptic nucleus (SON). I NMDA of magnocellular neurosecretory cells (MNCs) measured by nonselective NMDARs antagonist, AP5, at holding potential (V holding) -70 mV in low concentration of ECF Mg2+ ([Mg2+]o) was transiently but significantly increased 1-week post induction of a DOCA salt hypertensive model rat which was compatible with that induced by a NR2A-selective antagonist, PEAQX (I PEAQX) in both DOCA-H2O and DOCA-salt groups. In agreement, NR2B antagonist, ifenprodil, or NR2C/D antagonist, PPDA, did not affect the holding current (I holding) at V holding -70 mV. Increased ambient glutamate by exogenous glutamate (10 mM) or excitatory amino acid transporters (EAATs) antagonist (TBOA, 50 mM) abolished the I PEAQX difference between two groups, suggesting that attenuated EAATs activity increased ambient glutamate concentration, leading to the larger I PEAQX in DOCA-salt rats. In contrast, only ifenprodil but not PEAQX and PPDA uncovered I NMDA at V holding +40 mV under 1.2 mM [Mg2+]o condition. I ifenprodil was not different in DOCA-H2O and DOCA-salt groups. Finally, NR2A, NR2B, and NR2D protein expression were not different in the SON of the two groups. Taken together, NR2A-containing NMDARs efficiently detected the increased ambient glutamate concentration in the SON of DOCA-salt hypertensive rats due to attenuated EAATs activity.

Kv3.4 regulates cell migration and invasion through TGF-ß-induced epithelial-mesenchymal transition in A549 cells.

Epithelial-mesenchymal transition (EMT) is the process by which epithelial cells acquire mesenchymal characteristics. This process induces cell migration and invasion, which are closely related to cancer metastasis and malignancy. EMT consists of various intermediate states that express both epithelial and mesenchymal traits, called partial EMT. Recently, several studies have focused on the roles of voltage-gated potassium (Kv) channels associated with EMT in cancer cell migration and invasion. In this study, we demonstrate the relationship between Kv3.4 and EMT and confirm the effects of cell migration and invasion. With TGF-ß treatment, EMT was induced and Kv3.4 was also increased in A549 cells, human lung carcinoma cells. The knockdown of Kv3.4 blocked the EMT progression reducing cell migration and invasion. However, the Kv3.4 overexpressed cells acquired mesenchymal characteristics and increased cell migration and invasion. The overexpression of Kv3.4 also has a synergistic effect with TGF-ß in promoting cell migration. Therefore, we conclude that Kv3.4 regulates cancer migration and invasion through TGF-ß-induced EMT and these results provide insights into the understanding of cancer metastasis.

Tonic Activation of NR2D-Containing NMDARs Exacerbates Dopaminergic Neuronal Loss in MPTP-Injected Parkinsonian Mice.

NR2D subunit-containing NMDA receptors (NMDARs) gradually disappear during brain maturation but can be recruited by pathophysiological stimuli in the adult brain. Here, we report that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication recruited NR2D subunit-containing NMDARs that generated an Mg2+-resistant tonic NMDA current (INMDA) in dopaminergic (DA) neurons in the midbrain of mature male mice. MPTP selectively generated an Mg2+-resistant tonic INMDA in DA neurons in the substantia nigra pars compacta (SNpc) and ventral tegmental area (VTA). Consistently, MPTP increased NR2D but not NR2B expression in the midbrain regions. Pharmacological or genetic NR2D interventions abolished the generation of Mg2+-resistant tonic INMDA in SNpc DA neurons, and thus attenuated subsequent DA neuronal loss and gait deficits in MPTP-treated mice. These results show that extrasynaptic NR2D recruitment generates Mg2+-resistant tonic INMDA and exacerbates DA neuronal loss, thus contributing to MPTP-induced Parkinsonism. The state-dependent NR2D recruitment could be a novel therapeutic target for mitigating cell type-specific neuronal death in neurodegenerative diseases.SIGNIFICANCE STATEMENT NR2D subunit-containing NMDA receptors (NMDARs) are widely expressed in the brain during late embryonic and early postnatal development, and then downregulated during brain maturation and preserved at low levels in a few regions of the adult brain. Certain stimuli can recruit NR2D subunits to generate tonic persistent NMDAR currents in nondepolarized neurons in the mature brain. Our results show that MPTP intoxication recruits NR2D subunits in midbrain dopaminergic (DA) neurons, which leads to tonic NMDAR current-promoting dopaminergic neuronal death and consequent abnormal gait behavior in the MPTP mouse model of Parkinson's disease (PD). This is the first study to indicate that extrasynaptic NR2D recruitment could be a target for preventing neuronal death in neurodegenerative diseases.

Effects of synthetic peptide RP557 and its origin, LL-37, on carbapenem-resistant Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a common bacterium in nosocomial infection. The biofilm-forming ability and antimicrobial resistance make P. aeruginosa biofilm infection refractory to patients requiring hospitalization, especially patients in the intensive care unit. Therefore, many alternative compounds have been developed. A newly synthesized peptide, RP557, derived from human cathelicidin LL-37, was evaluated for its antimicrobial and antibiofilm effect toward carbapenem-resistant P. aeruginosa (CRPA). The results showed that regardless of the resistance to carbapenems, the minimal inhibition concentrations of RP557 and LL-37 against P. aeruginosa were 32 µg/mL and 256 µg/mL, respectively. Both RP557 and LL-37 significantly reduced the P. aeruginosa biofilm mass at subMICs, while subMICs of carbapenems induced biofilm formation. RP557 could also remove approximately 50% of the mature biofilm at a concentration of 64 µg/mL, while 256 µg/mL LL-37 was needed to remove it. A quarter MIC of RP557 and LL-37 was used together with carbapenems (ertapenem, imipenem, and meropenem). The results show that both RP-557 and LL-37 might increase the susceptibility to CRPA by 4-16 times. Significant gene expression level changes were observed in RP557- or LL-37-treated CRPA. Confocal images showed that biofilm structures and biofilm cell viability were significantly reduced in the LL-37- or RP557-treated groups. Therefore, RP557 and its structural origin, LL-37, could be potential treatments for carbapenem-resistant P. aeruginosa infection, especially for chronic biofilm infection. IMPORTANCE Pseudomonas aeruginosa is one of the major pathogens of nosocomial infection. Combined its biofilm-forming ability with carbapenem-resistance, it is hard to handle P. aeruginosa infection, especially for patients requiring hospitalization. Antimicrobial peptide is a type of potential compound for bacterial infection treatment. Among these, RP557 was found effective in inhibiting biofilm previously. By assessing its effect on both carbapenem-resistant P. aeruginosa planktonic cells and biofilm, our results offered a potential treatment for carbapenem-resistant P. aeruginosa infection. It could be helpful to treat severe nosocomial infection related to carbapenem-resistant bacteria and increase the patients' survival rate.

Photothermal plasmonic microballs for non-contact single-cell calcium ionophore delivery in heterogeneous cells.

Hierarchical plasmonic nanostructures comprising gold nanorod (AuNR)-covered microballs via syringe-injection reduction show good potential for selective single-cell calcium ionophore (A23187) delivery and apoptosis induction in heterogenous cancer cells.

MAO-B Inhibitor, KDS2010, Alleviates Spinal Nerve Ligation-induced Neuropathic Pain in Rats Through Competitively Blocking the BDNF/TrkB/NR2B Signaling.

MAO-B inhibitors have been implicated to reverse neuropathic pain behaviors. Our previous study has demonstrated that KDS2010 (KDS), a newly developed reversible MAO-B inhibitor, could attenuate Paclitaxel (PTX)-induced tactile hypersensitivity in mice through suppressing reactive oxidant species (ROS)-decreased inhibitory GABA synaptic transmission in the spinal cord. In this study, we evaluated the analgesic effect of KDS under a new approach, in which KDS acts on dorsal horn sensory neurons to reduce excitatory transmission. Oral administration of KDS effectively enhanced mechanical thresholds in the spinal nerve ligation (SNL) induced neuropathic pain in rats. Moreover, we discovered that although treatment with KDS increased brain-derived neurotrophic factor (BDNF) levels, KDS inhibited Tropomyosin receptor kinase B (TrkB) receptor activation, suppressing increased p-NR2B-induced hyperexcitability in spinal dorsal horn sensory neurons after nerve injury. In addition, KDS showed its anti-inflammatory effects by reducing microgliosis and astrogliosis and the activation of MAPK and NF-ᴋB inflammatory pathways in these glial cells. The levels of ROS production in the spinal cords after the SNL procedure were also decreased with KDS treatment. Taken together, our results suggest that KDS may represent a promising therapeutic option for treating neuropathic pain. PERSPECTIVE: Our study provides evidence suggesting the mechanisms by which KDS, a novel MAO-B inhibitor, can be effective in pain relief. KDS, by targeting multiple mechanisms involved in BDNF/TrkB/NR2B-related excitatory transmission and neuroinflammation, may represent the next future of pain medicine.

Antiallodynic effects of KDS2010, a novel MAO-B inhibitor, via ROS-GABA inhibitory transmission in a paclitaxel-induced tactile hypersensitivity model.

Monoamine oxidase (MAO) inhibitors have been investigated for the treatment of neuropathic pain. Here, we assessed the antiallodynic effects of a novel MAO-B inhibitor, KDS2010, on paclitaxel (PTX)-induced mechanical hypersensitivity. Oral administration of KDS2010 effectively relieved PTX-induced mechanical hypersensitivity in a dose-dependent manner. KDS2010 (25 mg/Kg) significantly prevented and suppressed PTX-induced pain responses with minimal effects on the body weight, motor activity, and working memory. KDS2010 significantly reduced reactive astrocytosis and reactive oxygen species (ROS) level in the L4-L6 spinal cord of PTX-treated mice. Furthermore, KDS2010 reversed the attenuation of GABAergic spontaneous inhibitory postsynaptic current (sIPSC) frequency in spinal dorsal horn neurons, although it failed to restore the reduced tonic GABAA inhibition nor the increased GABA transporter 1 (GAT1) expression in PTX-treated mice. In addition, bath application of a reactive oxygen species (ROS) scavenger (PBN) restored the sIPSC frequency in PTX-treated mice but not in control and PTX + KDS2010-treated mice. These results indicated that the antiallodynic effect of KDS2010 is not due to a MAO-B-dependent GABA production. Finally, PBN alone also exerted a similar analgesic effect as KDS2010, but a co-treatment of PBN with KDS2010 showed no additive effect, suggesting that inhibition of MAO-B-dependent ROS production is responsible for the analgesic effect by KDS2010 on PTX-induced allodynia. Overall, KDS2010 attenuated PTX-induced pain behaviors by restoring the altered ROS level and GABAergic inhibitory signaling in the spinal cord, suggesting that KDS2010 is a promising therapeutic strategy for chemotherapy-induced peripheral neuropathy.

Raman Thermometry Nanopipettes in Cancer Photothermal Therapy.

Raman thermometry based on surface-enhanced Raman scattering has been developed using nanopipettes in cancer cell photothermal therapy (PTT). Gold nanorods (AuNRs) are robustly epoxied on glass pipettes with a high surface coverage of ∼95% and less than 10 nm-wide nanogaps for intracellular thermometry and photothermal cancer therapy. The temperature changes could be estimated from the N≡C band shifts of 4-fluorophenyl isocyanide (FPNC)-adsorbed AuNRs on the Raman thermometry nanopipette (RTN) surfaces. An intracellular temperature change of ∼2.7 °C produced by altering the [Ca2+] in A431 cells was detected using the RTN in vitro, as checked from fura-2 acetoxymethyl ester (fura-2 AM) fluorescence images. For in vivo experiments, local temperature rises of ∼19.2 °C were observed in the mouse skin, whereas infrared camera images could not tract due to spatial resolution. In addition, a tumor growth suppression was observed in the PTT processes after an administration of the three AuNR-coated nanopipettes combined with a 671 nm laser irradiation for 5 min in 30 days. These results demonstrate not only the localized temperature sensing ability of FPNC-tagged AuNR nanopipettes in cell biology but also anti-cancer effects in photothermal cancer therapy.

Microglial activation induced by LPS mediates excitation of neurons in the hypothalamic paraventricular nucleus projecting to the rostral ventrolateral medulla.

Microglia are known to be activated in the hypothalamic paraventricular nucleus (PVN) of rats with cardiovascular diseases. However, the exact role of microglial activation in the plasticity of presympathetic PVN neurons associated with the modulation of sympathetic outflow remains poorly investigated. In this study, we analyzed the direct link between microglial activation and spontaneous firing rate along with the underlying synaptic mechanisms in PVN neurons projecting to the rostral ventrolateral medulla (RVLM). Systemic injection of LPS induced microglial activation in the PVN, increased the frequency of spontaneous firing activity of PVN-RVLM neurons, reduced GABAergic inputs into these neurons, and increased plasma NE levels and heart rate. Systemic minocycline injection blocked all the observed LPS-induced effects. Our results indicate that LPS increases the firing rate and decreases GABAergic transmission in PVN-RVLM neurons associated with sympathetic outflow and the alteration is largely attributed to the activation of microglia. Our findings provide some insights into the role of microglial activation in regulating the activity of PVN-RVLM neurons associated with modulation of sympathetic outflow in cardiovascular diseases. [BMB Reports 2021; 54(12): 620-625].

Association of Dietary Patterns with Weight Status and Metabolic Risk Factors among Children and Adolescents.

Unhealthy dietary patterns are associated with obesity in children and adolescents. However, few studies have investigated the relationships between dietary patterns and obesity-related metabolic disorders among Asians. We identified dietary patterns in children and adolescents and examined the associations between these patterns and obesity, insulin resistance, and metabolic syndrome in South Korea. This study is a cross-sectional design. We used baseline data from an intervention study of 435 Korean children and adolescents aged 6-17 years. Insulin resistance was assessed as HOMA-IR ≥ 2.6. Metabolic syndrome was diagnosed by cardiovascular disease risk factor clustering. Dietary intakes were estimated using 3-day food records. Factor analysis was used to obtain dietary patterns, and we examined the associations between dietary patterns and obesity-related markers adjusted for potential covariates. Three dietary patterns were identified as fast food and soda (FFS), white rice and kimchi (WRK), and oil and seasoned vegetable (OSV) patterns. Compared with participants in the lower intake of FFS pattern, those in the top intake were associated with a higher waist circumference (WC) (ß = 1.55), insulin level (ß = 1.25), and body mass index (BMI) (ß = 0.53) and it was positively associated with HOMA-IR ≥ 2.6 (OR = 2.11; 95% CI: 1.227-3.638) (p < 0.05). WRK pattern was associated with lower weight and higher HDL cholesterol, and the OSV pattern was associated with a lower weight, WC, and insulin level (p < 0.05). The FFS pattern showed a positive relation with WC, serum insulin, and BMI, and the other two dietary patterns indicated a preventive effect of those parameters. The FFS pattern was associated with significantly elevated insulin resistance among children and adolescents.

Kv3 channels contribute to cancer cell migration via vimentin regulation.

Cell migration is a complex and important process in cancer progression. Vimentin has pivotal roles in cancer cell migration, and various signaling pathways including the AKT pathway are involved in cancer cell migration via vimentin regulation. Recent studies have revealed that voltage-gated potassium (Kv) channels have important functions in cancer cell migration; however, the exact mechanism is still unclear. In the present study, we focused on Kv3 channels with vimentin in cancer migration using human cervical cancer cells (HeLa) and canine mammary tumor cells (CHMp). Cancer cell migration was significantly inhibited, and vimentin expression was significantly decreased by Kv3 blocker, BDS-II. The Kv3 blocker also inactivated the AKT pathway in HeLa cells. In addition, reduced expressions of vimentin and Kv3.4 were observed in HeLa cells when treated with AKT blocker, MK2206. These results suggest that Kv3 channels play important roles in cancer cell migration by regulating vimentin and having closely related with the AKT pathway in human cervical cancer cells.

The role of the voltage-gated potassium channel, Kv2.1 in prostate cancer cell migration.

Voltage-gated potassium (Kv) channels are involved in many important cellular functions and play pivotal roles in cancer progression. The expression level of Kv2.1 was observed to be higher in the highly metastatic prostate cancer cells (PC-3), specifically in their membrane, than in immortalized prostate cells (WPMY-1 cells) and comparatively less metastatic prostate cancer cells (LNCaP and DU145 cells). However, Kv2.1 expression was significantly decreased when the cells were treated with antioxidants, such as N-acetylcysteine or ascorbic acid, implying that the highly expressed Kv2.1 could detect reactive oxygen species (ROS) in malignant prostate cancer cells. In addition, the blockade of Kv2.1 with stromatoxin-1 or siRNA targeting Kv2.1 significantly inhibited the migration of malignant prostate cancer cells. Our results suggested that Kv2.1 plays an important role as a ROS sensor and that it is a promising therapeutic molecular target in metastasis of prostate cancer. [BMB Reports 2021; 54(2): 130-135].

High Salt Intake Recruits Tonic Activation of NR2D Subunit-Containing Extrasynaptic NMDARs in Vasopressin Neurons.

In addition to producing a classical excitatory postsynaptic current via activation of synaptic NMDA receptors (NMDARs), glutamate in the brain also induces a tonic NMDAR current (INMDA) via activation of extrasynaptic NMDARs (eNMDARs). However, since Mg2+ blocks NMDARs in nondepolarized neurons, the potential contribution of eNMDARs to the overall neuronal excitatory/inhibitory (E/I) balance remains unknown. Here, we demonstrate that chronic (7 d) salt loading (SL) recruited NR2D subunit-containing NMDARs to generate an Mg2+-resistant tonic INMDA in nondepolarized [Vh (holding potential) -70 mV] vasopressin (VP; but not oxytocin) supraoptic nucleus (SON) neurons in male rodents. Conversely, in euhydrated (EU) and 3 d SL mice, Mg2+-resistant tonic INMDA was not observed. Pharmacological and genetic intervention of NR2D subunits blocked the Mg2+-resistant tonic INMDA in VP neurons under SL conditions, while an NR2B antagonist unveiled Mg2+-sensitive tonic INMDA but not Mg2+-resistant tonic INMDA In the EU group VP neurons, an Mg2+-resistant tonic INMDA was not generated by increased ambient glutamate or treatment with coagonists (e.g., d-serine and glycine). Chronic SL significantly increased NR2D expression but not NR2B expression in the SON relative to the EU group or after 3 d under SL conditions. Finally, Mg2+-resistant tonic INMDA selectively upregulated neuronal excitability in VP neurons under SL conditions, independent of ionotropic GABAergic input. Our results indicate that the activation of NR2D-containing NMDARs constitutes a novel mechanism that generates an Mg2+-resistant tonic INMDA in nondepolarized VP neurons, thus causing an E/I balance shift in VP neurons to compensate for the hormonal demands imposed by a chronic osmotic challenge.SIGNIFICANCE STATEMENT The hypothalamic supraoptic nucleus (SON) consists of two different types of magnocellular neurosecretory cells (MNCs) that synthesize and release the following two peptide hormones: vasopressin (VP), which is necessary for regulation of fluid homeostasis; and oxytocin (OT), which plays a major role in lactation and parturition. NMDA receptors (NMDARs) play important roles in shaping neuronal firing patterns and hormone release from the SON MNCs in response to various physiological challenges. Our results show that prolonged (7 d) salt loading generated a Mg2+-resistant tonic NMDA current mediated by NR2D subunit-containing receptors, which efficiently activated nondepolarized VP (but not OT) neurons. Our findings support the hypothesis that NR2D subunit-containing NMDARs play an important adaptive role in adult brain in response to a sustained osmotic challenge.

A 24-week intervention based on nutrition care process improves diet quality, body mass index, and motivation in children and adolescents with obesity.

Higher motivation could support to lead behavioral change for obese children and adolescents. This study aimed to evaluate the effects of a nutrition care process (NCP)-based intervention targeted on diet and weight status in moderate to severe obese children and adolescents in Korea. One hundred four subjects (mean age: 10.95 years, body mass index (BMI) ≥97th percentile of age-sex) participated in the present study. Subjects were divided into a usual care group (UG) and a nutrition group (NG). All participants underwent nutrition education 6 times. The NG received individual access and continuous monitoring and setting goals with respect to nutritional problems. Consumption of high-calorie, low-nutrient (HCLN) food was significantly decreased (P < .05) and the Diet Quality Index-International (DQI-I) score also increased with respect to sodium (P < .001). The total self-efficacy score was increased from 9.15 to 10.14 points (P < .01). After 24 weeks, the BMI-z-score decreased from 2.27 to 2.19 in the NG (P < .05); however, no group difference was found. BMI-z-score was negatively associated with self-efficacy (ß = -0.03, P < .019). NCP-based intervention might be helpful to solve dietary problems by enhancing self-efficacy and lower BMI-z-score in moderately to severely obese children and adolescents.

Pharmacological inhibition of Kv3 on oxidative stress-induced cataract progression.

Oxidative stress is one of the most important risk factors for cataractogenesis. Previous studies have indicated that BDS-II, a Kv3 channel blocker, plays pivotal roles in oxidative stress-related diseases. This study demonstrates that BDS-II exerts a protective effect on cataractogenesis. Specifically, BDS-II was observed to inhibit lens opacity induced by H2O2. BDS-II was also determined to inhibit cataract progression in a sodium selenite-induced in vivo cataract model by inhibiting reduction of the total GSH. In addition, BDS-II was demonstrated to protect human lens epithelial cells against H2O2-induced cell death. Our results suggest that BDS-II is a potential pharmacological candidate in cataract therapy.

Acute Anemia Induces Erythropoiesis in Rat Organ Surface Primo-Vascular Tissue.

The primo-vascular system (PVS) is a newly identified vascular tissue composed of primo-nodes (PNs) and primo-vessels (PVs). Previously, we reported erythropoietic activity in the organ-surface PVS (osPVS) tissue of rats with heart failure. In this study, we further investigated whether acute anemia could induce erythropoiesis in the PVS of rats, based on the hypothesis that erythropoiesis in osPVS tissue is due to anemia accompanying heart failure. Acute anemia was induced by an intraperitoneal injection of phenylhydrazine (PHZ). Circulating red blood cells (RBCs) and hematocrit decreased by 31.6%, whereas reticulocytes and white blood cells increased at day 3 and day 6 after PHZ treatment. All these parameters recovered to control levels at day 10. At days 3 and 6, we observed an increase in the size of the PNs (P < 0.05), the number of the osPVS tissue samples per rat (P < 0.01), and the proportion of osPVS tissue samples with red chromophore (P < 0.001), which was from the RBCs in the PVS tissue. The number of RBCs, estimated from the PN sections stained with hematoxylin and eosin, increased at day 6 in the rats with anemia (P < 0.01). All these anemia-induced changes in the osPVS tissue recovered to the control levels by day 10. Taken together, the results showed that the morphological and cytological changes in the osPVS tissue appear to be related to the erythropoietic activity induced by acute anemia in rats. This study confirmed the previous findings that the osPVS can exert erythropoietic activity in disease states accompanied by anemia, such as heart failure.

Nanostars on Nanopipette Tips: A Raman Probe for Quantifying Oxygen Levels in Hypoxic Single Cells and Tumours.

Multiple sharp-edged gold nanostars were efficiently assembled on nanopipette tips through electrostatic interactions for use as a potent intracellular hypoxia-sensing Raman probe. Colloidal stability and surface immobilization were checked using scanning electron microscopy, light scattering, and zeta potential measurements. Site-specific intracellular hypoxia levels can be estimated in vitro and in vivo using Raman lancets (RL). Distinct Raman spectral changes for the nitro-(NO2 ) functional group of the redox marker 4-nitrothiophenol (4NTP) can be quantified according to the intracellular oxygen (O2 ) content, ranging from 1 % to 10 %. Redox potential changes in mitochondrial respiration were also examined through serial injections of inhibitors. 3D-cultured cells and in vivo tests were used to validate our method, and its application in the assessment of the aggressiveness of cancer cells by differentiating spectral changes between malignant and benign cells was demonstrated.

Exercise training normalizes elevated firing rate of hypothalamic presympathetic neurons in heart failure rats.

Exercise training (ExT) normalizes elevated sympathetic nerve activity in heart failure (HF), but the underlying mechanisms are not well understood. In this study, we examined the effects of 3 wk of ExT on the electrical activity of the hypothalamic presympathetic neurons in the brain slice of HF rats. HF rats were prepared by ligating the left descending coronary artery. The electrophysiological properties of paraventricular nucleus neurons projecting to the rostral ventrolateral medulla (PVN-RVLM) were examined using the slice patch-clamp technique. The neuronal firing rate was elevated in HF rats, and ExT induced a reduction in the firing rate ( P < 0.01). This ExT-induced decrease in the firing rate was associated with an increased frequency of spontaneous and miniature inhibitory postsynaptic current (IPSCs; P < 0.05). There was no significant change in excitatory postsynaptic current. Replacing Ca2+ with Mg2+ in the recording solution reduced the elevated IPSC frequency in HF rats with ExT ( P < 0.01) but not in those without ExT, indicating an increase in the probability of GABA release. In contrast, ExT did not restore the reduced GABAA receptor-mediated tonic inhibitory current in HF rats. A GABAA receptor blocker (bicuculline, 20 µM) increased the firing rate in HF rats with ExT ( P < 0.01) but not in those without ExT. Collectively, these results show that ExT normalized the elevated firing activity by increasing synaptic GABA release in PVN-RVLM neurons in HF rats. Our findings provide a brain mechanism underlying the beneficial effects of ExT in HF, which may shed light on the pathophysiology of other diseases accompanied by sympathetic hyperactivation.