scholarly journals Cholecystokinin Octapeptide Increases Spontaneous Glutamatergic Synaptic Transmission to Neurons of the Nucleus Tractus Solitarius Centralis

2005 ◽  
Vol 94 (4) ◽  
pp. 2763-2771 ◽  
Author(s):  
V. Baptista ◽  
Z. L. Zheng ◽  
F. H. Coleman ◽  
R. C. Rogers ◽  
R. A. Travagli
Keyword(s):  
Receptor Antagonist ◽  
Nucleus Tractus Solitarius ◽  
Dependent Manner ◽  
Excitatory Effect ◽  
Concentration Dependent Manner ◽  
Whole Cell Patch Clamp ◽  
Glutamatergic Synaptic Transmission ◽  
Immunohistochemical Techniques ◽  
20 Nm ◽  
Brain Stem Slices

Cholecystokinin (CCK) is released from enteroendocrine cells after ingestion of nutrients and induces multiple effects along the gastrointestinal tract, including gastric relaxation and short-term satiety. We used whole cell patch-clamp and immunohistochemical techniques in rat brain stem slices to characterize the effects of CCK. In 45% of the neurons of nucleus tractus solitarius subnucleus centralis (cNTS), perfusion with the sulfated form of CCK (CCK-8s) increased the frequency of spontaneous excitatory currents (sEPSCs) in a concentration-dependent manner (1–300 nM). The threshold for the CCK-8s excitatory effect was 1 nM, the EC50 was 20 nM, and Emax was 100 nM. The excitatory effects of CCK-8s were still present when the slices were preincubated with tetrodotoxin or bicuculline or when the recordings were conducted with Cs+ electrodes. Pretreatment with the CCK-A receptor antagonist, lorglumide (1 μM), antagonized the effects of CCK-8s, whereas perfusion with the CCK-B preferring agonist CCK-8 nonsulfated (CCK-ns, 1 μM) did not affect the frequency of sEPSCs. Similarly, pretreatment with the CCK-B receptor antagonist, triglumide (1 μM), did not prevent the actions of CCK-8s. Although the majority (i.e., 76%) of CCK-8s unresponsive cNTS neurons had a bipolar somata shape and were TH-IR negative, no differences were found in either the morphological or the neurochemical phenotype of cNTS neurons responsive to CCK-8s. Our results suggest that the excitatory effects of CCK-8s on terminals impinging on a subpopulation of cNTS neurons are mediated by CCK-A receptors; these responsive neurons, however, do not have morphological or neurochemical characteristics that automatically distinguish them from nonresponsive neurons.

scholarly journals Orexin depolarizes rat hypothalamic paraventricular nucleus neurons

2001 ◽  
Vol 281 (4) ◽  
pp. R1114-R1118 ◽  
Author(s):  
Tetsuro Shirasaka ◽  
Satoshi Miyahara ◽  
Takato Kunitake ◽  
Qing-Hua Jin ◽  
Kazuo Kato ◽  
...  
Keyword(s):  
Paraventricular Nucleus ◽  
Brain Slices ◽  
Hypothalamic Paraventricular Nucleus ◽  
Dependent Manner ◽  
Patch Clamp Recording ◽  
Concentration Dependent Manner ◽  
Whole Cell Patch Clamp ◽  
Orexin Receptors ◽  
Bath Application

Orexins, also called hypocretins, are newly discovered hypothalamic peptides that are thought to be involved in various physiological functions. In spite of the fact that orexin receptors, especially orexin receptor 2, are abundant in the hypothalamic paraventricular nucleus (PVN), the effects of orexins on PVN neurons remain unknown. Using a whole cell patch-clamp recording technique, we investigated the effects of orexin-B on PVN neurons of rat brain slices. Bath application of orexin-B (0.01–1.0 μM) depolarized 80.8% of type 1 ( n = 26) and 79.2% of type 2 neurons tested ( n = 24) in the PVN in a concentration-dependent manner. The effects of orexin-B persisted in the presence of TTX (1 μM), indicating that these depolarizing effects were generated postsynaptically. Addition of Cd2+(1 mM) to artificial cerebrospinal fluid containing TTX (1 μM) significantly reduced the depolarizing effect in type 2 neurons. These results suggest that orexin-B has excitatory effects on the PVN neurons mediated via a depolarization of the membrane potential.

Direct block of cloned hKv1.5 channel by cytochalasins, actin-disrupting agents

2005 ◽  
Vol 289 (2) ◽  
pp. C425-C436 ◽  
Author(s):  
Bok Hee Choi ◽  
Jung-Ah Park ◽  
Kyung-Ryoul Kim ◽  
Ggot-Im Lee ◽  
Yong-Tae Lee ◽  
...  
Keyword(s):  
Actin Filament ◽  
Cytochalasin B ◽  
Delayed Rectifier ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Independent Manner ◽  
Concentration Dependent Manner ◽  
Voltage Range ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent

The action of cytochalasins, actin-disrupting agents on human Kv1.5 channel (hKv1.5) stably expressed in Ltk− cells was investigated using the whole cell patch-clamp technique. Cytochalasin B inhibited hKv1.5 currents rapidly and reversibly at +60 mV in a concentration-dependent manner with an IC50 of 4.2 μM. Cytochalasin A, which has a structure very similar to cytochalasin B, inhibited hKv1.5 (IC50 of 1.4 μM at +60 mV). Pretreatment with other actin filament disruptors cytochalasin D and cytochalasin J, and an actin filament stabilizing agent phalloidin had no effect on the cytochalasin B-induced inhibition of hKv1.5 currents. Cytochalasin B accelerated the decay rate of inactivation for the hKv1.5 currents. Cytochalasin B-induced inhibition of the hKv1.5 channels was voltage dependent with a steep increase over the voltage range of the channel's opening. However, the inhibition exhibited voltage independence over the voltage range in which channels are fully activated. Cytochalasin B produced no significant effect on the steady-state activation or inactivation curves. The rate constants for association and dissociation of cytochalasin B were 3.7 μM/s and 7.5 s−1, respectively. Cytochalasin B produced a use-dependent inhibition of hKv1.5 current that was consistent with the slow recovery from inactivation in the presence of the drug. Cytochalasin B (10 μM) also inhibited an ultrarapid delayed rectifier K+ current ( IK,ur) in human atrial myocytes. These results indicate that cytochalasin B primarily blocks activated hKv1.5 channels and endogenous IK,ur in a cytoskeleton-independent manner as an open-channel blocker.

Mg2+ Inhibition of ATP-Activated Current in Rat Nodose Ganglion Neurons: Evidence That Mg2+ Decreases the Agonist Affinity of the Receptor

1997 ◽  
Vol 77 (6) ◽  
pp. 3391-3395 ◽  
Author(s):  
Chaoying Li ◽  
Robert W. Peoples ◽  
Forrest F. Weight
Keyword(s):  
Nodose Ganglion ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Concentration Dependent Manner ◽  
Agonist Affinity ◽  
Nodose Ganglion Neurons ◽  
Whole Cell Patch Clamp ◽  
Activation Rate ◽  
The Right ◽  
Ganglion Neurons

Li, Chaoying, Robert W. Peoples, and Forrest F. Weight. Mg2+ inhibition of ATP-activated current in rat nodose ganglion neurons: evidence that Mg2+ decreases the agonist affinity of the receptor. J. Neurophysiol. 77: 3391–3395, 1997. The effect of Mg2+ on ATP-activated current in rat nodose ganglion neurons was investigated with the use of the whole cell patch-clamp technique. Mg2+ decreased the amplitude of ATP-activated current in a concentration-dependent manner over the concentration range of 0.25–8 mM, with a 50% inhibitory concentration value of 1.5 mM for current activated by 10 μM ATP. Mg2+ shifted the ATP concentration-response curve to the right in a parallel manner, increasing the 50% effective concentration value for ATP from 9.2 μM in the absence of added Mg2+ to 25 μM in the presence of 1 mM Mg2+. Mg2+ increased the deactivation rate of ATP-activated current without changing its activation rate. The observations are consistent with an action of Mg2+ to inhibit ATP-gated ion channel function by decreasing the affinity of the agonist binding site on these receptors.

scholarly journals Extracellular ATP inhibits transport in medullary thick ascending limbs: role of P2X receptors

2009 ◽  
Vol 297 (5) ◽  
pp. F1168-F1173 ◽  
Author(s):  
Guillermo B. Silva ◽  
Jeffrey L. Garvin
Keyword(s):  
Nitric Oxide ◽  
Oxygen Consumption ◽  
Oxidative Phosphorylation ◽  
Receptor Antagonist ◽  
P2x Receptors ◽  
Extracellular Atp ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Nitric Oxide Synthase Inhibitor

Absorption of NaCl by the thick ascending limb (TAL) involves active transport and therefore depends on oxidative phosphorylation. Extracellular ATP has pleiotropic effects, including both stimulation and inhibition of transport and inhibition of oxidative phosphorylation. However, it is unclear whether ATP alters TAL transport and how this occurs. We hypothesized that ATP inhibits TAL Na absorption by reducing Na entry. We measured oxygen consumption in TAL suspensions. ATP reduced oxygen consumption in a concentration-dependent manner. The purinergic (P2) receptor antagonist suramin (300 μM) blocked the effect of ATP on TAL oxygen consumption (147 ± 15 vs. 146 ± 16 nmol O2·min−1·mg protein−1). In contrast, the adenosine receptor antagonist theophylline did not block the effect of ATP on oxygen consumption. When Na-K-2Cl cotransport and Na/H exchange were blocked with furosemide (100 μM) plus dimethyl amiloride (100 μM), ATP did not inhibit TAL oxygen consumption (from 78 ± 13 to 98 ± 5 nmol O2·min−1·mg protein−1). The Na ionophore nystatin (200 U/ml) increased TAL oxygen consumption to a similar extent in both ATP- and vehicle-treated samples (368 ± 41 vs. 397 ± 47 nmol O2·min−1·mg protein−1). The nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester (3 mM) blocked the ATP effects on TAL oxygen consumption (157 ± 10 vs. 165 ± 15 nmol O2·min−1·mg protein−1). The P2X-selective receptor antagonist NF023 blocked the effect of ATP on oxygen consumption, whereas the P2X-selective agonist β-γ-Me-ATP reduced oxygen consumption in a concentration-dependent manner. We conclude that ATP inhibits Na transport-related oxygen consumption in TALs by reducing Na entry and P2X receptors and nitric oxide mediate this effect.

scholarly journals Anandamide inhibits transport-related oxygen consumption in the loop of Henle by activating CB1 receptors

2013 ◽  
Vol 304 (4) ◽  
pp. F376-F381 ◽  
Author(s):  
Guillermo B. Silva ◽  
Douglas K. Atchison ◽  
Luis I. Juncos ◽  
Néstor H. García
Keyword(s):  
Oxygen Consumption ◽  
Receptor Antagonist ◽  
Cannabinoid Receptors ◽  
Cb1 Receptors ◽  
Dependent Manner ◽  
Cb2 Receptor ◽  
Na Transport ◽  
Concentration Dependent Manner ◽  
Selective Agonist

The energy required for active Na chloride reabsorption in the thick ascending limb (TAL) depends on oxygen consumption and oxidative phosphorylation (OXP). In other cells, Na transport is inhibited by the endogenous cannabinoid anandamide through the activation of the cannabinoid receptors (CB) type 1 and 2. However, it is unclear whether anandamide alters TAL transport and the mechanisms that could be involved. We hypothesized that anandamide inhibits TAL transport via activation of CB1 receptors and NO. For this, we measured oxygen consumption (QO2) in TAL suspensions to monitor the anandamide effects on transport and OXP. Anandamide reduced QO2 in a concentration-dependent manner. During Na-K-2Cl cotransport and Na/H exchange inhibition, anandamide did not inhibit TAL QO2. To test the role of the cannabinoid receptors, we used specific agonists and antagonists of CB1 and CB2 receptors. The CB1-selective agonist WIN55212–2 reduced QO2 in a concentration-dependent manner. Also, the CB1 receptor antagonist rimonabant blocked the effect of anandamide on QO2. In contrast, the CB2-selective agonist JHW-133 had no effect on QO2, while the CB2 receptor antagonist AM-630 failed to block the anandamide effects on QO2. To confirm these results, we measured CB1 and CB2 receptor expression and only CB1 expression was detected. Because CB1 receptors are strong nitric oxide synthase (NOS) stimulators and NO inhibits transport in TALs, we evaluated the role of NO. Anandamide stimulated NO production and the NOS inhibitor NG-nitro-l-arginine methyl ester blocked the anandamide effects on QO2. We conclude that anandamide inhibits TAL Na transport-related QO2 via activation of CB1 receptor and NOS.

scholarly journals Neuropeptide FF and neuropeptide VF inhibit GABAergic neurotransmission in parvocellular neurons of the rat hypothalamic paraventricular nucleus

2007 ◽  
Vol 292 (5) ◽  
pp. R1872-R1880 ◽  
Author(s):  
Jack H. Jhamandas ◽  
Frédéric Simonin ◽  
Jean-Jacques Bourguignon ◽  
Kim H. Harris
Keyword(s):  
Paraventricular Nucleus ◽  
Hypothalamic Paraventricular Nucleus ◽  
Inhibitory Input ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Gabaergic Neurotransmission ◽  
Whole Cell Patch Clamp ◽  
Neuropeptide Ff ◽  
Parvocellular Neurons ◽  
The Brain

Neuropeptide FF (NPFF) and neuropeptide VF (NPVF) are octapeptides belonging to the RFamide family of peptides that have been implicated in a wide variety of physiological functions in the brain, including central autonomic and neuroendocrine regulation. The effects of these peptides are mediated via NPFF1 and NPFF2 receptors that are abundantly expressed in the rat brain, including the hypothalamic paraventricular nucleus (PVN), an autonomic nucleus critical for the secretion of neurohormones and the regulation of sympathetic outflow. In this study, we examined, using whole cell patch-clamp recordings in the brain slice, the effects of NPFF and NPVF on inhibitory GABAergic synaptic input to parvocellular PVN neurons. Under voltage-clamp conditions, NPFF and NPVF reversibly and in a concentration-dependent manner reduced the evoked bicuculline-sensitive inhibitory postsynaptic currents (IPSCs) in parvocellular PVN neurons by 25 and 31%, respectively. RF9, a potent and selective NPFF receptor antagonist, blocked NPFF-induced reduction of IPSCs. Recordings of miniature IPSCs in these neurons following NPFF and NPVF applications showed a reduction in frequency but not amplitude, indicating a presynaptic locus of action for these peptides. Under current-clamp conditions, NPVF and NPFF caused depolarization (6–9 mV) of neurons that persisted in the presence of TTX but was abolished in the presence of bicuculline. Collectively, these data provide evidence for a disinhibitory role of NPFF and NPVF in the hypothalamic PVN via an attenuation of GABAergic inhibitory input to parvocellular neurons of this nucleus and explain the central autonomic effects of NPFF.

scholarly journals Toxicity and disruption of quorum sensing in Aliivibrio fisheri by environmental chemicals: Impacts of selected contaminants and microplastics

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
François Gagné
Keyword(s):  
Quorum Sensing ◽  
Fourier Transformation ◽  
Effective Concentration ◽  
Environmental Chemicals ◽  
Dependent Manner ◽  
Luminescent Bacterium ◽  
Concentration Dependent Manner ◽  
20 Nm ◽  
Toxic Concentrations ◽  
First Time

The purpose of this study was to examine the effects of dissolved and particulate compounds on quorum sensing in the marine luminescent bacterium Aliivibrio fisheri. Bacteria were exposed to increasing concentrations of CuSO4 (Cu2+), gadolinium chloride (Gd3+), 20-nm silver nanoparticles (nanoAg) and 1-3 μm microplastic polyethylene beads for 250 min. During this period, luminescence measurements were taken at 5-min intervals. Toxicity was first examined by measuring luminescence output at 5-min and 30-min incubation time. Based on the effective concentration that decreases luminescence by 20% (EC20), the compounds were toxic at the following concentrations in decreasing toxicity: Cu2+ (3.2 mg/L) < nanoAg (3.4 mg/L, reported) < Gd3+ (34 mg/L) < microplastics (2.6 g/L). The data revealed that luminescence changed non-linearly over time. In control bacteria, luminescence changed at eight specific major frequencies between 0.04 and 0.27 cycle/min after Fourier transformation of time-dependent luminescence data. The addition of dissolved Cu2+ and Gd3+ eliminated the amplitude changes at these frequencies in a concentration-dependent manner, indicating loss of quorum sensing between bacteria at concentrations below EC20. In the presence of nanoAg and microplastic beads, the decreases in amplitudes were modest but compressed the luminescence profiles, with shorter frequencies appearing at concentrations well below EC20. Thus, loss of communication between bacteria occurs at non-toxic concentrations. In addition, with exposure to a mixture of the above compounds at concentrations that do not produce effects for Gd3+, nanoAg and microplastics, Cu2+ toxicity was significantly enhanced, suggesting synergy. This study revealed for the first time that small microplastic particles and nanoparticles can disrupt quorum sensing in marine bacteria.

scholarly journals cGMP-Dependent and -Independent Inhibition of a K+ Conductance by Natriuretic Peptides

1999 ◽  
Vol 10 (3) ◽  
pp. 472-480
Author(s):  
JOCHEN R. HIRSCH ◽  
MARKUS MEYER ◽  
HANS-JURGEN MÄGERT ◽  
WOLF-GEORG FORSSMANN ◽  
STEEN MOLLERUP ◽  
...  
Keyword(s):  
Natriuretic Peptide ◽  
Natriuretic Peptides ◽  
Tyrosine Kinases ◽  
Human Kidney ◽  
Transport Processes ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Concentration Dependent Manner ◽  
Intracellular Cgmp ◽  
Whole Cell Patch Clamp

Abstract. In immortalized human kidney epithelial (IHKE-1) cells derived from proximal tubules, two natriuretic peptide receptors (NPR) were identified. In addition to NPR-A, which is bound by atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and urodilatin (URO), a novel form of NPR-B that might be bound by C-type natriuretic peptide (CNP) was identified using PCR. This novel splice variant of NPR-B (NPR-Bi) was also found in human kidney. Whereas ANP, BNP, and URO increased intracellular cGMP levels in IHKE-1 cells in a concentration-dependent manner, CNP had no effect on cGMP levels. To determine the physiologic responses to these agonists in IHKE-1 cells, the membrane voltage (Vm) was monitored using the slow whole-cell patch-clamp technique. ANP (10 nM), BNP (10 nM), and URO (16 nM) depolarized these cells by 3 to 4 mV (n = 47, 7, and 16, respectively), an effect that could be mimicked by 0.1 mM 8-Br-cGMP (n = 15). The effects of ANP and 8-Br-cGMP were not additive (n = 4). CNP (10 nM) also depolarized these cells, by 3 ± 1 mV (n = 28), despite the absence of an increase in cellular cGMP levels, indicating a cGMP-independent mechanism. In the presence of CNP, 8-Br-cGMP further depolarized Vm significantly, by 1.6 ± 0.3 mV (n = 5). The depolarizations by ANP were completely abolished in the presence of Ba2+ (1 mM, n = 4) and thus can be related to inhibition of a K+ conductance in the luminal membrane of IHKE-1 cells. The depolarizations attributable to CNP were completely blocked when genistein (10 μM, n = 6), an inhibitor of tyrosine kinases, was present. These findings indicate that natriuretic peptides regulate electrogenic transport processes via cGMP-dependent and -independent pathways that influence the Vm of IHKE-1 cells.

scholarly journals Neuroepithelial bodies in mammalian lung express functional serotonin type 3 receptor

2001 ◽  
Vol 281 (4) ◽  
pp. L931-L940 ◽  
Author(s):  
X. W. Fu ◽  
D. Wang ◽  
J. Pan ◽  
S. M. Farragher ◽  
V. Wong ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Dependent Manner ◽  
Induced Current ◽  
Patch Clamp Technique ◽  
Concentration Dependent Manner ◽  
Whole Cell Patch Clamp ◽  
Cell Plasma ◽  
Neuroepithelial Body ◽  
Inward Currents ◽  
Type 3

Serotonin (5-HT) type 3 receptor (5-HT3-R) is a ligand-gated ion channel found primarily in the central and peripheral nervous system. We report expression and functional characterization of 5-HT3-R in pulmonary neuroepithelial body (NEB) cells. Using nonisotopic in situ hybridization, we demonstrate expression of 5-HT3-R mRNA in NEB cells in the lungs of different mammals (hamster, rabbit, mouse, and human). Dual immunocytochemistry (for 5-HT and 5-HT3-R) and confocal microscopy localized 5-HT3-R on NEB cell plasma membrane from rabbit. The electrophysiological characteristics of 5-HT3-R in NEB cells were studied in fresh slices of neonatal hamster lung using the whole cell patch-clamp technique. Application of the 5-HT (5–150 μM) and 5-HT3-R agonist 2-methyl-5-HT (5–150 μM) induced inward currents in a concentration-dependent manner. The 5-HT-induced current was blocked (76.5 ± 5.9%) by the specific 5-HT3-R antagonist ICS-205–930 (50 μM), whereas katanserin and p-4-iodo- N-{2-[4-(methoxyphenyl)-1-piperazinyl]ethyl}- N-2-pyridinylbenzamide had minimal effects. Forskolin had no effect on desensitization and amplitude of the 5-HT-induced current. The reduction of Ca2+ and Mg2+ in the extracellular solution enhanced the amplitude of the 5-HT-induced current because of slower desensitization. Our studies suggest that 5-HT3-R in NEB cells may function as an autoreceptor and may potentially be involved in modulation of hypoxia signaling.

Stimulatory effect of bradykinin on insulin release from the perfused rat pancreas

1995 ◽  
Vol 268 (5) ◽  
pp. E1027-E1030
Author(s):  
C. Yang ◽  
W. H. Hsu
Keyword(s):  
Receptor Antagonist ◽  
Insulin Release ◽  
Glucose Concentration ◽  
Physiological Role ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Perfused Rat Pancreas ◽  
Pancreas Perfusion ◽  
Rat Pancreas ◽  
Hoe 140

Rat pancreas perfusion was performed to study the effect of bradykinin on insulin release. At the perfusate glucose concentration of 6 mM, bradykinin (0.01-1 microM) increased insulin release in a concentration-dependent manner. In addition, bradykinin (1 microM) increased the glucose (10 mM)-induced insulin release. HOE-140 (0.1 microM), a bradykinin B2-receptor antagonist, decreased the baseline insulin release and abolished the bradykinin (1 microM)-induced increase in insulin release. In addition, HOE-140 (0.1 microM) attenuated the glucose (10 mM)-induced increase in insulin release. Because the blockade of bradykinin receptors by HOE-140 attenuated the glucose-induced increased insulin release, our present findings suggest that bradykinin may play a physiological role in the regulation of insulin release.

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