PURPOSE: The mechanisms underlying repolarization abnormalities during pregnancy are not fully understood. Although maternal serotonin (5-hydroxytryptamine, 5-HT) production is an important determinant for normal fetal development in mice, its role in mothers remains unclear. We evaluated the role of serotonin in ventricular repolarization in mice hearts via 5Htr3 receptor (Htr3a) and investigated the mechanism of QT-prolongation during pregnancy. MATERIALS AND METHODS: We measured current amplitudes and the expression levels of voltage-gated K⁺ (Kv) channels in freshly-isolated left ventricular myocytes from wild-type non-pregnant (WT-NP), late-pregnant (WT-LP), and non-pregnant Htr3a homozygous knockout mice (Htr3a(−/−)-NP). RESULTS: During pregnancy, serotonin and tryptophan hydroxylase 1, a rate-limiting enzyme for the synthesis of serotonin, were markedly increased in hearts and serum. Serotonin increased Kv current densities concomitant with the shortening of the QT interval in WT-NP mice, but not in WT-LP and Htr3a(−/−)-NP mice. Ondansetron, an Htr3 antagonist, decreased Kv currents in WT-LP mice, but not in WT-NP mice. Kv4.3 directly interacted with Htr3a, and this binding was facilitated by serotonin. Serotonin increased the trafficking of Kv4.3 channels to the cellular membrane in WT-NP. CONCLUSION: Serotonin increases repolarizing currents by augmenting Kv currents. Elevated serotonin levels during pregnancy counterbalance pregnancy-related QT prolongation by facilitating Htr3-mediated Kv currents.
*Action Potentials/drug effects ; Animals ; Cell Membrane/drug effects/metabolism ; Disease Models, Animal ; Electrocardiography ; Female ; HSC70 Heat-Shock Proteins/metabolism ; HSP90 Heat-Shock Proteins/metabolism ; Heart Ventricles/drug effects/*metabolism ; Mice, Inbred C57BL ; Mice, Knockout ; Myocytes, Cardiac/drug effects/metabolism ; Potassium Channels/metabolism ; Pregnancy ; Rabbits ; Rats, Sprague-Dawley ; Receptors, Serotonin, 5-HT3/metabolism ; Serotonin/*metabolism ; Serotonin 5-HT3 Receptor Agonists/pharmacology

Cyproheptadine (CPH), a first-generation antihistamine, enhances the delayed rectifier outward K current (I) in mouse cortical neurons through a sigma-1 receptor-mediated protein kinase A pathway. In this study, we aimed to determine the effects of CPH on neuronal excitability in current-clamped pyramidal neurons in mouse medial prefrontal cortex slices. CPH (10 µmol/L) significantly reduced the current density required to generate action potentials (APs) and increased the instantaneous frequency evoked by a depolarizing current. CPH also depolarized the resting membrane potential (RMP), decreased the delay time to elicit an AP, and reduced the spike threshold potential. This effect of CPH was mimicked by a sigma-1 receptor agonist and eliminated by an antagonist. Application of tetraethylammonium (TEA) to block I channels hyperpolarized the RMP and reduced the instantaneous frequency of APs. TEA eliminated the effects of CPH on AP frequency and delay time, but had no effect on spike threshold or RMP. The current-voltage relationship showed that CPH increased the membrane depolarization in response to positive current pulses and hyperpolarization in response to negative current pulses, suggesting that other types of membrane ion channels might also be affected by CPH. These results suggest that CPH increases the excitability of medial prefrontal cortex neurons by regulating TEA-sensitive I channels as well as other TEA-insensitive K channels, probably I and inward-rectifier Kir channels. This effect of CPH may explain its apparent clinical efficacy as an antidepressant and antipsychotic.
Animals ; Cyproheptadine ; pharmacology ; Female ; Histamine H1 Antagonists ; pharmacology ; Membrane Potentials ; drug effects ; physiology ; Mice, Inbred C57BL ; Patch-Clamp Techniques ; Potassium Channel Blockers ; pharmacology ; Potassium Channels ; metabolism ; Prefrontal Cortex ; drug effects ; physiology ; Pyramidal Cells ; drug effects ; physiology ; Receptors, sigma ; agonists ; metabolism ; Tetraethylammonium ; pharmacology ; Tissue Culture Techniques

OBJECTIVETo explore the effects of iptkalim on myocardial enzymes and free radicals metabolism with hypoxic pulmonary hypertension (HPH), in order to provide evidence for the mechanism of iptkalim on clinical treat.

METHODS110 young men stayed at high altitude above 5 000 m were divided into iptkalim group (n = 74) and placebo group (n = 36), aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyltransferase (gamma-GT), creatine kinase (CK), lactate dehydrogenase (LDH), superoxide dismutase (SOD), malonaldehyde (MDA), nitric oxide(NO) and nitric oxide synthase(NOS) were detected before and after took medicines for 6 mouths.

RESULTSAfter took medication for 6 mouths, ALT, AST, gamma-GT, CK and LDH were reduced, SOD, NO, and NOS were increased, MDA were reduced, there were very significant difference (P < 0.05).

CONCLUSIONOxygen free radicals have taken part in the process of HPH, iptkalim have the effect of anti-peroxidation of lipid and protect myocardial cells stress injured by hypoxia which related with mitochondrial membrane and cell membrane's K(ATP) channel activation.

Adolescent ; Adult ; Altitude ; Creatine Kinase ; blood ; Free Radicals ; metabolism ; Humans ; Hypertension, Pulmonary ; blood ; etiology ; metabolism ; Hypoxia ; complications ; L-Lactate Dehydrogenase ; blood ; Male ; Myocardium ; enzymology ; Potassium Channels ; agonists ; Propylamines ; pharmacology ; Young Adult

Cinnamyl alcohol (CAL) is known as an antipyretic, and a recent study showed its vasodilatory activity without explaining the mechanism. Here we demonstrate the vasodilatory effect and the mechanism of action of CAL in rat thoracic aorta. The change of tension in aortic strips treated with CAL was measured in an organ bath system. In addition, vascular strips or human umbilical vein endothelial cells (HUVECs) were used for biochemical experiments such as Western blot and nitrite and cyclic guanosine monophosphate (cGMP) measurements. CAL attenuated the vasoconstriction of phenylephrine (PE, 1 microM)-precontracted aortic strips in an endothelium-dependent manner. CAL-induced vasorelaxation was inhibited by pretreatment with NG-nitro-L-arginine methyl ester (L-NAME; 10(-4) M), methylene blue (MB; 10(-5) M) and 1 H-[1,2,4]-oxadiazolole-[4,3-a] quinoxalin-10one, (ODQ; 10(-6) or 10(-7) M) in the endothelium-intact aortic strips. Atrial natriuretic peptide (ANP; 10(-8) or 10(-9) M) did not affect the vasodilatory effect of CAL. The phosphorylation of endothelial nitric oxide synthase (eNOS) and generation of nitric oxide (NO) were stimulated by CAL treatment in HUVECs and inhibited by treatment with L-NAME. In addition, cGMP and PKG1 activation in aortic strips treated with CAL were also significantly inhibited by L-NAME. Furthermore, CAL relaxed Rho-kinase activator calpeptin-precontracted aortic strips, and the vasodilatory effect of CAL was inhibited by the ATP-sensitive K+ channel inhibitor glibenclamide (Gli; 10(-5) M) and the voltage-dependent K+ channel inhibitor 4-aminopyridine (4-AP; 2 x 10(-4) M). These results suggest that CAL induces vasorelaxation by activating K+ channels via the NO-cGMP-PKG pathway and the inhibition of Rho-kinase.
Animals ; Aorta/drug effects/metabolism/physiology ; Atrial Natriuretic Factor/pharmacology ; Cyclic GMP/*metabolism ; Cyclic GMP-Dependent Protein Kinases/*metabolism ; Dipeptides/pharmacology ; Human Umbilical Vein Endothelial Cells/drug effects/metabolism ; Humans ; Male ; Methylene Blue/pharmacology ; NG-Nitroarginine Methyl Ester/pharmacology ; Nitric Oxide/*metabolism ; Nitric Oxide Synthase/metabolism ; Oxadiazoles/pharmacology ; Phenylephrine/pharmacology ; Phosphorylation ; Potassium Channel Blockers/pharmacology ; Potassium Channels/*agonists ; Propanols/*pharmacology ; Quinoxalines/pharmacology ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; Vasoconstriction/*drug effects ; Vasodilation/drug effects ; rho-Associated Kinases/antagonists & inhibitors/*metabolism

The aim of the present study was to study the effect of β-estradiol (β-E(2)) on the large-conductance Ca(2+)-activated potassium (BK(Ca)) channel in mesenteric artery smooth muscle cells (SMCs). The mesenteric arteries were obtained from post-menopause female patients with abdominal surgery, and the SMCs were isolated from the arteries using an enzymatic disassociation. According to the sources, the SMCs were divided into non-hypertension (NH) and essential hypertension (EH) groups. Single channel patch clamp technique was used to investigate the effect of β-E(2) and ICI 182780 (a specific blocker of estrogen receptor) on BK(Ca) in the SMCs. The results showed the opening of BK(Ca) in the SMCs was voltage and calcium dependent, and could be blocked by IbTX. β-E(2) (100 μmol/L) significantly increased open probability (Po) of BK(Ca) in both NH and EH groups. After β-E(2) treatment, NH group showed higher Po of BK(Ca) compared with EH group. ICI 182780 could inhibit the activating effect of β-E(2) on BK(Ca) in no matter NH or EH groups. These results suggest β-E(2) activates BK(Ca) in mesenteric artery SMCs from post-menopause women via estrogen receptor, but hypertension may decline the activating effect of β-E(2) on BK(Ca).
Aged ; Estradiol ; analogs & derivatives ; pharmacology ; Female ; Humans ; Hypertension ; physiopathology ; Large-Conductance Calcium-Activated Potassium Channels ; agonists ; metabolism ; physiology ; Mesenteric Arteries ; metabolism ; physiology ; Middle Aged ; Muscle, Smooth, Vascular ; cytology ; metabolism ; physiology ; Patch-Clamp Techniques ; Postmenopause ; physiology ; Receptors, Estrogen ; antagonists & inhibitors

Trigeminal neuralgia is a paroxysmal disorder with severely disabling facial pain and thus continues to be a real therapeutic challenge. At present there are few effective drugs for treatment of this pain. The present study was aimed to explore the involvement of BK(Ca) channels and Kv channels in the mechanical allodynia in a rat model of trigeminal neuropathic pain. Here the effectiveness of drug target injection at the trigeminal ganglion through the infraorbital foramen was first evaluated by immunofluorescence and animal behavior test. Trigeminal neuropathic pain model was established by chronic constriction injury of the infraorbital nerve (ION-CCI) in rats. BK(Ca) channel agonist and Kv channel antagonist were administered into the trigeminal ganglion in ION-CCI rats and sham rats by the above target injection method, and the facial mechanical pain threshold was measured. The results showed that the drug could accurately reach the trigeminal ganglion by target injection which was more effective than that by the normal injection around infraorbital foramen. Rats suffered significant mechanical allodynia in the whisker pad of the operated side from 6 d to 42 d after ION-CCI. BK(Ca) channel agonist NS1619 significantly and dose-dependently attenuated the facial mechanical allodynia and increased the facial mechanical pain threshold in ION-CCI rats 15 d after operation. Kv antagonist 4-AP was able to reduce the threshold in ION-CCI rats when facial mechanical threshold was partly recovered and relatively stable on the 35th day after operation. These results suggest that BK(Ca) channel agonist NS1619 and Kv channel antagonist 4-AP can significantly affect the rats' facial mechanical pain threshold after ION-CCI. Activation of BK(Ca) channels may be related to the depression of the primary afferent neurons in trigeminal neuropathic pain pathways. Activation of Kv channels may exert a tonic inhibition on the trigeminal neuropathic pain.
4-Aminopyridine ; administration & dosage ; Animals ; Benzimidazoles ; administration & dosage ; Constriction ; Facial Pain ; physiopathology ; Injections, Intralesional ; Kv1.4 Potassium Channel ; antagonists & inhibitors ; Large-Conductance Calcium-Activated Potassium Channels ; agonists ; Male ; Orbit ; innervation ; Pain Threshold ; physiology ; Rats ; Rats, Sprague-Dawley ; Trigeminal Ganglion ; drug effects ; Trigeminal Neuralgia ; drug therapy ; physiopathology

OBJECTIVETo investigate the mechanism of ATP-sensitive potassium channel (K(ATP)) activator cromakalim (CRK) on action potentials and transient inward current (I(ti)) in isolated guinea pig papillary and ventricular myocytes and to explore the mechanisms of effects of I(ti) and K(ATP) treatment in idiopathic ventricular tachycardia.

METHODSThe whole-cell patch clamp recording technique was used to detect the action potentials and I(ti) and K(ATP) current alterations during the stimulated and triggered activity. Myocytes were isolated from guinea pig ventricle by enzyme digestion. The experiment was divided into four groups: (1) Control; (2) Control + Ouabain; (3) Control + CRK; (4) Control + Ouabain + CRK. (5) Control + Ouabain + CRK + glibenclamide (GLB). The action potential of guinea pig papillary muscles was measured by using standard microelectrode. The parameters in the experiment included the amplitude (APA), resting potentials (RP), action potentials duration (APD), as well as maximum rise of the action potential (Vmax).

RESULTS(1) When the guinea pig ventricular papillary myocytes were pretreated with Ouabain 0.5 micromol/L, APD prolonged significantly, especially APD(20), APD(50), APD(90). Delayed after depolorazion (DAD) and triggered activity were elicited. I(ti) currents and DAD as well as triggered activity increased. I(ti) current was (126.9 +/- 10.8) pA, lagT (1173.0 +/- 70.9) ms (n = 10, P < 0.01). (2) When guinea pig ventricular myocytes were pretreated with CRK (10 micromol/L), APD was shortened and the amplitude of DAD was lowered. The coupling time in CRK group was significantly prolonged compared with Ouabain group (n = 10, P < 0.01). (3) CRK 50 micromol/L pretreatment of the ventricular myocytes led to an increase of K(ATP) up to (342 +/- 89) pA, which was statistically significant as compared with the control group (P < 0.01). ATP-sensitive potassium channel blocker glibenclamide (10 micromol/L) could antagonize the effects of CRK on APD and I(ti) currents.

CONCLUSIONCRK might reduce the toxic effect of Ouabain on cardiomyocytes, shorten APD, terminate DAD and trigger excitation, and have protective effect on cardiomyocytes. The effects of CRK, may be associated with the inhibiting I(ti) current and increasing K(ATP).

Action Potentials ; drug effects ; Animals ; Cromakalim ; pharmacology ; Guinea Pigs ; Heart Ventricles ; drug effects ; Myocytes, Cardiac ; drug effects ; physiology ; Patch-Clamp Techniques ; Potassium Channels, Inwardly Rectifying ; agonists

In the present study, whole-cell patch-clamp technique was used to observe the effects of SNC162, a selective agonist of δ-opioid receptors, on L-type Ca(2+) current (I(Ca-L)) and transient outward K(+) current (I(to)) in rat ventricular myocytes. The results showed that SNC162 significantly inhibited I(Ca-L) and I(to) in rat ventricular myocytes. The maximal inhibition rate of I(Ca-L) and I(to) reached (46.13±4.12)% and (36.53±10.57)%, respectively. SNC162 at 1×10(-4) mol/L inhibited the current density of I(Ca-L) from (8.98±0.40) pA/pF to (4.84±0.44) pA/pF (P<0.01, n=5) and inhibited that of I(to) from (18.69±2.42) pA/pF to (11.73±1.67) pA/pF (P<0.01, n=5). Furthermore, the effects of naltrindole, a highly selective antagonist of δ-opioid receptors, on I(Ca-L) and I(to) were also observed. The results showed that naltrindole alone had no effects on I(Ca-L) and I(to), while it abolished the inhibitory effects of SNC162 on I(Ca-L) and I(to). In conclusion, SNC162 concentration-dependently inhibited I(Ca-L) and I(to) in rat ventricular myocytes via activation of the δ-opioid receptors, which may be a fundamental mechanism underlying the antiarrhythmic effect of activating δ-opioid receptors.
Animals ; Anti-Arrhythmia Agents ; Benzamides ; pharmacology ; Calcium Channels, L-Type ; metabolism ; Cells, Cultured ; Heart Ventricles ; cytology ; Myocytes, Cardiac ; drug effects ; metabolism ; Naltrexone ; analogs & derivatives ; pharmacology ; Patch-Clamp Techniques ; Piperazines ; pharmacology ; Potassium Channels ; metabolism ; Rats ; Receptors, Opioid, delta ; agonists

The effects of ginkgolide B on the carotid sinus baroreflex (CSB) were studied in the perfused isolated carotid sinus of 30 anesthetized Sprague-Dawley male rats. The results were as follows. (1) By perfusing with ginkgolide B (0.1, 1, 10 μmol/L), the functional curve of the baroreflex was shifted to the right and upward. There was a marked decrease in peak slope (PS) and reflex decrease (RD) in mean arterial pressure (P<0.01), while the threshold pressure (TP), equilibrium pressure (EP) and saturation pressure (SP) were significantly increased (P<0.05, P<0.01). Among the functional parameters of CSB, the changes in PS, RD, TP, EP and SP were dose-dependent. (2) Pretreatment with Bay K8644 (500 nmol/L), an agonist of L-type calcium channel, completely eliminated the effects of ginkgolide B (1 μmol/L) on the CSB. (3) Pretreatment with tetraethylammonium (TEA, 1 mmol/L), an inhibitor of potassium channel, completely abolished the above effects of ginkgolide B (1 μmol/L) on the CSB. These results suggest that ginkgolide B inhibits the CSB in anesthetized rats, which is mediated by decreased calcium influx and increased potassium efflux in baroreceptor nerve endings.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; pharmacology ; Animals ; Baroreflex ; drug effects ; Calcium Channel Agonists ; pharmacology ; Calcium Channels, L-Type ; Carotid Sinus ; physiopathology ; Ginkgolides ; pharmacology ; Lactones ; pharmacology ; Male ; Potassium Channel Blockers ; pharmacology ; Pressoreceptors ; metabolism ; Rats ; Rats, Sprague-Dawley ; Tetraethylammonium ; pharmacology

This study was designed to characterize ureteral smooth muscle motility and also to study the effect of forskolin (FSK) and isoproterenol (ISO) on smooth muscle contractility in murine ureter. High K+ (50 mM) produced tonic contraction by 0.17+/-0.06 mN (n=19). Neuropeptide and neurotransmitters such as serotonin (5microM), histamine (20microM), and carbarchol (CCh, 10~50microM) did not produce significant contraction. However, CCh (50microM) produced slow phasic contraction in the presence of 25 mM K+. Cyclopiazonic acid (CPA, 10microM), SR Ca2+-ATPase blocker, produced tonic contraction (0.07 mN). Meanwhile, inhibition of mitochondria by protonophore carbnylcyanide m-chlorophenylhydrazone (CCCP) also produced weak tonic contraction (0.01 mN). The possible involvement of K+ channels was also pursued. Tetraethyl ammonium chloride (TEA, 10 mM), glibenclamide (10microM) and quinidine (20 microM) which are known to block Ca2+-activated K+ channels (KCa channel), ATP-sensitive K+ channels (KATP) and nonselective K+ channel, respectively, did not elicit any significant effect. However, Ba2+ (1~2 mM), blocker of inward rectifier K+ channels (KIR channel), produced phasic contraction in a reversible manner, which was blocked by 1microM nicardipine, a blocker of dehydropyridine-sensitive voltage-dependent L-type Ca2+ channels (VDCCL) in smooth muscle membrane. This Ba2+-induced phasic contraction was significantly enhanced by 10microM cyclopiazonic acid (CPA) in the frequency and amplitude. Finally, regulation of Ba2+-induced contraction was studied by FSK and ISO which are known as adenylyl cyclase activator and beta-adrenergic receptor agonist, respectively. These drugs significantly suppressed the frequency and amplitude of Ba2+-induced contraction (p<0.05). These results suggest that Ba2+ produces phasic contraction in murine ureteral smooth muscle which can be regulated by FSK and beta-adrenergic stimulation.
Adenylyl Cyclases ; Adrenergic beta-Agonists ; Ammonium Chloride ; Colforsin ; Glyburide ; Histamine ; Isoproterenol ; Membranes ; Mitochondria ; Muscle, Smooth* ; Neuropeptides ; Neurotransmitter Agents ; Nicardipine ; Potassium Channels, Calcium-Activated ; Potassium Channels, Inwardly Rectifying ; Quinidine ; Serotonin ; Ureter*