Methods: Whole cell and single channel patch clamp techniques were used to investigate the effects of isoflurane and the PTK inhibitor genistein on the cardiac sarcolemmal KATP channel in acutely dissociated guinea pig ventricular myocytes.
Results: At 0.5 mm internal ATP, genistein (50 [mu]m) elicited whole cell KATP current (22.5 +/- 7.9 pA/pF). Genistein effects were concentration-dependent, with an EC50 of 32.3 +/- 1.4 [mu]m. Another PTK inhibitor, tyrphostin B42, had a similar effect. The inactive analog of genistein, daidzein (50 [mu]m), did not elicit KATP current. Isoflurane (0.5 mm) increased genistein (35 [mu]m)- activated whole cell KATP current from 14.5 +/- 3.1 to 32.5 +/- 6.6 pA/pF. Stimulation of receptor PTKs with epidermal growth factor, nerve growth factor, or insulin attenuated genistein and isoflurane effects, and the protein tyrosine phosphatase inhibitor orthovanadate (1 mm) prevented their actions on KATP current. In excised inside-out membrane patches, and at fixed 0.2 mm internal ATP, genistein (50 [mu]m) increased channel open probability from 0.053 +/- 0.016 to 0.183 +/- 0.039, but isoflurane failed to further increase open probability (0.162 +/- 0.051) of genistein-activated channels. However, applied in the presence of genistein and protein tyrosine phosphatase 1B (1 [mu]g/ml), isoflurane significantly increased open probability to 0.473 +/- 0.114. 相似文献
Methods: The effects of isoflurane on sarcolemmal KATP channels were investigated at pHi 7.4 and pHi 6.8 in excised inside-out membrane patches from ventricular myocytes of guinea pig hearts.
Results: At pHi 7.4, intracellular ATP (1-1,000 [mu]m) inhibited KATP channels and decreased channel open probability (Po) in a concentration-dependent manner with an IC50 of 8 +/- 1.5 [mu]m, and isoflurane (0.5 mm) either had no effect or decreased channel activity. Lowering pHi from 7.4 to 6.8 enhanced channel opening by increasing Po and reduced channel sensitivity to ATP, with IC50 shifting from 8 +/- 1.2 to 45 +/- 5.6 [mu]m. When applied to the channels activated at pHi 6.8, isoflurane (0.5 mm) increased Po and further reduced ATP sensitivity, shifting IC50 to 110 +/- 10.0 [mu]m. 相似文献
Methods: Live cell microscopy was used to visualize and measure autofluorescence of flavoproteins, a direct reporter of mitoKATP channel activity, in response to the direct and highly selective mitoKATP channel opener diazoxide, or to diazoxide following exposure to various anesthetics commonly used in experimental and clinical medicine. A cellular model of ischemia with subsequent hypoosmolar trypan blue staining served to substantiate the effects of the anesthetics on mitoKATP channels with respect to myocyte viability.
Results: Diazoxide-induced mitoKATP channel opening was significantly inhibited by the anesthetics R-ketamine, and the barbiturates thiopental and pentobarbital. Conversely, urethane, 2,2,2-trichloroethanol (main metabolite of [alpha]-chloralose and chloral hydrate), and the opioid fentanyl potentiated the channel-opening effect of diazoxide, which was abrogated by coadministration of chelerythrine, a specific protein kinase C inhibitor. S-ketamine, propofol, xylazine, midazolam, and etomidate did not affect mitoKATP channel activity. The significance of these modulatory effects of the anesthetics on mitoKATP channel activity was substantiated in a cellular model of simulated ischemia, where diazoxide-induced cell protection was mitigated by R-ketamine and the barbiturates, while urethane, 2,2,2-trichloroethanol, and fentanyl potentiated myocyte protection. 相似文献
Methods: Experiments were conducted in dogs 8 weeks after long-term implantation of a left anterior descending coronary artery (LAD) ameroid constrictor to stimulate coronary collateral growth. Dogs were instrumented for measurement of retrograde LAD blood flow (an index of large coronary collateral blood flow) and LAD tissue flow (via radioactive microspheres; an index of small collateral blood flow). Coronary collateral perfusion and normal (left circumflex coronary artery [LCCA]) zone tissue blood flow were determined in four groups of dogs pretreated with intracoronary glyburide (50 [micro sign]g/kg) or vehicle in the presence or absence of sevoflurane (1 minimum alveolar concentration). Dose-response relationships to the KATP channel agonist nicorandil were established in each dog using doses (25, 50, and 100 [micro sign]g/min) previously shown to increase coronary collateral blood flow.
Results: Sevoflurane increased blood flow through large and small collaterals and increased collateral vascular conductance in the presence of glyburide but did not affect LCCA blood flow or conductance. In contrast, nicorandil increased blood flow through small but not large collaterals. Nicorandil also increased LCCA blood flow and conductance, actions that were attenuated by glyburide. 相似文献
Methods: A cellular model of ischemia with subsequent hypoosmolar trypan blue staining served to determine the effects of 5-hydroxydecanoate, a selective mitoKATP channel blocker, HMR-1098, a selective sarcKATP channel blocker, diazoxide, a preconditioning mimicking agent, and various modulators of putative signaling pathways on cardioprotection elicited by sevoflurane and isoflurane. Microscopy was used to visualize and measure autofluorescence of flavoproteins, a direct index of mitoKATP channel activity.
Results: Volatile anesthetics significantly enhanced diazoxide-mediated activation of mitoKATP channels as assessed by autofluorescence of myocytes. Conversely, volatile anesthetics alone did not alter mitoKATP channel activity, implying a priming effect of volatile anesthetics on mitoKATP channels. Administration of the protein kinase C inhibitor chelerythrine completely blocked this effect. Also, pretreatment with volatile anesthetics potentiated diazoxide-mediated protection against ischemia, as indicated by a reduction in trypan blue-positive myocytes. Importantly, cardioprotection afforded by volatile anesthetics was unaffected by the sarcKATP channel blocker HMR-1098 but sensitive to modulations of nitric oxide and adenosine-Gi signaling pathways. 相似文献
Methods: Barbiturate-anesthetized rats (n = 131) were instrumented for measurement of hemodynamics and subjected to a 30 min coronary artery occlusion followed by 2 h of reperfusion. Myocardial infarct size was determined using triphenyltetrazolium staining. Rats were randomly assigned to receive 0.9% saline, isoflurane (0.5 and 1.0 minimum alveolar concentration [MAC]), morphine (0.1 and 0.3 mg/kg), or morphine (0.3 mg/kg) plus isoflurane (1.0 MAC). Isoflurane was administered for 30 min and discontinued 15 min before coronary occlusion. In eight additional groups of experiments, rats received 5-hydroxydecanoic acid (5-HD; 10 mg/kg) or naloxone (6 mg/kg) in the presence or absence of isoflurane, morphine, and morphine plus isoflurane.
Results: Isoflurane (1.0 MAC) and morphine (0.3 mg/kg) reduced infarct size (41 +/- 3%; n = 13 and 38 +/- 2% of the area at risk; n = 10, respectively) as compared to control experiments (59 +/- 2%; n = 10). Morphine plus isoflurane further decreased infarct size to 26 +/- 3% (n = 11). 5-HD and naloxone alone did not affect infarct size, but abolished cardioprotection produced by isoflurane, morphine, and morphine plus isoflurane. 相似文献
Methods: Hearts were randomly assigned to (1) a nontreated hypothermic ischemia group (CON), (2) a group given 3.5 vol% sevoflurane for 15 min with a 15-min washout before hypothermic ischemia (SPC), and (3) an SPC group in which anesthetic exposure was bracketed with 200 [mu]m 5-hydroxydecanoate (5-HD) from 5 min before until 5 min after sevoflurane (SPC + 5-HD). Cytosolic [Ca2+] was measured in the left ventricular (LV) free wall with the intracellularly loaded fluorescence probe indo-1.
Results: Initial reperfusion in CON hearts markedly increased systolic and diastolic [Ca2+] and reduced contractility (dLVP/dtmax), relaxation (diastolic LVP, dLVP/dtmin), myocardial oxygen consumption (Mvo2), and cardiac efficiency. In SPC hearts, cytosolic [Ca2+] overloading (especially diastolic [Ca2+]) was decreased with increased myocardial [Ca2+] influx (d[Ca2+]/dtmax) and efflux (d[Ca2+]/dtmin), improved contractility, relaxation, coronary flow, Mvo2, cardiac efficiency, and decreased infarct size. In SPC + 5HD hearts, the reduction in infarct size was antagonized by 5-HD, but functional return was less affected by 5-HD. 相似文献
Methods: Intrathecal catheters were implanted in male Sprague-Dawley rats. Antinociception was assessed by measuring withdrawal latency to immersion of the tail in a 52[degrees]C water bath. Nerve injury was produced by ligation of the L5 and L6 spinal nerves. Testing was performed 4-14 days after spinal nerve ligation, when tactile allodynia and thermal hyperalgesia were established. Tactile allodynia was quantitated using the threshold to withdrawal of the hind paw on probing with von Frey filaments. Thermal hyperalgesia was quantitated using the latency to withdrawal of the hind paw from radiant heat. Motor function was tested using a rotarod apparatus.
Results: Spinal administration of the GABAA receptor antagonist bicuculline or the GABAB receptor antagonist phaclofen produced tactile allodynia and thermal hyperalgesia in normal rats. The GABAB receptor agonist baclofen, administered spinally, produced antinociception in the tail-flick test, whereas the GABAA receptor agonist isoguvacine did not. Isoguvacine and baclofen each reversed tactile allodynia and thermal hyperalgesia produced by spinal nerve ligation. Baclofen but not isoguvacine prolonged thermal withdrawal latency in nerve-injured rats beyond preoperative values. Baclofen but not isoguvacine impaired motor function. 相似文献
Methods: Isolated rat hearts were perfused by the Langendorff method at a constant flow rate, and left ventricular function and coronary pressures were assessed using standard methods. Energy metabolites were also determined. To assess the role of KATP channels, hearts were pretreated with the KATP blocker glyburide (10 [mu]M). Hearts were then exposed to either control buffer or buffer containing HOE 642 (5 [mu]M), propofol (35 [mu]M), sevoflurane (2.15 vol%), the KATP opener pinacidil (1 [mu]M), or the combination of propofol and HOE 642. Each heart was then subjected to 1 h of global ischemia followed by 1 h of reperfusion.
Results: Hearts treated with propofol, sevoflurane, pinacidil, or HOE 642 showed significantly higher recovery of left ventricular developed pressure and reduced end-diastolic pressures compared with controls. The combination of propofol and HOE 642 provided superior protection toward the end of the reperfusion period. Propofol, sevoflurane, and HOE 642 also attenuated the onset and magnitude of ischemic contracture and preserved high-energy phosphates (HEPs) compared with controls. Glyburide attenuated the cardioprotective effects of sevoflurane and abolished the protection observed with pinacidil. In contrast, glyburide had no effect on the cardioprotection associated with propofol treatment. 相似文献
Methods: A functional study was conducted to evaluate the effects of edrophonium on the concentration-response curves for the negative chronotropic effect and the bronchoconstricting effect of carbachol in spontaneously beating right atria and tracheas of guinea pigs. An electrophysiologic study was conducted to compare the effects of edrophonium on carbachol-, guanosine triphosphate (GTP)[gamma] S-, and adenosine-induced outward K+ currents in guinea pig atrial cells by whole cell voltage clamp technique. A radioligand binding study was conducted to examine the effects of edrophonium on specific [3H]N-methyl-scopolamine (NMS) binding to guinea pig atrial (M2) and submandibular gland (M3) membrane preparations, and on atropine-induced dissociation of [3H]NMS.
Results: Edrophonium shifted rightward the concentration-response curves for the negative chronotropic and bronchoconstricting effects of carbachol in a competitive manner. The pA2 values for cardiac and tracheal muscarinic receptors were 4.61 and 4.03, respectively. Edrophonium abolished the carbachol-induced outward current without affecting the GTP[gamma] S- and adenosine-induced currents in the atrial cells. Edrophonium inhibited [3H]NMS binding to M2 and M3 receptors in a concentration-dependent manner. The pseudo-Hill coefficient values and apparent dissociation constants of edrophonium for M2 and M3 receptors were 1.02 and 1.07 and 21 and 34 [mu]m, respectively. Edrophonium also changed dissociation constant values of [3H]NMS without affecting its maximum binding capacities. 相似文献
Methods: Fifteen conditioned, male mongrel dogs were fitted with instruments for long-term monitoring to measure the left pulmonary vascular pressure-flow relation. The dose-response relation to the KATP+ channel agonist, lemakalim, and the pulmonary vascular response to circulatory hypotension were assessed in conscious and isoflurane-anesthetized (approximately 1.2 minimum alveolar concentration) dogs. The effect of the selective KATP+ channel antagonist, glibenclamide, on the pulmonary vascular response to hypotension was also assessed in conscious and isoflurane-anesthetized dogs.
Results: Isoflurane had no effect on the baseline pulmonary circulation, but it attenuated (P < 0.05) the pulmonary vasodilator response to lemakalim. Reducing the mean systemic arterial pressure to approximately 50 mmHg resulted in pulmonary vasoconstriction (P < 0.05) in the conscious state, and this response was attenuated (P < 0.05) during isoflurane. Glibenclamide had no effect on the baseline pulmonary circulation, but it potentiated (P < 0.05) the pulmonary vasoconstrictor response to hypotension in conscious and isoflurane-anesthetized dogs. 相似文献
Methods: After institutional approval and informed patient consent were obtained, 23 patients scheduled to undergo supratentorial tumor surgery were randomly assigned to remifentanil or fentanyl infusion groups in a double-blinded manner. Midazolam, thiopental, and pancuronium induction was followed by equipotent narcotic loading infusions of remifentanil (1 [micro sign]g [middle dot] kg-1 [middle dot] min-1) or fentanyl (2 [micro sign]g [middle dot] kg-1 [middle dot] min-1) for 5-10 min. Patients were ventilated with 2:1 nitrous oxide-oxygen, and opioid rates were reduced and then titrated to a stable hemodynamic effect. After dural exposure, CBF was measured by the intravenous133 xenon technique at normocapnia and hypocapnia. Reactivity of CBF to carbon dioxide was calculated as the absolute increase in CBF per millimeters of mercury increase in the partial pressure of carbon dioxide (PaCO2). Data were analyzed by repeated-measures analysis of variance, unpaired Student's t tests, or contingency analysis.
Results: In the remifentanil group (n = 10), CBF decreased from 36 +/- 11 to 27 +/- 8 ml [middle dot] 100 g-1 [middle dot] min-1 as PaCO2 decreased from 33 +/- 5 to 25 +/- 2 mmHg. In the fentanyl group (n = 8), CBF decreased from 37 +/- 11 to 25 +/- 6 ml [middle dot] 100 g-1 [middle dot] min-1 as PaCO2 decreased from 34 +/- 3 to 25 +/- 3 mmHg. Absolute carbon dioxide reactivity was preserved with both agents: 1 +/- 1.2 ml [middle dot] 100 g-1 [middle dot] min-1 [middle dot] mmHg-1 for remifentanil and 1.5 +/- 0.5 ml [middle dot] 100 g-1 [middle dot] min-1 [middle dot] mmHg-1 for fentanyl (P = 0.318). 相似文献
Methods: Forty-two parturients undergoing elective cesarean delivery with use of combined spinal-epidural anesthesia received intrathecal hyperbaric bupivacaine in doses of 6, 7, 8, 9, 10, 11, or 12 mg in equal volumes with an added 10 [mu]g intrathecal fentanyl and 200 [mu]g intrathecal morphine. Sensory levels (pinprick) were evaluated every 2 min until a T6 level was achieved. The dose was a success(induction) if a bilateral T6 block occurred in 10 min; otherwise, it was a failure(induction). In addition to being a success(induction), the dose was a success(operation) if no intraoperative epidural supplement was required; otherwise, it was a failure(operation). ED50 and ED95 for both success(induction) and success(operation) were determined with use of a logistic regression model.
Results: ED50 for success(induction) and success(operation) were 6.7 and 7.6 mg, respectively, whereas the ED95 for success(induction) and success(operation) were 11.0 and 11.2 mg. Speed of onset correlated inversely with dose. Although no clear advantage for low doses could be demonstrated (hypotension, nausea, vomiting, pruritus, or maternal satisfaction), this study was underpowered to detect significance in these variables. 相似文献
Methods: After institutional review board approval and written informed consent were obtained, 48 parturients undergoing elective cesarean delivery under combined spinal-epidural anesthesia were enrolled in this double-blind, randomized, dose-ranging study. Patients received a 5-, 6-, 7-, 8-, 9-, 10-, 11-, or 12-mg intrathecal isobaric bupivacaine dose with 10 [mu]g fentanyl and 200 [mu]g morphine. Overall anesthetic success was recorded when no intraoperative epidural supplement was required during the cesarean delivery. ED50 and ED95 values for overall anesthetic success were determined using a logistic regression model.
Results: ED50 and ED95 values for overall anesthetic success were 7.25 and 13.0 mg, respectively. No advantages for low doses could be demonstrated with regard to hypotension, nausea, vomiting, pruritus, or maternal satisfaction, although this study was underpowered to detect significant differences in secondary outcome variables. 相似文献
Methods: Using a double-blind, crossover design, 14 healthy volunteers completed the protocol and were randomized to receive one dose of loratadine (20 mg), ranitidine (300 mg), or placebo on each of three separate testing sessions. Continuous electrocardiogram and BP recordings were obtained before and 3 h after administration of study drug. Effects on cardiac autonomic control were quantified using power spectral analysis of heart rate variability and calculation of spontaneous baroreflex sensitivity.
Results: Neither placebo nor loratadine significantly altered indices of autonomic cardiovascular control. Conversely, H2 antagonism with ranitidine resulted in a 23.3% decrease in baroreflex sensitivity (P < 0.05) and a corresponding 25.0% decrease in the ratio of high frequency to total power of heart rate variability, both indices of parasympathetic modulation (P < 0.01). Furthermore, ranitidine evoked a concomitant 103.8% increase in the ratio of low to high frequency power of heart rate variability, an index of sympathetic control (P < 0.01). 相似文献
Methods: GTP hydrolysis by G[alpha]i-3 and the G[alpha]i-3[beta]1[gamma]2HF heterotrimer expressed in Spodoptera frugiperda cells was measured using a phosphohydrolase assay with [[gamma]32Pi]-labeled GTP. Anesthetic binding to G[alpha]i-3 was measured by saturation transfer difference nuclear magnetic resonance spectroscopy. G[alpha]i-3 nucleotide exchange was measured in crude membranes prepared from COS-7 cells transiently coexpressing the M2 muscarinic receptor and G[alpha]i-3. A radioactive analog of GTP, [35S]GTP[gamma]S, was used as a reporter for G[alpha]i-3 nucleotide exchange.
Results: Although spectroscopy demonstrated halothane binding to G[alpha]i-3, this binding had no effect on [[gamma]32Pi]-labeled GTP hydrolysis by the G[alpha]i-3[beta]1[gamma]2HF heterotrimer expressed in Spodoptera frugiperda cells, nor basal G[alpha]i-3 nucleotide exchange measured in crude membranes when the muscarinic receptor agonist acetylcholine was omitted from the assay. Conversely, halothane caused a concentration-dependent inhibition of G[alpha]i-3 nucleotide exchange with acetylcholine included in the assay. 相似文献
Methods: Ventricular myocytes were isolated from guinea pig hearts for the whole cell patch clamp recordings of the sarcolemmal KATP channel current (IKATP). Free radical scavengers N-acetyl-l-cysteine, carnosine, superoxide dismutase, and catalase were used to investigate whether reactive oxygen species mediate isoflurane facilitation of the channel opening by pinacidil. A possible role of the mitochondrial KATP channels was tested using a blocker of these channels, 5-hydroxydecanoate.
Results: The mean density (+/- SEM) of IKATP elicited by pinacidil (20 [mu]m) was 18.9 +/- 1.8 pA/pF (n = 11). In the presence of isoflurane (0.55 mm), the density of pinacidil-activated IKATP increased to 38.5 +/- 2.4 pA/pF (n = 9). Concurrent application of isoflurane and N-acetyl-l-cysteine decreased the sensitization effect by isoflurane in a concentration-dependent manner, whereby the densities of IKATP were 32.6 +/- 1.4 (n = 6), 26.2 +/- 2.3 (n = 6), and 19.4 +/- 2.1 pA/pF (n = 8) at 100, 250, and 500 [mu]m N-acetyl-l-cysteine, respectively. Concurrent application of isoflurane and carnosine (100 [mu]m), superoxide dismutase (100 U/ml), or catalase (100 U/ml) attenuated the densities of IKATP to 27.9 +/- 2.6, 27.2 +/- 2.9, and 25.9 +/- 2.2 pA/pF, respectively. None of the scavengers affected activation of IKATP by pinacidil alone. 5-Hydroxydecanoate (100 [mu]m) did not alter the sensitization effect by isoflurane, and the density of IKATP in this group was 37.1 +/- 3.8 pA/pF (n = 6). 相似文献
Methods: [gamma]-Aminobutyric acid type A [alpha]1[beta]1[gamma]2 receptor, [alpha]7 and [alpha]4[beta]2 nAChRs were expressed in Xenopus oocytes and studied with two-electrode voltage clamp recording. The authors tested the ability of droperidol at concentrations from 1 nm to 100 [mu]m to modulate activation of these receptors by their native agonists.
Results: Droperidol inhibited the GABA response by a maximum of 24.7 +/- 3.0%. The IC50 for inhibition was 12.6 +/- 0.47 nm droperidol. At high concentrations, droperidol (100 [mu]m) activates the GABAA receptor in the absence of GABA. Inhibition of the GABA response is significantly greater at hyperpolarized membrane potentials. The activation of the [alpha]7 nAChR is also inhibited by droperidol, with an IC50 of 5.8 +/- 0.53 [mu]m. The Hill coefficient is 0.95 +/- 0.1. Inhibition is noncompetitive, and membrane voltage dependence is insignificant. 相似文献
Methods: Human embryonic kidney 293 cells were transiently transfected with rat complementary DNAs of [alpha]1[beta]2, [alpha]1[beta]2[gamma]2L, [alpha]1[beta]2[gamma]2S, [alpha]5[beta]3, or [alpha]5[beta]3[gamma]2S subunits. Using rapid application and whole cell patch clamp techniques, cells were exposed to 10- and 2,000-ms pulses of [gamma]-aminobutyric acid (1 mm) in the presence or absence of isoflurane (0.25, 0.5, 1.0 mm). Anesthetic effects on decay kinetics, peak amplitude, net charge transfer and rise time were measured. Statistical significance was assessed using the Student t test or one-way analysis of variance followed by the Tukey post hoc test.
Results: Under control conditions, incorporation of a [gamma]2 subunit conferred faster deactivation kinetics and reduced desensitization. Isoflurane slowed deactivation, enhanced desensitization, and reduced peak current amplitude in [alpha][beta] receptors. Coexpression with a [gamma]2 subunit caused these effects of isoflurane to be substantially reduced or abolished. Although the two [gamma]2 splice variants imparted qualitatively similar macroscopic kinetic properties, there were significant quantitative differences between effects of isoflurane on deactivation and peak current amplitude in [gamma]2S- versus [gamma]2L-containing receptors. The net charge transfer resulting from brief pulses of [gamma]-aminobutyric acid was decreased by isoflurane in [alpha][beta] but increased in [alpha][beta][gamma] receptors. 相似文献