scholarly journals Volatile Anesthetic Vascular Pharmacology: Changes in Vascular Responsiveness to Volatile Anesthetics Associated with Aging, Hypertension, and Diabetes Mellitus in Systemic Resistance Arteries

2007 ◽  
Vol 27 (3) ◽  
pp. 207-217
Author(s):  
Takashi AKATA ◽  
Kaoru IZUMI ◽  
Jun YOSHINO ◽  
Kazuhiro SHIROZU
Keyword(s):  
Diabetes Mellitus ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Systemic Resistance ◽  
Resistance Arteries ◽  
Vascular Responsiveness

Comparison of Volatile Anesthetic Actions on Intracellular Calcium Stores of Vascular Smooth Muscle

2001 ◽  
Vol 94 (5) ◽  
pp. 840-850 ◽  
Author(s):  
Takashi Akata ◽  
Mikio Nakashima ◽  
Kaoru Izumi
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Isometric Force ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Mesenteric Arteries ◽  
Systemic Resistance ◽  
Release Mechanism ◽  
Calcium Stores ◽  
Resistance Arteries

Background Volatile anesthetic actions on intracellular Ca2+ stores (ie., sarcoplasmic reticulum [SR]) of vascular smooth muscle have not been fully elucidated. Methods Using isometric force recording method and fura-2 fluorometry, the actions of four volatile anesthetics on SR were studied in isolated endothellum-denuded rat mesenteric arteries. Results Halothane (> or = 3%) and enflurane (> or = 3%), but not isoflurane and sevoflurane, increased the intracellular Ca2+ concentration ([Ca2+]i) in Ca2+-free solution. These Ca2+-releasing actions were eliminated by procaine. When each anesthetic was applied during Ca2+ loading, halothane (> or = 3%) and enflurane (5%), but not isoflurane and sevoflurane, decreased the amount of Ca2+ in the SR. However, if halothane or enflurane was applied with procaine during Ca2+ loading, both anesthetics increased the amount of Ca2+ in the SR. The caffeine-induced increase in [Ca2+], was enhanced in the presence of halothane (> or = 1%), enflurane (> or = 1%), and isoflurane (> or = 3%) but was attenuated in the presence of sevoflurane (> or = 3%). The norepinephrine-induced increase in [Ca2+], was enhanced only in the presence of sevoflurane (> or = 3%). Not all of these anesthetic effects on the [Ca2+]i were parallel with the simultaneously observed anesthetic effects on the force. Conclusions In systemic resistance arteries, the halothane, enflurane, isoflurane, and sevoflurane differentially influence the SR functions. Both halothane and enflurane cause Ca2+ release from the caffeine-sensitive SR. In addition, both anesthetics appear to have a stimulating action on Ca2+ uptake in addition to the Ca2+-releasing action. Halothane, enflurane, and isoflurane all enhance, while sevoflurane attenuates, the Ca2+-induced Ca2+-release mechanism. However, only sevoflurane stimulates the inositol 1,4,5-triphosphate-induced Ca2+ release mechanism. Isoflurane and sevoflurane do not stimulate Ca2+ release or influence Ca2+ uptake.

scholarly journals Diabetes-associated Alterations in Volatile Anesthetic Actions on Contractile Response to Norepinephrine in Isolated Mesenteric Resistance Arteries

2010 ◽  
Vol 112 (3) ◽  
pp. 595-606 ◽  
Author(s):  
Jun Yoshino ◽  
Takashi Akata ◽  
Kazuhiro Shirozu ◽  
Kaoru Izumi ◽  
Sumio Hoka
Keyword(s):  
Response Curve ◽  
Contractile Response ◽  
Isometric Force ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Mesenteric Arteries ◽  
Resistance Arteries ◽  
Calcitonin Gene ◽  
The Right ◽  
Concentration Response Curve

Background Clinical concentrations of volatile anesthetics significantly influence contractile response to the sympathetic neurotransmitter norepinephrine although its precise mechanisms remain unclarified. In this study, we investigated its possible alterations in diabetes, as well as its underlying mechanisms. Methods Isometric force was recorded in small mesenteric arteries from streptozotocin-induced diabetic and age-matched control rats. Results The concentration-response curve for acetylcholine-induced endothelium-dependent relaxation was shifted to the right in diabetic arteries compared with controls. The concentration-response curve for norepinephrine-induced contraction was shifted to the left and upward by both endothelial denudation and diabetic induction. In the presence of endothelium, isoflurane or sevoflurane enhanced norepinephrine-induced contraction in control arteries but not in diabetic arteries; however, in its absence, both anesthetics identically inhibited norepinephrine-induced contraction in both groups. In control arteries, the isoflurane- or sevoflurane-induced enhancement was not affected by adrenomedullin22-52, calcitonin gene-related peptide8-37, 18beta-glycyrrhetinic acid, N-nitro l-arginine, ouabain, Ba, indomethacin, losartan, ketanserin, BQ-123, and BQ-788. Conclusions In diabetes, vascular responses to acetylcholine, norepinephrine, and volatile anesthetics are altered in mesenteric resistance arteries, presumably reflecting endothelial dysfunction and possibly underlying circulatory instability during administration of either anesthetic. Some endothelial mechanisms that are impaired in diabetes would be involved in the anesthetic-induced enhancement of norepinephrine-induced contraction. However, the vasoregulatory mechanism mediated by adrenomedullin, calcitonin gene-related peptide, myoendothelial gap junction, nitric oxide, endothelium-derived hyperpolarizing factor, cyclooxygenase products, angiotensin II, serotonin, or endothelin-1, all of which have been suggested to be impaired in diabetes, would not be involved in the enhancement.

Effects of Volatile Anesthetics on Acetylcholine-induced Relaxation in the Rabbit Mesenteric Resistance Artery 

1995 ◽  
Vol 82 (1) ◽  
pp. 188-204 ◽  
Author(s):  
Takashi Akata ◽  
Mikio Nakashima ◽  
Kenji Kodama ◽  
Walter A. Boyle ◽  
Shosuke Takahashi
Keyword(s):  
Endothelial Function ◽  
Sodium Nitroprusside ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Mesenteric Arteries ◽  
K Channel ◽  
Resistance Arteries ◽  
Anesthetic Action ◽  
Endothelium Dependent Relaxation

Background Vascular endothelium plays an important role in the regulation of vascular tone. Volatile anesthetics have been shown to attenuate endothelium-mediated relaxation in conductance arteries, such as aorta. However, significant differences in volatile anesthetic pharmacology between these large vessels and the small vessels that regulate systemic vascular resistance and blood flow have been documented, yet little is known about volatile anesthetic action on endothelial function in resistance arteries. Furthermore, endothelium-dependent relaxation mediated by factors other than endothelium-derived relaxing factor (EDRF) has recently been recognized, and there is no information available regarding volatile anesthetic action on non-EDRF-mediated endothelium-dependent relaxation. Methods Employing isometric tension recording and microelectrode methods, the authors first characterized the endothelium-dependent relaxing and hyperpolarizing actions of acetylcholine (ACh) in rabbit small mesenteric arteries, and tested the sensitivities of these actions to EDRF pathway inhibitors and K+ channel blockers. They then examined the effects of the volatile anesthetics isoflurane, enflurane, and sevoflurane on ACh-induced endothelium-dependent relaxation that was sensitive to EDRF inhibitors and that which was resistant to the EDRF inhibitors but sensitive to blockers of ACh-induced hyperpolarization. The effects of the volatile anesthetics on endothelium-independent sodium nitroprusside (SNP)-induced relaxation were also studied. Results Acetylcholine concentration-dependently caused both endothelium-dependent relaxation and hyperpolarization of vascular smooth muscle. The relaxation elicited by low concentrations of ACh (< or = 0.1 microM) was almost completely abolished by the EDRF inhibitors NG-nitro-L-arginine (LNNA), oxyhemoglobin (HbO2), and methylene blue (MB). The relaxation elicited by higher concentrations of ACh (> or = 0.3 microM) was only attenuated by the EDRF inhibitors. The remaining relaxation, as well as the ACh-induced hyperpolarization that was also resistant to EDRF inhibitors, were both specifically blocked by tetraethylammonium (TEA > or = 10 mM). Sodium nitroprusside, a NO donor, produced dose-dependent relaxation, but not hyperpolarization, in the endothelium-denuded (E[-]) strips, and the relaxation was inhibited by MB and HbO2, but not TEA (> or = 10 mM). One MAC isoflurane, enflurane, and sevoflurane inhibited both ACh relaxation that was sensitive to the EDRF inhibitors and the ACh relaxation resistant to the EDRF inhibitors and sensitive to TEA, but not SNP relaxation (in the E[-] strips). An additional finding was that the anesthetics all significantly inhibited norepinephrine (NE) contractions in the presence and absence of the endothelium or after exposure to the EDRF inhibitors. Conclusions The results confirm that ACh has a hyperpolarizing action in rabbit small mesenteric resistance arteries that is independent of EDRF inhibitors but blocked by the K+ channel blocker TEA. The ACh relaxation in these resistance arteries thus appears to consist of distinct EDRF-mediated and hyperpolarization-mediated components. Isoflurane, enflurane, and sevoflurane inhibited both components of the ACh-induced relaxation in these small arteries, indicating a more global depression of endothelial function or ACh signaling in endothelial cells, rather than a specific effect on the EDRF pathway. All these anesthetics exerted vasodilating action in the presence of NE, the primary neurotransmitter of the sympathetic nervous system, which plays a major role in maintaining vasomotor tone in vivo. This strongly indicates that the vasodilating action of these anesthetics probably dominates over their inhibitory action on the EDRF pathway and, presumably, contributes to their known hypotensive effects in vivo. Finally, the vasodilating action of these anesthetics is, at least in part, independent from endothelium.

Volatile Anesthetics Affect Nutrient Availability in Yeast

Genetics ◽  
2002 ◽  
Vol 161 (2) ◽  
pp. 563-574
Author(s):  
Laura K Palmer ◽  
Darren Wolfe ◽  
Jessica L Keeley ◽  
Ralph L Keil
Keyword(s):  
Amino Acids ◽  
Nutrient Availability ◽  
Wild Type Strain ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Wild Type ◽  
Anesthetic Exposure ◽  
Sites Of Action ◽  
Insight Into ◽  
Lines Of Evidence

Abstract Volatile anesthetics affect all cells and tissues tested, but their mechanisms and sites of action remain unknown. To gain insight into the cellular activities of anesthetics, we have isolated genes that, when overexpressed, render Saccharomyces cerevisiae resistant to the volatile anesthetic isoflurane. One of these genes, WAK3/TAT1, encodes a permease that transports amino acids including leucine and tryptophan, for which our wild-type strain is auxotrophic. This suggests that availability of amino acids may play a key role in anesthetic response. Multiple lines of evidence support this proposal: (i) Deletion or overexpression of permeases that transport leucine and/or tryptophan alters anesthetic response; (ii) prototrophic strains are anesthetic resistant; (iii) altered concentrations of leucine and tryptophan in the medium affect anesthetic response; and (iv) uptake of leucine and tryptophan is inhibited during anesthetic exposure. Not all amino acids are critical for this response since we find that overexpression of the lysine permease does not affect anesthetic sensitivity. These findings are consistent with models in which anesthetics have a physiologically important effect on availability of specific amino acids by altering function of their permeases. In addition, we show that there is a relationship between nutrient availability and ubiquitin metabolism in this response.

Mechanisms of Direct Inhibitory Action of Isoflurane on Vascular Smooth Muscle of Mesenteric Resistance Arteries

2003 ◽  
Vol 99 (3) ◽  
pp. 666-677 ◽  
Author(s):  
Takashi Akata ◽  
Tomoo Kanna ◽  
Jun Yoshino ◽  
Shosuke Takahashi
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Vascular Reactivity ◽  
Channel Blocker ◽  
Isometric Force ◽  
Systemic Resistance ◽  
Resistance Arteries ◽  
Voltage Gated ◽  
Fura 2 ◽  
Force Relation

Background Isoflurane has been shown to directly inhibit vascular reactivity. However, less information is available regarding its underlying mechanisms in systemic resistance arteries. Methods Endothelium-denuded smooth muscle strips were prepared from rat mesenteric resistance arteries. Isometric force and intracellular Ca2+ concentration ([Ca2+]i) were measured simultaneously in the fura-2-loaded strips, whereas only the force was measured in the beta-escin membrane-permeabilized strips. Results Isoflurane (3-5%) inhibited the increases in both [Ca2+]i and force induced by either norepinephrine (0.5 microM) or KCl (40 mM). These inhibitions were similarly observed after depletion of intracellular Ca2+ stores by ryanodine. Regardless of the presence of ryanodine, after washout of isoflurane, its inhibition of the norepinephrine response (both [Ca2+]i and force) was significantly prolonged, whereas that of the KCl response was quickly restored. In the ryanodine-treated strips, the norepinephrine- and KCl-induced increases in [Ca2+]i were both eliminated by nifedipine, a voltage-gated Ca2+ channel blocker, whereas only the former was inhibited by niflumic acid, a Ca2+-activated Cl- channel blocker. Isoflurane caused a rightward shift of the Ca2+-force relation only in the fura-2-loaded strips but not in the beta-escin-permeabilized strips. Conclusions In mesenteric resistance arteries, isoflurane depresses vascular smooth muscle reactivity by directly inhibiting both Ca2+ mobilization and myofilament Ca2+ sensitivity. Isoflurane inhibits both norepinephrine- and KCl-induced voltage-gated Ca2+ influx. During stimulation with norepinephrine, isoflurane may prevent activation of Ca2+-activated Cl- channels and thereby inhibit voltage-gated Ca2+ influx in a prolonged manner. The presence of the plasma membrane appears essential for its inhibition of the myofilament Ca2+ sensitivity.

Behavioral Effects of Volatile Anesthetics in Caenorhabditis elegans

1996 ◽  
Vol 85 (4) ◽  
pp. 901-912 ◽  
Author(s):  
Michael C. Crowder ◽  
Laynie D. Shebester ◽  
Tim Schedl
Keyword(s):  
Nervous System ◽  
Caenorhabditis Elegans ◽  
Time Course ◽  
Model Organism ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Effective Concentration ◽  
Forward Genetics ◽  
C Elegans ◽  
Median Effective Concentration

Background The nematode Caenorhabditis elegans offers many advantages as a model organism for studying volatile anesthetic actions. It has a simple, well-understood nervous system; it allows the researcher to do forward genetics; and its genome will soon be completely sequenced. C. elegans is immobilized by volatile anesthetics only at high concentrations and with an unusually slow time course. Here other behavioral dysfunctions are considered as anesthetic endpoints in C. elegans. Methods The potency of halothane for disrupting eight different behaviors was determined by logistic regression of concentration and response data. Other volatile anesthetics were also tested for some behaviors. Established protocols were used for behavioral endpoints that, except for pharyngeal pumping, were set as complete disruption of the behavior. Time courses were measured for rapid behaviors. Recovery from exposure to 1 or 4 vol% halothane was determined for mating, chemotaxis, and gross movement. All experiments were performed at 20 to 22 degrees C. Results The median effective concentration values for halothane inhibition of mating (0.30 vol%-0.21 mM), chemotaxis (0.34 vol%-0.24 mM), and coordinated movement (0.32 vol% - 0.23 mM) were similar to the human minimum alveolar concentration (MAC; 0.21 mM). In contrast, halothane produced immobility with a median effective concentration of 3.65 vol% (2.6 mM). Other behaviors had intermediate sensitivities. Halothane's effects reached steady-state in 10 min for all behaviors tested except immobility, which required 2 h. Recovery was complete after exposure to 1 vol% halothane but was significantly reduced after exposure to immobilizing concentrations. Conclusions Volatile anesthetics selectively disrupt C. elegans behavior. The potency, time course, and recovery characteristics of halothane's effects on three behaviors are similar to its anesthetic properties in vertebrates. The affected nervous system molecules may express structural motifs similar to those on vertebrate anesthetic targets.

Halothane and Isoflurane Alter the Calcium sup 2+ Binding Properties of Calmodulin

1995 ◽  
Vol 83 (1) ◽  
pp. 120-126. ◽  
Author(s):  
Aaron Levin ◽  
Thomas J. J. Blanck
Keyword(s):  
Binding Protein ◽  
Fluorescence Emission ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Bovine Brain ◽  
Hill Coefficient ◽  
Excitation Wavelength ◽  
Binding Properties ◽  
Fluorescence Measurements ◽  
The Hill

Background Ca2+ plays an important role in signal transduction and anesthetic mechanisms. To date, no one has observed a direct effect of volatile anesthetics on a Ca(2+)-binding protein. We therefore examined the effects of halothane and isoflurane on the Ca(2+)-binding properties of bovine brain calmodulin. Methods The fluorescence emission of calmodulin was obtained over a range of Ca2+ concentrations (10(-7)-10(-4)M) in the presence and absence of halothane and isoflurane. The intrinsic tyrosine fluorescence of calmodulin was measured at an excitation wavelength of 280 nm and an emission wavelength of 320 nm. Fluorescence measurements were carried out in 50 mM hydroxyethylpiperazineethane sulfonic acid, 100 mM KC1, and 2 mM ethyleneglycol-bis-(beta-aminoethyl ether) tetraacetic acid at pH 7.0 and 37 degrees C. Experiments were performed in polytetrafluorethylene-sealed cuvettes so that the volatile anesthetic concentrations remained constant. The titration data were analyzed in two ways. The data were fit to the Hill equation by using nonlinear regression analysis to derive the Hill coefficient and the dissociation constant. The data were also analyzed by two-way analysis of variance with multiple comparisons to determine statistically significant effects. Volatile anesthetic concentrations were measured by gas chromatography. Results The presence of volatile anesthetics altered the Ca(2+)-binding affinity of calmodulin in a dose-dependent fashion. At 0.57% (0.25 mM) halothane and 1.7% (0.66 mM) isoflurane, the affinity of calmodulin for Ca2+ relative to control was decreased. However, at higher concentrations of both anesthetics, the affinity for Ca2+ was increased. When the volatile anesthetics were allowed to evaporate from the experimental solutions, the observed rightward shift of the calmodulin-Ca2+ binding curve for Ca2+ at low concentrations of the anesthetics returned to the control position. The leftward shift seen at high concentrations of the anesthetics was irreversible after evaporation of 8.7% (3.3 mM) isoflurane and 5.7% (2.5 mM) halothane. Conclusions These data demonstrate a complex interaction of two hydrophobic volatile anesthetics with calmodulin. A biphasic effect was observed both for halothane and for isoflurane. Calmodulin, an EF-hand Ca(2+)-binding protein, undergoes a conformational shift when binding Ca2+, exposing several hydrophobic residues. These residues may be sites at which the anesthetics act.

Differential Modulation of the Cardiac Adenosine Triphosphate-sensitive Potassium Channel by Isoflurane and Halothane

2002 ◽  
Vol 97 (1) ◽  
pp. 50-56 ◽  
Author(s):  
Wai-Meng Kwok ◽  
Anne T. Martinelli ◽  
Kazuhiro Fujimoto ◽  
Akihiro Suzuki ◽  
Anna Stadnicka ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Adenosine Triphosphate ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Channel Activation ◽  
Beneficial Effects ◽  
Channel Current ◽  
Channel Opening

Background The cardiac adenosine triphosphate-sensitive potassium (K(ATP)) channel is activated during pathophysiological episodes such as ischemia and hypoxia and may lead to beneficial effects on cardiac function. Studies of volatile anesthetic interactions with the cardiac K(ATP) channel have been limited. The goal of this study was to investigate the ability of volatile anesthetics halothane and isoflurane to modulate the cardiac sarcolemmal K(ATP) channel. Methods The K(ATP) channel current (I(KATP)) was monitored using the whole cell configuration of the patch clamp technique from single ventricular cardiac myocytes enzymatically isolated from guinea pig hearts. I(KATP) was elicited by extracellular application of the potassium channel openers 2,4-dinitrophenol or pinacidil. Results Volatile anesthetics modulated I(KATP) in an anesthetic-dependent manner. Isoflurane facilitated the opening of the K(ATP) channel. Following initial activation of I(KATP) by 2,4-dinitrophenol, isoflurane at 0.5 and 1.3 mm further increased current amplitude by 40.4 +/- 11.1% and 58.4 +/- 20.6%, respectively. Similar results of isoflurane were obtained when pinacidil was used to activate I(KATP). However, isoflurane alone was unable to elicit K(ATP) channel opening. In contrast, halothane inhibited I(KATP) elicited by 2,4-dinitrophenol by 50.6 +/- 5.8% and 72.1 +/- 11.6% at 0.4 and 1.0 mm, respectively. When I(KATP) was activated by pinacidil, halothane had no significant effect on the current. Conclusions The cardiac sarcolemmal K(ATP) channel is differentially modulated by volatile anesthetics. Isoflurane can facilitate the further opening of the K(ATP) channel following initial channel activation by 2,4-dinitrophenol or pinacidil. The effect of halothane was dependent on the method of channel activation, inhibiting I(KATP) activated by 2,4-dinitrophenol but not by pinacidil.

Potent vasodilator responses to human urotensin-II in human pulmonary and abdominal resistance arteries

2001 ◽  
Vol 280 (2) ◽  
pp. H925-H928 ◽  
Author(s):  
Alison Stirrat ◽  
Marie Gallagher ◽  
Stephen A. Douglas ◽  
Eliot H. Ohlstein ◽  
Colin Berry ◽  
...  
Keyword(s):  
Sodium Nitroprusside ◽  
Vascular Function ◽  
Pulmonary Arteries ◽  
Systemic Resistance ◽  
Internal Diameter ◽  
Urotensin Ii ◽  
Resistance Arteries ◽  
Pulmonary Vessels ◽  
Potent Vasodilator ◽  
Abdominal Arteries

The peptide human urotensin-II (hUT-II) and its receptor have recently been cloned. The vascular function of this peptide in humans, however, has yet to be determined. Vasoconstrictor and vasodilator responses to hUT-II were investigated in human small muscular pulmonary arteries [∼170 μm internal diameter (ID)] and human abdominal resistance arteries (∼200 μm ID). Vasodilator responses were investigated in endothelin-1 (3 nM) precontracted vessels and, in the small pulmonary vessels, compared with the known vasodilators adrenomedullin, sodium nitroprusside, and acetylcholine. In human small pulmonary arteries, hUT-II did not induce vasoconstriction but was a potent vasodilator [−log M concentration causing 50% of the maximum vasodilator effect (pIC50) 10.4 ± 0.5; percentage of reduction in tone ( E max) 81 ± 8% (vs. 23 ± 11% in time controls), n = 5]. The order of potency for vasodilation was human urotensin-II = adrenomedullin (pIC50 10.1 ± 0.4, n = 6) > sodium nitroprusside (pIC50 7.4 ± 0.2, n = 6) = acetylcholine (pIC50 6.8 ± 0.3, n = 6). In human abdominal arteries, hUT-II did not induce vasoconstriction but was a potent vasodilator [pIC50 10.3 ± 0.7; E max96 ± 8% (vs. 43 ± 16% in time controls), n = 4]. This is the first report that hUT-II is a potent vasodilator but not a vasoconstrictor of human small pulmonary arteries and systemic resistance arteries.

Halothane and Isoflurane Augment Depolarization-induced Cytosolic CA2+Transients and Attenuate Carbachol-stimulated CA2+Transients

2000 ◽  
Vol 92 (6) ◽  
pp. 1746-1756 ◽  
Author(s):  
Fang Xu ◽  
Jin Zhang ◽  
Esperanza Recio-Pinto ◽  
Thomas J. J. Blanck
Keyword(s):  
Neuronal Excitability ◽  
Neuroblastoma Cell ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Neuroblastoma Cell Line ◽  
Inositol Triphosphate ◽  
Human Neuroblastoma Cell ◽  
Human Neuroblastoma ◽  
Voltage Dependent ◽  
Voltage Dependent Calcium Channels

Background Neuronal excitability is in part determined by Ca2+ availability that is controlled by regulatory mechanisms of cytosolic Ca2+ ([Ca2+]cyt). Alteration of any of those mechanisms by volatile anesthetics (VAs) may lead to a change in presynaptic transmission and postsynaptic excitability. Using a human neuroblastoma cell line, the effects of halothane and isoflurane on cytosolic Ca2+ concentration ([Ca2+]cyt) in response to K+ and carbachol stimulation were investigated. Methods Volatile anesthetic (0.05-1 mm) action on stimulated [Ca2+]cyt transients were monitored in suspensions of SH-SY5Y cells loaded with fura-2. Potassium chloride (KCl; 100 mm) was used to depolarize and activate Ca2+ entry through voltage-dependent calcium channels; 1 mm carbachol was used to activate muscarinic receptor-mediated inositol triphosphate (IP3)-dependent intracellular Ca2+ release. Sequential stimulations, KCl followed by carbachol and vice versa, were used to investigate interactions between intracellular Ca2+ stores. Results Halothane and isoflurane in clinically relevant concentrations enhanced the K+-evoked [Ca2+]cyt transient whether intracellular Ca2+ stores were full or partially depleted. In contrast, halothane and isoflurane reduced the carbachol-evoked [Ca2+]cyt transient when the intracellular Ca2+ stores were full but had no effect when the Ca2+ stores were partially depleted by KCl stimulation. Conclusions Volatile anesthetics acted on sites that differently affect the K+- and carbachol-evoked [Ca2+]cyt transients. These data suggest the involvement of an intracellular Ca2+ translocation from the caffeine-sensitive Ca2+ store to the inositol triphosphate-sensitive Ca2+ store that was altered by halothane and isoflurane.

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