Hypothermia Inhibits Dexmedetomidine-Induced Contractions in Isolated Rat Aortae.

Dexmedetomidine is widely used to induce sedation in the perioperative period. This study examined the effect of hypothermia (33 and 25 °C) on dexmedetomidine-induced contraction in an endothelium-intact aorta with or without the nitric oxide synthase inhibitor NW-nitro-L-arginine methyl ester (L-NAME). In addition, the effect of hypothermia on the contraction induced by dexmedetomidine in an endothelium-denuded aorta with or without a calcium-free Krebs solution was examined. The effects of hypothermia on the protein kinase C (PKC), myosin light chain (MLC20) phosphorylation, and Rho-kinase membrane translocation induced by dexmedetomidine were examined. Hypothermia inhibited dexmedetomidine-induced contraction in the endothelium-intact aorta with L-NAME or endothelium-denuded aorta. Hypothermia had almost no effect on the dexmedetomidine-induced contraction in the endothelium-denuded aorta with the calcium-free Krebs solution; however, the subsequent contraction induced by the addition of calcium was inhibited by hypothermia. Conversely, the transition from profound hypothermia back to normothermia reversed the hypothermia-induced inhibition of subsequent calcium-induced contractions. Hypothermia inhibited any contraction induced by KCl, PDBu, and NaF, as well as PKC and MLC20 phosphorylation and Rho-kinase membrane translocation induced by dexmedetomidine. These results suggest that hypothermia inhibits dexmedetomidine-induced contraction, which is mediated mainly by the impediment of calcium influx and partially by the attenuation of pathways involving PKC and Rho-kinase activation.

Epidermal growth factor receptor phosphorylation contributes to levobupivacaine-induced contraction in isolated rat aorta.

Vasoconstriction induced by levobupivacaine, a local anesthetic, is mediated by increased levels of calcium, tyrosine kinase, c-Jun NH2-terminal kinase (JNK), and phospholipase D, which are associated with prolonged local anesthesia. Epidermal growth factor receptor (EGFR) phosphorylation is associated with vasoconstriction. However, its role in levobupivacaine-induced contractions remains unknown. We determined whether EGFR phosphorylation is associated with levobupivacaine-induced contractions in isolated rat thoracic aortas and identified the underlying cellular signaling pathways. The effects of various inhibitors and a calcium-free solution alone or in combination on levobupivacaine-induced contractions were then assessed. Furthermore, we examined the effects of various inhibitors on levobupivacaine-induced EGFR and JNK phosphorylation and calcium levels in vascular smooth muscle cells (VSMCs) of rat aortas. The EGFR tyrosine kinase inhibitor AG1478, matrix metalloproteinase (MMP) inhibitor GM6001, Src kinase inhibitors PP1 and PP2, and JNK inhibitor SP600125 attenuated levobupivacaine-induced contractions. Moreover, although the calcium-free solution abolished levobupivacaine-induced contractions, calcium reversed this inhibitory effect. The magnitude of the calcium-mediated reversal of abolished levobupivacaine-induced contractions was lower in the combination treatment with calcium-free solution and AG1478 than in the treatment with calcium-free solution alone. Levobupivacaine induced EGFR and JNK phosphorylation. However, AG1478, GM6001, and PP2 attenuated levobupivacaine-induced EGFR and JNK phosphorylation. Moreover, although levobupivacaine induced JNK phosphorylation in control siRNA-transfected VSMCs, EGFR siRNA inhibited levobupivacaine-induced JNK phosphorylation. Furthermore, AG1478 inhibited levobupivacaine-induced calcium increases in VSMCs. Collectively, these findings suggest that levobupivacaine-induced EGFR phosphorylation, which may occur via the Src kinase-MMP pathway, contributes to vasoconstriction via JNK phosphorylation and increased calcium levels.

Theophylline-induced endothelium-dependent vasodilation is mediated by increased nitric oxide release and phosphodiesterase inhibition in rat aorta.

This study aimed to examine the endothelial dependence of vasodilation induced by the phosphodiesterase inhibitor theophylline in isolated rat thoracic aortas and elucidate the underlying mechanism, with emphasis on endothelial nitric oxide (NO). The effects of various inhibitors and endothelial denudation on theophylline-induced vasodilation, and the effect of theophylline on vasodilation induced by NO donor sodium nitroprusside, cyclic guanosine monophosphate (cGMP) analog bromo-cGMP, and ß-agonist isoproterenol in endothelium-denuded aorta were examined. The effects of theophylline and sodium nitroprusside on cGMP formation were also examined. We examined the effect of theophylline on endothelial nitric oxide synthase (eNOS) phosphorylation and intracellular calcium levels. Theophylline-induced vasodilation was greater in endothelium-intact aortas than that in endothelium-denuded aortas. The NOS inhibitor, NW-nitro-L-arginine methyl ester; non-specific guanylate cyclase (GC) inhibitor, methylene blue; and NO-sensitive GC inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a] quinoxalin-1-one inhibited theophylline-induced vasodilation in endothelium-intact aortas. Theophylline increased the vasodilation induced by sodium nitroprusside, bromo-cGMP, and isoproterenol. Theophylline increased cGMP formation in endothelium-intact aortas, and sodium nitroprusside-induced cGMP formation in endothelium-denuded aortas. Moreover, theophylline increased stimulatory eNOS (Ser1177) phosphorylation and endothelial calcium levels, but decreased the phosphorylation of inhibitory eNOS (Thr495). These results suggested that theophylline-induced endothelium-dependent vasodilation was mediated by increased endothelial NO release and phosphodiesterase inhibition.

Correction: Chloroquine inhibits vasodilation induced by ATP-sensitive potassium channels in isolated rat aorta.

Another affiliation: 2 Department of Anesthesiology and Pain Medicine, Gyeongsang National University College of Medicine, Jinju-si, Gyeongsangnam-do, Republic of Korea was added for the author Kyeong-Eon Park at his own request.

Lipid Emulsion Inhibits Amlodipine-Induced Nitric Oxide-Mediated Vasodilation in Isolated Rat Aorta.

This study aimed to examine the effect of lipid emulsion on the vasodilation induced by a toxic dose of amlodipine in isolated rat aorta and elucidate its mechanism, with a particular focus on nitric oxide. The effects of endothelial denudation, NW-nitro-L-arginvine methyl ester (L-NAME), methylene blue, lipid emulsion, and linolenic acid on the amlodipine-induced vasodilation and amlodipine-induced cyclic guanosine monophosphate (cGMP) production were examined. Furthermore, the effects of lipid emulsion, amlodipine, and PP2, either alone or combined, on endothelial nitric oxide synthase (eNOS), caveolin-1, and Src-kinase phosphorylation were examined. Amlodipine-induced vasodilation was higher in endothelium-intact aorta than in endothelium-denuded aorta. L-NAME, methylene blue, lipid emulsion, and linolenic acid inhibited amlodipine-induced vasodilation and amlodipine-induced cGMP production in the endothelium-intact aorta. Lipid emulsion reversed the increased stimulatory eNOS (Ser1177) phosphorylation and decreased inhibitory eNOS (Thr495) phosphorylation induced via amlodipine. PP2 inhibited stimulatory eNOS, caveolin-1, and Src-kinase phosphorylation induced via amlodipine. Lipid emulsion inhibited amlodipine-induced endothelial intracellular calcium increase. These results suggest that lipid emulsion attenuated the vasodilation induced via amlodipine through inhibiting nitric oxide release in isolated rat aorta, which seems to be mediated via reversal of stimulatory eNOS (Ser1177) phosphorylation and inhibitory eNOS (Thr495) dephosphorylation, which are also induced via amlodipine.

Chloroquine inhibits vasodilation induced by ATP-sensitive potassium channels in isolated rat aorta.

This study examined the effect of chloroquine on vasodilation induced by levcromakalim in isolated endothelium-denuded rat aortas and clarified the underlying mechanisms. We examined the effects of chloroquine, hydroxychloroquine, lipid emulsion, reactive oxygen species (ROS) scavenger N-acetyl-ʟ-cysteine (NAC), and KATP channel inhibitor glibenclamide on levcromakaliminduced vasodilation. The effects of chloroquine, hydroxychloroquine, NAC, and levcromakalim on membrane hyperpolarization and ROS production were examined in aortic vascular smooth muscle cells (VSMCs). Chloroquine inhibited levcromakalim-induced vasodilation more than hydroxychloroquine. NAC attenuated chloroquine-mediated inhibition of levcromakalim-induced vasodilation, while lipid emulsion had no effect. Glibenclamide eliminated levcromakalim-induced vasodilation in aortas pretreated with chloroquine. Chloroquine and hydroxychloroquine inhibited levcromakalim-induced membrane hyperpolarization in VSMCs. Chloroquine and hydroxychloroquine both produced ROS, but chloroquine produced more. NAC inhibited chloroquine-induced ROS production in VSMCs. Collectively, these results suggest that, partially through ROS production, chloroquine inhibits levcromakalim-induced vasodilation. In addition, chloroquine-induced KATP channel-induced vasodilation impairment was not restored by lipid emulsion.

Dexmedetomidine-Induced Aortic Contraction Involves Transactivation of the Epidermal Growth Factor Receptor in Rats.

In this study, we examined whether aortic contraction, induced by the alpha-2 adrenoceptor agonist dexmedetomidine, is involved in the transactivation of the epidermal growth factor receptor (EGFR) in isolated endothelium-denuded rat aortas. Additionally, we aimed to elucidate the associated underlying cellular mechanisms. The effects of the alpha-2 adrenoceptor inhibitor rauwolscine, EGFR tyrosine kinase inhibitor AG1478, Src kinase inhibitors PP1 and PP2, and matrix metalloproteinase inhibitor GM6001 on EGFR tyrosine phosphorylation and c-Jun NH2-terminal kinase (JNK) phosphorylation induced by dexmedetomidine in rat aortic smooth muscles were examined. In addition, the effects of these inhibitors on dexmedetomidine-induced contraction in isolated endothelium-denuded rat aorta were examined. Dexmedetomidine-induced contraction was inhibited by the alpha-1 adrenoceptor inhibitor prazosin, rauwolscine, AG1478, PP1, PP2, and GM6001 alone or by a combined treatment with prazosin and AG1478. AG1478 (3 × 10-6 M) inhibited dexmedetomidine-induced contraction in isolated endothelium-denuded rat aortas pretreated with rauwolscine. Dexmedetomidine-induced EGFR tyrosine and JNK phosphorylation were inhibited by rauwolscine, PP1, PP2, GM6001, and AG1478. Furthermore, dexmedetomidine-induced JNK phosphorylation reduced upon EGFR siRNA treatment. Therefore, these results suggested that the transactivation of EGFR associated with dexmedetomidine-induced contraction, mediated by the alpha-2 adrenoceptor, Src kinase, and matrix metalloproteinase, caused JNK phosphorylation and increased calcium levels.

Ultrasound-guided central venous catheterization via internal jugular vein in a patient with subcutaneous neck emphysema: A case report.

In patients with subcutaneous neck emphysema, ultrasound images of the internal jugular vein are unclear due to air bubbles. Central venous catheterization can be safely achieved by pushing the accumulated air laterally using an ultrasound probe.

Lipid Emulsion Enhances Vasoconstriction Induced by Dexmedetomidine in the Isolated Endothelium-Intact Aorta.

This study aimed to examine the effect of lipid emulsion (LE) on the vasoconstriction induced by dexmedetomidine (DMT) in the isolated rat aorta and elucidate the associated cellular mechanism. The effect of LE, NW-nitro-L-arginine methyl ester (L-NAME), and methyl-ß-cyclodextrin (MßCD) on the DMT-induced contraction was examined. We investigated the effect of LE on the DMT-induced cyclic guanosine monophosphate (cGMP) formation and DMT concentration. The effect of DMT, LE, 4-Amino-3-(4-chlorophenyl)-1-(t-butyl)-1H-pyrazolo[3,4-d]pyrimidine,4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2), and rauwolscine on the phosphorylation of endothelial nitric oxide synthase (eNOS), caveolin-1, and Src kinase was examined in the human umbilical vein endothelial cells. L-NAME, MßCD, and LE (1%, standardized mean difference (SMD): 2.517) increased the DMT-induced contraction in the endothelium-intact rat aorta. LE (1%) decreased the DMT (10-6 M) concentration (SMD: -6.795) and DMT-induced cGMP formation (SMD: -2.132). LE (1%) reversed the DMT-induced eNOS (Ser1177 and Thr496) phosphorylation. PP2 inhibited caveolin-1 and eNOS phosphorylation induced by DMT. DMT increased the Src kinase phosphorylation. Thus, LE (1%) enhanced the DMT-induced contraction by inhibition of NO synthesis, which may be caused by the decreased DMT concentration. DMT-induced NO synthesis may be caused by the increased eNOS (Ser1177) phosphorylation and decreased eNOS (Thr495) phosphorylation potentially mediated by Src kinase-induced caveolin-1 phosphorylation.

Reinforced conservative management of post-dural puncture headache in a patient with a rare case of tethered cord syndrome using an abdominal binder: A case report.

An abdominal binder could be used effectively in a patient showing CSF leakage in the coccygeal area with post-dural puncture headache, which is not controlled by conventional compressive dressing.

Lipid emulsion attenuates extrinsic apoptosis induced by amlodipine toxicity in rat cardiomyoblasts.

Amlodipine-induced toxicity has detrimental effects on cardiac cells. The aim of this study was to examine the effect of lipid emulsion on decreased H9c2 rat cardiomyoblast viability induced by amlodipine toxicity. The effects of amlodipine, lipid emulsion, LY 294002, and glibenclamide, either alone or in combination, on cell viability and count, apoptosis, and expression of cleaved caspase-3 and -8, and Bax were examined. LY 294002 and glibenclamide partially reversed lipid emulsion-mediated attenuation of decreased cell viability and count induced by amlodipine. Amlodipine increased caspase-3 and -8 expression, but it did not alter Bax expression. LY 294002 and glibenclamide reversed lipid emulsion-mediated inhibition of cleaved caspase-3 and -8 expression induced by amlodipine. Lipid emulsion inhibited early and late apoptosis induced by amlodipine. LY 294002 and glibenclamide inhibited lipid emulsion-mediated inhibition of late apoptosis induced by amlodipine, but they did not significantly alter lipid emulsion-mediated inhibition of early apoptosis induced by amlodipine. Lipid emulsion decreased amlodipine-induced TUNEL-positive cells. These results suggest that lipid emulsion inhibits late apoptosis induced by amlodipine at toxic dose via the activation of phosphoinositide-3 kinase and ATP-sensitive potassium channels in the extrinsic apoptotic pathway.

Linolenic acid enhances contraction induced by phenylephrine in isolated rat aorta.

This study examined the effect of linolenic acid on the contraction of isolated endothelium-intact and -denuded rat aorta induced by phenylephrine and its underlying mechanism. This was conducted in the presence or absence of NW-nitro-L-arginine methyl ester (L-NAME), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), methylene blue, and calmidazolium. The effects of linolenic acid on contraction induced by calcium chloride in calcium-free Krebs solution containing 60 mM potassium chloride were also examined. Moreover, the effect of linolenic acid on the association between intracellular calcium level ([Ca2+]i) and tension induced by phenylephrine was examined. Finally, we examined the effects of linolenic acid on cGMP formation and endothelial nitric oxide synthase (eNOS) phosphorylation induced by phenylephrine. Linolenic acid (5 × 10-5 M) increased phenylephrine-induced contraction in endothelium-intact aorta (standardized mean difference [SMD] of log ED50: 2.23), whereas it decreased this contraction in endothelium-denuded aorta (SMD: 1.96). L-NAME, ODQ, methylene blue, and calmidazolium increased phenylephrine-induced contraction in endothelium-intact aorta. Linolenic acid decreased contraction induced by calcium chloride in calcium-free Krebs solution containing 60 mM potassium chloride in endothelium-denuded aorta. Linolenic acid caused an increase in [Ca2+]i (SMD at 3 × 10-7 M phenylephrine: 1.63) and calcium sensitivity induced by phenylephrine in endothelium-intact aorta. Conversely, linolenic acid decreased [Ca2+]i (SMD: 0.99) induced by phenylephrine in endothelium-denuded aorta. Linolenic acid decreased cGMP formation and eNOS phosphorylation induced by phenylephrine. These results suggest that linolenic acid increases phenylephrine-induced contraction, which is attributed to linolenic acid inhibition of endothelial NO release rather than its decrease of [Ca2+]i in vascular smooth muscle.

Lipofundin MCT/LCT Inhibits Levcromakalim-Induced Vasodilation by Inhibiting Endothelial Nitric Oxide Release.

The goal of this study was to examine the effect of lipid emulsion on the vasodilation induced by ATP-sensitive potassium (KATP) channels in isolated rat aortae and the underlying mechanism. The effects of Intralipid, containing 100% long-chain fatty acids, and Lipofundin MCT/LCT, containing 50% long-chain fatty acids plus 50% medium-chain fatty acids, on the vasodilation induced by levcromakalim in endothelium-intact aorta with or without NW-nitro-L-arginine methyl ester (L-NAME) and in endothelium-denuded aorta were examined. The effects of L-arginine, L-NAME, glibenclamide, and Lipofundin MCT/LCT, alone or combined, on the levcromakalim-induced vasodilation were examined. Lipofundin MCT/LCT inhibited the levcromakalim-induced vasodilation of isolated endothelium-intact aortae, whereas Intralipid did not. In addition, Lipofundin MCT/LCT had no effect on the levcromakalim-induced vasodilation of endothelium-denuded rat aortae and endothelium-intact aortae with L-NAME. L-arginine and Lipofundin MCT/LCT produced more levcromakalim-induced vasodilation than Lipofundin MCT/LCT alone. Glibenclamide inhibited levcromakalim-induced vasodilation. Levcromakalim did not significantly alter endothelial nitric oxide synthase phosphorylation, whereas Lipofundin MCT/LCT decreased cyclic guanosine monophosphate. Lipofundin MCT/LCT did not significantly alter levcromakalim-induced membrane hyperpolarization. Taken together, these results suggest that Lipofundin MCT/LCT inhibits the vasodilation induced by levcromakalim by inhibiting basally released endothelial nitric oxide, which seems to occur through medium-chain fatty acids.

Linolenic Acid Attenuates the Vasodilation Induced by Acetylcholine in Isolated Rat Aortae.

This study aims to examine the effect of linolenic acid on the vasodilation or vasoconstriction induced by acetylcholine and bupivacaine in isolated rat aortae and its underlying mechanism. The effect of linolenic acid on the vasodilation induced by acetylcholine, the calcium ionophore A23187, sodium nitroprusside, and 8-bromoguanosine 3',5'-cyclic monophosphate sodium salt (bromo-cyclic guanosine monophosphate [bromo-cGMP]) in endothelium-intact and endothelium-denuded aortae was examined. Linolenic acid inhibited vasodilation induced by acetylcholine, calcium ionophore A23187, and sodium nitroprusside. However, this fatty acid increased bromo-cGMP-induced vasodilation in endothelium-denuded aortae. Linolenic acid increased bupivacaine-induced contraction in endothelium-intact aortae, whereas it decreased bupivacaine-induced contraction in endothelium-intact aortae with Nω-nitro-l-arginine methyl ester and endothelium-denuded aortae. Linolenic acid inhibited acetylcholine- and bupivacaine-induced phosphorylation of endothelial nitric oxide synthase. Sodium nitroprusside increased cGMP in endothelium-denuded aortic strips, whereas bupivacaine decreased cGMP in endothelium-intact aortic strips. Linolenic acid decreased cGMP levels produced by bupivacaine and sodium nitroprusside. Together, these results suggest that linolenic acid inhibits acetylcholine-induced relaxation by inhibiting a step just prior to nitric oxide-induced cGMP formation. In addition, linolenic acid-mediated inhibition of vasodilation induced by a toxic concentration (3 × 10-4 M) of bupivacaine seems to be partially associated with inhibition of the nitric oxide-cGMP pathway.

Bupivacaine-induced Vasodilation Is Mediated by Decreased Calcium Sensitization in Isolated Endothelium-denuded Rat Aortas Precontracted with Phenylephrine.

BACKGROUND: A toxic dose of bupivacaine produces vasodilation in isolated aortas. The goal of this in vitro study was to investigate the cellular mechanism associated with bupivacaine-induced vasodilation in isolated endotheliumdenuded rat aortas precontracted with phenylephrine. METHODS: Isolated endothelium-denuded rat aortas were suspended for isometric tension recordings. The effects of nifedipine, verapamil, iberiotoxin, 4-aminopyridine, barium chloride, and glibenclamide on bupivacaine concentration-response curves were assessed in endothelium-denuded aortas precontracted with phenylephrine. The effect of phenylephrine and KCl used for precontraction on bupivacaine-induced concentration-response curves was assessed. The effects of verapamil on phenylephrine concentration-response curves were assessed. The effects of bupivacaine on the intracellular calcium concentration ([Ca(2+)]i) and tension in aortas precontracted with phenylephrine were measured simultaneously with the acetoxymethyl ester of a fura-2-loaded aortic strip. RESULTS: Pretreatment with potassium channel inhibitors had no effect on bupivacaine-induced relaxation in the endothelium-denuded aortas precontracted with phenylephrine, whereas verapamil or nifedipine attenuated bupivacaine-induced relaxation. The magnitude of the bupivacaine-induced relaxation was enhanced in the 100 mM KCl-induced precontracted aortas compared with the phenylephrine-induced precontracted aortas. Verapamil attenuated the phenylephrine-induced contraction. The magnitude of the bupivacaine-induced relaxation was higher than that of the bupivacaine-induced [Ca(2+)]i decrease in the aortas precontracted with phenylephrine. CONCLUSIONS: Taken together, these results suggest that toxic-dose bupivacaine-induced vasodilation appears to be mediated by decreased calcium sensitization in endothelium-denuded aortas precontracted with phenylephrine. In addition, potassium channel inhibitors had no effect on bupivacaine-induced relaxation. Toxic-dose bupivacaine- induced vasodilation may be partially associated with the inhibitory effect of voltage-operated calcium channels.

Systemic blockage of nitric oxide synthase by L-NAME increases left ventricular systolic pressure, which is not augmented further by Intralipid®.

Intravenous lipid emulsions (LEs) are effective in the treatment of toxicity associated with various drugs such as local anesthetics and other lipid soluble agents. The goals of this study were to examine the effect of LE on left ventricular hemodynamic variables and systemic blood pressure in an in vivo rat model, and to determine the associated cellular mechanism with a particular focus on nitric oxide. Two LEs (Intralipid(®) 20% and Lipofundin(®) MCT/LCT 20%) or normal saline were administered intravenously in an in vivo rat model following induction of anesthesia by intramuscular injection of tiletamine/zolazepam and xylazine. Left ventricular systolic pressure (LVSP), blood pressure, heart rate, maximum rate of intraventricular pressure increase, and maximum rate of intraventricular pressure decrease were measured before and after intravenous administration of various doses of LEs or normal saline to an in vivo rat with or without pretreatment with the non-specific nitric oxide synthase inhibitor N(ω)-nitro-L-arginine-methyl ester (L-NAME). Administration of Intralipid(®) (3 and 10 ml/kg) increased LVSP and decreased heart rate. Pretreatment with L-NAME (10 mg/kg) increased LSVP and decreased heart rate, whereas subsequent treatment with Intralipid(®) did not significantly alter LVSP. Intralipid(®) (10 ml/kg) increased mean blood pressure and decreased heart rate. The increase in LVSP induced by Lipofundin(®) MCT/LCT was greater than that induced by Intralipid(®). Intralipid(®) (1%) did not significantly alter nitric oxide donor sodium nitroprusside-induced relaxation in endothelium-denuded rat aorta. Taken together, systemic blockage of nitric oxide synthase by L-NAME increases LVSP, which is not augmented further by intralipid(®).

A Patient with Kikuchi's Disease: What Should Pain Clinicians Do?

Kikuchi's disease (KD) is an idiopathic and self-limiting necrotizing lymphadenitis that predominantly occurs in young females. It is common in Asia, and the cervical lymph nodes are commonly involved. Generally, KD has symptoms and signs of lymph node tenderness, fever, and leukocytopenia, but there are no reports on treatment for the associated myofacial pain. We herein report a young female patient who visited a pain clinic and received a trigger point injection 2 weeks before the diagnosis of KD. When young female patients with myofascial pain visit a pain clinic, doctors should be concerned about the possibility of KD, which is rare but can cause severe complications.

Mepivacaine-induced contraction is attenuated by endothelial nitric oxide release in isolated rat aorta.

Mepivacaine is an aminoamide-linked local anesthetic with an intermediate duration that intrinsically produces vasoconstriction both in vivo and in vitro. The aims of this in-vitro study were to examine the direct effect of mepivacaine in isolated rat aortic rings and to determine the associated cellular mechanism with a particular focus on endothelium-derived vasodilators, which modulate vascular tone. In the aortic rings with or without endothelium, cumulative mepivacaine concentration-response curves were generated in the presence or absence of the following antagonists: N(ω)-nitro-L-arginine methyl ester [L-NAME], indomethacin, fluconazole, methylene blue, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one [ODQ], verapamil, and calcium-free Krebs solution. Mepivacaine produced vasoconstriction at low concentrations (1 × 10(-3) and 3 × 10(-3) mol/L) followed by vasodilation at a high concentration (1 × 10(-2) mol/L). The mepivacaine-induced contraction was higher in endothelium-denuded aortae than in endothelium-intact aortae. Pretreatment with L-NAME, ODQ, and methylene blue enhanced mepivacaine-induced contraction in the endothelium-intact rings, whereas fluconazole had no effect. Indomethacin slightly attenuated mepivacaine-induced contraction, whereas verapamil and calcium-free Krebs solution more strongly attenuated this contraction. The vasoconstriction induced by mepivacaine is attenuated mainly by the endothelial nitric oxide - cyclic guanosine monophosphate pathway. In addition, mepivacaine-induced contraction involves cyclooxygenase pathway activation and extracellular calcium influx via voltage-operated calcium channels.