Perinatal outcome of vaginal delivery with epidural analgesia initiated at the early or late phase of labor period: A retrospective cohort study in the Japanese population.

AIM: We compared the perinatal outcomes of vaginal delivery with epidural analgesia initiated at the early versus late phase in a Japanese population. METHODS: Women enrolled in this retrospective cohort study received intrapartum analgesia via combined spinal epidural analgesia after labor onset between May 2010 and August 2015. We compared the perinatal outcomes between two different timings of epidural analgesia: at the early phase (≤3 cm cervical dilatation) and the late phase (≥4 cm) or at the new definition-based early phase (≤5 cm) and late phase (≥6 cm). RESULTS: One hundred twenty-eight singleton pregnant women were eligible. In nulliparous women, there was no marked difference in perinatal outcomes between the early and late phase except for in the first-stage labor period (13.7 h vs 10.1 h, P = 0.016). In multiparous women, there was no marked difference in perinatal outcomes between the early and late phase except for a higher proportion of Apgar score ≤7 at 1 min in the early phase (20.0% vs 0.0%, P = 0.033). In nulliparous women, the first-stage labor period in the new early phase was significantly longer than in the new late phase (13.3 h vs 6.9 h, P = 0.035). Other variables for nulliparous women and all for multiparous women were not different between the new early and late phases. CONCLUSION: Most perinatal outcomes between the early and late phases of initiated epidural analgesia were not markedly different in our Japanese population, even when using a new definition of labor phase.

Emergency right lower lobectomy for severe pulmonary abscess in a pregnant woman at the 25th week of gestation: a case report.

BACKGROUND: Pulmonary abscess is a severe infection commonly seen in patients with chronic obstructive pulmonary disease, interstitial pneumonia, immune deficiency disease, drug-induced immunocompromised state, and congenital pulmonary disease. The treatment strategy in pregnant women with a pulmonary abscess is considered challenging since adverse effects on the fetus must be avoided to ensure safe delivery. CASE PRESENTATION: A 34-year-old female patient at 24 weeks of gestation (G2P1) was admitted to the Department of Obstetrics and Gynecology due to sudden right chest pain. The patient had no significant medical history, including congenital anomalies, and no history of drug addiction or smoking. Laboratory data indicated high levels of inflammation (white blood cell 12,000/µL, C-reactive protein 16.0 mg/dL), and computed tomography demonstrated a large intrapulmonary cyst located in the middle of the right lower lobe, with some fluid collection. As the patient had no medical history of congenital pulmonary anomalies, she was initially diagnosed with a pulmonary cyst infection and treated with intravenous antibiotics. However, the infection did not resolve for over a week, and a spike in fever developed after admission. There was no definitive evidence concerning the risk of preterm delivery and fetal abortion during non-obstetric surgery. However, to control the severely infected pulmonary abscess that was refractory to antibiotics and obtain a pathological diagnosis while saving the life of both the mother and fetus, we elected to perform an emergent right lower lobectomy by open thoracotomy with a fissureless maneuver after receiving informed consent. Postoperatively, the infection gradually improved, and the patient was discharged on the 16th postoperative day without any major complications in the mother or fetus. Although she later experienced coronavirus disease-19 at 29 weeks of gestation, a boy was born at 40th weeks of gestation without any complications. Pathologically, no infectious agents, malignancies, or congenital anomalies other than lung abscesses associated with the pulmonary infarction were observed. The mother and child were healthy 1 year postoperatively. CONCLUSIONS: We experienced a rare case of a pulmonary abscess in a pregnant woman who needed an emergent right lower lobectomy to control the severe infection and obtain a correct pathological diagnosis. Under cooperation from an obstetrician and anesthesiologist, emergency pulmonary resection can be performed safely for serious abscess formation even for pregnant women who have several months left until delivery.

Survival and unique clinical practices of extremely preterm infants born at 22-23 weeks' gestation in Japan: a national survey.

OBJECTIVES: To investigate prognosis and clinical practices of infants born at 22-23 weeks' gestational age (wkGA) in Japan. DESIGN: A national institutional-level electronic questionnaire surveys performed in September 2021. SETTING: All perinatal centres across Japan. PATIENTS: Infants born at 22-23 wkGA in 2018-2020. MAIN OUTCOME MEASURES: Proportion of active resuscitation and survival at neonatal intensive care unit (NICU) discharge, and various clinical practices. RESULTS: In total, 255 of 295 NICUs (86%) responded. Among them, 145 took care of infants born at 22-23 wkGA and answered the questions regarding their outcomes and care. In most NICUs (129 of 145 (89%)), infants born at 22+0 wkGA can be actively resuscitated. In almost half of the NICUs (79 of 145 (54%)), infants born at ≥22+0 wkGA were always actively resuscitated. Among 341 and 757 infants born alive at 22 and 23 wkGA, respectively, 85% (291 of 341) and 98% (745 of 757) received active resuscitation after birth. Among infants actively resuscitated at birth, 63% (183 of 291) and 80% (594 of 745) of infants born at 22 and 23 wkGA survived, respectively. The survey revealed unique clinical management for these infants in Japan, including delivery with caul in caesarean section, cut-cord milking after clamping cord, immediate intubation at birth, hydrocortisone use for chronic lung disease, analgesia/sedation use for infants on mechanical ventilation, routine echocardiography and brain ultrasound, probiotics administration, routine glycerin enema and skin dressing to prevent pressure ulcers. CONCLUSIONS: Many 22-23 wkGA infants were actively resuscitated in Japan and had a high survival rate. Various unique clinical practices were highlighted.

The role of 20-hydroxyeicosatetraenoic acid in cerebral arteriolar constriction and the inhibitory effect of propofol.

BACKGROUND: We conducted this study to examine, in cerebral parenchymal arterioles, whether 20-hydroxyeicosatetraenoic acid (20-HETE) induces constrictor responses via superoxide and whether propofol reduces this constriction. METHODS: Electrical field stimulation or 20-HETE was applied to rat brain slices monitored by computer-assisted microscopy. In some experiments, a Na(+) channel antagonist tetrodotoxin, a 20-HETE synthesis inhibitor HET0016, a superoxide scavenger, Tiron, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors diphenyleneiodonium (DPI) and gp91ds-tat, or propofol was added. The superoxide level in the brain slice and the production rate in the absence of slices were evaluated by dihydroethidium fluorescence or cytochrome c reduction with a superoxide-generating system, respectively. RESULTS: Electrical stimulation induced constriction of the cerebral parenchymal arteriole, whereas this response was abolished by tetrodotoxin, HET0016, Tiron, or DPI. 20-HETE (10(-8)-10(-6) mol/L) produced arteriolar constriction, which was inhibited by Tiron or DPI. Propofol reduced the constriction induced by electrical stimulation or 20-HETE. 20-HETE induced superoxide production in the brain slice, which was reduced by Tiron, gp91ds-tat, or propofol. However, propofol did not alter the superoxide production rate in the absence of brain slices. CONCLUSIONS: Either neuronal transmission-dependent or exogenous 20-HETE seems to induce cerebral parenchymal arteriolar constriction via superoxide production resulting from NADPH oxidase activation. Propofol is likely to prevent this constriction via inhibition of NADPH oxidase, but not by its scavenging effect on superoxide.

Cholinesterase inhibitor donepezil dilates cerebral parenchymal arterioles via the activation of neuronal nitric oxide synthase.

BACKGROUND: An acetylcholinesterase inhibitor donepezil currently is used to treat patients with Alzheimer disease. However, its direct effect on cerebral blood vessels has not been evaluated. The present study was designed to examine whether donepezil induces acute cerebral arteriolar dilation and whether neuronal nitric oxide synthase contributes to this vasodilator response. METHODS: Brain slices were obtained from neuronal nitric oxide synthase knock-out or C57BL/6J strain (control) mice as well as Wistar rats. Parenchymal arterioles were monitored using videomicroscopy. During constriction to prostaglandin F2alpha (5 x 10 m), donepezil (10-10 m) or acetylcholine (10-10 m) was added. In some experiments, brain slices were treated with a nonselective or a selective nitric oxide synthase inhibitor (N-nitro-L-arginine methyl ester [10 m] and S-methyl-L-thiocitrulline [10 m], respectively). An immunohistochemical analysis was performed using antibodies for neuronal nitric oxide synthase and acetylcholinesterase. RESULTS: Acetylcholine concentration-dependently dilated rat parenchymal arterioles, while S-methyl-L-thiocitrulline as well as N-nitro-L-arginine methyl ester completely abolished this response. Donepezil produced arteriolar dilation, which was inhibited by S-methyl-L-thiocitrulline or N-nitro-L-arginine methyl ester. Donepezil failed to induce arteriolar dilation in the brain slice from the neuronal nitric oxide synthase knock-out mice. Immunohistochemical analysis revealed spatial relationship between neuronal nitric oxide synthase and acetylcholinesterase in the arteriolar wall. CONCLUSIONS: Donepezil produces acute vasodilation induced by a selective activation of neuronal nitric oxide synthase in the cerebral parenchymal arterioles. This agent may be capable of enhancing this enzymatic activity directly or via acetylcholinesterase existing on the arteriolar wall.

Propofol restores brain microvascular function impaired by high glucose via the decrease in oxidative stress.

BACKGROUND: Vascular dysfunction induced by hyperglycemia has not been studied in cerebral parenchymal circulation. The current study was designed to examine whether high glucose impairs dilation of cerebral parenchymal arterioles via nitric oxide synthase, and whether propofol recovers this vasodilation by reducing superoxide levels in the brain. METHODS: Cerebral parenchymal arterioles in the rat brain slices were monitored using computer-assisted videomicroscopy. Vasodilation induced by acetylcholine (10 to 10 m) was obtained after the incubation of brain slices for 60 min with any addition of l-glucose (20 mm), d-glucose (20 mm), or propofol (3 x 10 or 10 m) in combination with d-glucose (20 mm). Superoxide production in the brain slice was determined by dihydroethidium (2 x 10 m) fluorescence. RESULTS: Addition of d-glucose, but not l-glucose, reduced arteriolar dilation by acetylcholine, whereas the dilation was abolished by the neuronal nitric oxide synthase inhibitor S-methyl-l-thiocitrulline (10 m). Both propofol and the superoxide dismutase mimetic Tempol (10 m) restored the arteriolar dilation in response to acetylcholine in the brain slice treated with d-glucose. Addition of d-glucose increased superoxide production in the brain slice, whereas propofol, Tempol, and the nicotinamide adenine dinucleotide phosphate (NAD[P]H) oxidase inhibitor apocynin (1 mm) similarly inhibited it. CONCLUSIONS: Clinically relevant concentrations of propofol ameliorate neuronal nitric oxide synthase-dependent dilation impaired by high glucose in the cerebral parenchymal arterioles via the effect on superoxide levels. Propofol may be protective against cerebral microvascular malfunction resulting from oxidative stress by acute hyperglycemia.

Effects of perinatal blood pressure on maternal brain functional connectivity.

Perinatal hypertensive disorder including pre-eclampsia is a systemic syndrome that occurs in 3-5% of pregnant women. It can result in various degrees of brain damage. A recent study suggested that even gestational hypertension without proteinuria can cause cardiovascular or cognitive impairments later in life. We hypothesized that perinatal hypertension affects the brain functional connectivity (FC) regardless of the clinical manifestation of brain functional impairment. In the present study, we analyzed regional global connectivity (rGC) strength (mean cross-correlation coefficient between a brain region and all other regions) using resting-state functional magnetic resonance imaging to clarify brain FC changes associated with perinatal blood pressure using data from 16 women with a normal pregnancy and 21 pregnant women with pre-eclampsia. The rGC values in the bilateral orbitofrontal gyri were negatively correlated with diastolic blood pressure (dBP), which could not be explained by other pre-eclampsia symptoms. The strength of FC seeding at the left orbitofrontal gyrus was negatively correlated with dBP in the anterior cingulate gyri and right middle frontal gyrus. These results suggest that dBP elevation during pregnancy can affect the brain FC. Since FC is known to be associated with various brain functions and diseases, our findings are important for elucidating the neural correlate of cognitive impairments related to hypertension in pregnancy.

Sevoflurane, but not propofol, prevents Rho kinase-dependent contraction induced by sphingosylphosphorylcholine in the porcine coronary artery.

BACKGROUND: Sphingosylphosphorylcholine may induce coronary vasospasm by the activation of Rho kinase. We designed the current study to examine the differential effects of anesthetics on Rho kinase activation induced by sphingosylphosphorylcholine in porcine coronary arteries. METHODS: Rings of porcine coronary artery without endothelium were prepared in tissue bath containing modified Krebs-Ringer bicarbonate solution. Using isometric force recording, concentration-response curves in response to sphingosylphosphorylcholine were obtained in the absence or in the presence of sevoflurane, propofol, or a selective Rho kinase inhibitor Y27632, which was added 15 min before the application of sphingosylphosphorylcholine. Intracellular translocation of Rho A toward the plasma membrane and phosphorylation of the myosin-targeting subunit of myosin light chain phosphatase were also evaluated by Western blotting. RESULTS: Sphingosylphosphorylcholine (10(-7) to 10(-5) M) produced contraction of the porcine coronary artery, which was abolished by a selective Rho kinase inhibitor Y27632 (2 x 10(-6) M). Sevoflurane (1.7%) reduced sphingosylphosphorylcholine-induced coronary artery constriction, and the higher concentration (3.4%) abolished it (P < 0.05). In contrast, propofol (3 x 10(-6) M and 10(-5) M) had no effect on coronary artery constriction due to sphingosylphosphorylcholine. Sevoflurane, but not propofol, reduced intracellular translocation of Rho A toward the plasma membrane. Sevoflurane and Y27632, but not propofol, similarly decreased (64.4% or 70.8% reduction, respectively, P < 0.05) phosphorylation of the myosin-targeting subunit of myosin light chain phosphatase. CONCLUSIONS: Sphingosylphosphorylcholine induces coronary vasocontriction via activation of Rho kinase. Sevoflurane, but not propofol, inhibits this pathway, resulting in prevention of vasoconstriction.

[Introduction of labor epidural analgesia in Wakayama].

Labor epidural analgesia is unfamiliar to parturients in Wakayama Prefecture partly because of insufficient information and medical services for expectant mothers given by anesthesiologists and other medical staffs. We offered introductory approaches for providing epidural analgesia for labor and delivery in our obstetric care unit. The preliminary survey among midwives, who are crucial for gravitas, revealed their negative attitude to painless labor assisted by epidural technique, while they opted for natural childbirth. Obstetricians also responded negatively toward epidural analgesia during labor because of their concern about forceps and prolonged delivery. We spent considerable time to achieve better communication with midwives and obstetricians in order to improve our professional qualities for caring labor pain. After practical approach of labor epidural analgesia, midwives came to accept epidural analgesia as an option during childbirth.

Augmented activity of adenosine triphosphate-sensitive K+ channels induced by droperidol in the rat aorta.

Droperidol produces the inhibition of K+ channels in cardiac myocytes. However, the effects of droperidol on K+ channels have not been studied in blood vessels. Therefore, we designed the present study to determine whether droperidol modulates the activity of adenosine triphosphate (ATP)-sensitive K+ channels in vascular smooth muscle cells. Rat aortic rings without endothelium were suspended or used for isometric force and membrane potential recordings, respectively. Vasorelaxation and hyperpolarization induced by levcromakalim (10(-8) to 10(-5) M or 10(-5) M, respectively) were completely abolished by the ATP-sensitive K+ channel antagonist glibenclamide (10(-5) M). Droperidol (10(-7) M) and an alpha-adrenergic receptor antagonist phentolamine (3 x 10(-9) M) caused a similar vasodilator effect (approximately 20% of vasorelaxation compared with maximal vasorelaxation induced by papaverine [3 x 10(-4) M]), whereas glibenclamide did not alter vasorelaxation induced by droperidol. Droperidol (3 x 10(-8) M to 10(-7) M) augmented vasorelaxation and hyperpolarization produced by levcromakalim, whereas phentolamine (3 x 10(-9) M) did not alter this vasorelaxation. Glibenclamide (10(-5) M) abolished the vasodilating and hyperpolarizing effects of levcromakalim in the aorta treated with droperidol (10(-7) M). These results suggest that droperidol augments vasodilator activity via ATP-sensitive K+ channels. However, it is unlikely that this augmentation is mediated by the inhibition of alpha-adrenergic receptors in vascular smooth muscles.

Vasodilation mediated by inward rectifier K+ channels in cerebral microvessels of hypertensive and normotensive rats.

Although inward rectifier K+ channels contribute to the regulation of cerebral circulation, dilation of cerebral microvasculature mediated by these channels has not been demonstrated in chronic hypertension. We designed the present study to examine the roles of inward rectifier K+ channels in the vasodilation produced by increased levels of extracellular K+ in cerebral parenchymal arterioles from hypertensive and normotensive rats. During constriction to prostaglandin F2alpha (5 x 10(-7) M), the arterioles within brain slices were evaluated using computer-assisted microscopy. Potassium chloride (KCl) induced vasodilation in cerebral arterioles from normotensive (5-10 mM) and hypertensive (5-15 mM) rats, whereas an inward rectifier K+ channel antagonist barium chloride (BaCl2; 10(-5) M) completely abolished the vasodilation in both strains. In arterioles of hypertensive rats, vasodilator responses to KCl were augmented compared with those in normotensive rats. In contrast, the vasodilator responses induced by sodium nitroprusside (3 x 10(-8) to 3 x 10(-6) M) in these two strains were similar. These results suggest that in cerebral cortex parenchymal microvessels, inward rectifier K+ channels play a crucial role in vasodilation produced by extracellular K+ and that the dilation of cerebral arterioles via these channels is augmented in chronic hypertension.

Inhibitory effect of high concentration of glucose on relaxations to activation of ATP-sensitive K+ channels in human omental artery.

OBJECTIVE: The present study was designed to examine in the human omental artery whether high concentrations of D-glucose inhibit the activity of ATP-sensitive K+ channels in the vascular smooth muscle and whether this inhibitory effect is mediated by the production of superoxide. METHODS AND RESULTS: Human omental arteries without endothelium were suspended for isometric force recording. Changes in membrane potentials were recorded and production of superoxide was evaluated. Glibenclamide abolished vasorelaxation and hyperpolarization in response to levcromakalim. D-glucose (10 to 20 mmol/L) but not l-glucose (20 mmol/L) reduced these vasorelaxation and hyperpolarization. Tiron and diphenyleneiodonium, but not catalase, restored vasorelaxation and hyperpolarization in response to levcromakalim in arteries treated with D-glucose. Calphostin C and Gö6976 simultaneously recovered these vasorelaxation and hyperpolarization in arteries treated with D-glucose. Phorbol 12-myristate 13 acetate (PMA) inhibited the vasorelaxation and hyperpolarization, which are recovered by calphostin C as well as Gö6976. D-glucose and PMA, but not l-glucose, significantly increased superoxide production from the arteries, whereas such increased production was reversed by Tiron. CONCLUSIONS: These results suggest that in the human visceral artery, acute hyperglycemia modulates vasodilation mediated by ATP-sensitive K+ channels via the production of superoxide possibly mediated by the activation of protein kinase C.

Protective effects of anesthetics on vascular function related to K⁺ channels.

K(+) channels play an essential role in the membrane potential of arterial smooth muscle, and also in regulating contractile tone. Especially, in vascular smooth muscle, the opening of adenosine triphosphate (ATP)-sensitive K(+) (KATP) channels leads to membrane hyperpolarization, resulting in muscle relaxation and vasodilation. This activation also plays a role in tissues during pathophysiologic events such as ischemia, hypoxia, and vasodilatory shock. In this review, we will describe the physiological and pathophysiological roles of vascular smooth muscle KATP channels in relation to the effects of anesthetics. Although accumulated evidence suggests that many anesthetics modify the above function of K(+) channels as a metabolic sensor, further studies are certainly needed to resolve certain issues, especially in clinical settings of anesthesia use.

RET PLCγ phosphotyrosine binding domain regulates Ca2+ signaling and neocortical neuronal migration.

The receptor tyrosine kinase RET plays an essential role during embryogenesis in regulating cell proliferation, differentiation, and migration. Upon glial cell line-derived neurotrophic factor (GDNF) stimulation, RET can trigger multiple intracellular signaling pathways that in concert activate various downstream effectors. Here we report that the RET receptor induces calcium (Ca(2+)) signaling and regulates neocortical neuronal progenitor migration through the Phospholipase-C gamma (PLCγ) binding domain Tyr1015. This signaling cascade releases Ca(2+) from the endoplasmic reticulum through the inositol 1,4,5-trisphosphate receptor and stimulates phosphorylation of ERK1/2 and CaMKII. A point mutation at Tyr1015 on RET or small interfering RNA gene silencing of PLCγ block the GDNF-induced signaling cascade. Delivery of the RET mutation to neuronal progenitors in the embryonic ventricular zone using in utero electroporation reveal that Tyr1015 is necessary for GDNF-stimulated migration of neurons to the cortical plate. These findings demonstrate a novel RET mediated signaling pathway that elevates cytosolic Ca(2+) and modulates neuronal migration in the developing neocortex through the PLCγ binding domain Tyr1015.

Roles of phosphatidylinositol 3-kinase-Akt and NADPH oxidase in adenosine 5'-triphosphate-sensitive K+ channel function impaired by high glucose in the human artery.

The present study was designed to examine roles of the phosphatidylinositol 3-kinase-Akt pathway and reduced nicotinamide-adenine dinucleotide phosphate oxidases in the reduced ATP-sensitive K(+) channel function via superoxide produced by high glucose in the human artery. We evaluated the activity of the phosphatidylinositol 3-kinase-Akt pathway, as well as reduced nicotinamide-adenine dinucleotide phosphate oxidases, the intracellular levels of superoxide and ATP-sensitive K(+) channel function in the human omental artery without endothelium. Levels of the p85-alpha subunit and reduced nicotinamide-adenine dinucleotide phosphate oxidase subunits, including p47phox, p22phox, and Rac-1, increased in the membrane fraction from arteries treated with D-glucose (20 mmol/L) accompanied by increased intracellular superoxide production. High glucose simultaneously augmented Akt phosphorylation at Ser 473, as well as Thr 308 in the human vascular smooth muscle cells. A phosphatidylinositol 3-kinase inhibitor LY294002, as well as tiron and apocynin, restored vasorelaxation and hyperpolarization in response to an ATP-sensitive K(+) channel opener levcromakalim. Therefore, it can be concluded that the activation of the phosphatidylinositol 3-kinase-Akt pathway, in combination with the translocation of p47phox, p22phox, and Rac-1, contributes to the superoxide production induced by high glucose, resulting in the impairment of ATP-sensitive K(+) channel function in the human visceral artery.

Synthetic peroxisome proliferator-activated receptor-gamma agonists restore impaired vasorelaxation via ATP-sensitive K+ channels by high glucose.

The present study was designed to examine whether in the human artery, synthetic peroxisome proliferator-activated receptor (PPAR)-gamma agonists restore vasorelaxation as well as hyperpolarization via ATP-sensitive K+ channels impaired by the high concentration of D-glucose and whether the restoration may be mediated by the antioxidant capacity of these agents. The isometric force and membrane potential of human omental arteries without endothelium were recorded. The production rate of superoxide was evaluated using a superoxide-generating system with xanthine-xanthine oxidase in the absence of smooth muscle cells. Glibenclamide abolished vasorelaxation and hyperpolarization in response to levcromakalim. Addition of D-glucose (20 mM) but not L-glucose (20 mM) reduced this vasorelaxation and hyperpolarization. Synthetic PPAR-gamma agonists (troglitazone and rosiglitazone) and/or an inhibitor of superoxide generation (4,5-dihydroxy-1,3-benzene-disulfonic acid, Tiron), but not a PPAR-alpha agonist (fenofibrate), restored vasorelaxation and hyperpolarization in response to levcromakalim in arteries treated with D-glucose. Troglitazone and rosiglitazone, but not fenofibrate, decreased the production rate of superoxide without affecting uric acid generation. These findings suggest that synthetic PPAR-gamma agonists recover the function of ATP-sensitive K+ channels reduced by the high concentration of glucose in human vascular smooth muscle cells and that the effect of these agonists may be mediated in part by their antioxidant capacity.

Inhibitory effects of lidocaine and mexiletine on vasorelaxation mediated by adenosine triphosphate-sensitive K+ channels and the role of kinases in the porcine coronary artery.

BACKGROUND: Effects of antiarrhythmic drugs on coronary vasodilation mediated by K channels have not been studied. Modulator roles of protein kinase C and tyrosine kinase in the activity of K channels have also been unclear in the coronary artery. The current study examined whether lidocaine and mexiletine in the porcine coronary artery modify the vasorelaxation mediated by adenosine triphosphate-sensitive K channels via activation of protein kinase C and tyrosine kinase. METHODS: Porcine coronary arteries without endothelium were suspended for isometric force recording, and vasorelaxation to levcromakalim (10 to 10 m) was obtained. Changes in membrane potentials produced by levcromakalim (10 m) were also recorded. RESULTS: Glibenclamide completely abolished vasorelaxation as well as hyperpolarization in response to levcromakalim. Lidocaine and mexiletine significantly reduced these responses. Calphostin C, Go 6976, genistein, and erbstatin A partly restored vasorelaxation or hyperpolarization in response to levcromakalim in arteries treated with mexiletine but not in those with lidocaine, whereas these inhibitors did not alter the vasorelaxation to levcromakalim. Phorbol 12-myristate 13-acetate produced reduction of vasorelaxation in response to levcromakalim, which is recovered by calphostin C or Go 6976. CONCLUSIONS: Therefore, lidocaine and mexiletine inhibit vasorelaxation mediated by the activation of adenosine triphosphate-sensitive K channels in the coronary artery. Protein kinase C and tyrosine kinase seem to have roles in the inhibitory effect of mexiletine but not in that of lidocaine. Class Ib antiarrhythmic drugs may reduce coronary vasodilation mediated by adenosine triphosphate-sensitive K channels via the differential modulator effects on these kinases.