Kyeong-Eon Park

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.

A supraclinical dose of tramadol stereoselectively attenuates endothelium-dependent relaxation in isolated rat aorta.

Tramadol, a combination of R(−) and S(+) enantiomers, inhibits both the acetylcholine-mediated response of muscarinic receptors and the muscarine-induced accumulation of cyclic guanosine monophosphate. Our goals in this in vitro study were to investigate the effects of tramadol on endothelium-dependent relaxation induced by acetylcholine, to determine whether this effect of tramadol is stereoselective, and to elucidate the associated cellular mechanism in rat aorta. In endothelium-intact rings precontracted with phenylephrine with or without naloxone, dose-response curves for acetylcholine, histamine, and calcium ionophore A23187 were generated in the presence and absence of tramadol (racemic, R(−) and S(+)). Sodium nitroprusside dose-response curves were generated in the presence and absence of racemic tramadol. Racemic tramadol (5 × 10−5 10−4 M) attenuated acetylcholine-induced relaxation in the rings with or without naloxone. R(−) tramadol, 5 × 10−5 M, attenuated acetylcholine-induced relaxation, whereas S(+) tramadol, 5 × 10−5 M, did not. Racemic tramadol (10−4 M) had no effect on dose-response curves for calcium ionophore A23187 or sodium nitroprusside. Taken together, these results indicate that tramadol, at a supraclinical dose (5 × 10−5 M), stereoselectively attenuates endothelium-dependent relaxation via an inhibitory effect at levels proximal to nitric oxide synthase activation on a pathway involving nonspecific endothelial receptor activation.

Propofol has delayed myocardial protective effects after a regional ischemia/reperfusion injury in an in vivo rat heart model

Background It is well known that propofol protects myocardium against myocardial ischemia/reperfusion injury in the rat heart model. The aim of this study was to investigate whether propofol provides a protective effect against a regional myocardial ischemia/reperfusion injury in an in vivo rat heart model after 48 h of reperfusion. Methods Rats were subjected to 25 min of left coronary artery occlusion followed by 48 h of reperfusion. The sham group received profopol without ischemic injury. The control group received normal saline with ischemia/reperfusion injury. The propofol group received profopol with ischemia/reperfusion injury. The intralipid group received intralipid with ischemia/reperfusion injury. A microcatheter was advanced into the left ventricle and the hemodynamic function was evaluated. The infarct size was determined by triphenyltetrazolium staining. The serum level of cardiac troponin-I (cTn-I) was determined by ELISA (enzyme-linked immunosorbent assay). Results Propofol demonstrated protective effects on hemodynamic function and infarct size reduction. In the propofol group, the +dP/dtmax (P = 0.002) was significantly improved compared to the control group. The infarct size was 49.8% of the area at risk in the control group, and was reduced markedly by administration of propofol to 32.6% in the propofol group (P = 0.014). The ischemia/reperfusion-induced serum level of cTn-I was reduced by propofol infusion during the peri-ischemic period (P = 0.0001). Conclusions Propofol, which infused at clinically relevant concentration during the peri-ischemic period, has delayed myocardial protective effect after regional myocardial ischemia/reperfusion injury in an in vivo rat heart model after 48 h of reperfusion.

Inhibitory effect of tramadol on vasorelaxation mediated by ATP-sensitive K+ channels in rat aorta

PurposeTramadol produces a conduction block similar to lidocaine by exerting a local anesthetic-like effect. The aims of this in vitro study were to determine the effects of tramadol on the vasorelaxant response induced by the adenosine triphos-phate-sensitive K+ (KATP) channel opener, levcromakalim, in an endothelium-denuded rat aorta, and to determine whether this effect of tramadol is stereoselective.MethodsThe effects of tramadol (racemic, R(-) and S(+): 10-6, 10−5, 5 × 10−5 M), and glibenclamide on the levcromakalim dose-response curve were assessed in aortic rings that had been pre-contracted with phenylephrine. In the rings pretreated independently with naloxone, and glibenclamide, the levcromakalim dose-response curves were generated in the presence or absence of tramadol. The effect of tramadol on the dose-response curve of diltiazem was assessed.ResultsRacemic, R(-) and S(+) tramadol (10−5, 5 × 10−5 M) attenuated (P < 0.0001) levcromakalim-induced relaxation in the ring with or without naloxone in a dose-dependent manner. The magnitude of the R(-)-tramadol-induced attenuation of vasorelaxant response induced by levcromakalim was greater (P < 0.05) than that induced by S(+)-tramadol. Glibenclamide almost abolished the levcromakalim-induced relaxation. Tramadol, 5 × 10−5 M, did not significantly alter the diltiazem-induced relaxation.ConclusionThese results suggest that a supraclinical dose ( 10−5 M) of tramadol [racemic, R(-) and S(+)] attenuates the vasorelaxation mediated by the KATP channels in the rat aorta. The R(-) tramadol-induced attenuation of vasorelaxation induced by levcromaklim was more potent than that induced by S(+) tramadol. This attenuation is independent of opioid receptor activation.RésuméObjectifLe tramadol produit un bloc de conduction similaire à la lidocaïne en exerçant un effet semblable à celui d’un anesthésique local. Les objectifs de cette étude in vitro étaient de déterminer les effets du tramadol sur la réaction de vasorelaxation induite par le levcromakalim, une molécule provoquant l’ouverture des canaux potassiques (KATP) sensibles à l’adénosine triphosphate, sur l’en-dothélium dénudé de l’aorte de rat, et de déterminer si l’effet du tramadol est stéréosélectif.MéthodeLes effets du tramadol (racémique, R(-) et S(+) : 10−6, 10−6,5 × 10−6 M), et du glibenclamide sur la courbe dose-réponse du levcromakalim ont été évalués sur des anneaux aortiques précontractés avec de la phényléphrine. Sur les anneaux indépendamment prétraités au naloxone et au glibenclamide, les courbes de dose-réponse du levcromakalim ont été générées en présence ou en l’absence de tramadol. L’effet du tramadol sur la courbe dose-réponse du diltiazem a été évalué.RésultatLe tramadol racémique R(-) et S(+) a atténué (P < 0,0001) la relaxation de l’anneau induite par le levcromakalim, avec ou sans naloxone, dépendamment de la dose. L’atténuation induite par le tramadol R(-) sur la réaction de vasorelaxation induite par le levcromakalim était plus grande (P < 0,05) que celle induite par le tramadol S(+). Le glibenclamide a pratiquement aboli la relaxation induite par le levcromakalim. Le tramadol, 5 ×10−6 M, n’a pas modifié significativement la relaxation induite par le diltiazem.ConclusionCes résultats suggèrent qu’une dose supraclinique (10−6 M) de tramadol [racémique, R(-) et S(+)] atténue la vasorelaxation médiée par les canaux KATP dans l’aorte du rat. L’atténuation induite par le tramadol R(-) de la vasorelaxation induite par le levcromakalim était plus puissante que celle induite par le tramadol S(+). Cette atténuation est indépendante d’une activation des récepteurs opiacés.

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 Nω-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®.

Diazepam attenuates phenylephrine-induced contractions in rat aorta.

In this in vitro study we examined the effects of diazepam on a phenylephrine-induced contraction in rat aorta and determined the associated cellular mechanism focusing on the endothelium-derived vasodilators. The concentration-response curves for phenylephrine and potassium chloride were generated in the presence or absence of diazepam. Phenylephrine concentration-response curves were generated from the endothelium-intact rings pretreated independently with NW-nitro-l-arginine methyl ester, PK 11195, tetraethylammonium, and indomethacin in the presence or absence of diazepam. Diazepam (7 × 10−7 M) attenuated the phenylephrine-induced contraction in the endothelium-intact rings, whereas a large dose (5 × 10−6 M) of diazepam attenuated the phenylephrine-induced contraction in the aortic rings with or without the endothelium. A pretreatment with the NW-nitro-l-arginine methyl ester completely abolished the diazepam (7 × 10−7 M)-induced attenuation of the phenylephrine concentration-response curve, as well as the diazepam (5 × 10−6 M)-induced attenuation of the maximal contractile response to phenylephrine. The NW-nitro-l-arginine methyl ester (10−4 M)-induced contraction was enhanced in the rings pretreated with diazepam (5 × 10−6 M). These results indicate that a supraclinical concentration of diazepam attenuates phenylephrine-induced contraction by increasing endothelial nitric oxide activity and directly affecting vascular smooth muscle.

Alfentanil attenuates phenylephrine-induced contraction in rat aorta.

Background and objectives: Alfentanil was reported to relax the rat aorta by direct action on the vascular smooth muscle. The aims of this in vitro study were to examine the effect of alfentanil on phenylephrine‐induced contractions in the rat aorta and to determine the cellular mechanism associated with this process. Methods: Endothelium‐denuded aortic rings were suspended in order to record isometric tension. In the rings with or without 10−6 mol naloxone or 10−5 mol verapamil, the concentration–response curves for phenylephrine and potassium chloride were generated in the presence or absence of alfentanil (10−6, 5 × 10−5, 10−4 mol). In the rings exposed to a calcium‐free isotonic depolarizing solution, the contractile response induced by the addition of calcium was assessed in the presence or absence of alfentanil (5 × 10−5, 10−4 mol). Results: Alfentanil (5 × 10−5, 10−4 mol) attenuated (P < 0.05) the phenylephrine‐induced contraction in the ring with or without 10−6 mol naloxone but had no effect on the phenylephrine‐induced contraction in the rings pretreated with verapamil. Alfentanil (5 × 10−5, 10−4 mol) produced a significant rightward shift (P < 0.01) in the potassium chloride dose–response curve, and attenuated the contractile response (P < 0.001) induced by calcium in the calcium‐free isotonic depolarizing solution in a dose‐dependent manner. Conclusions: A supraclinical dose of alfentanil attenuates the phenylephrine‐induced contraction via an inhibitory effect on calcium influx by blocking the l‐type calcium channels in the rat aortic vascular smooth muscle.

Inhibitory Effect of Fentanyl on Phenylephrine-Induced Contraction of the Rat Aorta

Purpose Fentanyl was reported to inhibit the α1-adrenoceptor agonist-induced contraction. The goal of this in vitro study was to identify the α1-adrenoceptor subtype primarily involved in the fentanyl-induced attenuation of phenylephrine-induced contraction in isolated endothelium-denuded rat aorta. Materials and Methods Aortic rings were suspended in order to record isometric tension. Concentration-response curves for phenylephrine (10-9 to 10-5 M) were generated in the presence or absence of one of the following drugs: fentanyl (3×10-7, 10-6, 3×10-6 M), 5-methylurapidil (3×10-8, 10-7, 3×10-7 M), chloroethylclonidine (10-5 M) and BMY 7378 (3×10-9, 10-8, 3×10-8 M). Phenylephrine concentration-response curves were generated in the presence or absence of fentanyl in rings pretreated with either 3×10-9 M prazosin, 10-9 M 5-methylurapidil or 3×10-9 M BMY 7378. Results Fentanyl (10-6, 3×10-6 M) attenuated phenylephrine-induced contraction in the rat aorta. 5-Methylurapidil and BMY 7378 produced a parallel rightward shift in the phenylephrine concentration-response curve. The pA2 values for 5-methylurapidil and BMY 7378 were estimated to be 7.71 ± 0.15 and 8.99 ± 0.24, respectively. Fentanyl (10-6 M) attenuated phenylephrine-induced contraction in rings pretreated with 10-9 M 5-methylurapidil, but did not alter the rings when pretreated with 3×10-9 M BMY 7378. Pretreatment of the rings with chloroethylclonidine showed a 72.9 ± 2.3% reduction in phenylephrine-induced maximal contraction. Conclusion The results suggest that fentanyl attenuates phenylephrine-induced contraction by inhibiting the pathway involved in the α1D-adrenoceptor-mediated contraction of the rat aorta.

Phantom bladder pain

A phantom syndrome is a pain syndrome that occurs when part of the body, such as the nose, tongue, breast, tooth, testis, penis, bladder, or anus, has been lost as the result of an accident or operation. Its frequency and etiology remain unclear [1]. Phantom bladder pain is a rare phantom syndrome that has not been reported previously in South Korea. This phantom urinary phenomenon occurs in patients with cystectomies, undergoing hemodialysis, or after spinal cord injury, in the forms of lower abdominal pain during urination, frequent urination, acute inconvenience with a full-bladder sensation, or urination with a sharp and burning pain [2]. Here, we report a patient who acquired phantom bladder pain 2 years after a cystectomy; pain was controlled successfully through a sympathetic ganglion block. A 59-year-old male patient presented with paroxysmal urgency and extreme pain accompanying bladder fullness and a bursting sensation that had started 1 month previously. He had undergone a cystectomy and prostatectomy, Miles operation, and uretero-ileal conduit 2 years earlier due to rectal cancer. Defecation and urination were achieved through the connection of a colostomy and uretero-ileal conduit. A phantom sensation of the anus occurred a few months after the Miles operation, but without pain or any other inconvenience. Thus, the patient did not undergo any further treatment. Owing to celiac metastasis with leakage, an ileo-colic anastomosis had been conducted 7 months before his visit to the pain clinic, and one month before his visit the patient had complained of bladder fullness and a bursting sensation with a desire to micturate and defecate. A spasmolytic agent, tiropramide 100 mg, was prescribed but resulted in no improvement. A psychiatric consultation revealed that the patient had clear consciousness without depression. The pain was increasing in frequency and strength, and the patient reported a continuous burning sensation with an intermittent sharp stinging sensation in the suprapubic region about 30 times per day. He scored the continuous pain as 6 on a visual analog scale (VAS), and he scored the intermittent paroxysmal pain that lasted 20-30 min as 9-10. No aggravating or relieving factors were present, and no related symptoms were observed, except sleep disorders due to the pain. Gabapentin 1,200 mg/d, amitriptyline 10 mg/d, oxycodone 40 mg/d, and a fentanyl patch 50 µg/h were provided with no effect. We injected 0.5% bupivacaine dextrose 6 mg into the patients L4/5 subarachnoid space, and required him to maintain a sitting position for 30 min to exclude a sympathetic ganglion blocking effect. The pain decreased to VAS 4 temporarily, then returned to the same level after 12 h. Then, a lumbar sympathetic ganglion block was conducted instead of a superior hypogastric plexus block. The needle was placed on the lower one-third of the L2 vertebral body using a C-arm fluoroscope, then 0.5% bupivacaine 5 ml was injected on the left, followed by confirmation of a warm sensation in the left foot. Then, the block was done on the right side, and the warm sensation was felt on the right side too. Because the VAS score diminished to 5, treatment with a neurolytic agent was advised, but lumbar sympathetic ganglion block at both the L2 and L3 levels was conducted two more times at the patients request. The pain decreased to VAS 1-2, without recurrence, so the patient was discharged after 2 weeks. Phantom limb pain is well-known, but other phantom pains are rare. A phantom sensation and pain can occur in almost any organ, and is difficult to control despite the use of various drugs. A phantom sensation appears in 25% of patients 3 months after a mastectomy, and is consistent a year after the operation, and phantom pain appears in 13% of these patients. Additionally, 10-20% of patients report phantom pain of the anus after anal excision due to rectal cancer. However, phantom pain of the bladder is rarely reported. Brena and Sammons [2] reported phantom pain after cystectomy due to intractable cystitis, and the effects of lumbar sympathetic ganglion block. Fonseca et al. [3] reported phantom pain after metastatic bladder cancer operations. The nerve system of the bladder is not fully understood, but is divided into a parasympathetic nerve system, starting from the sacral nerve and continuing to the pelvic nerve, and a sympathetic nerve system, from the lower thoracic and upper lumbar vertebrae via the hypogastric nerve. The bladder base is occupied by a terminal nerve of the hypogastric nerve, and the pelvic nerve is widely distributed throughout the bladder. The pelvic nerve, the A-delta, and the C fiber of the hypogastric nerve convey mechanosensitive reactions by sending urgency and pain signals when the bladder is expanded, not during bladder filling. The afferent fiber of the bladder changes according to bladder tissue status. For example, the bladder indicates urgency and pain during inflammation by overexcitement of afferent C fibers [4]. Generally, internal organs indicate extreme pain with strong expansion and contraction, and the pain is stronger with ischemia [4]. The sympathetic hypogastric nerve is important in the urgent and painful sensations of the pathological bladder. The effectiveness of sympathetic ganglion block has been reported in intractable interstitial cystitis that was not improved with repeated or continuous epidural block. Some reports indicate that sympathetic ganglion block is effective in deafferentation pain [5]. In this case, a saddle block was attempted to exclude effects of the sympathetic nerve, but it resulted in only temporary pain relief. Next, a sympathetic nerve block was planned with a lumbar sympathetic nerve block; this procedure resulted in marked pain relief, presumably because phantom limb pain is widely distributed deafferentation pain as a result of amputation of autonomic and somatic nerve systems, while internal organs have only autonomic nerve systems. This difference might also explain the remarkable result of the sympathetic nerve block. Because the nerve system of the bladder is not completely understood, the mechanosensitive reactions of the A-delta and C fibers require more study to clarify the neuronal mechanism(s) behind phantom bladder pain.