Takeyoshi Sata

The Effects of Tramadol and Its Metabolite on Glycine, ??-Aminobutyric AcidA, and N-Methyl-d-Aspartate Receptors Expressed in Xenopus Oocytes

We assessed the effects of tramadol, a centrally acting analgesic, and its major metabolite, on neurotransmitter-gated ion channels. Tramadol binds to &mgr;-opioid receptors with low affinity and inhibits reuptake of monoamines in the central nervous system. These actions are believed to primarily contribute to its antinociceptive effects. However, little is known about other sites of tramadols action. We tested the effects of tramadol and its M1 metabolite (0.1–100 &mgr;M) on human recombinant neurotransmitter-gated ion channels, including glycine, γ-aminobutyric acidA (GABAA), and N-methyl-d-aspartate (NMDA) receptors, expressed in Xenopus oocytes. Tramadol and M1 metabolite did not have any effects on glycine receptors. GABAA receptors were significantly inhibited only at large concentrations (100 &mgr;M). NMDA receptors were inhibited in a concentration-dependent manner. Tramadol and M1 metabolite inhibited the glutamate-concentration response curve without changing the half-maximal effective concentration or the Hill coefficient, indicating a noncompetitive inhibition. This study suggests that glycine receptors do not provide the antinociceptive effect of tramadol and that the inhibition of GABAA receptors at large concentration might correlate with convulsions. The inhibitory effect on NMDA receptors may contribute to the antinociceptive effect of tramadol at relatively large concentrations.

Cricoid pressure impedes positioning and ventilation through the laryngeal mask airway

PurposeTo assess the effect of cricoid pressure on the positioning of and ventilation through the laryngeal mask airway (LMA).MethodsIn a double-blind, randomized design, the LMA was inserted with (CP[+] group, n = 20) or without double-handed cricoid pressure (CP[−] group, n = 20). Ventilation through the LMA was assessed by measuring expiratory tidal volume and judged as adequate when a mean expiratory tidal volume of ≥10 ml · kg−1 could be obtained. The LMA position was examined by fibreoscopy. The position of the mask relative to the cricoid cartilage and the cervical spine was radiologically examined (n = 10 in each group).ResultsVentilation was adequate in all patients in the CP[−] group but in only five patients (25%) of the CP[+] group (P < 0.001). The glottis was visible fibreoptically below the mask aperture in all patients in the CP[−] group, but in only three patients in the CP[+] group (P < 0.001). Fibreoscopy showed that the mask was not inserted far enough in the remaining 17 patients of the CP[+] group. The reason for unsuccessful ventilation in the CP[+] group was excessive gas leakage (n = 2) and/or partial or complete airway obstruction (n = 13), which was noted fibreoptically. The radiographs showed that the tip of the mask in the CP[−] group was located below the level of the cricoid cartilage (C6 or C7 vertebra). The mask tip in the CP[+] group was above this level (C4 or C5 vertebra) (P < 0.01).ConclusionCricoid pressure impedes positioning of and ventilation through the LMA.RésuméObjectifVérifier l’influence de la pression cricoïdienne sur la ventilation au masque laryngé (ML) et son positionnement.MéthodesAu cours de cette étude aléatoire et en double aveugle, le LM a été inséré avec (groupe CP[+], n = 20) ou sans pression cricoïdienne manuelle (groupe CP[−], n = 20). La ventilation par masque laryngée était évaluée par la mesure du volume courant expiré et jugée suffisante lorsqu’on obtenait un volume minute expiré ≥10 ml · kg−1. La position du ML était vérifiée par fibroscopie. Chez dix patients de chaque groupe, l’examen radiologique a déterminé la position du ML relativement au cartilage cricoïde et à la colonne cervicale.RésultatsLa ventilation a été adéquate chez tous les patients du groupe CP[−] mais chez seulement cinq (25%) du groupe CP[+] (P < 0,001). La glotte était visible par fibroscopie sous l’ouverture du masque chez tous les patients du groupe CP[−], mais chez seulement trois du groupe CP[+]. La fibroscopie a montré que le masque n ’était pas inséré assez profondément chez les 17 autres patients du groupe CP[+]. Cet échec ventilatoire dans le groupe CP[+] était causé par une fuite de gaz exagérée (n = 2) ou/et par l’obstruction des voies aériennes partielle ou complète (n = 13), vérifiée par fibroscopie. Les radiographies ont révélé que la pointe du masque dans le groupe CP[−] était située sous le niveau du cartilage cricoïde (C6 ou C7). Dans le groupe CP[+], la pointe du masque était située à un niveau plus élevé (C4 ou C5, P < 0,01).ConclusionLa pression cricoïdienne nuit et à la ventilation au masque laryngé et a son positionnement.

Inhibitory Effect of Adrenomedullin on Rat Mesangial Cell Mitogenesis

We investigated the effects of adrenomedullin on rat mesangial cell proliferation. Adrenomedullin (10(-10)-10(-7) M inhibited both [3H]thymidine incorporation into cultured rat mesangial cells and cell proliferation in a concentration-dependent manner. Adrenomedullin (10(-10)-10(-6) M) stimulated cyclic adenosine monophosphate accumulation in rat mesangial cells in a concentration-dependent manner. These findings suggest that adrenomedullin inhibits proliferation of rat mesangial cells probably through a cyclic adenosine monophosphate-dependent mechanism.

KETAMINE INTERACTS WITH THE NORADRENALINE TRANSPORTER AT A SITE PARTLY OVERLAPPING THE DESIPRAMINE BINDING SITE

Effects of the intravenous anaesthetic ketamine on the desipramine-sensitive noradrenaline transporter (NAT) were examined in cultured bovine adrenal medullary cells and in transfected Xenopus laevis oocytes expressing the bovine NAT (bNAT). Incubation (1–3 h) of adrenal medullary cells with ketamine (10–300 µM) caused an increase in appearance of catecholamines in culture medium. Ketamine (10–1000 µM) inhibited desipramine-sensitive uptake of [3H] noradrenaline (NA) (IC50=97 µM). Saturation analysis showed that ketamine reduced Vmax of [3H]NA uptake without changing Km, indicating a non-competitive inhibition. Other inhibitors of NAT, namely cocaine and desipramine, showed a competitive inhibition of [3H]NA uptake while a derivative of ketamine, phencyclidine, showed a mixed type of inhibition. Ketamine (10–1000 µM) also inhibited the specific binding of [3H]desipramine to plasma membranes isolated from bovine adrenal medulla. Scatchard analysis of [3H]desipramine binding revealed that ketamine increased Kd without altering Bmax, indicating a competitive inhibition. In transfected Xenopus oocytes expressing the bNAT, ketamine attenuated [3H]NA uptake with a kinetic characteristic similar to that of cultured adrenal medullary cells. These findings are compatible with the idea that ketamine non-competitively inhibits the transport of NA by interacting with a site which partly overlaps the desipramine binding site on the NAT.

The Antinociceptive Effect of Intrathecal Administration of Glycine Transporter-2 Inhibitor ALX1393 in a Rat Acute Pain Model

BACKGROUND: Glycinergic neurons in the spinal dorsal horn have been implicated in the inhibition of spinal pain processing in peripheral inflammation and chronic pain states. Neuronal isoform glycine transporter-2 (GlyT2) reuptakes presynaptically released glycine and regulates the glycinergic neurotransmission. In this study, we examined whether a selective GlyT2 inhibitor, ALX1393, elicits an antinociceptive effect in a rat acute pain model. METHODS: Male Sprague-Dawley rats were implanted with a catheter intrathecally. The effects of intrathecal administration of ALX1393 (4, 20, or 40 &mgr;g) on thermal, mechanical, and chemical nociception were evaluated by tail flick, hot plate, paw pressure, and formalin tests. Furthermore, to explore whether ALX1393 affects motor function, a rotarod test was performed. RESULTS: ALX1393 exhibited antinociceptive effects on the thermal and mechanical stimulations in a dose-dependent manner. The maximal effect of ALX1393 was observed at 15 min after administration, and a significant effect lasted for about 60 min. These antinociceptive effects were reversed completely by strychnine injected immediately after the administration of ALX1393. In the formalin test, ALX1393 inhibited pain behaviors in a dose-dependent manner, both in the early and late phases, although the influence was greater in the late phase. In contrast to antinociceptive action, ALX1393 did not affect motor function up to 40 &mgr;g. CONCLUSIONS: This study demonstrates the antinociceptive action of ALX1393 on acute pain. These findings suggest that the inhibitory neurotransmitter transporters are promising targets for the treatment of acute pain and that the selective inhibitor of GlyT2 could be a novel therapeutic drug.

The Mechanism of Inhibitory Actions of Propofol on Rat Supraoptic Neurons

BACKGROUND In the perioperative period, plasma osmotic pressure, systemic blood pressure, and blood volume often change dramatically. Arginine vasopressin is a key factor in the regulation of these parameters. This study was performed to evaluate the direct and the mechanism of the actions of propofol on arginine vasopressin release from magnocellular neurosecretory neurons in the rat supraoptic nucleus. METHODS Somatodendritic arginine vasopressin release from supraoptic nucleus slice preparations was measured by radioimmunoassay. Ionic currents were measured using the whole-cell mode of the patch-clamp technique in supraoptic nucleus slice preparations or in single dissociated supraoptic nucleus neurons of the rat. RESULTS Propofol at concentrations greater than 10(-5) M inhibited the arginine vasopressin release stimulated by potassium chloride (50 mM). This inhibition by propofol was not reversed by picrotoxin, a gamma-aminobutyric acid(A)(GABA(A)) receptor antagonist, whereas arginine vasopressin release induced by glutamate (10(-3) M) was also inhibited by propofol at a clinically relevant concentration (10(-6) M). The latter effect was reversed by picrotoxin. Propofol evoked Cl- currents at concentrations ranging 10(-6) to 10(-4) M. Propofol (10(-6) M) enhanced the GABA (10(-6) M)-induced current synergistically. Moreover, propofol (10(-6) M) prolonged the time constant of spontaneous GABA-mediated inhibitory postsynaptic currents. Furthermore, propofol (10(-5) M and 10(-4) M) reversibly inhibited voltage-gated Ca2+ currents, whereas it did not affect currents induced by glutamate (10(-3) M). CONCLUSIONS Propofol inhibits somatodendritic arginine vasopressin release from the supraoptic nucleus, and the enhancement of GABAergic inhibitory synaptic inputs and the inhibition of voltage-gated Ca2+ entry are involved in the inhibition of arginine vasopressin release.

Gargling with sodium azulene sulfonate reduces the postoperative sore throat after intubation of the trachea

Postoperative sore throat (POST) is a complication that remains to be resolved in patients undergoing endotracheal intubation. In this study, we investigated whether preoperative gargling with sodium 1,4-dimethyl-7-isopropylazulene-3-sulfonate monohydrate (sodium azulene sulfonate, Azunol) reduces POST after endotracheal intubation. Forty patients scheduled for elective surgery under general anesthesia were randomized into Azunol and control groups. In the Azunol group, patients gargled with 4 mg Azunol diluted with 100 mL tap water (40 &mgr;g/mL). In the control group, patients gargled with 100 mL of tap water. After emergence from general anesthesia, the patients with POST were counted and POST was evaluated using a verbal analog pain scale. There were no significant differences between the two groups by age, height, body weight, gender distribution, or duration of anesthesia and surgery. In the control group, 13 patients (65%) complained of POST, which remained 24 h later in nine patients (45%). In the Azunol group, five patients (25%) also complained of POST, which completely disappeared by 24 h later. The incidence of POST and verbal analog pain scale scores in the Azunol group decreased significantly compared with the control group. We demonstrated that gargling with Azunol effectively attenuated POST with no adverse reactions.

Inhibition of TASK1‐like channels by muscarinic receptor stimulation in rat adrenal medullary cells

The muscarinic receptor is known to be involved in the acetylcholine‐induced secretion of catecholamines in the adrenal medulla (AM) cells of various mammals. The ionic mechanisms, however, have not been elucidated yet. Thus, we investigated the issue in acutely isolated rat AM cells with the perforated patch clamp method. Bath application of 30 μM muscarine induced depolarization with the consequent generation of action potentials or an inward current at negative membrane potentials. The muscarine‐sensitive current instantaneously changed in amplitude upon application of command pulses without a time‐dependent component, altered the polarity as a K+‐electrode, and showed rectification of the Goldman‐Hodgkin‐Katz (GHK) type. The whole‐cell current at −20 mV was inhibited by external H+ ions with a concentration responsible for half inhibition of pH 7.09 and muscarine failed to induce a further inward current during exposure to a saline in which pH decreased to 6.5. A similar occlusion occurred in secretion when pH in muscarine‐containing saline decreased to 6.6. RT‐PCR, immunoblotting, and immunocytochemistry suggested that rat AM cells mainly express the TASK1 channel. This TASK channel in AM cells may directly sense a decrease in blood pH, which occurs during exercise. The muscarine action was mimicked by oxotremorine–methiodide, but not by oxotremorine. The present results indicate that activation of muscarinic receptors or a decrease in external pH in the rat AM cell induces secretion through the inhibition of TASK1‐like channels.

The triple airway manoeuvre for insertion of the laryngeal mask airway in paralyzed patients.

The efficacy of the triple airway manoeuvre (mouth opening, head extension and jaw thrust) for insertion of the laryngeal mask airway (LMA) was compared with the standard insertion method. One hundred paralyzed patients were allocated randomly into two groups: in the control group (n = 50) the LMA was inserted by the standard method, and in the other (TAM group, n = 50) by the triple airway manoeuvre. In ten patients of each group, the position of the LMA and the epiglottis was assessed radiographically before insertion, after insertion but before cuff inflation, and after cuff inflation. In all patients the position was examined using fibrescopy before and after cuff inflation. The mean distance between the epiglottis and the posterior pharyngeal wall, measured radiographically before LMA insertion, was greater in the TAM group (16.3 (SD 4.3) mm) than in the control group (7.0 (2.8) mm) (P < 0.001). Before cuff inflation, radiography and fibrescopy showed that the LMA compressed the epiglottis downwards more frequently in the control group. After cuff inflation the glottis was completely visible fibreoptically in 66% in the TAM group, compared with 14% in the control group (P < 0.001). Complete downfolding of the epiglottis was seen in 10% in the control group and none in the TAM group (P < 0.05). We conclude that in paralyzed patients LMA insertion with the triple airway manoeuvre provides wider pharyngeal space and decreases the incidence of epiglottic downfolding by the LMA compared with the standard method.RésuméCette étude compare avec la méthode d’insertion standard, l’efficacité de la triple manoeuvre de libération des votes aériennes (ouverture de la bouche, extension de la tête et élévation du mandibule) pour l’insertion du masque laryngé (ML). Cent patients paralysés sont répartis au hasard entre deux groupes: dans le groupe contrôle (n = 50), le ML est inséré suivant la méthode standard, et dans l’autre (le groupe TM = 50) suivant la triple manoeuvre. Chez dix patients de chaque groupe, la position du ML et de l’épiglotte est évaluée par radiographie, avant l’insertion, après l’insertion et avant l’insufflation de la manchette, et après celleci. Chez tons les patients, la position a été vérifiée par fibroscopie avant et après l’insufflation. La distance moyenne entre l’épiglotte et la paroi pharyngée postérieure, mesurée par radiographie avant l’insertion du ML, est plus grande dans le groupe TM (16,3 ± ET 4,3 mm) que dans le groupe contrôle (7,0 ± 2,8 mm) (P < 0,001). Avant l’insufflation de la manchette, la radiographie et la fibroscopie montrent que le ML comprime l’épiglotte vers le bas plus fréquemment dans le groupe contrôle. Après l’insufflation de la manchette, la glotte est visualisée dans son entier par fibroscopie chez 66% du groupe TM comparativement à 14% du groupe contrôle (P < 0,001). Un affaissement complet de l’épiglotte est constaté chez 10% du groupe contrôle et chez aucun patient du groupe TM (P < 0,05). Les auteurs concluent que pour l’insertion du ML chez les patients paralysés, la triple manoeuvre procure un espace pharyngé plus vaste et diminue l’incidence de l’affaissement de l’épiglotte par le ML comparativement à la méthode standard.

The effects of the local anesthetics Lidocaine and procaine on glycine and γ-aminobutyric acid receptors expressed in Xenopus oocytes

BACKGROUND:The voltage-dependent sodium channel is the primary site of action for local anesthetics (LAs). Although systemically administered low-dose LAs have been shown to exert antihyperalgesic effects, the molecular targets responsible for these effects are not fully known and their functional effects on inhibitory neurotransmitter receptors associated with antinociception have not been sufficiently studied. METHODS:We examined the effects of lidocaine and procaine (0.1 &mgr;M to 3 or 10 mM) on recombinant human &agr;1 glycine, &agr;1&bgr;2&ggr;2S &ggr;-aminobutyric acid type A (GABAA), and &rgr;1 GABAC receptors expressed in Xenopus laevis oocytes, using a two-electrode voltage-clamp system. We also evaluated the effects of LAs on two mutant glycine receptors, &agr;1(S267C) and &agr;1(S267Q), in an effort to clarify the interaction between LAs and glycine receptors. RESULTS:Low concentrations of both lidocaine and procaine enhanced glycine receptor function, whereas high concentrations of lidocaine and procaine inhibited glycine receptor function. Lidocaine (10 &mgr;M) produced a significant leftward shift in the glycine concentration-response curve, indicating an increase in the apparent affinity for glycine. This enhancement was not altered in the mutant receptors. Both lidocaine and procaine at high concentrations inhibited GABAA receptor currents, whereas neither lidocaine nor procaine affected GABAC receptor function. CONCLUSIONS:Lidocaine and procaine enhanced glycine receptor function at low concentrations and inhibited the functions of glycine and GABAA receptors at high concentrations. The mechanism of the LA-induced enhancement of glycine receptor function probably differs from that of general anesthetics. These findings may explain the pharmacological effects of LAs, such as antinociception and convulsion.