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PubMedDate not supplied

[Possible mechanism of the regulation of smooth muscle relaxation by calcium ions].

Kinetics of Ca2+ energy-dependent transport in sarcolemma and mitochondrion fractions of myometrium was studied. On the basis of the results obtained the mechanism of calcium control of smooth muscle relaxation was analysed. In terms of this mechanism kinetic curves of myometrium relaxation were calculated. It follows from their pattern that the mitochondria play the role of the main intercellular depo of Ca2+, while the calcium pump of the sarcolemma carries out fine regulation of this process making its contribution to relaxation at its later stage.

Animals↗
PubMed1984

Effect of some smooth muscle relaxant drugs on calcium-related phenomena.

Some smooth muscle relaxant drugs devoid of anticholinergic action have been tested for their interaction with calmodulin, calmodulin-stimulated cyclic nucleotide phosphodiesterase activity, and uterine membrane binding sites for nitrendipine and adenosine. The myolytic activity of octylonium bromide and pinaverium bromide may be due to their interaction with calmodulin-dependent systems. Trimebutine maleate does not bind either to calmodulin or to nitrendipine and adenosine receptors. Tiropramide has no effect on calmodulin-dependent systems and on Ca2+ channels but it shows a competition for the A2-type adenosine receptors.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1995

New skeletal muscle relaxants.

In a little over 10 years, six new muscle relaxants have been introduced in clinical practice. The first two, intermediate-duration vecuronium and atracurium, were outstanding drugs and clearly an advance over the earlier, longer-acting drugs. With their introduction, the phenomenon of "recurarization" largely disappeared. The next two, long-acting doxacurium and pipecuronium, were relics of an earlier era and have made little clinical impact. Mivacurium created a new class, the short-acting nondepolarizing relaxant, and caused succinylcholine to be reclassified as an ultra-short-acting drug. However, mivacurium has neither the rapid onset nor the ultra-short duration of succinylcholine. Rocuronium is the first nondepolarizing relaxant with an onset approaching that of succinylcholine. It is likely that we will see the introduction of at least two more drugs, Org 9487 and 51W89, by the end of this decade, and the goal of developing a nondepolarizing relaxant that is a complete replacement for succinylcholine may not be too far in the future.

Androstanols↗
PubMed1989

Electrophysiological studies with a 2,3-benzodiazepine muscle relaxant: GYKI 52466.

The effects of GYKI 52466, a new 2,3-benzodiazepine with muscle relaxant and anticonvulsant properties, were investigated and compared to those of midazolam in electrophysiological experiments. The effects of the drugs on the reflex potentials evoked by afferent nerve stimulation and recorded from the spinal roots in unanesthetized spinal cats were studied. GYKI 52466 exerted a strong inhibitory effect on the monosynaptic as well as the polysynaptic ventral root reflexes, while the dorsal root responses decreased slightly. In contrast, midazolam markedly enhanced the dorsal root responses, did not modify the monosynaptic reflex and partially inhibited the polysynaptic reflex. The spontaneous firing of cerebellar Purkinje cells was depressed by midazolam, but not by GYKI 52466. These results suggest strongly that, contrary to the classical 1,4-benzodiazepines, potentiation of the GABA-A receptor-mediated inhibition does not play a significant role in the pharmacological actions of GYKI 52466.

Animals↗
PubMed2004

Propofol and remifentanil for intubation without muscle relaxant: the effect of the order of injection.

BACKGROUND: Common practice in intubation without muscle relaxant is to inject the opioid drug prior to the hypnotic drug. Because remifentanil reaches adequate cerebral concentration more rapidly than does propofol, we tested the hypothesis that injection of remifentanil after propofol might lead to better intubating conditions. METHODS: Thirty ASA I-II patients scheduled for elective surgery and with no anticipated difficult intubation were enrolled in the study. Five minutes after midazolam 30 microg kg(-1), patients were randomized into two groups: group PR received propofol 2.5 mg kg(-1) followed by remifentanil 1 microg kg(-1), and group RP received remifentanil 1 microg kg(-1) followed by propofol 2.5 mg kg(-1). Intubating conditions were compared using a well-validated score, and continuous arterial pressure was recorded non-invasively. RESULTS: Compared with group RP, intubating conditions were significantly better in group PR. The mean arterial pressure decrease was more pronounced in group RP. CONCLUSIONS: We therefore conclude that in premedicated healthy patients with no anticipated risk of difficult intubation, intubating and haemodynamic conditions are better when remifentanil is injected after propofol.

Adolescent↗
PubMed2003

Nitric oxide and vasoactive intestinal peptide as co-transmitters of airway smooth-muscle relaxation: analysis in neuronal nitric oxide synthase knockout mice.

BACKGROUND: Both vasoactive intestinal peptide (VIP) and nitric oxide (NO) relax airway smooth muscle and are potential co-transmitters of neurogenic airway relaxation. The availability of neuronal NO synthase (nNOS) knockout mice (nNOS-/-) provides a unique opportunity for evaluating NO. OBJECTIVE: To evaluate the relative importance of NO, especially that generated by nNOS, and VIP as transmitters of the inhibitory nonadrenergic, noncholinergic (NANC) system. STUDY DESIGN: In this study, we compared the neurogenic (tetrodotoxin-sensitive) NANC relaxation of tracheal segments from nNOS-/- mice and control wild-type mice (nNOS(+/+)), induced by electrical field stimulation (EFS). We also examined the tracheal contractile response to methacholine and its relaxant response to VIP. RESULTS: EFS (at 60 V for 2 ms, at 10, 15, or 20 Hz) dose-dependently reduced tracheal tension, and the relaxations were consistently smaller (approximately 40%) in trachea from nNOS-/- mice than from control wild-type mice (p < 0.001). VIP (10(- 8) to 10(-6) mol/L) induced concentration-dependent relaxations that were approximately 50% smaller in nNOS-/- tracheas than in control tracheas. Methacholine induced concentration-dependent contractions that were consistently higher in the nNOS-/- tracheas relative to wild-type mice tracheas (p > 0.05). CONCLUSION: Our data suggest that, in mouse trachea, NO is probably responsible for mediating a large (approximately 60%) component of neurogenic NANC relaxation, and a similar (approximately 50%) component of the relaxant effect of VIP. The results imply that NO contributes significantly to neurogenic relaxation of mouse airway smooth muscle, whether due to neurogenic stimulation or to the neuropeptide VIP.

Airway Resistance↗
PubMed1995

The effect of isoflurane and temperature on the actions of muscle relaxants in rat in vitro.

Hypothermia and isoflurane alone increase the potencies of steroidal muscle relaxants (MRs). We studied the combined influence of isoflurane and hypothermia on MR potency. Phrenic nerve-hemidiaphragm preparations of rats were mounted in modified Krebs' solution and aerated with 5% CO2-95% O2 gas mixture at 37 degrees C and 4% CO2 at 27 degrees C to maintain the CO2 content constant. Phrenic nerves were stimulated with 0.1 Hz supramaximal impulses and elicited tension of the diaphragm was recorded. Isoflurane 1% was added after stabilization of twitch tension and MR was added 60 min later. Twitch tension was reduced by 20% +/- 2.5% at 37 degrees C and 3.5% +/- 0.7% at 27 degrees C from control with only isoflurane. The IC50 (inhibitory concentration, 50%) values of the MRs decreased significantly (P < 0.05) with isoflurane at both temperatures. The ratios of the IC50 values without and with isoflurane of the benzylisoquinolinium MRs were significantly more at both temperatures (P < 0.05) indicating the enhancement of potentiation of their action by isoflurane over steroidal MRs. When the soluble concentration of isoflurane at 27 degrees C was kept similar to that of at 37 degrees C, the ratios of all the MRs were reduced significantly from the ratios at 37 degrees C, indicating a reduction of potentiation. When the partial pressure of isoflurane was kept constant at 37 degrees C and 27 degrees C, the potentiating action of the MRs by isoflurane was similar. But when the partial pressure was decreased to keep the concentration of isoflurane constant, the potentiation was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Interactions of nifedipine and diltiazem with muscle relaxants and reversal of neuromuscular blockade with edrophonium and neostigmine.

The effects and interactions of nifedipine and diltiazem with tubocurarine, gallamine and pancuronium and their reversal by edrophonium and neostigmine were studied on isolated skeletal muscle of the chick. The nerve-muscle preparation of the chick biventer cervicis was set up in an organ bath containing Krebs-Henseleit solution and the mechanical responses produced either by motor nerve stimulation or by drug application were recorded isometrically. The results showed that nifedipine (29-1015 microM) and diltiazem (22-572 microM) reduced, in a dose-dependent manner, the amplitude of indirectly-elicited twitch tension, evoked at 0.2 Hz with 5-10 V and 0.2 msec pulse duration, and increased the neuromuscular blockade produced by d-tubocurarine (1-254 microM), gallamine (0.01-2.0 microM) and pancuronium (0.01-7.0 microM). Edrophonium (250 nM) and neostigmine (150 nM) completely reversed the neuromuscular blockade produced by the muscle relaxants, alone and in combination with nifedipine or diltiazem. The mean IC50 values (concentrations to produce 50% of maximum inhibition) of nifedipine and diltiazem-induced depression of twitch response were 324 +/- 16 microM and 143 +/- 11 microM respectively (means +/- S.E., n = 6). Nifedipine, in high concentrations, produced small contractions (0.4 +/- 0.1 g of tension, n = 6), in the chick muscle. In contrast, diltiazem produced no such contractions in the muscle. However, in concentrations which had little effect on twitch response, diltiazem (20 microM) and nifedipine (50 microM) both increased the neuromuscular blockade produced by tubocurarine, gallamine and pancuronium by about 2-fold. Increasing the external calcium concentration, by a 2-fold, did not reverse or antagonize the inhibitory effects of diltiazem or nifedipine. It was concluded that diltiazem and nifedipine inhibit indirectly-elicited twitch tension and intensify neuromuscular blockade produced by muscle relaxants. These effects of nifedipine and diltiazem may be due to blocking influx of calcium and on release of acetylcholine from presynaptic nerve terminals.

Animals↗
PubMed2005

Improving pharmacokinetic-pharmacodynamic models of muscle relaxants using potentiation modelling.

Repeated motor nerve stimulation performed during neuromuscular monitoring enhances the evoked mechanical response of the corresponding muscle resulting in an increased twitch response. This is known as twitch potentiation or the staircase phenomenon. For neuromuscular modelling research twitch stabilisation techniques are often used to reduce the visible effect of potentiation, but such techniques are not always effective. Our objective was to model pharmacokinetic-pharmacodynamic (PK-PD) and twitch potentiation and to estimate neuromuscular block (NMB) in the presence of twitch potentiation. We combined a standard PK-PD model with a model describing the degree of twitch potentiation. The combined model was used to predict mechanomyographic twitch measurements and estimate NMB and twitch potentiation during muscle relaxation monitoring. Model parameters and prediction accuracy were compared to the standard PK-PD model with and without linear baseline correction. The PK-PD-potentiation model allows NMB to be estimated in the presence of twitch potentiation. It also accurately predicts data from twitch stabilisation, which is ignored with the standard PK-PD model. Compared to the standard PK-PD model, estimated PD parameters ec50 and gamma were found to be higher using the PK-PD-potentiation model. Compared to linear baseline correction, estimated PD parameters ke0 and ec50 were found to be higher. A PK-PD-potentiation model can estimate the degree of twitch potentiation and the degree of NMB during neuromuscular monitoring. This model leads to different PD parameter estimations than the standard PK-PD model however the differences are small enough to be unlikely to cause great concern among researchers.

Algorithms↗
PubMed2003

Regulator of G-protein signaling-2 mediates vascular smooth muscle relaxation and blood pressure.

Nitric oxide (NO) inhibits vascular contraction by activating cGMP-dependent protein kinase I-alpha (PKGI-alpha), which causes dephosphorylation of myosin light chain (MLC) and vascular smooth muscle relaxation. Here we show that PKGI-alpha attenuates signaling by the thrombin receptor protease-activated receptor-1 (PAR-1) through direct activation of regulator of G-protein signaling-2 (RGS-2). NO donors and cGMP cause cGMP-mediated inhibition of PAR-1 and membrane localization of RGS-2. PKGI-alpha binds directly to and phosphorylates RGS-2, which significantly increases GTPase activity of G(q), terminating PAR-1 signaling. Disruption of the RGS-2-PKGI-alpha interaction reverses inhibition of PAR-1 signaling by nitrovasodilators and cGMP. Rgs2-/- mice develop marked hypertension, and their blood vessels show enhanced contraction and decreased cGMP-mediated relaxation. Thus, PKGI-alpha binds to, phosphorylates and activates RGS-2, attenuating receptor-mediated vascular contraction. Our study shows that RGS-2 is required for normal vascular function and blood pressure and is a new drug development target for hypertension.

Animals↗
PubMed1992

Tracheal intubation without the use of muscle relaxants: a technique using propofol and varying doses of alfentanil.

We have noted that tracheal intubation can be accomplished in many patients after induction of anesthesia with propofol and alfentanil without the simultaneous use of muscle relaxants. This study was designed to evaluate airway and intubating conditions after administration of propofol and alfentanil in 75 ASA physical status I or II outpatients with Mallampati class I airways undergoing various surgical procedures. The patients were randomly assigned to one of five groups for induction of anesthesia. All patients received midazolam 1 mg IV before induction of anesthesia. Group I patients (n = 15) received d-tubocurarine 3 mg, thiamylal 4 mg/kg, and succinylcholine 1 mg/kg IV. Groups II-V patients (n = 15 each) received alfentanil 30, 40, 50, or 60 micrograms/kg followed by propofol 2 mg/kg IV. No muscle relaxants were given to patients in groups II-V. Airway management was performed by one of the authors who was blinded as to the dose of alfentanil administered. After loss of consciousness, patients' lungs were ventilated via face mask, and the ease of ventilation was recorded. Jaw mobility was also assessed. Ninety seconds after administration of the propofol or thiamylal, laryngoscopy was performed and exposure of the glottis and position of the vocal cords were noted. Intubation of the trachea was performed and patient response was noted. Heart rate and arterial blood pressure were also recorded before induction of anesthesia, after induction, and then again after intubation of the trachea. The lungs of all patients were easily ventilated via mask, and the jaw was judged to be relaxed in all patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

[Muscle relaxants in the morphometric study of the respiratory muscles in human beings].

The morphological examination of respiratory muscle can be affected by muscular contraction following biopsy. Most morphometric studies of respiratory muscles, however, have been carried out without taking into account this factor, the effect of which can be reduced by using relaxants when taking samples. Objective. To examine the effect of using a relaxant in the morphometric analysis of muscle fibers. We examined 31 muscle samples from 7 patients. Immediately after removal, each pipe was divided in half. One was placed in an isotonic physiological solution and the other in a solution of curare 0.02%. Later, both samples were processed for morphometric study with ATP-ase, NADTH and PAS tincture. Morphological data recorded for the different types of fibers included measurement of minimum diameter (Dmin), atrophy and hypertrophy indices (AI and HI) and heterogeneity of distribution (SDDmin). The Dmin was smaller in fibers transported in a curare solution than in those transported in physiological solution (67 +/- 2 microns vs. 71 +/- microns, p < 0.05). The same was true of SDDmin (13 +/- 3 vs. 12 +/- 3, p < 0.05), HI (300 +/- 88 vs. 457 +/- 107, p < 0.05). Likewise, we found a similar direct correlation between size of fibers processed with physiological solution and those processed in curare (Dmin, r = 0.731, p < 0.001; HI, r = 0.827, p < 0.001; SDDmin, r = 0.636, p < 0.0001). The use of relaxants in processing muscle samples prevents contraction and should be used systematically in the morphological analysis of muscle fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopsy↗
PubMed1996

Comparative use of muscle relaxants and their reversal in three European countries: a survey in France, Germany and Great Britain.

A survey was conducted among British, French and German anaesthetists to evaluate possible national differences in the peri-operative use of muscle relaxants and their reversal agents. The same non-depolarizing relaxants are used in all three countries, with the exception of d-tubocurarine, which is only available in Great Britain, and alcuronium which is mainly used in Germany. The French anaesthetists seem to use significantly less succinylcholine than their peers in Great Britain or Germany for both elective and emergency intubation. Monitoring of neuromuscular blockade still relies mainly on "clinical judgement'. Reversal of non-depolarizing muscle relaxants is performed routinely in Great Britain, while a substantial number of French anaesthetists avoid the use of a reversal. Dose regimes for neostigmine vary largely, with German anaesthetists administering the lowest, and British anaesthetists administering the highest doses. Side effects of reversal agents are reported by colleagues from all three countries in too high a percentage to justify uncritical administration of these drugs. In Germany there seems to be a noteworthy lack of recovery facilities.

Alcuronium↗
PubMed1979

Liquid chromatography in pharmaceutical analysis XI: determination of muscle relaxant--analgesic mixture using reversed-phase and ion-pair techniques.

High pressure liquid chromatography using reversed-phase and/or ion-pair techniques was used to optimize resolution of aspirin-containing muscle relaxant mixtures as well as other therapeutic agents commonly found in muscle relaxant-analgesic mixtures. The compounds were chromatographed on an octadecylsilane column using methanol--water solvent systems, some of which contained tetrabutylammonium cation as counterion. Mixtures of methocarbamol--aspirin and chlorzoxazone--acetaminophen were selected to demonstrate separation and quantification. The methocarbamol--aspirin mixture was chromatographed with methanol--water (40:60, pH 6.8) containing 0.01 M tetrabutylammonium cation at a flow rate of 2.0 ml/min. The chlorzoxazone--acetaminophen mixture was chromatographed with methanol--water (50:50) at a 2.0 ml/min flow rate. The separation and quantitation of each mixture were achieved in approximately 8 min with accuracy in the 2--3% range.

Acetaminophen↗
PubMed1985

Effects of progressive muscle relaxation training on anxiety and health locus of control among hypertensive adults.

The effects of progressive muscle relaxation (PMR) on anxiety and perceptions of personal control over health status are evaluated in this study. After collection of baseline data, 22 hypertensive clients received relaxation training in a series of weekly group sessions followed by individual monitoring sessions over a 6-week period. The 22 hypertensive clients in the control group received blood pressure monitoring, weight checks, and health counseling but were given no relaxation training during the study period. The group instructed in relaxation exhibited significantly lower anxiety than the control group at 4-month followup. After training, the relaxation group also scored significantly higher than the control group on beliefs in personal control of health and lower in beliefs that chance or luck affected health outcomes. At followup, the groups did not differ significantly on perceived influence of powerful others over health status. Findings support the potential usefulness of relaxation training in modifying affective and cognitive characteristics of hypertensive clients.

Anxiety↗