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Deep muscle relaxation has been used as an adjunct to many somatic and psycho-therapies since its introduction by Jacobsen in 1929. It is a therapeutic technique which is taught as a motor skill through the use of instruction, practice, and feedback about progress. The material in this paper provides a script for preparing a relaxation tape for clients to use between or in addition to regular therapy sessions.
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The present study was conducted to determine the effects of skeletal muscle relaxants on contractions of bladder smooth muscle. Rat, rabbit and human bladder muscle strips were incubated in a 50 ml. organ bath filled with physiological salt solution, aerated with 95 per cent O2, 5 per cent CO2 and maintained at 37C. Contractions were induced both electrically and with acetylcholine. Contractile strength was measured before and after 30 to 70 minute incubations with diazepam (0.25 to 1.0 microgram./ml.), dantrolene sodium (4 micrograms./ml.) or baclofen (4 micrograms./ml.). Neither baclofen nor dantrolene sodium had any effect (p greater than 0.3) on electrically or acetylcholine-induced contractions in any of the 3 species tested but diazepam potentiated both electrically induced (115 per cent of predrug contractile strength, p less than 0.05) and acetylcholine-induced (122 per cent of predrug contractile strength, p less than 0.01) contractions of rat, but not rabbit or human, bladder muscle. In rabbits diazepam significantly reduced maximal bladder pressures in vivo (p less than 0.05) but had no effect on bladder capacity. Dantrolene sodium had no effect on rabbit bladder pressure or capacity in vivo. While diazepam is thought to exert its effects on skeletal muscle through CNS inhibition, these results suggest that diazepam may affect rat but not rabbit or human bladder smooth muscle directly.
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INTRODUCTION: Centrally muscle relaxants (CMRs) are used mainly for treating muscle spasticities of neurological origin, and painful muscle spasms due to rheumatologic conditions. Their use is frequently associated with dose-limiting adverse effects. New drugs with improved side-effect characteristics are badly needed. However, there is no general agreement in the pharmacological literature on what methods are adequate to assess CMR effect and side effects in behaving rodents, which may hinder the development of new drugs. Here we report on the establishment of a simple pharmacological test battery, which was used to compare efficacies and side effect profiles of 11 compounds with central muscle relaxant action, in mice (intraperitoneal application). METHODS: For measuring muscle relaxant activity, (1) a new tremor model (GYKI 20039-induced tremor) and (2) the morphine-induced Straub-tail assay were used. The former, newly developed method has advantages over harmaline- or LON-954-induced tremor. For detecting side effect liability (ataxia, sedation, impairment of voluntary motor functions), (1) the rota-rod test, (2) measurement of spontaneous motility, (3) the weight-lifting test and (4) the thiopental sleep test were used. RESULTS: Among the 11 muscle relaxant compounds tested (tolperisone, eperisone, silperisone, diazepam, baclofen, tizanidine, afloqualon, mephenesin, zoxazolamine, memantine and carisoprodol), the calculated safety ratios (i.e. ID50 for side effect/ID50 for muscle relaxant effect) varied in a wide range. Silperisone seems to have the most advantageous profile (safety ratios range between 1.7 and 3.3 in the different pairs of assays) compared to the other tested drugs with lower (one or more ratios below 1.5, and often far below 1) and more varying ratios. DISCUSSION: Therapeutic indices calculated from the results of these in vivo experiments for the clinically used muscle relaxants are in agreement with their adverse effect profiles in humans. Thus the present test battery seems to be suitable for predicting the possible clinical utility of newly synthesized compounds.
1. Pharmacological properties of a new centrally acting muscle relaxant (NC-1200) were tested in isolated muscle preparations. 2. NC-1200 acted as a Ca-blocker in the guinea pig taenia caecum. The pA2-value was 5.67. 3. In the rabbit aorta, NC-1200 competed with serotonin at serotonin receptors and also shifted the concentration response curves of histamine and norepinephrine suggesting the possibility that NC-1200 interacted with histamine and norepinephrine receptors. The pA2-value of NC-1200 against serotonin was 6.02. 4. There was no evidence that NC-1200 interacted with drug-receptors in the muscles except the rabbit aorta. 5. The present results are similar to the previous findings that the properties of serotonin, histamine and norepinephrine receptors in the rabbit aorta were different from those in other muscles.
Anaphylaxis to muscle relaxants appears to be a very useful model to study the IgE-dependent mechanisms of mediator release in humans. The serum IgE binding sites of the drugs appeared to be the ammonium ion determinants. In patients allergic to suxamethonium, one of the most frequently used muscle relaxants for general anesthesia, significant histamine release could be obtained in each case with simple diammonium salts. The length of the chain linking the ammonium groups appears to play an important role. In fact, when the length was less than or equal to 4 A, no significant histamine release could be obtained, whereas the optimal length for histamine release appeared to be greater than or equal to 6 A. Furthermore, muscle relaxants with a rigid backbone between the ammonium determinants (such as pancuronium) are less active than flexible molecules (such as suxamethonium) in initiating mediator release. This study suggests that small divalent molecules can induce anaphylactic shock in sensitized patients and that the length and the flexibility of the chain bearing the haptenic determinants appear to be important factors in the elicitation of mediator release.
Smooth muscle relaxation in vertebrates is regulated by a variety of neuronal signalling molecules, including neuropeptides and nitric oxide (NO). The physiology of muscle relaxation in echinoderms is of particular interest because these animals are evolutionarily more closely related to the vertebrates than to the majority of invertebrate phyla. However, whilst in vertebrates there is a clear structural and functional distinction between visceral smooth muscle and skeletal striated muscle, this does not apply to echinoderms, in which the majority of muscles, whether associated with the body wall skeleton and its appendages or with visceral organs, are made up of non-striated fibres. The mechanisms by which the nervous system controls muscle relaxation in echinoderms were, until recently, unknown. Using the cardiac stomach of the starfish Asterias rubens as a model, it has been established that the NO-cGMP signalling pathway mediates relaxation. NO also causes relaxation of sea urchin tube feet, and NO may therefore function as a 'universal' muscle relaxant in echinoderms. The first neuropeptides to be identified in echinoderms were two related peptides isolated from Asterias rubens known as SALMFamide-1 (S1) and SALMFamide-2 (S2). Both S1 and S2 cause relaxation of the starfish cardiac stomach, but with S2 being approximately ten times more potent than S1. SALMFamide neuropeptides have also been isolated from sea cucumbers, in which they cause relaxation of both gut and body wall muscle. Therefore, like NO, SALMFamides may also function as 'universal' muscle relaxants in echinoderms. The mechanisms by which SALMFamides cause relaxation of echinoderm muscle are not known, but several candidate signal transduction pathways are discussed here. The SALMFamides do not, however, appear to act by promoting release of NO, and muscle relaxation in echinoderms is therefore probably regulated by at least two neuronal signalling systems acting in parallel. Recently, other neuropeptides that influence muscle tone have been isolated from the sea cucumber Stichopus japonicus using body wall muscle as a bioassay, but at present SALMFamide peptides are the only ones that have been found to have a direct relaxing action on echinoderm muscle. One of the Stichopus japonicus peptides (holothurin 1), however, causes a reduction in the magnitude of electrically evoked muscle contraction in Stichopus japonicus and also causes 'softening' of the body wall dermis, a 'mutable connective tissue'. It seems most likely that this effect of holothurin 1 on body wall dermis is mediated by constituent muscle cells, and the concept of 'mutable connective tissue' in echinoderms may therefore need to be re-evaluated to incorporate the involvement of muscle, as proposed recently for the spine ligament in sea urchins.
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Muscle relaxants are used for tracheal intubation, surgical procedures and in the intensive care unit. This review describes muscle relaxants available in Germany, with special focus on their use in endotracheal intubation. We compare the advantages and disadvantages of succinylcholine (the only depolarising agent) with those of short- and intermediate-acting non-depolarising agents in an attempt to define the characteristics of the ideal muscle relaxant. The effective doses required to attain 95% neuromuscular block and maximum effect (onset time) are compared for adults and children. It is documented that, with non-depolarising agents, increasing the dose and using either the priming or timing principle possibly reduce the onset time of neuromuscular block during a rapid sequence induction. The advantages and disadvantages of using non-depolarising instead of depolarising agents are discussed using data from our studies and those of other research groups. Possible side-effects due to the chemical structure and the necessary dosage for intubation of different agents are also discussed. Two points are emphasized: firstly, the use of non-depolarising agents for intubation requires the possibility of safe ventilation of the patient via mask, and, secondly, it is important that procedures be performed by an experienced anaesthetist.
Smooth muscle myosin bound phosphatase (MBP) purified from chicken gizzard, which is a holoenzyme of type 1 delta protein phosphatase and dephosphorylated intact myosin, catalyzed the dephosphorylation of calponin phosphorylated by protein kinase C (PK-C). The Km of MBP for calponin was 0.6 microM and the Vmax was 350 nmol/min/mg. All of the multiple sites of phosphorylation by PK-C of calponin were completely dephosphorylated by MBP. Functionally, calponin dephosphorylated by MBP recovered its inhibitory effect on the actin-activated Mg(2+)-ATPase activity of myosin. Therefore, these results suggest that a type 1 delta protein phosphatase causes relaxation of smooth muscle by the dephosphorylation not only of myosin but also of calponin.
Automatic muscle relaxation control may reduce anesthesiologists' workload freeing them for other patient care requirements. In this report we describe a muscle relaxation controller designed for routine clinical application using rocuronium and the train-of-four count. A muscle relaxation monitor (TOF Watch SX) was connected to a laptop computer running a controller algorithm program that communicates with a syringe pump to form a closed-loop muscle relaxation system. The control algorithm uses proportional-integral and lookup table components and is designed to avoid the usability restrictions of existing controllers. The controller is optimized using an objective method to avoid the uncertainties of ''hand-crafted'' controller algorithms. Controller target was train-of-four count 1 or 2 and controller performance was evaluated in 15 patients. During 39 hours of closed-loop control, 96.1% of all twitches recorded were in the target range. Average rocuronium infusion rate was 0.36 mg.kg(-1).h(-1) (sd 0.18 mg.kg(-1).h(-1)). We show that the controller remains useful even in the presence of disturbances that can arise in routine clinical conditions. The muscle relaxation controller maintained the target train-of-four count values and may serve as a basis for the design of hardware and user interfaces for closed-loop muscle relaxation control in clinical conditions.
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