Effects of Isoprenaline, Levodopa and a Phosphodiesterase Inhibitor (Ici 63,197) on Cyclic Amp Levels and Contractions of Soleus Muscles in Anaesthetized Cats

Merican, Z.; Nott, M. W.

doi:10.1111/j.1440-1681.1981.tb00134.x

Cited by 5 publications

(5 citation statements)

References 16 publications

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“…The tremor was shown to be mediated by cyclic AMP (Nott & Merican 1978;Merican & Nott 1981). It is likely that the tremor (and muscle weakness) of thyrotoxicosis occur by a similar mechanism.…”

Section: Discussionmentioning

confidence: 96%

“…Another effect of a decrease in the duration of the active state of slow contracting mammalian skeletal muscles brought about by either catecholamines or phosphodiesterase inhibitors is tremor (Bowman & Nott 1970Nott & Raper 1972). The tremor was shown to be mediated by cyclic AMP (Nott & Merican 1978;Merican & Nott 1981). It is likely that the tremor (and muscle weakness) of thyrotoxicosis occur by a similar mechanism.…”

Section: Discussionmentioning

confidence: 99%

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Effects of Thyroxine Treatment on Contractions of Soleus Muscles of Anaesthetized Cats

Merican

Morat

1984

Clin Exp Pharma Physio

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The effects of chronic thyroxine treatment on cat soleus muscle contractions were studied. Maximum twitch tension, contraction time, half relaxation time and tension-time integral of maximal twitches of the soleus muscles of thyroxine treated cats were significantly decreased. Consequently, there was a decrease in tension and degree of fusion of incomplete tetanic contractions of the soleus muscle. The maximum tetanic tension was not statistically significantly changed, suggesting that the effects may be due to a decrease in the duration of the active state of the muscle. Isoprenaline given intravenously during incomplete tetanic contractions of the soleus muscle caused a statistically significant depression of tension in the control group but not in the thyroxine treated group. This further suggests reduction in the duration of the active state of soleus muscles of thyroxine treated cats. Propranolol injected chronically with thyroxine reversed or prevented the depression of tension caused by thyroxine treatment, suggesting the involvement of beta-adrenoceptors in these effects. The decrease in tension and degree of fusion during incomplete tetanic contractions of the thyroxine treated soleus could be responsible, at least partly, for the muscle weakness and tremor of thyrotoxicosis. Cyclic AMP may possibly be the mediator of these effects.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Effects of Thyroxine Treatment on Contractions of Soleus Muscles of Anaesthetized Cats

Merican

Morat

1984

Clin Exp Pharma Physio

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“…Thus Merican & Nott (1981) showed a close correlation between isoprenaline-induced increase in cyclic AMP levels and depression of soleus contractions. There are two likely trains of events intervening between the rise in cyclic AMP and the effect on contraction.…”

Section: Discussionmentioning

confidence: 97%

“…Evidence suggests that cyclic 3',5' adenosine monophosphate (cyclic AMP) mediates the effects of sympathomimetic amines on contractions of nonfatigued, fast-and slow-contracting skeletal muscles (Sullivan & Zaimis, 1973;Nott & Merican, 1978;Al-Jeboory & Marshal, 1978;Merican & Nott, 1981). The present experiments examine whether cyclic AMP mediates the effects caused by increasing the frequency of twitches.…”

Section: Introductionmentioning

confidence: 99%

Effects of increasing the frequency of twitches and of isoprenaline on maximal twitches and cyclic AMP levels in slow‐ and fast‐contracting cat skeletal muscles

Merican

Nott

Sunbhanich

1983

British J Pharmacology

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1Increasing the frequency of twitches and treatment with isoprenaline have been been compared for effects on twitch tension, tension-time integral and cyclic adenosine 3', 5'-monophosphate (cyclic AMP) levels in the slow-contracting soleus muscle of cats, anaesthetized with chloralose and pentobarbitone. The effect of change in frequency of contractions on cyclic AMP in the fastcontracting extensor digitorum longus muscle was also examined. 2 Although both isoprenaline and increasing the frequency of contractions depressed twitch tension in the soleus, only isoprenaline enhanced cyclic AMP levels. The effects of isoprenaline were independent of the existing frequency of contractions of the muscle. Increasing the frequency of contractions enhanced twitches in the extensor digitorum longus muscle but did not change cyclic AMP levels. 3 It is concluded that cyclic AMP may mediate effects of ,B-adrenoceptor agonists but not those caused by increasing the frequency of contractions on slow-or fast-contracting skeletal muscles.

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“…This depressive effect of IBMX on the slowcontracting soleus muscle resembled that described for isoprenaline (Bowman & Zaimis 1958;Waldeck 1977) but was not blocked by propranolol which excludes a direct stimulation of P-adrenoceptors. Merican & Nott (1981) showed that both ICI 63,197 (a potent, non-xanthine phosphodiesterase inhibitor) and isoprenaline increased c-AMP in the soleus muscle and depressed the subtetanic contractions in anaesthetized cat. Since IBMX is about 100 times more potent than theophylline as an inhibitor of phosphodiesterase in the skeletal muscle (Kramer & Wells 1980) it seems probable that the isoprenaline-like effect of IBMX is caused by accumulation of c-AMP.…”

Section: Hteraction With P-adrenoceptor Agonisrs On [He Trachea and mentioning

confidence: 99%

Dissociation between the Effects of some Xanthine Derivatives on the Tracheal Smooth Muscle and on the Skeletal Muscle

Jeppsson

Johansson

Waldeck

1982

Acta Pharmacologica et Toxicologica

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The ability of some xanthine derivatives to relax the trachea, contracted by pilocarpine, and to increase the force of contraction of directly stimulated skeletal muscles from the guinea‐pig was studied in vitro. No relationship was found between these two effects. Relaxation of the trachea occurred at lower concentrations and with a different order of potency as compared with the effects on the slow‐contracting soleus muscle or on the fast‐contracting extensor digitorum longus. One of the compounds, IBMX, 1‐methyl‐3‐isobytylxanthine, showed an isoprenaline‐like effect on the soleus muscle i.e. it depressed the force and fusion of subtetanic contractions. The relaxing effect of theophylline and IBMX on the trachea was additive to that of terbutaline but no clear potentiation was observed. The depression of the contractions of the soleus muscle elicited by terbutaline was reinforced by IBMX but not by theophylline. Theophylline in concentrations which used alone enhanced the contractions of the soleus muscle inhibited the effect of terbutaline. We conclude that the relative contribution of the various effects of xanthine derivatives differs from compound to compound.

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Effects of Isoprenaline, Levodopa and a Phosphodiesterase Inhibitor (Ici 63,197) on Cyclic Amp Levels and Contractions of Soleus Muscles in Anaesthetized Cats

Cited by 5 publications

References 16 publications

Effects of Thyroxine Treatment on Contractions of Soleus Muscles of Anaesthetized Cats

Effects of Thyroxine Treatment on Contractions of Soleus Muscles of Anaesthetized Cats

Effects of increasing the frequency of twitches and of isoprenaline on maximal twitches and cyclic AMP levels in slow‐ and fast‐contracting cat skeletal muscles

Dissociation between the Effects of some Xanthine Derivatives on the Tracheal Smooth Muscle and on the Skeletal Muscle

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