Mechanical Responses to Catecholamines in Isolated Strips of the Guinea-Pig Stomach Muscle

Yamaguchi, Tsuyoshi; Tomita, Tadao

doi:10.1254/jjp.24.911

Cited by 6 publications

(8 citation statements)

References 16 publications

(23 reference statements)

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“…Adrenaline produced a complicated response depending on the concentration and the prevalent muscle tone, as previously found (Yamaguchi & Tomita, 1974). Furthermore, the response changed during the course of repeated applications of adrenaline at 20-30 min intervals.…”

Section: Resultssupporting

confidence: 68%

“…This effect was not studied in the present experiments, but since prostaglandin E2 could induce a clear contraction at less than 10 nm in the presence of 0.3fM meclofenamate, the receptor blocking action against prostaglandin E2 in this tissue must be weak. Since existing muscle tone affects the adrenaline-induced change in muscle tone (Yamaguchi & Tomita, 1974), the change of the adrenaline response into simple contraction in the presence of meclofenamate may result from the decreased muscle tone. However, full recovery of the response pattern was never achieved by raising the muscle tone to the control level with prostaglandin E2 in the presence of meclofenamate, and the response pattern differed depending on the substance used to increase the muscle tone (e.g., prostaglandin E2, F2e, carbachol) (unpublished observations).…”

Section: Discussionmentioning

confidence: 99%

“…The relative contribution of contraction and relaxation varies in different regions of the stomach wall and with endogenous muscle tone (Guimaraes, 1969;Bailey, 1971;Haffner, 1971;1972;Yamaguchi & Tomita, 1974). It has been shown that in the corpus, noradrenaline produces contraction at low concentrations through activation of a2-adrenoceptors, but relaxation at high concentrations through al-adrenoceptors (Sahyoun et al, 1982a,b).…”

Section: Introductionmentioning

confidence: 99%

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Receptors involved in mechanical responses to catecholamines in the circular muscle of guinea‐pig stomach treated with meclofenamate

Syed

Parekh

Tomita

1990

British J Pharmacology

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1 In circular muscle strips of the fundus and corpus of guinea-pig stomach, mechanical responses to catecholamines were studied mainly in the presence of a prostaglandin biosynthesis inhibitor, meclofenamate.2 Normal preparations developed considerable muscle tone, and adrenaline (10-100gM) in the presence of 3-5 gM propranolol produced a multiphasic response, generally consisting of transient relaxation and contraction, followed by slow relaxation and then contraction. Responses to phenylephrine were similar to those of adrenaline. 3 Meclofenamate (0.3 pM) nearly abolished the muscle tone and under this condition, both adrenaline and phenylephrine produced a simple contraction. This response was strongly inhibited by prazosin, but only weakly by yohimbine. 4 When muscle tone was maintained by prostaglandin E2 (10 nM) in the presence of meclofenamate, phenylephrine (30,uM) produced transient relaxation followed by slow contraction in most preparations.These were strongly inhibited by prazosin. Adrenaline produced a similar response, but the relaxation was only partially reduced by prazosin. The remaining relaxation was more dominant in the middle fundic region and this was considered to be mediated through /i-adrenoceptors.5 It is concluded that in the circular muscle of the fundic region of guinea-pig stomach, endogenous prostaglandins are involved in maintaining muscle tone and in modifying the response to catecholamines and that both contraction and relaxation are mediated by a1-adrenoceptors.

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Section: Resultssupporting

confidence: 68%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Receptors involved in mechanical responses to catecholamines in the circular muscle of guinea‐pig stomach treated with meclofenamate

Syed

Parekh

Tomita

1990

British J Pharmacology

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“…This contraction was blocked by phentolamine, an cc-blocking agent. Similar long-lasting contractions were also observed by transmural field stimulation (YAMAGUCHI and TOMITA, 1974). However, the mechanisms of the long-lasting contractions induced by catecholamines or by transmural stimulation remained to be elucidated.…”

mentioning

confidence: 61%

The long-lasting contraction induced by transmural stimulation in the longitudinal muscle of the guinea-pig gastric corpus.

1987

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“…Furthermore, the relative degree of these effects varies in different regions and muscle layers of the stomach (Guimaraes, 1969;Bailey, 1971;Haffner, 1971;Yamaguchi & Tomita, 1974). In the circular muscle of the guinea-pig corpus, noradrenaline is considered to produce contraction at low concentrations by activating x2-adrenoceptors, while at high concentrations m,-adrenoceptors mediate relaxation (Sahyoun et al, 1982a,b).…”

Section: Introductionmentioning

confidence: 99%

Mechanical and electrical responses to α‐adrenoceptor activation in the circular muscle of guinea‐pig stomach

Chihara

Tomita

1987

British J Pharmacology

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1In the circular muscle of the corpus region of the guinea-pig stomach, the effects ofcatecholamines on mechanical activity were studied with simultaneous recording of membrane potential by use of intracellular microelectrodes. In order to investigate responses mediated through a-adrenoceptors, the P-adrenoceptors were blocked by propranolol (10-6 M) in most experiments. 2 Adrenaline (< 10-M) produced a monophasic contraction with little change in membrane potential. At higher concentrations (>l0-M), adrenaline usually produced an early transient contraction followed by a slow tonic contraction. During the early phase, the membrane was hyperpolarized and slow waves were reduced in amplitude. 3 The phasic contractions superimposed on the late slow phase of the contractile response were higher in frequency and larger in amplitude than in controls before adrenaline application. These changes were associated with an increase in the amplitude and frequency of slow waves, and with a spike-like component appearing on the top of each slow wave. 4 Adrenaline-induced changes in mechanical and electrical activity were inhibited by prazosin, but largely unaffected by yohimbine. In some preparations, there was a transient weak inhibition ofphasic contraction before muscle tone was increased by adrenaline, and this became more pronounced in the presence of yohimbine. 5 Phenylephrine, selective for a,-receptors, produced responses very similar to those of adrenaline, whereas agonists selective for a,-receptors, clonidine and B-HT 920, produced only a small slow contraction without any clear change in membrane potential. 6 It is concluded that in the circular muscle of guinea-pig stomach, the contractile response and changes in the electrical slow wave activity produced by adrenaline are both mediated mainly through the activation of a,-receptors.

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Mechanical Responses to Catecholamines in Isolated Strips of the Guinea-Pig Stomach Muscle

Abstract: Japan. J. Pharmacol. 24, 911-922 (1974)

Cited by 6 publications

References 16 publications

Receptors involved in mechanical responses to catecholamines in the circular muscle of guinea‐pig stomach treated with meclofenamate

Receptors involved in mechanical responses to catecholamines in the circular muscle of guinea‐pig stomach treated with meclofenamate

The long-lasting contraction induced by transmural stimulation in the longitudinal muscle of the guinea-pig gastric corpus.

Mechanical and electrical responses to α‐adrenoceptor activation in the circular muscle of guinea‐pig stomach

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