The effects of the selective κ-opioid agonist MR 2034 on the guinea-pig ileum

Coupar, Ian M.; Quinn, Michael J.

doi:10.1111/j.2042-7158.1988.tb05274.x

Cited by 3 publications

(2 citation statements)

References 13 publications

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“…The results confirm previous observations with another selective Kagonist, MR 2034 (Coupar & Quinn, 1988) and may explain the negative results obtained by Chahl (1986Chahl ( , 1991 with some K-opioid agonists; when concentrations of U-50,488H as high as those used by the latter author, are employed, naloxone elicits a withdrawal response only after the removal of the K-opioid agonist from the bath. However, with agonist concentrations lower than 10-M, naloxone elicits the same…”

Section: Discussionsupporting

confidence: 90%

“…The present study demonstrates that following a brief period of contact (5min) with the selective K-opioid agonist, U-50,488H, the guinea-pig ileum exhibits a withdrawal response precipitated by the addition of naloxone. The results confirm previous observations with another selective Kagonist, MR 2034 (Coupar & Quinn, 1988) and may explain the negative results obtained by Chahl (1986Chahl ( , 1991 with some K-opioid agonists; when concentrations of U-50,488H as high as those used by the latter author, are employed, naloxone elicits a withdrawal response only after the removal of the K-opioid agonist from the bath. However, with agonist concentrations lower than 10-M, naloxone elicits the same a x E 0 x E 0 contractile response either with or without a previous washout.…”

Section: Discussionsupporting

confidence: 90%

See 1 more Smart Citation

Withdrawal contractures of guinea‐pig isolated ileum after acute activation of κ‐opioid receptors

Morrone

Romanelli

Amico

et al. 1993

British J Pharmacology

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The present study was undertaken to investigate firstly whether a brief exposure for 5 min of guinea‐pig isolated ileum to the κ‐opioid agonist, U‐50,488H produced a withdrawal contracture on addition of naloxone and secondly to ascertain whether the response was due to the activation of κ‐opioid receptors. Naloxone (10−6 m) did not elicit a response in preparations exposed to U‐50,488H (5 × 10−7 M‐2 × 10−6 m). However, after exposure to U‐50,488H (5 × 10−7 m), naloxone (10−6 m) produced a strong contracture if the agonist was washed out 1 min before the addition of the antagonist. The addition of naloxone (10−6 m) to the ileum preparation exposed to U‐50,488H (10−7 m or lower) caused a response of similar intensity irrespective of whether the agonist had been washed out. The selective κ‐opioid antagonist, nor‐binaltorphimine (2.7 × 10−9 m and 2.7 × 10−7 m), injected before the opioid agonists, prevented the naloxone‐induced contracture after exposure to U‐50,488H (8 × 10−8 m) but did not affect the contracture after exposure to morphine (5 × 10−7 m). Nor‐binaltorphimine (2.7 × 10−9 m) caused a contraction of the ileum preparation when injected min after exposure to U‐50,488H (8 × 10−8 m) but not after morphine (5 × 10−7 m). The α2‐adrenoceptor agonist, clonidine (3 × 10−8 m) and the calcium channel blocker, nifedipine (3 × 10−8 m), injected 1 min before naloxone, blocked the ileum contraction to naloxone after exposure to U‐50,488H (8 × 10−8 m). The results demonstrate that the stimulation of K‐opioid receptors can induce a similar dependence in guinea‐pig ileum to that produced by activation of μ receptors.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 90%

Withdrawal contractures of guinea‐pig isolated ileum after acute activation of κ‐opioid receptors

Morrone

Romanelli

Amico

et al. 1993

British J Pharmacology

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Determination of structural factors affecting binding to mu, kappa and delta opioid receptors

2020

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Manifestations of acute opiate withdrawal contracture in rabbit jejunum after μ‐, κ‐ and δ‐receptor agonist exposure

Valeri

Morrone

Romanelli

1992

British J Pharmacology

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Following a 5 min in vitro exposure to morphine (1.3 × 10−7 m), U‐50,488H (2.5 × 10−8 m) and deltorphin (1.6 × 10−8 − 6.5 × 10−9 m), the rabbit isolated jejunum exhibited a precipitated contracture after the addition of naloxone (2.75 × 10−7 m). The precipitated responses to U‐50,488H and deltorphin but not to morphine were reproducible in the same tissue. The precipitated contractures were blocked completely by tetrodotoxin (3 × 10−7 m), partially by atropine (1.5 × 10−7 m) and not affected by hexamethonium (1.4 × 10−5 m). Naloxone administration (2.75 × 10−7 m) before the agonist prevented the development of the adaptive response to morphine and U‐50,488H but not to deltorphin. The selective antagonists norbinaltorphimine (2.7 × 10−8 − 2.7 × 10−9 m) and naltrindole (1.1 × 10−7 m) prevented the adaptive response development only to the respective agonists. The opioid agonists partially inhibited the spontaneous activity of the tissue. This study has shown that independent activation of μ‐, κ‐ and δ‐opioid receptors can induce dependence in this isolated tissue. Rabbit jejunum is a suitable tissue for studying the acute effects of opioids on the adaptative processes determined by their administration.

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The effects of the selective κ-opioid agonist MR 2034 on the guinea-pig ileum

Cited by 3 publications

References 13 publications

Withdrawal contractures of guinea‐pig isolated ileum after acute activation of κ‐opioid receptors

Withdrawal contractures of guinea‐pig isolated ileum after acute activation of κ‐opioid receptors

Determination of structural factors affecting binding to mu, kappa and delta opioid receptors

Manifestations of acute opiate withdrawal contracture in rabbit jejunum after μ‐, κ‐ and δ‐receptor agonist exposure

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