The effects of opiate antagonists on food intake are stereospecific

Sanger, D. J.; McCarthy, P. S.; Metcalf, G.

doi:10.1016/0028-3908(81)90040-x

Cited by 69 publications

(6 citation statements)

References 14 publications

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“…The depression of food and water intake caused by MR2266 is consistent with previous findings (Sanger et al, 1981;Leander, 1984;, and provides evidence that the drug was active throughout the period of treatment. Similarly the fact that ingestive behaviour returned to normal, one day after removal of the minipumps indicates that the concentration of MR2266 in the brain had fallen rapidly upon cessation of treatment.…”

Section: Discussionsupporting

confidence: 89%

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Inability of an opioid antagonist lacking negative intrinsic activity to induce opioid receptor up‐regulation in vivo

Morris

Millan

1991

British J Pharmacology

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It has recently been suggested that opioid antagonists may be divided into those possessing negative intrinsic activity (e.g. naloxone) and those with neutral intrinsic activity (e.g. MR2266). MR2266 was chronically administered to rats by subcutaneous infusion at a dose of 0.3 mg kg−1 h−1 for 1 week. This dose reduced ingestive behaviour and blocked the antinociceptive effects of a κ‐agonist, indicating occupation of opioid receptors in vivo. No supersensitivity could be detected to the antinociceptive actions of μ or κ agonists, either one or two days after cessation of treatment. No up‐regulation of μ, δ or κ binding sites was observed. Since naloxone induces both supersensitivity and receptor up‐regulation under equivalent conditions, the results suggest that negative intrinsic activity may be required for these phenomena to occur.

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Section: Discussionsupporting

confidence: 89%

“…However, it has also been used alone in order to interrupt any K receptormediated activity of the endogenous opioids. In general, the behavioural effects of MR2266 administration have then been interpreted as a result of the blockade of p or K receptors (Sanger et al, 1981;Leander, 1984).…”

Section: Discussionmentioning

confidence: 99%

Inability of an opioid antagonist lacking negative intrinsic activity to induce opioid receptor up‐regulation in vivo

Morris

Millan

1991

British J Pharmacology

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“…Brown et al (6) and Sanger et al (7) indicated that these suppressions by naloxone are mediated through the blockade of endogeneous opiate receptors (u receptors). If this contention is valid, morphine, an opiate agonist, might facilitate feeding and water drinking in non fasted and fasted rats.…”

mentioning

confidence: 99%

Opposite effects of morphine on feeding and drinking in rats relative to administration time.

1983

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Abstract-The present study was undertaken to examine how morphine changes food and water intake in non-fasted or fasted rats with different administration times. Morphine (1, 3 and 10 mg/kg) was intraperitoneally administered at 10:45 (light period) or 18:45 (dark period). Morphine increased food and water intake in non-fasted rats 2 hr after the administration during the light period, whereas the total daily intakes were decreased. In contrast, morphine decreased food and water intake in non-fasted rats during the dark period and in fasted rats during both the light and dark period. These results suggest that morphine disorders the baseline levels of feeding and water drinking of naive rats.

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“…In contrast, the (+)-benzomorphan enantiomer, Mr 1453, which is not only inactive as an opioid antagonist but also ineffective in reducing food intake in deprived rats (Sanger et al, 1981), did not suppress either meptazinol or levorphanol-induced food consumption. These findings confirm the involvement of opioid receptors in meptazinol and levorphanol-hyperphagia and establish the stereoselective reversibility of these ingestive responses by opioid antagonists.…”

Section: Introductionmentioning

confidence: 92%

Characterization of the effects of (±)‐meptazinol, its individual enantiomers and N‐methyl meptazinol on food consumption in the rat

Jackson

Sewell

1986

British J Pharmacology

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Both (±)‐meptazinol (2 mg kg−1) and levorphanol (1 mg kg−1) produced hyperphagia over a 4 h period after intraperitoneal injection in free feeding rats during the daylight phase. The individual (+)‐ and (−)‐enantiomers of meptazinol (2 mg kg−1 i.p.) induced comparable increases in cumulative food intake. N‐methyl meptazinol (2–10 mg kg−1 i.p.), the quaternary analogue of meptazinol, produced no modification of food intake though it increased food consumption when injected intracerebroventricularly (10–100 μg per animal). Meptazinol and levorphanol hyperphagia was abolished by 1 mg kg−1 doses (i.p.) of the opioid antagonists naltrexone, naloxonazine and (−)‐Mr 1452 but not by its (+)‐enantiomer Mr 1453 which is not effective as an opioid antagonist. Intracerebroventricular administration of the δ‐opioid receptor antagonist ICI 154,129 (10 μg per animal) suppressed meptazinol but not levorphanol hyperphagia. It was concluded that meptazinol produces centrally mediated stereospecifically reversible hyperphagia through a μ‐opioid receptor mechanism common to levorphanol, and also through δ‐opioid receptor mechanism(s).

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The effects of opiate antagonists on food intake are stereospecific

Cited by 69 publications

References 14 publications

Inability of an opioid antagonist lacking negative intrinsic activity to induce opioid receptor up‐regulation in vivo

Inability of an opioid antagonist lacking negative intrinsic activity to induce opioid receptor up‐regulation in vivo

Opposite effects of morphine on feeding and drinking in rats relative to administration time.

Characterization of the effects of (±)‐meptazinol, its individual enantiomers and N‐methyl meptazinol on food consumption in the rat

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