Neuropharmacological actions of enkephalin after systemic administration

Plotnikoff, Nicholas P.; Kastin, Abba J.; Coy, David H.; Christensen, Carl W.; Schally, Andrew V.; Spirtes, Morris A.

doi:10.1016/0024-3205(76)90265-4

Cited by 101 publications

(21 citation statements)

References 13 publications

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“…It appears, thus, that only a small number of cells, possibly those which have already responded to activation signals, express opioid receptors and have the ability to elicit the response. T-cell-stimulatory effect of analogs (1) and (2) was found to be completely inhibited by 10 -5 M concentration of naloxone, an opioid antagonist [38]. The blockade of enkephalin-induced immune response by naloxone suggests that the stimulatory effect is due to the opioid moiety [2] and also implicates the mediation of the response by the classical opioid receptors on the immune cells [29].…”

Section: Peptide Concentrationmentioning

confidence: 84%

“…At a similar concentration, ß-FNA did not inhibit Met-enkephalin-stimulated proliferation (table 2). It could significantly inhibit proliferation stimulated with 10 -8 M concentration of analog (1) and analog (2). Nor-BNI showed no inhibitory effect on Met-enkephalin or analog (1)-and analog (2)-stimulated proliferation (table 3).…”

Section: Resultsmentioning

confidence: 99%

“…2 Represents statistical significance of inhibition of proliferation by antagonist (peptide only compared with peptide plus antagonist, ß-FNA at 10 -5 M ). …”

Section: Discussionmentioning

confidence: 99%

“…Although their precise physiological significance still remains elusive, the enkephalins have been reported to exhibit analgesic, antidepressant, antianxiety and anticonvulsant activities [2]. Furthermore, enkephalins have also been found to act as immunomodulators [3][4][5][6][7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

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δ-Opioid Receptor Antagonist Inhibits Immunomodulation by Met-Enkephalin Analogs

Singh¹,

Bajpai²,

Narayan³

et al. 1999

Neuroimmunomodulation

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The methionine-enkephalin (Met-enkephalin, Tyr-Gly- Gly-Phe-Met) analogs Tyr-D-Ala-Gly-MePhe-Met NHC₃H₇- iso (1) and Tyr-D-Ala-Gly-MePhe-Gly-NHC₃H₇-iso (2) have been shown to enhance human T cell proliferation in in vitro treatment. Their immunomodulatory activities were completely blocked by naloxone, an opioid antagonist. Now we demonstrate that a selective δ-opioid receptor antagonist, ICI-174,864, completely blocks enhancement of T cell proliferation by analogs (1) and (2). The T cell-stimulatory effect was only partially inhibited by the µ-receptor-selective antagonist, β-funaltrexamine hydrochloride. The κ-opioid receptor antagonist, nor-binaltorphimine dihydrochloride, showed no effect on T cell-proliferation stimulated by analogs (1) and (2). These observations suggest that analogs (1) and (2) of Met-enkephalin stimulate T cell proliferation predominantly via δ-opioid receptor present on T cells.

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Section: Peptide Concentrationmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 99%

“…2 Represents statistical significance of inhibition of proliferation by antagonist (peptide only compared with peptide plus antagonist, ß-FNA at 10 -5 M ). …”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

δ-Opioid Receptor Antagonist Inhibits Immunomodulation by Met-Enkephalin Analogs

Singh¹,

Bajpai²,

Narayan³

et al. 1999

Neuroimmunomodulation

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“…While enkephalins administered parenterally are known to have central effects (Plotnikoff et al, 1976) and have been found to enter brain tissue readily in one study ), Cornford et al, (1978 and Rapoport and his colleagues (1980) have found that the opiate peptides have very low permeability into central sites. One possibility is that Met enkephalin enters discrete areas of the brain adjacent to neurones involved in cardiovascular control such as the area postrema or the circumventricular organs that have fenestrated capillaries (Weindl & Joynt, 1972).…”

Section: Resultsmentioning

confidence: 99%

Reduction by phentolamine of the hypotensive effect of methionine enkephalin in anaesthetized rabbits

Eulie

Rhee

1984

British J Pharmacology

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In intact rabbits anaesthetized with pentobarbitone, methionine enkephalin (Met enkephalin, 1−1,000 μg kg−1 i.v.) produced a dose‐dependent bradycardia and hypotension. The bradycardia and hypotension were antagonized by naloxone hydrochloride (1 mg kg−1), but not by naloxone methobromide (1.3 mg kg−1). Phentolamine (1 and 4 mg kg−1 i.v.) blocked both the hypotension and bradycardia produced by Met enkephalin. The inhibitory effect of phentolamine was not due to a simple hypotensive action of this drug per se because a similar degree of hypotension induced by nitroprusside (15 μg kg−1, i.v.) caused a further reduction of pressure when Met enkephalin was added. Atropine (2 mg kg−1) reduced the bradycardia but not the hypotensive response to Met enkephalin. Met enkephalin did not antagonize the vasopressor effect of exogenous noradrenaline (2–8 μg kg−1, i.v.). Met enkephalin had no significant effects in superfused thoracic aortic strips and in isolated perfused hearts of rabbits. It is concluded that the cardiovascular effects of Met enkephalin are more probably due to an action on the central nervous system, although a peripheral site of action cannot be completely excluded.

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Endorphins in Psychiatry

Verebey¹

1978

Arch Gen Psychiatry

132

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Neuropharmacological actions of enkephalin after systemic administration

Cited by 101 publications

References 13 publications

δ-Opioid Receptor Antagonist Inhibits Immunomodulation by Met-Enkephalin Analogs

δ-Opioid Receptor Antagonist Inhibits Immunomodulation by Met-Enkephalin Analogs

Reduction by phentolamine of the hypotensive effect of methionine enkephalin in anaesthetized rabbits

Endorphins in Psychiatry

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