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  • 1
    ISSN: 1432-1912
    Keywords: Key words Cardiomyocytes ; Opioid receptors ; G proteins ; Pertussis toxin ; Dynorphin ; U-50 ; 488 ; Naloxone ; Nor-binaltorphimine ; DADLE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Opioids directly decrease the contractile response of isolated ventricular cardiomyocytes to electrical stimulation. To investigate whether these effects are mediated via GTP-binding Gi/o proteins we examined the influence of pertussis toxin on the effects of the κ-opioid receptor agonist trans-(±)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamide (U-50,488) methanesulphonate and on the as yet undescribed effects of the opioid peptide dynorphin A (1–8) on contraction. In isolated, electrically driven, rat ventricular cardiomyocytes both agents concentration dependently reduced cell shortening within 15 min, decreasing the contractile response by 79±4% (n=5) and 62±2% (n=6) of control values at maximal effective concentrations of 10 µM (U-50,488) and 1 µM [dynorphin A (1–8)], respectively. Pertussis toxin pre-treatment (200 ng/ml; 4.5–5 h) completely abolished the effects of U-50,488 and dynorphin A (1–8) on the contractile response, indicating that these effects are mediated via Gi/o proteins. In addition, the non-selective opioid receptor antagonist (–)-naloxone and the κ-opioid receptor antagonist nor-binaltorphimine antagonized the effects of U-50,488 and dynorphin A (1–8) on the contractile response. Furthermore, the µ- and δ-opioid receptor agonist (D-Ala2, D-Leu5)-enkephalin (DADLE) had no effects on contraction. These results indicate that the decrease in cell shortening is due to stimulation of κ-opioid receptors. The direct effect of κ-opioid receptor agonists on the contractile response thus represents an additional mechanism for decreasing cardiac contractility, besides the M-cholinoceptor- or adenosine receptor-mediated pathway. It is conceivable that increased release of endogenous dynorphins from the heart during hypoxia may protect the heart in a similar manner to adenosine.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 43 (1997), S. 99-117 
    ISSN: 0006-3525
    Keywords: milk proteins ; opioid peptides ; opioid receptor ligands ; milk opioids ; alpha-casein exorphins ; beta-casomorphins ; beta-casorphin ; casoxin A, B, C or D ; alpha-lactorphins ; beta-lactorphin ; lactoferroxins ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Milk is a mammalian characteristic and is of particular importance for humans: Mother's milk or its substitutes from cows' milk are absolutely essential nutriments for the neonate and cows' milk also represents a basic foodstuff for adults.However, in addition to their well-known nutritive role, milk constituents apparently are also able to carry specific information from the milk producer's to the milk receiver's organism: Thus, a number of milk protein fragments has been shown to behave like opioid receptor ligands able to address opioidergic systems in the adult's or in the neonate's organism.With respect to the proteins, which they are derived off, these peptides have been named α-casein exorphins or casoxin D (α-casein), β-casomorphins or β-casorphin (β-casein), casoxin or casoxin A, B, or C (κ-casein), α-lactorphins (α-lactalbumin), β-lactorphin (β-lactoglobulin) or lactoferroxins (lactoferrin). Only casoxins and lactoferroxins display antagonistic properties; the other peptides behave like opioid receptor agonists.Most of the information available so far has been collected about β-casomorphins. These peptides obviously can be released from β-casein in the adult's or in the neonate's organism, where they might elicit opioid effects in the frame of a regulatory role as “food hormones”. Several synthetic β-casomorphin derivatives have been shown to be highly specific and potent μ-type opioid receptor ligands which frequently have been used as standard tools in opioid research. © 1997 John Wiley & Sons, Inc. Biopoly 43: 99-117, 1997
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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