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The opioid receptors involved in the supraspinal and spinal actions of [D-Pen2, D-Pen5]enkephalin (DPDPE) for production and/or modulation of analgesia were investigated in two thermal analgesic tests, the mouse warm water (55 degrees C) tail-withdrawal assay and the radiant heat tail-flick test. Two approaches were used at supraspinal and spinal sites:(More)
The objective of this study was to describe, quantitate and compare naloxone-induced abstinence syndromes in rats infused centrally (Sylvian aqueduct) with agonists that are currently the most selective for mu [( D-Ala2, MePhe4, Gly-ol5]enkephalin), delta [( D-Pen2, D-Pen5]enkephalin) and kappa (3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)(More)
Three agonists with the highest degree of selectivity available for mu ([D-Ala2,NMePhe4,Gly-ol]enkephalin, DAGO), delta ([ D-Pen2,D-Pen5]enkephalin, DPDPE) and kappa (U-50,488H, U50) opioid receptors were compared for their activity in inhibiting acetic acid-induced writhing in mice. Additionally, three reference agonists for mu (morphine), delta ([(More)
Substantial evidence has been accumulated which suggests that opioid delta receptors may be distinguished on the basis of their involvement in the modulation (i.e., increase or decrease in potency) of mu-mediated antinociception. On this basis, it has been hypothesized that some opioid delta receptors exist within a functional complex with mu receptors(More)
Tetrapeptides of primary sequence Tyr-X-Phe-YNH2, where X is D-Cys or D-Pen (penicillamine) and where Y is D-Pen or L-Pen, were prepared and were cyclized via the side chain sulfurs of residues 2 and 4 to disulfide or dithioether-containing analogs. These peptides are related to previously reported penicillamine-containing pentapeptide enkephalin analogs(More)
The previously described cyclic, delta opioid receptor-selective tetrapeptide H-Tyr-D-Cys-Phe-D-Pen-OH, where Pen, penicillamine, is beta-beta-dimethylcysteine, was modified at residues 2 and 4 by varying combinations of D- and L-Cys and D- and L-Pen, and effects on mu and delta opioid receptor binding affinities and on potency in the mouse vas deferens(More)
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