morphine and deltorphin

A series of novel cyclic ureidopeptides, analogues of dermorphine/deltorphine tetrapeptide, were synthesized by solid phase peptide synthesis and/or in solution. The antinociceptive activity of N-substituted amides 1-10 was evaluated using hot-plate and tail-flick tests. Analogue 1 showed significant, stronger than morphine, antinociceptive effect after systemic applications. All analogues were also tested for their in vitro resistance to proteolysis by means of mass spectroscopy and it was found that all substituted amides 1-10 showed full stability during incubation with large excess of chymotrypsin and pepsin. Compound 1 is a lead molecule for further evaluation.

Topics: Analgesics, Opioid; Animals; Chymotrypsin; Hot Temperature; Hydrolysis; Hyperalgesia; Indoles; Male; Mice; Mice, Inbred BALB C; Models, Chemical; Molecular Structure; Oligopeptides; Opioid Peptides; Pepsin A; Proteolysis; Spectrometry, Mass, Electrospray Ionization; Styrenes

To investigate the value of the 2',6'-dimethylphenylalanine (Dmp) residue as an aromatic amino acid substitution, we prepared analogues of the mu opioid receptor-selective dermorphin tetrapeptide Tyr-D-Arg-Phe-betaAla-NH(2) (YRFB) in which Dmp or its D-isomer replaced Tyr(1) or Phe(3). Replacing Phe(3) with Dmp essentially tripled mu receptor affinity and the receptor's in vitro biological activities as determined with the guinea pig ileum (GPI) assay but did not change delta receptor affinity. Despite an inversion of the D configuration at this position, mu receptor affinity and selectivity remained comparable with those of the L-isomer. Replacing the N-terminal Tyr residue with Dmp produced a slightly improved mu receptor affinity and a potent GPI activity, even though the substituted compound lacks the side chain phenolic hydroxyl group at the N-terminal residue. Dual substitution of Dmp for Tyr(1) and Phe(3) produced significantly improved mu receptor affinity and selectivity compared with the singly substituted analogues. Subcutaneous injection of the two analogues, [Dmp(3)]YRFB and [Dmp(1)]YRFB, in mice produced potent analgesic activities that were greater than morphine in the formalin test. These lines of evidence suggest that the Dmp residue would be an effective aromatic amino acid surrogate for both Tyr and Phe in the design and development of novel opioid mimetics.

Topics: Amino Acids, Aromatic; Analgesics, Opioid; Animals; Dose-Response Relationship, Drug; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Guinea Pigs; Ileum; In Vitro Techniques; Indicators and Reagents; Kinetics; Male; Mice; Muscle Contraction; Muscle, Smooth; Oligopeptides; Opioid Peptides; Pain Measurement; Phenylalanine; Receptors, Opioid, mu; Vas Deferens

The solid phase procedure, based on the Fmoc chemistry, was used to prepare some opioid deltorphin (H-Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH2, DEL C) and dermorphin (H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2, DER) analogues in which a D-glucopyranosyl moiety is beta-O-glycosidically linked to a Thr4 or Thr7 side chain. Their activities were determined in binding studies based on displacement of mu- and delta-receptor selective radiolabels from rat brain membrane synaptosomes, in guinea pig ileum and rabbit jejenum bioassays, and, in vivo, by a mouse tail-flick test after intracerebroventricular (icv) and subcutaneous (sc) administrations. The glyco analogues modified at position 4 displayed low opioid properties, while Thr7-glycosylated peptides retained high delta- or mu-selectivity and remarkable activity in vivo. In particular, as systemic antinociceptive agents, the latter glucoside-bearing compounds were more potent than the parent unglycosylated peptide counterparts, showing a high blood to brain rate of influx which may be due to the glucose transporter GLUT-1.

Topics: Amino Acid Sequence; Analgesics, Opioid; Animals; Binding, Competitive; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Glycopeptides; Guinea Pigs; Ileum; In Vitro Techniques; Indicators and Reagents; Jejunum; Kinetics; Male; Mice; Muscle Contraction; Muscle, Smooth; Oligopeptides; Opioid Peptides; Pain; Rabbits; Rats; Rats, Sprague-Dawley; Receptors, Opioid; Structure-Activity Relationship; Synaptosomes

In order to study the structure-activity relationships of natural opioid deltorphins (H-Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2 and H-Tyr-D-Ala-Phe-Asp [or Glu]-Val-Val-Gly-NH2), 15 analogues were synthesized by the solution method. Their activities were determined in binding studies based on displacement of mu- and delta-receptor selective radiolabels from rat brain membranes and in two bioassays, using guinea pig ileum and mouse vas deferens. The obtained data indicate that the high delta-selectivity of deltorphins can be due to the constitution/conformation of the C-terminal part and, at least in part, to preselection by charge.

Topics: Amino Acid Sequence; Animals; Binding, Competitive; Chemical Phenomena; Chemistry; Guinea Pigs; Male; Mice; Molecular Sequence Data; Muscle, Smooth; Oligopeptides; Rats; Rats, Inbred Strains; Receptors, Opioid; Structure-Activity Relationship