Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: CAS:338-69-2 (D-Ala)
 1,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A dimeric pentapeptide enkephalin (DPE2) consisting of two molecules of [D-Ala 2, Leu 5] enkephalin linked at C-terminal leucine with ethylenediamine, (H-Tyr-D-Ala-Gly-Phe-Leu-NH-Ch2)2 is a bivalent ligand for the delta enkephalin receptors of rat brain and neuroblastoma-glioma hybrid (NG108-15) cells. This new enkephalin analog shows dramatically increased affinity in radioligand assays using whole brain membranes when delta but not mu specific radioligands are employed. When membranes from NG108-15 cells are used, the dimer shows greatly increased activity irrespective of the mu or delta specificity of the tracer. The dimer DPE2 shows a four-fold, "sodium shift" in its IC50 for competition with [3H]naloxone, suggestive of agonist behavior. Agonist activity was confirmed by demonstrating that DPE2 inhibits cyclic AMP production in prostaglandin E1 stimulated NG108-15 cells, and by demonstrating very high potency in the mouse vas deferens bioassay. DPE2 binds to the same delta sites as the delta-selective monomer [D-Ala2, D-Leu5] enkephalin, since the two ligands show complete crossdisplacement. Radiolabeled 3H-DPE2 shows a five-fold higher affinity constant, a 2.5-fold higher association rate constant, and a two-fold lower dissociation rate than the monomer. These results are consistent with the hypothesis that the dimeric pentapeptide enkephalin can bridge two delta receptors. This enkephalin dimer provides a valuable new probe of opiate receptors and their organization in cell membranes.
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PMID:Dimeric pentapeptide enkephalin: a novel probe of delta opiate receptors. 629 43

The interaction of metkephamid (Tyr-D-Ala-Gly-Phe-N(Me)Met-NH2) with 3H-dihydromorphine and 3H-D-Ala2-D-Leu5-enkephalin binding has been examined in rat brain homogenates. Displacements of both 3H-ligands by metkephamid indicate that metkephamid interacts competitively with greatest potency to the high affinity binding component for both ligands (mu1 site). Unlike most enkephalins and opiates, metkephamid binds equipotently to both morphine-selective (mu2) and enkephalin-selective (delta) binding sites. Metkephamid is differentiated from morphine by its better than 12-fold higher affinity for the delta receptor. Blockade of the high affinity (mu1) binding in vivo with high doses of naloxazone dramatically reduces metkephamid's analgesic potency.
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PMID:Metkephamid (Tyr-D-ala-Gly-Phe-N(Me)Met-NH2), a potent opioid peptide: receptor binding and analgesic properties. 629 39

The 2-nitro-4-azidophenyl(NAP)-D-Ala2-Leu5-Enkephalin derivatives: Try-D-Ala-Gly-Phe-Leu CONCH2CH2NH-NAP (E-NAP-EDA) and Try-D-Ala-Gly-Phe-Leu CONCH2CH2NH-COCH2CH2NHNAP(E-NAP- -Ala-EDA) were synthesized by conventional peptide methods. Their structure was determined by amino acid analysis, ultra violet, visible and infra red spectroscopy. Both peptides were shown a) to bind with high affinity to the opiate receptors of rat brain membranes and b) to inhibit strongly the contractions of electrically stimulated vas deferens and the adenyl cyclase of the NG 108-15 cell membranes. These effects were reversed by the antagonist naloxone. Photoloysis of the rat brain membranes-(E-NAP- -Ala-EDA) complex caused a 20-30% inactivation of the opiate receptors. Inactivation was prevented when the complex was irradiated in the presence of naloxone. The radio-labeled derivatives of these enkephalin analogs may prove useful photochemical labels of the opiate receptor.
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PMID:Photolabile ligands for opiate receptors. 629 69

The differential distributions of [3H]naloxone-labeled and [3H]D-Ala-D-Leu-enkephalin-labeled opiate receptors in rat cerebral cortex were localized autoradiographically and quantified by grain counting and computerized densitometry. In addition, receptor distributions were compared to terminal patterns of thalamocortical projections labeled by axoplasmic transport of [3H]amino acids. Opiate receptors labeled with [3H]naloxone in a mu ligand selectivity pattern show striking laminar heterogeneity and are densest in limbic cortical areas, intermediate in the motor cortex, and fewest in the primary sensory areas. By contrast, opiate receptors labeled with [3H]D-Ala2-D-Leu5-enkephalin in a delta ligand selectivity pattern are much more homogeneously distributed across both regions and laminae within regions. Mu receptors in most cortical areas have density peaks in layers I and VI and each peak shows a density gradient that is sloped within the layer so that the highest densities are at the most superficial and the deepest portions of cortex. In addition, there is an intermediate peak whose laminar position varies depending on the area in which it is found. In rostral agranular cortex, including limbic and motor areas, the [3H]naloxone binding peaks are in layers I, III, and VI. In primary somatosensory cortex, the intermediate peak is in layer Va and in most of remaining homotypical cortex it is in layer IV. Some areas have only bilaminar labeling, in superficial and deep layers; these include portions of the sulcal and retrosplenial cortices. Piriform and entorhinal cortices have dense [3H]naloxone binding only in the deepest layer and show a descending gradient of density toward the superficial layer. The positions of the mu receptor peaks were compared with termination patterns of projections originating in the thalamus. Close correspondence was found between receptor binding in the prelimbic, primary somatosensory, and entorhinal areas and projection terminations arising from the thalamic mediodorsal, posterior, and central medial nuclei, respectively. Although regional variations in [3H]D-Ala2-D-Leu5-enkephalin-labeled receptor density are uncommon, a gradual decrease in the number of sites along the dorsomedial wall of the cortex from anterior cingulate to caudal retrosplenial limbic cortex can be observed. Laminar variations in binding density are small as well; higher concentrations of the peptide binding sites are usually found in the deep cortical layers. These findings emphasize aspects of opiate receptor architecture which may be relevant to identifying cortical "opiatergic" neurocircuitry and raise the possibility of opiate modulation of thalamocortical transmission.
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PMID:Opiate receptor localization in rat cerebral cortex. 630 69

Treatment of the isolated mouse was deferens with the enzyme arylsulfatase (E.C. 3.1.6.1) had an effect on the ability of this tissue to respond to various opiates. It increased the IC50 values and slopes of their dose-response curve for enkephalins and their analogs, and shifted to the right the curves for FK33824, levorphanol and normorphine. There was no effect on the action of etorphine, beta-endorphin or dynorphin. With morphine there was a biphasic effect, IC50 values increasing at low enzyme concentrations and decreasing at high enzyme concentrations. A further comparison of arylsulfatase effects on morphine and on D-Ala-2-D-Leu5-enkephalin indicated that the morphine effect, unlike the D-Ala-2-D-Leu5-enkephalin effect, could not be reversed by washing and that morphine, unlike D-Ala2-D-Leu5-enkephalin, became much less sensitive to naloxone antagonism. The observed modifications in the shape of the dose-response curves indicate that the effect of the opiates in the mouse vas deferens is more complex than that expected through the occupation of a simple receptor. There is either more than one type of functional receptor for each agonist or only one receptor, which can interact with every drug in different ways; this complexity is discussed in terms of various possibilities, including fractional occupancy, positive cooperativity and multiple sites.
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PMID:Functional opiate receptor in mouse vas deferens: evidence for a complex interaction. 631 79

The cyclic partial retro-inverso modified enkephalins, H-Tyr-cyclo[-D-Glu-Gly-gPhe-D-Leu-] (I), H-Tyr-cyclo[-D-A2bu-Gly-gPhe-R&S-mLeu-] (IIf, IIs), H-Tyr-cyclo[-D-Glu-Gly-Phe-gLeu-] (III), and their corresponding acyclic analogs, H-Tyr-D-Ala-Gly-gPhe-D-Leu-For (Ia), H-Tyr-D-Ala-Gly-gPhe-R,S-mLeu-NH2 (IIa), H-Tyr-D-Ala-Gly-Phe-gLeu-For (IIIa) have been evaluated in in vitro bioassays. Relative to Leu-enkephalin, the modified compounds are more potent in the guinea pig ileum assay and more effectively displace [3H]naloxone from rat brain receptors, while they are generally less potent in the mouse vas deferens assay and only weakly able to displace [3H] (D-Ala2, D-Leu5)enkephalin. The analogs are highly resistant to proteolytic degradation by rat brain membrane preparations that readily hydrolyze Leu-enkephalin.
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PMID:Cyclic and acyclic partial retro-inverso enkephalinamides: Mu receptor selective enzyme resistant analogs. 631 99

Morphiceptin (Tyr-Pro-Phe-Pro-NH2), a nonenkephalin peptide, is an opioid agonist highly selective for mu opiate receptors. Chemical modification of Tyr-Pro-Phe-Pro-NH2 was carried out by substituting structurally related amino acids at residues 2, 3 and 4. The morphiceptin analogs synthesized were then examined for receptor binding activities using 125I-labeled FK 33,824 (Tyr-D-Ala-Gly-NMePhe-Met(O)-ol) as the mu-ligand and 125I-labeled D-Ala2,D-Leu5-enkephalin as the delta-ligand, and for inhibitory activities on electrically evoked smooth muscle contraction of mouse vas deferens and isolated myenteric plexus-longitudinal muscle strips of guinea-pig ileum. All of these analogs showed virtually no activity at delta opiate receptor binding sites. Methylation of the nitrogen atom of phenylalanine and the substitution at the C-terminal of L-proline by D-proline produced potent mu-agonists, the prototype analog being Tyr-Pro-NMePhe-D-Pro-NH2 (PL017). The IC50 values of morphiceptin and its analogs for mu receptor binding were correlated to the ED50 values in the guinea-pig ileum assay, suggesting that the ileum effects were mediated by mu receptor interactions. A similar correlation between mu receptor binding activity and the ED50 values in the mouse vas deferens assay suggested that morphiceptin and its analogs also acted on mu receptors in this tissue. This idea is supported by the observation that naloxone has a high pA2 value of 8.71 against PL017 in mouse vas deferens. In in vivo studies, PL017 administered centrally into the rostral portion of the 4th ventricle produced long-lasting, naloxone-reversible analgesia in rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Potent morphiceptin analogs: structure activity relationships and morphine-like activities. 631 1

We have characterized the autoradiographic distribution of mu and delta opiate receptors in rat brain using [3H]-Tyr-D-Ala-Gly-NMe-Phe-Gly-ol (DAGO) and [3H]D-Thr2, Thr6leu-enkephalin (DTLET), two highly selective ligands for mu and delta opiate receptors, respectively. Both ligands label an apparent single class of sites. Ligand selectivity shows that [3H]DAGO and [3H]DTLET are more selective ligands for their respective receptors than [3H]dihydromorphine (DHM) and [3H][D-Ala2,D-Leu5]enkephalin (DADLE). Autoradiographically, mu opiate receptors are highly discretely distributed in certain areas. High densities are found in "patches" in caudate-putamen, nucleus accumbens, cingulate cortex, habenula, various thalamic nuclei, amygdala, superior colliculus, and interpeduncular nucleus. Delta opiate receptors are mostly concentrated in the external plexiform layers of the olfactory bulb, caudate-putamen, olfactory tubercule, claustrum, and deep layers (layers V and VI) of the cortex. Since [3H]DAGO and [3H]DTLET are more selective ligands for their respective opiate receptor subtypes, they should be better ligands to characterize the fine distribution of mu and delta opiate receptors.
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PMID:Autoradiographic distribution of mu and delta opiate receptors in rat brain using highly selective ligands. 631 67

In order to examine the capacity of pharmacologically useful opiates to stimulate human mast cell secretion, subjects were skin tested with morphine, codeine, or meperidine hydrochloride. All three agents acted equipotently in eliciting positive immediate skin reactions from all subjects tested. Each agent demonstrated 10 mm of net whealing at 5 to 10 micrograms base (16.7 to 40.4 nmol) injected intradermally. The ability to elicit immediate skin test reactions with endogenous opioid peptides was examined with the use of dynorphin, [D-Ala, 2-D-Leu5] enkephalin, beta-endorphin, and morphiceptin . All four compounds induced wheal-and-flare reactions with the order of potency: dynorphin, greater than beta-endorphin, and greater than [D-Ala, 2-D-Leu5] enkephalin approximately equal to morphiceptin at dose ranges of 0.3 to 8.45 nmol. The inhibition of reactivity by hydroxyzine and the demonstration of mast cell degranulation by electron microscopy suggest that the immediate skin responses to opioid stimulation occur as a consequence of mast cell degranulation. Experiments with the opioid receptor antagonist, naloxone, suggest that both opioid and nonopioid receptors may be involved. These results imply that endogenous opioid peptides possibly may play a role in mast cell function and/or degradulation .
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PMID:Induction of human cutaneous mast cell degranulation by opiates and endogenous opioid peptides: evidence for opiate and nonopiate receptor participation. 632 90

We report a method for measuring and expressing the binding selectivity of ligands for mu, delta, and kappa opioid binding sites. We used radioligands that are partially selective for these sites in combination with membrane preparations enriched in each site. Enrichment was obtained by treatment of membranes with the alkylating agent beta-chlornaltrexamine in the presence of appropriate protecting ligands, sufentanil for mu sites, [D-Ala2, D-Leu5] enkephalin for delta sites, and dynorphin A for kappa sites. After enrichment for mu receptors, [3H] dihydromorphine bound to a single type of site as judged by the slope of competition binding curves. After enrichment for delta or kappa receptors, binding sites for [3H] [D-Ala2, D-Leu5]enkephalin and [3H]ethylketocyclazocine, respectively, were still not homogeneous. There were residual mu sites in delta-enriched membranes but we found no evidence for residual mu or delta sites in kappa-enriched membranes. We used this method to identify ligands that are highly selective for each of the three types of sites: Tyr-D-Ala-Gly-(Me)Phe-Gly-ol, sufentanil, and morphiceptin for mu sites; (D- Pen2 , D- Pen5 ]enkephalin and [D- Pen2 ,L- Pen5 ]enkephalin for delta sites; and tifluadom and U50 ,488 for kappa sites.
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PMID:Site-directed alkylation of multiple opioid receptors. I. Binding selectivity. 632 59


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