Delta Opioid Peptide Research Articles

Inhibition of (+)[3H]SKF 10,047 binding to rat brain membranes by FAB fragments from a monoclonal antibody directed against the opioid receptor.

Examination of the binding of (+)[3H]SKF 10,047 to rat brain membranes indicated that at a low concentration most of the binding was to the haloperidol-sensitive binding site. Titration curves exhibited a displacement potency order of haloperidol greater than (+)SKF 10,047 = 1,3-diorthotolyl-guanidine much much greater than (-)SKF 10,047 much greater than phencyclidine analogues. The effect of Fab fragments from a monoclonal antibody, OR-689.2.4, directed against the opioid receptor on the binding of (+)[3H]SKF 10,047 to rat brain membranes was examined. The specificity of this antibody for the opioid receptor has been determined by its ability to inhibit the binding of mu and delta opioid peptides to rat brain but not the binding of kappa opioid ligands or nonopioid ligands specific for other receptors. The Fab fragments blocked and displaced specifically bound (+)[3H]SKF 10,047 in a titratable manner. Increasing the incubation time of the membranes with the Fab fragments increased the percent inhibition obtained. The Fab fragments acted as noncompetitive inhibitors of (+)[3H]SKF 10,047 binding. A (+)SKF 10,047 binding site in rat brain appears to share a common structural domain with mu and delta opioid receptors.

The conformational properties of the delta opioid peptide [cyclic] [D-pen2,D-pen5]enkephalin in aqueous solution determined by NMR and energy minimization calculations

The conformational properties of the delta opioid peptide [cyclic] [D-pen2,D-pen5]enkephalin in aqueous solution determined by NMR and energy minimization calculations

Functional opioid receptor sites in human placentas.

We characterized the presence of opioid peptide receptor sites in plasma membranes and cells from human midterm and term placentas. Incubations with [3H]ethylketo-cyclazocine (EKC) at increasing doses revealed the presence of high affinity, low capacity, opioid peptide receptor-specific binding of the kappa-type. Scatchard analysis of the binding data showed, in the plasma membranes, linear plots at both stages of pregnancy with similar mean equilibrium association constants of 1.31 +/- 0.29 (+/- SE) X 10(9) mol/L-1 (n = 4) at midterm and 0.52 +/- 0.63 X 10(9) mol/L-1 at term (n = 4). In placental cells (n = 4) from term gestations, the binding plots were curvilinear; the first component had a Ka of 5.51 +/- 0.50 X 10(9) mol/L-1, and the second component had a Ka of 1.33 +/- 0.81 X 10(8) mol/L-1 (P less than 0.01). When standardized per mg tissue protein, the number of binding sites in plasma membranes increased from 13.8 +/- 9.8 fmol at midterm to 50.0 +/- 18.6 fmol at term (P less than 0.05). For term placental cells, the concentration of binding sites was 81.2 +/- 36.0 fmol for the high affinity sites and 713 +/- 390 fmol for the lower affinity sites. Specificity for the kappa-type of OPR was found based on the inability of mu- or delta-opioid peptides, as well as LHRH and TRH, to compete for [3H]EKC binding. Term placental cells incubated with various doses of opioid peptides had a 50% increase in placental lactogen production. The increase was significantly higher than controls only with kappa-agonists (P less than 0.05), maximal with 10(-9) mol/L EKC, and completely inhibited by 5 X 10(-6) mol/L naloxone. These results expand on previous data demonstrating the presence of opioid peptide receptor in placental plasma membranes and suggest a role for opioid peptides in regulating secretion of placental lactogen by placental cells.

Visualization of multiple opioid-receptor types in rat striatum after specific mesencephalic lesions.

In order to gain insight into a possible modulatory role for mu, delta, and kappa opioid receptors of the nigrostriatal dopaminergic pathway, we investigated the topographical organization of the receptors with respect to pre- and postsynaptic membranes. Dopaminergic terminals projecting from the substantia nigra to the corpus striatum were destroyed by unilateral injection of 6-hydroxydopamine into the substantia nigra. Quantitative receptor assays using highly specific radioligands were used to measure the density of striatal mu, delta, and kappa receptors before and after denervation. Denervation caused a 34 +/- 2% loss of striatal mu receptors and a 32 +/- 1% loss of striatal delta receptors on the lesioned side of the brain; in contrast, kappa receptors did not change significantly in density. Quantitative in vitro autoradiography was used to visualize the neuroanatomical pattern of receptors on lesioned and nonlesioned sides of the brain under the light microscope. Loss of mu receptors in striatal patches was striking in the ventrolateral areas of the striatum, whereas the most notable loss of delta receptors was found in the central striatum. Other brain areas did not differ significantly in mu receptor density between the lesioned and nonlesioned sides, as determined by autoradiography. These findings suggest that a high percentage of mu and delta receptors in the striatum are located on the nigrostriatal dopaminergic terminals and support the concept of a modulatory role for mu and delta opioid peptides in the nigrostriatal dopaminergic pathway.

Suppression or differentiation of solvent resonance by a combination of DEFT with a two-dimensional sequence

A new pulse sequence is described which combines the driven equilibrium Fourier transform (DEFT) and 2D pulse scheme, and allows simultaneous suppression of the solvent peak (H 2O/D 2O) in 1D and 2D experiments without perturbing the nearby solute signals. To overcome the sensitivity problem, and to allow for 2D experiments in a reasonably short time, a steady-state condition was set up by adjusting τ 1 (pulse delay) and D (recycle delay) to be 2–4 times the longest spin-lattice relaxation time T 1 (peptide) such that M z (solvent) was nulled prior to the 2D pulse sequence. Longitudinal and transverse relaxation rates of the solvent were analyzed in the steady state, and a direct calculation of T 1 (solvent) was performed using an equation derived in the present work. This novel pulse sequence is also extended to 2D NOE experiments with effective solvent suppression. The method is demonstrated in a variety of 1D and 2D experiments on the cyclic delta opioid receptor selective peptide ▪.

Pain control by endogenous enkephalins is mediated by MU opioid receptors

The analgesic effects of bestatin and thiorphan, two enzymatic inhibitors protecting endogenous enkephalins from their degradation, and those of DAGO and deltakephalin, respectively mu and delta opioid peptides, are assessed on the electrical stimulation test of the mouse tail. The relative analgesic potency of DAGO and deltakephalin is in good agreement with their relative potency on mu pharmacological assays : inhibition of electrically-induced contractions of guinea-pig ileum, displacement of 3H DAGO on rat brain. Finally, the analgesic effects of DAGO, deltakephalin and bestatin + thiorphan, are antagonized by the my antagonist naloxone with similar pA 2, and they are not modified by the delta antagonist ICI 154, 129. We conclude that only mu and not delta receptors are involved in the analgesic effects of enkephalins.