Design of potent dynorphin A-(1-9) analogues devoid of supraspinal motor effects in mice

Four analogues of dynorphin (Dyn) A-(1-9) incorporating D-Leu in position 8 alone or in combination with the nonhydrolysable psi [CS-NH] thiopeptide bond surrogate between positions 6 and 7 were tested in vitro for their ability to compete with the binding of selective kappa, mu, and delta opioid ligands, using membrane preparations of guinea pig cerebellum (kappa) and rat brain (mu and delta), for their ability to block the electrically induced contractions of the guinea pig ileum, and for their in vivo antinociceptive (writhing test) and motor (motor dysfunction assay) activities in mice. [D-Leu8]Dyn A-(1-9) displayed an affinity and a selectivity for the kappa opioid receptor that were comparable with those of Dyn A-(1-9). The potencies of [D-Leu8]Dyn A-(1-9) in the guinea pig ileum, writhing, and motor dysfunction assays were markedly enhanced (8-12 fold) compared with those of Dyn A-(1-9). [6 psi 7(CS-NH),D-Leu8]Dyn A-(1-9), [Lys6, 6 psi 7(CS-NH),D-Leu8] Dyn A-(1-9), and [Leu6, 6 psi 7(CS-NH), D-Leu8]Dyn A-(1-9) were somewhat less potent than [D-Leu8]Dyn A-(1-9) in all opioid assays. However, the thiopeptides were more potent analgesics than Dyn A-(1-9)(ED50 of 29.5, 23.9, and 15.5 nmol/mouse, respectively, compared with 90.7 nmol/mouse for Dyn A-(1-9)) and caused little or no motor impairment at analgesic doses.

Interactions of dynorphin A and related peptides with cardiac ouabain binding sites

The effect of dynorphin A (Dyn A) and related peptides on the binding of [3H]ouabain was examined in rat cardiac sarcolemma. Scatchard analysis of [3H]ouabain binding revealed the existence of two distinct sites: a high affinity (Kd: 20.4 nM) low capacity (Bmax: 1.55 pmol/mg protein) site and a low affinity (Kd: 3695 nM) high capacity (Bmax: 39.3 pmol/mg protein) site. Dyn A-(1-13) (10 microM) interacted selectively with the low affinity [3H]ouabain binding site causing a significant decrease in the Bmax (from 39.3 to 22.2 pmol/mg protein) without altering the Kd. Dyn A-(1-13) inhibited the binding of [3H]ouabain (500 nM) with an IC50 of 2.9 microM and a maximal inhibition of 77% of the specific binding activity. The non-opioid fragments Dyn A-(2-13), Dyn A-(3-13) and Dyn A-(6-10) displayed 36%, 32% and 14% of the potency of Dyn A-(1-13) respectively; whereas 100 microM of Dyn A-(1-8), Leu-enkephalin (Leu-Enk) and selective ligands for kappa (U-50, 488H) mu [(D-Ala2-Me-Phe4.Glyol5]Enk) and delta [(D-Ser2.Thr6]Leu-Enk) opioid receptors caused little or no inhibition of [3H]ouabain binding. The relative potency of various analogs and fragments of Dyn A in inhibiting the binding of [3H]ouabain correlated well (r = 0.89-0.90) with their potency in inhibiting the binding of [3H]Dyn A-(1-13) to non-opioid Dyn sites (Dumont and Lemaire, 1996) and to block [3H]NA uptake by cardiac synaptosomes (Dumont and Lemaire, 1995). In spontaneously hypertensive rats. [3H]ouabain binding displayed a 3.8-fold enhanced sensitivity to the action of Dyn A-(1-13) an effect that correlated with the enhanced ability of the peptide to inhibit Na+/K+-ATPase and [3H]NA uptake. The results indicate that Dyn A and related peptides may modulate cardiac functions through a non-opioid interaction with the low affinity ouabain binding site.

Corrigendum to 'the pentadecapeptide [Ser1]histogranin impairs passive avoidance learning in mice' [Eur. J. Pharmacol. 283 (1995) 251-254]

The peptides, histogranin and [Ser1]histogranin, were recently shown to modulate NMDA receptor function. In the present study, the effects of intracerebroventricular (i.c.v.) administration of [Ser1]histogranin and of the histogranin receptor antagonist, histogranin-(1-10), were examined on step-down type passive avoidance learning in mice. [Ser1]Histogranin (30-60 nmol) impaired retention, after post-training administration, but not when it was administered just prior to the retention assay. Histogranin-(1-10) (60 nmol) facilitated learning during training, without affecting retention. Co-administration of histogranin-(1-10) with [Ser1]histogranin (60 nmol each) led to a significant prevention of [Ser1]histogranin-induced learning impairment. These results indicate that [Ser1]histogranin impairs passive avoidance learning according to the pattern of NMDA receptor antagonists and involving specific histogranin sites.

The pentadecapeptide [Ser1]histogranin impairs passive avoidance learning in mice

The peptides, histogranin and [Ser1]histogranin, were recently shown to modulate NMDA receptor function. In the present study, the effects of intracerebroventricular (i.c.v.) administration of [Ser1]histogranin and of the histogranin receptor antagonist, histogranin-(1-10), were examined on step-down type passive avoidance learning in mice. [Ser1]Histogranin (30-60 nmol) impaired retention, after post-training administration, but not when it was administered just prior to the retention assay. Histogranin-(1-10) (60 nmol) facilitated learning during training, without affecting retention. Co-administration of histogranin-(1-10) with [Ser1]histogranin (60 nmol each) led to a significant prevention of [Ser1]histogranin-induced learning impairment. These results indicate that [Ser1]histogranin impairs passive avoidance learning according to the pattern of NMDA receptor antagonists and involving specific histogranin sites.

High-level expression of recombinant pea chloroplast fructose-1,6-bisphosphatase and mutagenesis of its regulatory site

The cDNA fragment coding for mature chloroplast pea fructose-1,6-bisphosphatase [Fru(1,6)P2ase] was introduced by PCR into the expression vector pET-3d resulting in the construction pET-FBP. After transformation of BL21 (DE3) Escherichia coli cells by the pET-FBP plasmid and induction with isopropyl thio-beta-D-galactoside, high-level expression of the recombinant enzyme was achieved. The protein could be purified in three days by a simple procedure which includes heat treatment, ammonium sulfate fractionation, DEAE Sephacel and ACA 44 chromatographies with a yield of 20 mg/l culture. In every respect, the recombinant enzyme was similar to plant chloroplast Fru(1,6)P2ase and, in particular, its reactivity with Mg2+ and redox regulatory properties were conserved. In a second series of experiments based on three-dimensional modeling of the chloroplast protein and sequence alignments, two cysteine residues of the recombinant enzyme (Cys173 and Cys178) were mutated into serine residues. An active enzyme, which did not respond to thiol reagents and to light activation, was obtained, confirming the putative regulatory role of the insertional sequence characteristic of the chloroplast enzyme.

Inhibitory effects of dynorphin-A on norepinephrine uptake by cardiac synaptosomal-mitochondrial fractions

The effect of dynorphin A-(1-13) (Dyn A-(1-13)) on [3H]norepinephrine ([3H]NE) uptake was examined in cardiac synaptosomal-mitochondrial fractions of control rats (Wistar, WR; Wistar-Kyoto, WKY) and spontaneously hypertensive rats (SHR). In adult WR, Dyn A-(1-13) caused naloxone-insensitive dose-dependent inhibition of [3H]NE uptake with an IC50 of 4.0 microM. The nonopioid Dyn A fragments Dyn A-(2-13) and Dyn A-(6-10) displayed 89 and 11% of the potency of Dyn A-(1-13), respectively, whereas Dyn A-(1-8), Leu-enkephalin, and the selective opioid agonists [D-Ala2, N-MePhe4, Glyol5]enkephalin (DAGO, mu), [D-Ser2, Thr6]Leu-enkephalin (DSLET, delta), and U-50488H (kappa) were inactive. The relative potency of various analogues and fragments of Dyn A in inhibiting [3H]NE uptake correlated well (r = 0.96) with their potency in inhibiting binding of [3H]Dyn A-(1-13) to nonopioid sites on cardiac membrane preparations. Dyn A-(1-13) showed the same potency in inhibiting [3H]NE uptake in prehypertensive (4-week-old) SHR as in age-matched WR and WKY. However, at ages 8 and 16 weeks Dyn A-(1-13) was twice as potent in SHR as in WR and WKY. The increased inhibitory potency of Dyn A-(1-13) in 8-week-old SHR was accompanied by a 1.3-fold increase in number of cardiac nonopioid [3H]Dyn A-(1-13) binding sites. Dyn A and related peptides inhibit [3H]NE uptake by cardiac synaptosomes by a nonopioid mechanism. The possible involvement of such a mechanism in development of hypertension in SHR is discussed.

Histogranin, a modified histone H4 fragment endowed with N-methyl-D-aspartate antagonist and immunostimulatory activities

Histogranin is a naturally-occurring pentadecapeptide with a structure 80% homologous with that a fragment-(86-100) of histone H4. First isolated from bovine adrenal medulla, the peptide was also shown to be present in the pituitary, brain, adrenal glands, blood plasma, lungs and spleen. At the subcellular level, histogranin is concentrated in secretory vesicles and it is released from perfused bovine adrenal glands 15-35 min after stimulation with carbamylcholine as opposed to catecholamines and [Leu5]enkephalin which are released immediately after stimulation. Rat brain membranes possess specific binding sites for [125I][Ser1]histogranin with characteristics of a receptor, namely high affinity, saturability, reversibility and sensitivity to heat and proteolytic enzyme treatments. Intracerebroventricular injections of synthetic histogranin (10-100 nmol) in mice protect them against N-methyl-D-aspartate (NMDA)-induced convulsions without affecting convulsions induced by (R,S)-alpha-amino-3-hydroxy -5-methyl-4-isoxazole-propionate (AMPA), kainate and bicuculline. The peptide also binds to specific sites on human peripheral blood mononuclear cells and it evokes the release of tumor necrosis factor-alpha (TNF), interleukin-1 (IL-1) and interleukin-6 (IL-6) from isolated rat macrophages in culture. Since the structure of histone H4 is considered as one of the most conservative, it is presumed that histogranin possesses its own precursor and that its gene is distinctly expressed.

Synthesis and biological activity of histogranin and related peptides

Histogranin (HN) was first isolated from bovine adrenal medulla and shown to be a pentadecapeptide displaying N-methyl-D-aspartate (NMDA) receptor antagonist activity. To determine the active pharmacophore of HN, fragments of the peptide were synthesized and their structure-activity relationships studied by measuring their ability to displace the binding of [125I][Ser1]HN to rat brain membrane preparations and to block NMDA-induced convulsions in mice. In the binding assay, only the full length peptide HN and HN(1-10) displayed a high affinity (Ki of 72 and 162 nM, respectively). All other tested fragments with deletions at the N- and (or) C-terminals of the molecule showed large (16- to 2500-fold) decreases in potency. The least active peptide fragment tested was HN(6-10) (Ki of 164 microM). In vivo, HN and HN(2-15) (100 nmol; i.c.v.) produced 94 and 40% protection against NMDA-induced convulsions in mice, respectively. None of the other peptide fragments displayed significant anticonvulsant activity. The protective activity of HN (60 and 100 nmol) was markedly antagonized by coadministration of HN(1-10) (100 nmol). The results indicate that the in vivo anti-NMDA and in vitro binding activities of HN and related peptides, with the exception of HN(1-10), depend upon the integrity of the molecule. On the other hand, the high affinity of HN(1-10) for HN binding sites correlates well with its antagonist effects towards the activity of the parent peptide.

N-methyl-D-aspartate receptor antagonist activity and phencyclidine-like behavioral effects of the pentadecapeptide, [Ser1]histogranin

The behavioral and pharmacologic profiles of [Ser1]histogranin ([Ser1]HN) were assessed by monitoring its ability to displace the binding of the specific N-methyl-D-aspartate (NMDA) receptor ligand, [3H]CGP 39653, to block the convulsant effects of NMDA and other excitatory agents in mice, and to produce phencyclidine (PCP)-like behavioral effects in rats. The peptide potently inhibited [3H]CGP 39653 binding to membrane preparations of rat brain with an IC50 of 198 nM and a maximal inhibition of 34% of the specific binding activity. Saturation binding experiments with [3H]CGP 39653 in the absence and presence of [Ser1]HN (2 microM) indicated that the inhibitory effect of the peptide was noncompetititive, producing a decrease in the maximal number of binding sites (Bmax of 62.5 fmol/mg protein as compared with 91.3 fmol/mg protein in control), but no significant change in the affinity (Kd of 4.5 nM as compared with 5.1 nM in control). Intracerebroventricular (ICV) injection of [Ser1]HN (10-100 nmol) in mice evoked a dose-dependent and selective blockade of NMDA-induced convulsions. In rats, [Ser1]HN (2.5-100 nmol, ICV) produced dose-dependent stereotypy, ataxia, and locomotion similar to those observed with PCP, at doses ranging between 50 and 400 nmol. The data indicate that [Ser1]HN noncompetitively interacts with the NMDA receptor, an action that goes along with its in vivo NMDA receptor antagonist activity and PCP-like behavioral effects.

Dynorphin potentiation of [3H]CGP-39653 binding to rat brain membranes

Dynorphin A-(1-13) and related peptide fragments were tested for their ability to modulate the binding of the competitive NMDA receptor antagonist, [3H]2-amino-4-propyl-5-phosphono-3-pentanoic acid ([3H]CGP-39653), to rat brain membranes. Dynorphin A-(1-13) produced a dose-dependent (1 nM to 10 microM) potentiation of [3H]CGP-39653 binding. The potentiation was insensitive to the kappa-opioid receptor antagonist norbinaltorphimine and it was also observed with the non-opioid peptides dynorphin A-(2-13) and dynorphin A-(6-10). Among various compounds which interact with distinct sites on the NMDA receptor complex, glycine (Gly; 1 microM) and the Gly receptor antagonist, (+/-)-3-amino-1-hydroxy-2-pyrrolidone ((+/-)-HA-966; 10 microM), blocked the dynorphin A-(1-13) induced potentiation of [3H]CGP-39653 binding. In equilibrium binding experiments, dynorphin A-(1-13) (10 microM) caused a significant increase in the binding capacity (Bmax) of [3H]CGP-39653 (from 111 to 306 fmol/mg protein) but not change in the apparent dissociation constant (Kd of 8.5 nM as compared with 8.7 nM in the absence of the peptide). The results indicate that dynorphin A and related peptides modify the expression of [3H]CGP-39653 binding sites consecutive to a non-opioid interaction with the NMDA receptor complex.

Non-opioid effects of dynorphins: possible role of the NMDA receptor

Dynorphin A (dynA) and related opioid peptides produce moderate analgesic effects with restricted types of pain stimuli that are often accompanied by a large variety of naloxone-insensitive biochemical and behavioural effects. In binding assays in vitro, dynA possesses a high affinity for mu-, delta- and kappa- opioid receptors with some selectivity for kappa sites, but it also binds to specific non-opioid sites. The involvement of the NMDA receptor has been suggested to explain some of the non-opioid effects of dynA and related peptides. In this article, Vijay Shukla and Simon Lemaire review the experimental evidence that suggests a role for the NMDA receptor in some of the pharmacological effects of dynA and related peptides.

Agonist and antagonist opioid activity of axial and equatorial conformations of S-methyl- and S-allyl-morphinans

Resolved axial (beta) and equatorial (alpha) forms of S-methyl (beta-sulforphanol, alpha-sulforphanol) and S-allyl (beta-sulfallorphan, alpha-sulfallorphan) morphinans were tested for their ability to depress the electrically evoked contractions of the guinea pig ileum and of the mouse vas deferens, to compete with the binding of prototype ligands selective for mu-, delta-, and kappa-opioid receptors in membrane preparations of rat brain and guinea pig cerebellum and to produce analgesia in a rat thermal pain assay. beta-Sulforphanol was more potent than alpha-sulforphanol in the guinea pig ileum (relative potencies of 93% and 29% respectively, as compared with levorphanol). beta-Sulfallorphan and alpha-sulfallorphan were both inactive in the guinea pig ileum assay. In the mouse vas deferens preparation, beta-sulforphanol and alpha-sulforphanol had relative potencies of 2.1% and 1.2% as compared with levorphanol, respectively, while the S-allyl derivatives were inactive. All morphinan derivatives displayed marked binding selectivity for mu-opioid receptors but alpha-sulfallorphan also showed significant binding potency on delta-opioid receptors (12% as compared to levorphanol). The compounds were also tested for their ability to antagonize the biological activity of morphine. In the guinea pig ileum, alpha-sulfallorphan potently inhibited morphine with a Ke value of 41.7 nM. alpha-Sulforphanol also antagonized morphine but with a smaller potency (Ke = 350 nM). In the mouse vas deferens, no antagonist activity against morphine was observed with any morphinan derivative tested at 1 microM. In the rat thermal pain assay, beta-sulforphanol (intracisternally, i.c.) was more potent than alpha-sulforphanol in producing analgesia while the other morphinan derivatives were inactive.(ABSTRACT TRUNCATED AT 250 WORDS)

Up-regulation of cytokine production in alveolar macrophages by histogranin, a novel endogenous pentadecapeptide

Recently, histogranin (HN), a newly found pentadecapeptide, was shown to enhance tumor necrosis factor (TNF) production by alveolar macrophages (AM). In this study, we have investigated whether HN was present in tissues rich with immune cells and further explored the effect of HN and [Ser1]HN on the production of TNF and other key cytokines. Relatively high levels of immunoreactive (ir)-HN were found in rat lung (14.9 pmol/g) and spleen (12.3 pmol/g), indicating its localization in close proximity to macrophages/monocytes and lymphocytes. Furthermore, HN and [Ser1]HN (10(-8)-10(-7) M) stimulated basal and lipopolysaccharide (LPS)-induced interleukin 1 (IL-1) mRNA expression and IL-1 release from rat AM. [Ser1]HN also stimulated basal and LPS-induced interleukin-6 (IL-6) release. Although HN did not affect the kinetics of cytokine production, the maximal enhancing effect of HN was seen at 3 h for TNF, 6 h for IL-1 and 18 h for IL-6. These data indicate that HN can up-regulate a cytokine cascade involving TNF, IL-1 and IL-6 and suggest a role for this endogenous peptide in immune regulation.

Interaction of histogranin and related peptides with [3H]dextromethorphan binding sites in rat brain

Histogranin (HN) and related peptides were tested for their ability to modulate the binding of the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, [3H]dextromethorphan ([3H]DM), to rat brain membranes. HN, [Ser1]HN and the C-terminal fragment HN-(6-15) (0.1 nM-1 microM) potentiated (up to 1.6-fold) the binding of [3H]DM (5 nM) whereas the N-terminal fragment HN-(1-10) had no effect. The potentiation of [3H]DM binding by [Ser1]HN was blocked by NMDA (100 microM) and the NMDA receptor antagonist, CPP (1 microM) but not by the sigma (sigma) receptor ligand, (+)-pentazocine (0.1 microM) and the phencyclidine (PCP) receptor ligand, TCP (1 microM). Equilibrium binding experiments in presence of TCP (1 microM) to block PCP receptors indicated that [Ser1]HN (1 microM) causes a significant increase in the binding capacity (Bmax) of [3H]DM (from 2.46 to 3.46 pmol/mg protein) but no change in the apparent dissociation constant (Kd of 428 nM as compared with 487 nM). The results indicate that HN and related peptides specifically enhance the number of [3H]DM binding sites associated to the NMDA receptor complex.

Expression of beta 1-6-branched N-linked oligosaccharides is associated with activation in human T4 and T8 cell populations

Activation of human T lymphocytes by phorbol 12-myristate 13-acetate and leukoagglutinin from Phaseolus vulgaris (L-PHA) results in important changes in N-glycosylation. The most important event is the increase, in both T4 and T8 cells (especially the latter), of L-PHA+ structures characterized by beta 1-6-branching of complex-type oligosaccharides. Moreover, the existence of a CD4-mediated increase of these beta 1-6-branched structures on positively selected T4 cells, as compared with the negatively selected ones, suggests that the presence of these structures, not detectable on T8 resting cells, could be related to stimulation events triggered by both selection methods. This beta 1-6-branching on N-glycans, strongly associated with a metastatic phenotype in human and rodent tumors, is exhibited by numerous glycoproteins on stimulated cells, as shown by blot analysis.

Characterization of [125I][Ser1]histogranin binding sites in rat brain

The binding characteristics of histogranin (HN), an endogenous peptide first recognized for its antagonism of N-methyl-D-aspartate (NMDA) responses, were determined in membrane preparations of rat brain. [125I][Ser1]HN, a stable bioactive analog of HN, bound specifically and reversibly to a homogenous population of high-affinity sites with a Kd of 25 nM and a Bmax of 410 fmol/mg protein. The binding of [125I][Ser1]HN increased linearly with membrane protein concentration and was destroyed upon membrane pretreatment with trypsin. The binding displayed rapid association and dissociation kinetics and was blocked by peptides possessing close homology with HN in the following order: [Ser1]HN-(1-15) > HN > [Ser1]HN-(1-14) > HN-(2-15) > [Ser1]-HN-(1-10) > HN-(6-10). Unrelated peptides such as substance P, beta-endorphin, neuropeptide Y, [Met5]enkephalin, [Leu5]enkephalin, dynorphin A(1-13) and neuromedin C were inactive in competition binding assays against [125I]Ser1]HN. Ligands of the binding domains of the NMDA receptor, such as (+)3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid, (+) 5-methyl-10,11-dihydro 5H-dibenzo[a, d]cyclohepten-5,10-imine hydrogen maleate, 1-N-(2-thienyl)cyclohexylpiperidine, glycine and glutamate were also ineffective in competing for [125I][Ser1]HN binding sites. Interestingly, specific ligands for the polyamine site on the NMDA receptor, as well as the cations Mg++ and Zn++ inhibited [125I][Ser1]HN binding. The polyamine antagonist diethylenetriamine produced a noncompetitive inhibition with an IC50 (175 nM) comparable to that of HN (75 nM). The cations Zn++ and Mg++ displaced [125I][Ser1]HN binding with IC50 values of 18 and 240 microM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of histogranin receptors in human peripheral blood lymphocytes

Histogranin (HN), a peptide recently isolated from bovine adrenal medulla, is also present in the spleen. In present studies, specific high affinity binding sites for HN were characterized on membrane preparations of human lymphocytes by radioligand binding. [125I]-[Ser1]HN binding was found to be dependent on time and protein concentration and to be sensitive to trypsin treatment. The binding displayed high affinity (Kd = 1.1 +/- 0.3 nM) and saturability (Bmax = 40.2 +/- 5.0 fmol/mg protein), and it was reversed upon addition of unlabelled [Ser1]HN and closely related peptides. The relative potency of various fragments in displacing [125I][Ser1]HN binding indicated that the active core of the molecule resides inside the C-terminal fragment, HN-(6-15). Interestingly, depressed patients displayed a marked decrease in the binding activity (from 15.4 to 8.55 fmol/mg protein at 0.5 nM of [125I][Ser1]HN). The presence of high affinity HN binding sites on lymphocytes provides evidence for a modulatory role for HN in the regulation of lymphocyte functions.

Characterization of non-opioid [3H]dynorphin A-(1-13) binding sites in the rat heart

The binding characteristics of [3H]Dynorphin A-(1-13) ([3H]Dyn A-(1-13) were examined in membrane preparations of rat heart. Saturation binding studies with increasing concentrations between 2.5 and 500 nM indicated that [3H]Dyn A-(1-13) binds to a single population of sites with a Kd of 285 nM and a Bmax of 215 pmol/mg protein. [3H]Dyn A-(1-13) binding is sensitive to trypsin treatment and it is inhibited by Zn2+ and Mg2+ with IC50 values of 159 and 310 microM, respectively. Dyn A and related peptides competes with the binding of [3H]Dyn A-(1-13) with the following order of potency: Dyn A-(1-13) > Dyn A > Dyn B > alpha-neo-endorphin > Dyn A-(1-8). The non-opioid peptides Dyn A-(2-13), Dyn A-(3-13) and Dyn A-(5-13) are as potent (Ki of 0.35, 0.44 and 0.59 microM, respectively) as Dyn A-(1-13) (Ki of 0.36 microM) in inhibiting [3H]Dyn A-(1-13) binding while Leu-enkephalin (Leu-Enk) exhibits no inhibitory effect at 100 microM. Selective ligands for kappa (kappa: U-50,488H, U-69,593), mu (mu: [D-Ala2, MePhe4, Glyol5]Enk) and delta (delta: [D-Ser2, Thr6]Leu-Enk) opioid receptors as well as for phencyclidine (PCP: MK-801, TCP) and sigma (sigma: (+)-SKF-10047, DTG, 3(+)-PPP) receptors show little or no inhibition of [3H]Dyn A-(1-13) binding at 100 microM. These results indicate that the heart contains a low affinity high capacity binding site for Dyn A and related peptides, distinct from opioid, PCP and sigma receptors.

Isolation and characterization of histogranin, a natural peptide with NMDA receptor antagonist activity

Histogranin, was co-purified with bombesin-like immunoreactive peptides from bovine adrenal medulla. Its structure, H-Met-Asn-Tyr-Ala-Leu-Lys-Gly-Gln-Gly-Arg-Thr-Leu-Tyr-Gly-Phe-COOH, was determined by gas-phase Edman degradation. It was in accordance with its amino acid composition and corresponded to a 15 amino acid fragment (fragment 86-100) of histone H4 with substitutions in positions 1 (Val), 2 (Val) and 7 (Arg). The peptide was synthesized by the solid-phase procedure and the synthetic product was identical to the natural peptide as determined by its retention time on three analytical high-performance liquid chromatography systems. An antibody was raised against synthetic [Ser1]histogranin and used to monitor the presence of histogranin in various rat tissues and subcellular fractions of bovine adrenal medulla. In rats, immunoreactive histogranin was mainly concentrated in the pituitary (5065 pmol/g) and the adrenal glands (268 pmol/g), but it was also present in other tissues including the brain (1.6 pmol/g) and blood plasma (24 fmol/ml). A neuropeptide function for the adrenal peptide was suggested by its relative high concentration in chromaffin granules (42 fmol/mg protein as compared with 1 fmol/mg protein in cytosol) and its release from perfused bovine adrenal glands. In rat brain membrane preparations, synthetic histogranin displaced the binding of [3H]CGP 39653, a specific ligand of N-methyl-D-aspartate (NMDA) receptor. The displacement curve was biphasic with IC50 of 0.6 and 3955 nM, representing 33% and 67% of the binding sites, respectively. Intracerebroventricular (i.c.v.) injection of the peptide (5-100 nmol) in mice produced a dose-dependent protection against NMDA (0.5-1.0 nmol) -induced convulsions but not against (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA, 0.25-2.0 nmol), kainate (0.25-0.75 nmol) and bicuculline (1-10 nmol)-induced convulsions. These results suggest that histogranin may be an endogenous modulator of NMDA receptor functions.

Design of potent and selective dynorphin A related peptides devoid of supraspinal motor effects in mice

Dynorphin A-(1-13)-Tyr-Leu-Phe-Asn-Gly-Pro (Dyn Ia) was previously shown to be a highly potent and selective kappa opioid peptide. Four analogs of Dyn Ia are synthesized by the solid-phase procedure, introducing pseudo CH2NH linkage between positions 6 and 7 as follows: analog 1, [6 psi 7 (CH2NH)]Dyn Ia; analog 2, [6 psi 7 (CH2NH), D-Leu8]Dyn Ia; analog 3, [N(Me)-Tyr1, 6 psi 7 (CH2NH)]Dyn Ia; and analog 4, [N(Me)-Tyr1, 6 psi 7 (CH2NH), D-Leu8]Dyn Ia. The purified peptides are compared in vitro with Dyn Ia for their ability to compete with the binding of selective kappa, mu, and delta opioid ligands using membrane preparations of guinea pig cerebellum (kappa) and rat brain (mu and delta). The synthetic compounds are also compared in vivo in mice (intracerebroventricularly administered) for their analgesic activity against acetic acid induced writhing and their ability to produce motor dysfunction. All compounds display a high affinity (Ki = 0.5-1.8 nM) and a good selectivity for the kappa opioid receptor, and their rank order of potency on the kappa site (analog 2 > analog 1 > analog 3 > analog 4) closely parallels their potency (AD50 = 1.57-5 nmol/mouse) in inhibiting acetic acid induced writhing in mice (analog 2 > analog 1 > analog 4 > analog 3). On the other hand, all the synthetic analogs are less potent than Dyn Ia in producing motor effects, analog 2 being the least potent (CD50 = 15.4 nM as compared with 2.9 nM for Dyn Ia).(ABSTRACT TRUNCATED AT 250 WORDS)

Norbinaltorphimine protection against N-methyl-D-aspartic acid-induced convulsions and mortality

The kappa-selective opioid antagonist, norbinaltorphimine (Nor-BNI), was tested against convulsions and mortality induced by the excitatory amino acids, N-methyl-D-aspartic acid (NMDA), (R,S)-alpha-amino-3- hydroxy-5-methyl-4-isoxazole propionate (AMPA) and kainic acid and the gamma-aminobutyric acid antagonist, bicuculline. Nor-BNI (10-40 nmol; intracerebroventricularly, i.c.v.) protected against NMDA (0.5-2.0 nmol i.c.v.)-induced convulsions and NMDA (2 nmol i.c.v.) and AMPA (2 nmol i.c.v.)-induced mortality. The opioid antagonist, naloxone (10 nmol i.c.v.), had no protecting activity. In vitro, Nor-BNI competed with the binding of the specific NMDA receptor ligand, [3H]D,L-(E)-2-amino-4-propyl- 5-phosphono-3-pentenoic acid ([3H]CGP 39653, 10 nM; IC50 of 1.63 +/- 0.20 microM) to mouse brain membrane preparations. The results indicate that the protecting activities of Nor-BNI are mediated by NMDA receptor-related mechanisms.