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F Porreca

Publications and source records attributed to F Porreca.

At least 163 records · Page 9Linked to original sources
PubMed1994

Delta opioid receptor selective ligands; DPLPE-deltorphin chimeric peptide analogues.

Further efforts to correlate the topography of the bioactive structures of DPDPE and the deltorphins, two delta-opioid receptor active peptide families, are reported. A number of DPLPE-deltorphin chimeric peptides have been synthesized in which the C-terminal dipeptide delta-address of the deltorphins (-Val-GlyNH2, -Nle-GlyNH2) have been linked to the highly delta-opioid selective cyclic peptides DPDPE or DPLPE. These studies demonstrate that a major structural feature determining high potency of hybrid analogues is the chirality of the amino acid residue in position 5. The radioligand binding assays have revealed a decrease in potency (compared to DPDPE) at delta-receptors when the C-terminal dipeptides were added to DPDPE. On the other hand, chimeric peptides of DPLPE with these same C-terminal dipeptides retained high delta-selectivity and affinity. Similar results were obtained using the mouse vas deferens (MVD) and guinea pig ileum (GPI) bioassays. The importance of the hydrophilicity of amino acids in positions 2 and 5 for delta-selectivity is consistent with the previous finding for DPLPE and DPDPE. On the other hand, the replacement of phenylalanine-4 with p-chlorophenylalanine-4 did not increase delta-selectivity as in DPDPE. These findings suggest that the delta-receptor interacts with hybridized enkephalins and deltorphins somewhat differently than with DPDPE.

Amino Acid Sequence↗
PubMed1994

Tonic regulation of mouse ileal ion transport by nitric oxide.

The possible role of nitric oxide (NO) in the regulation of intestinal ion transport was studied in isolated sheets of mouse ileum mounted in Ussing flux chambers. The competitive NO-synthase inhibitors NG-methyl-L-arginine (L-NMA), and NG-nitro-L-arginine (L-NNA) and the effects of NO released from acidified sodium nitrite solution were evaluated in tissues pretreated with guanethidine and atropine. Serosal L-NMA or L-NNA (10-300 microM), but not NG-methyl-D-arginine (D-NMA), produced a sustained concentration-related increase in short-circuit current (Isc) and potential difference (PD) with maximal Isc increases of 50.8 +/- 8.2 and 45.5 +/- 5.8 microAmps/cm2, respectively; mucosal application of L-NMA or L-NNA produced transient increases in Isc. The A50 (and 95% CL) values for serosal L-NMA and L-NNA were 25.6 (15.7-41.9) and 8.7 (5.1-14.9) microM, respectively. L-Arginine (0.1-10 mM), but not D-arginine, produced both a concentration-related reversal of L-NMA or L-NNA-induced increases in Isc. Additionally, pretreatment with L-arginine blocked the L-NMA or L-NNA effects, suggesting a competitive interaction. L-NMA-mediated increases in Isc were unaffected by bicarbonate-free buffer, whereas replacement of chloride ions with gluconate ions almost completely attenuated the response to L-NMA. Further, the effects of L-NMA or L-NNA were blocked by tetrodotoxin or chlorisondamine, suggesting neural actions involving ganglionic transmission.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMed1994

Characterization of SNF 9007, a novel cholecystokinin/opoid ligand in mouse ileum in vitro: evidence for involvement of cholecystokininA and cholecystokininB receptors in regulation of ion transport.

The effects of cholecystokinin (CCK) fragments and Asp-Tyr-D-Phe-Gly-Trp-[N-Me]Nle-Asp-Phe-NH2 1(SNF 9007), a synthetic CCK analog which binds with high affinity to CCKB and opioid delta receptors, were evaluated in isolated sheets of mouse ileum mounted in Ussing flux chambers. Serosal, but not mucosal, administration of cholecystokinin octapeptide-sulfated [CCK8(s)] and cholecystokinin tetrapeptide (30-33) [CCK4(30-33)] produced a brief, concentration-related increase in short circuit current (Isc) without changing tissue conductance. Serosal, but not mucosal, SNF 9007 produced a similar concentration-related increase in Isc which was followed by an immediate concentration-related and sustained decrease in Isc; no decrease in Isc was observed for either CCK8 or CCK4(30-33). The increase and subsequent decrease in the SNF 9007 Isc response were respectively classified as phase I (i.e., CCK-like) and phase II (opioid-like) activity. CCK8(s) and SNF 9007 (phase I) were active at low nanomolar concentrations, whereas CCK4(30-33) was active only at high nanomolar concentrations: the rank order of potencies to increase Isc was CCK8(s) > SNF 9007 > CCK4(30-33). Devazepide (L364,718), a selective antagonist of CCKA receptors, effectively blocked the action of CCK8(s), but not that of CCK4(30-33) or SNF 9007 (phase I). In contrast, 3R[+]-N-[2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-benzodiazepin-3-yl ]-N'- [3-methyl-phenyl]urea (L365,260), a selective CCKB receptor antagonist, blocked the action of CCK4(30-33) and SNF 9007 (phase I), and also antagonized CCK8(s), though to a lesser degree.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Characterization of [3H]naltrindole binding to delta opioid receptors in mouse brain and mouse vas deferens: evidence for delta opioid receptor heterogeneity.

Naltrindole (NTI) is a potent and selective nonpeptide delta opioid receptor antagonist. This study reports on the binding characteristics of [3H]NTI (specific activity = 30.5 Ci/mmole) for mouse brain and vas deferens (MVD) tissues. In brain, [3H]NTI had unusually high specific binding to delta receptors (80% at its Kd concentration) relative to other selective delta receptor radioligands. Saturation Kd values with 95% confidence intervals for mouse brain and MVD tissue preparations were 56.2 (41.8-75.7) and 104 (25.8-420) pM, respectively. These Kd values were significantly different (P = .028) and [3H]NTI binding to both tissues was best fit by a one-site model. Receptor densities were 83.9 (66.8-106) fmol/mg of protein for mouse brain and 14.8 (7.03-31.2) fmol/mg of protein for the MVD. Binding inhibition studies showed that NTI and the delta opioid receptor agonists [4'-Cl-Phe4]DPDPE and [D-Ala2, Glu4]deltorphin had high affinity for the sites labeled by [3H]NTI in both tissue preparations whereas mu [Tyr-Pro-psi-MePhe-D-Pro-NH2 (PL-17)] and kappa (U-69593) agonists had micromolar affinity. Both agonists recognized multiple sites in mouse brain under control (with 5 mM Mg++) and treatment (with 50 microM guanylyl-5'-imido-diphosphate and 100 mM NaCl) conditions but only single-site binding was observed for MVD (only control condition tested). [D-Ala2, Glu4]deltorphin showed about 6.5-fold selectivity for a portion (approximately 33%) of mouse brain sites (Ki = 130 pM) compared to sites labeled by [3H]NTI in MVD (Ki = 1200 pM) under control conditions. No significant difference was observed for [4'-Cl-Phe4]DPDPE binding affinity to both tissues (Ki = 450-680 pM) under control conditions. The affinity of opioid agonists, but not antagonists at [3H]NTI binding sites in mouse brain, was substantially reduced by the presence of guanylyl-5'-imidodiphosphate and sodium ions consistent with guanine nucleotide-binding protein regulation of the delta receptors. The portions of high- and low-affinity sites recognized by [4'-Cl-Phe4]DPDPE and [D-Ala2, Glu4]deltorphin in mouse brain labeled by [3H]NTI under treatment conditions were not significantly different (each subtype represented approximately 50% of the total population) suggesting delta receptor heterogeneity in this tissue. It is concluded that [3H]NTI binds to delta opioid receptor affinity states and subtypes with equal affinity and can be used for their characterization in conjunction with different treatment conditions and ligands.

Animals↗
PubMed1993

Binding of BW 373U86, a non-peptidic delta opioid receptor agonist, is not regulated by guanine nucleotides and sodium.

BW 373U86 is a novel, non-peptidic delta-opioid receptor ligand with agonist properties in mouse brain and in the mouse isolated vas deferens. The sensitivity of BW 373U86, and of the peptide delta-opioid agonists [D-Pen2,D-Pen5]enkephalin (DPDPE) and [D-Ala2,Glu4]deltorphin, to regulation by guanine nucleotides and sodium was evaluated in competition studies against the 5 selective radioligand [3H]naltrindole. The IC50 values for DPDPE and [D-Ala2,Glu4]deltorphin were significantly increased in brain and mouse vas deferens in the presence of Gpp(NH)p and NaCl. In contrast, the IC50 values for BW 373U86 were not altered in the presence of Gpp(NH)p and NaCl in either tissue. The data indicate that the agonist properties of BW 373U86 may not be affected by the supposed uncoupling of the alpha-subunit of the G-protein from a receptor thought to be G-protein linked.

Animals↗
PubMed1993

Lack of cross-tolerance between U69,593 and bremazocine suggests kappa-opioid receptor multiplicity in mice.

The development of tolerance, and the possibility of cross-tolerance, to the kappa-opioid receptor-mediated antinociceptive effects of U69,593 and bremazocine was studied in mice. U69,593 and bremazocine elicited dose-related and kappa-receptor-mediated antinociception following i.c.v. administration to mice. After a 3 day treatment regimen (twice daily injections) with an approximate antinociceptive A90 dose (90 nmol, i.c.v.) of U69,593, tolerance developed as demonstrated by a 5.6-fold rightward shift of the U69,593 dose-response line. The i.c.v. dose-response line for bremazocine was unaltered in U69,593-tolerant mice. Pretreatment with an approximate antinociceptive A90 dose of bremazocine (30 nmol, i.c.v.) for 3 days also produced tolerance as shown by a greater than 15-fold rightward shift in the bremazocine antinociceptive dose-response line. The i.c.v. dose-response line for U69,593 was unaltered in bremazocine-tolerant mice. These data demonstrate that while tolerance develops to the antinociceptive effects of both U69,593 and bremazocine, a two-way lack of cross-tolerance can be demonstrated between these kappa-agonists in this endpoint. These data suggest mechanistic differences in the antinociceptive effects of these kappa-agonists. Such suggestions are consistent with antinociceptive action of these agonists at subtypes of kappa-receptors.

Analgesics↗
PubMed1993

Design and synthesis of highly potent and selective cyclic dynorphin A analogs. 2. New analogs.

We have designed and synthesized several cyclic disulfide-containing peptide analogs of dynorphin A (Dyn A) which are conformationally constrained in the putative "address" segment of the opioid ligand. Several of these Dyn A analogs exhibit unexpected apparent selectivities for the kappa and mu opioid receptors(s) of the central vs peripheral nervous systems. Thus, incorporation of conformational constraint in the putative "address" segment of Dyn A analogs has resulted in the kappa/mu opioid receptor ligands [L-Pen5,Cys11]Dyn A1-11-NH2 (4), [Cys5,Cys10]Dyn A1-11-NH2 (5), [Cys5,Cys9]DynA1-11-NH2 (6), and [Cys4,Cys9,Arg10]DynA1-11-NH2(7). All of these analogs possess high kappa and mu opioid receptor affinities for the central receptor (guinea pig brain), but effect only weak potency at peripheral kappa and mu opioid receptors (GPI). In fact cyclic dynorphin A analog 4 shows > 19,000-fold differences between central kappa opioid affinity and potency in the guinea pig ileum (GPI). Additionally analog 4 is not an antagonist in the GPI, suggesting possible receptor differences between these sites. Substitution of Tyr1 by Phe1 in the cyclic 1-11 series gave the analog [Phe1,Cys5,Cys11]Dyn A1-11-NH2 (1) that was surprisingly potent in the guinea pig brain binding assay (IC50 = 15.1 nM) at the kappa receptor, but was inactive in the GPI and mouse vas deferens bioassays. D-Ala2 and Tic4 analogs of 1 had lower affinity at brain kappa receptors and had very weak potencies in the GPI and MVD bioassays. On the other hand, [Cys6,Cys10]DynA1-11-NH2 (8), [Cys8,D-Cys13]DynA1-13-NH2 (9), [D-Cys8,D-Cys12]DynA1-13-NH2 (10), and [D-Pro10,Cys5,Cys13]-Dyn A1-13-NH2 (11) were surprisingly potent in the GPI bioassay, though considerable apparent selectivity for central receptors is still retained. The apparent lack of correlation between the pharmacological profiles observed in smooth muscle and in the brain binding assays, particularly with 1 and 4, may suggest the existence of different subtypes of the kappa and mu opioid receptors in the brain and peripheral systems.

Amino Acid Sequence↗
PubMed1993

Thermodynamic parameters for [D-Pen2,5]enkephalin at delta-opioid receptors in the mouse isolated vas deferens.

Dissociation constants (KA) for [D-Pen2,5]enkephalin (DPDPE) inhibition of the electrically evoked twitch of the mouse isolated vas deferens preparation (MVD) were calculated at five temperatures (25, 30, 34, 37 and 40 degrees C). These values were determined from the equiactive concentrations obtained before (A) and after (A') partial irreversible blockade of a fraction of the receptor population by beta-chlornaltrexamine (beta-CNA) plotted as (1/A') where KA = (slope -1)/intercept. The values of KA tended to increase (approximately doubled) over this temperature range, indicating that the affinity of DPDPE for the opioid delta receptor is an inverse function of temperature. From these results, thermodynamic parameters were calculated from a Van't Hoff plot of 1n(KA) against 1/T. The relative magnitudes of the change in enthalpy (delta Ho' = -6.67 kcal mol-1), the change in entropy (delta So' = +0.009 kcal mol-1 degrees K-1) and the change in free energy (delta Go' = -9.43 kcal mol-1) suggest that the interaction between DPDPE and the delta-opioid receptor in MVD is an exothermic exergonic reaction, predominantly enthalpy-driven and results in an increase in the entropy of the system.

Animals↗
PubMed1993

Naltrindole, an opioid delta receptor antagonist, blocks cocaine-induced facilitation of responding for rewarding brain stimulation.

Recent experimental results have led to the suggestion that opioid antagonists can modulate the reinforcing properties of cocaine. In this experiment, rats were fixed with chronically indwelling bipolar electrodes for stimulation of the medial forebrain bundle (MFB) as it courses through the hypothalamus. Rats were taught to press a lever for brief trains of electrical stimulation of the MFB. Subsequently, they were allowed to press for varying intensities of stimulation daily until their response rates were stable. Cocaine (5 mg/kg, s.c.) enhanced the rate of pressing for lower intensities of brain stimulation. Naltrindole (3 mg/kg, i.p.) had no effect on response rate alone but blocked the cocaine-induced facilitation of pressing for rewarding brain stimulation. An implication that can be drawn from these data is that naltrindole, or other delta-selective opioid antagonists, might be effective as medicines for use in treating cocaine abuse.

Analysis of Variance↗
PubMed1993

Syntheses, opioid binding affinities, and potencies of dynorphin A analogues substituted in positions, 1, 6, 7, 8 and 10.

Structural, stereochemical, stereoelectronic and conformational requirements for biological activity of dynorphin A1-11-NH2 analogues at opioid receptors were explored by substitution of Tyr1, Arg6, Arg7, Ile8 and Pro10 with other amino acid residues. Interestingly, substitution of Tyr1 with N alpha-Ac-Tyr1, D-Tyr1, Phe1 or p-BrPhe1 led to analogues that were quite potent at kappa opioid receptors, and additional substitution of Ile8 with D-Ala8 and/or Pro10 with D-Pro10 retained high potency in brain binding assay: [N alpha-Ac-Tyr1]- (1), [D-Tyr1]-(2) [Phe1]- (3), [Phe1,D-Ala8]- (5), [-BrPhe1, D-Ala8]- (6), [Phe1, D-Pro10]- (7) and [Phe1,D-Ala8, D-Pro10]- Dyn A1-11-NH2 (8) had IC50 (nM) binding affinities of 13.2, 18.6, 1.64, 1.26, 1.84, 2.44 and 1.62 nM, respectively. The D-Phe1 analogue 4, however, was only weakly active (610 nM). All of the analogues except 4 were modestly selective for kappa vs. mu guinea pig brain opioid receptor (11- to 88-fold) and quite selective for kappa vs. delta receptors (65-576). However, all of the analogues appeared to have very low or essentially no activity in the guinea pig ileum and mouse vas deference functional bioassays, and one analogue, 5, appeared to have weak antagonist activities. On the other hand, if constrained amino acids such as beta-methylphenylalanine or 1,2,3,4-tetrahydroisoquinoline carboxylic acid, and hydroxyproline were placed in the 1 position, inactive analogues or analogues with greatly reduced potency and biological activity were obtained (compounds 12-14). It had previously been suggested that the Arg6 and Arg7 residues were critical for biological activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Modulation of morphine antinociception by swim-stress in the mouse: involvement of supraspinal opioid delta-2 receptors.

The present study evaluated the effect of a brief exposure of mice to cold-water swim-stress (CWSS) on the antinociceptive potency of i.c.v. given morphine. No significant antinociceptive response could be demonstrated in the warm-water tail-flick test, 10 min after a 30-sec exposure of mice to water at 5 degrees C. However, the i.c.v. morphine dose-response curve in mice exposed to CWSS was displaced significantly to the left when compared to that obtained in control (i.e., non-CWSS-exposed) mice. Although coadministration of the delta antagonist, N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH 1 (ICI 174,864), with i.c.v. morphine did not produce antagonism of the antinociceptive action of this mu opiate, the leftward displacement of the i.c.v. morphine dose-response curve seen in CWSS-exposed mice was blocked in ICI 174,864-treated mice suggesting involvement of opioid delta receptors in the modulatory effect. Pretreatment of mice with the delta-1 antagonist, [D-Ala2, Leu5, Cys6] enkephalin, did not antagonize the antinociception of morphine and further did not antagonize the leftward displacement produced by exposure to CWSS. Pretreatment of mice with the delta-2 antagonist, 5'-isothiocyanate, also did not antagonize the antinociceptive effects of morphine but blocked the leftward displacement in the morphine dose-response curve associated with CWSS, suggesting involvement of an opioid delta-2 receptor in this effect. Pretreatment of mice with the mu antagonist, beta-funaltrexamine, produced a significant antagonism of the morphine antinociceptive effect as seen by a rightward displacement of the morphine dose-effect curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Antinociceptive actions of BW373U86 in the mouse.

This study explored the antinociceptive properties of (+-)-4-[(alpha- R*)-alpha-[(2S*,5R*)-4-allyl-2,5-dimethyl-1-piperazinol]-3-hydroxy benzyl] - N,N-diethyl-benzamide dihydrochloride (BW373U86) a nonpeptidic compound proposed to be a delta opioid agonist, using three models of nociception and four routes of administration in mice. BW373U86 produced dose- and time-dependent, naloxone-sensitive antinociception in both the tail-flick and tail-pinch assays when given intrathecally (i.t.). However, at doses up to 187 nmol/mouse, i.c.v. BW373U86 was inactive in the tail-flick or tail-pinch assays. Additionally, at doses up to 187 mumol/kg, BW373U86 was not active after i.p. or p.o. administration in these endpoints. Further, in the tail-flick test, i.c.v. BW373U86 did not antagonize the antinociceptive effects of i.c.v. [D-Pen2,D-Pen5]enkephalin or [D-Ala2,Glu4]deltorphin, but partially antagonized the effects of i.c.v. morphine. In the acetic-acid abdominal constriction assay, BW373U86 produced dose-dependent antinociceptive effects when given by the i.p., i.c.v. or i.t., but not by the p.o., routes. Intrathecal BW373U86 was 663-fold more potent in the abdominal constriction assay than when given by the same route in the tail-flick test. The effects of an A70 dose of i.p. or i.c.v. BW373U86 in the abdominal constriction assay were partially antagonized by i.c.v. naloxone, but not by i.c.v. N,N-diallyl-Tyr-Aib- Aib-Phe-Leu-OH, where Aib is alpha-aminoisobutyric acid (ICI-174,864) or naltrindole. In contrast, i.t. naloxone, ICI-174,864 or naltrindole antagonized the antinociceptive effect of i.p. or i.t. BW373U86 in the abdominal constriction assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1993

Ontogenic differences in the inhibition of gastric acid secretion by epidermal growth factor.

Gastric secretions were studied in rats by pyloric ligation in vivo. The effects of epidermal growth factor (EGF) administered s.c. on gastric secretion were evaluated at different stages of development (8, 14, 20 and 30 postnatal days). The rates of fluid, protein and acid outputs were very low in developing rats but increased in maturing rats. The rate of acid output in 8- day-old rats (3.83 +/- 1.16) was not different from that in 14-day-old rats (4.84 +/- 0.99), whereas the rate of acid output in 20-day-old rats was 11-fold greater than that in 14-day-old rats, and it was 21-fold greater in 30-day-old rats. Subcutaneous administration of 30 micrograms/kg b.wt. of EGF significantly suppressed the gastric secretion of fluid, protein and acid in 20- and 30-day-old rats. In 30-day-old rats, acid output was 85% lower at 1 hr after EGF administration and in 20-day-old rats it was 85% lower at 2 hr and 50% lower at 3 hr. Interestingly, EGF had no effect on basal gastric secretions in 8- and 14-day-old rats; EGF also had no effect on the gastric acid output that was stimulated by pentagastrin administration in 14-day-old rats. In 20-day-old rats, inhibitory effects of EGF lasted for 3 hr before gastric secretions rebounded to normal levels, but inhibition lasted for only 1 hr in 30-day-old rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

Evidence for a single functional opioid delta receptor subtype in the mouse isolated vas deferens.

The identification of opioid delta receptor subtypes in mouse brain led to the investigation of the nature of the opioid delta receptors in the mouse isolated vas deferens in vitro. Noncumulative concentration-effect curves were constructed for DPDPE (delta 1 agonist) and [D-Ala2, Glu4]deltorphin (delta 2 agonist) in control tissues, or in tissues which had been incubated with either [D-Ala2, Leu5, Cys6] enkephalin (DALCE) (noncompetitive delta 1 antagonist) or 5'-naltrindole isothiocyanate (5'-NTII) (noncompetitive delta 2 antagonist). Incubation of the tissues with DALCE, under either oxygenated or nonoxygenated conditions, did not alter the concentration-effect curves for either agonist. In contrast, incubation of the tissues with 5'-NTII resulted in a significant rightward displacement of the concentration-effect curves of both DPDPE and [D-Ala2, Glu4] deltorphin. Additionally, naltriben, a selective and competitive delta 2 antagonist, showed no significant difference in its ability to antagonize a fixed, submaximal concentration of either DPDPE or [D-Ala2, Glu4]deltorphin. Furthermore, there was no significant difference in the affinity of naloxone (i.e., pA2) at the receptor(s) acted upon by either DPDPE or [D-Ala2, Glu4]deltorphin. Tolerance to DPDPE or [D-Ala2, Glu4]deltorphin was produced by incubation of the tissues with these agonists; construction of the [D-Ala2, Glu4]deltorphin concentration-effect curve in DPDPE-tolerant tissues demonstrated cross-tolerance between these agonists and, conversely, construction of DPDPE concentration-effect curves in [D-Ala2, Glu4]deltorphin-tolerant tissues revealed cross-tolerance between these agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Agonist and antagonist profiles of [D-Ala2,Glu4]deltorphin and its [Cys4]- and [Ser4]-substituted derivatives: further evidence of opioid delta receptor multiplicity.

Pharmacological evidence has suggested the presence of two supraspinal opioid delta receptor subtypes in the mouse, termed delta-1 and delta-2. [D-Pen2,D-Pen5]enkephalin (DPDPE) is thought to be primarily an agonist at the opioid delta-1 subtype, whereas H2N-Tyr-D-Ala-Phe-Glu-Val-Val-Gly-NH2 ([D-Ala2,Glu4]deltorphin) is a selective agonist at the delta-2 subtype. Based on previous reports suggesting that a receptor sulfhydryl group may be critical for ligand binding to the opioid delta receptor, the present investigation has attempted to discover whether this concept extends to the opioid delta-2 receptor. For this purpose, a cysteine-substituted deltorphin was synthesized and the potential agonist and antagonist properties of this compound, H2N-Tyr-D-Ala-Phe-Cys-Val-Val-Gly-NH2 ([D-Ala2,Cys4]deltorphin), were evaluated in an antinociceptive assay after i.c.v. administration to mice and stability in mouse brain was determined. As a control a serine-substituted deltorphin was also prepared and the potential agonist and antagonist properties of this compound, H2N-Tyr-D-Ala-Phe-Ser-Val-Val-Gly-NH2 ([D-Ala2,Ser4]deltorphin), as well as those of the parent deltorphin, [D-Ala2,Glu4]deltorphin, were evaluated. Acutely, [D-Ala2,Cys4]deltorphin, [D-Ala2,Ser4]deltorphin and [D-Ala2,Glu4]deltorphin each produced dose-related antinociceptive effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

In vitro potency, affinity and agonist efficacy of highly selective delta opioid receptor ligands.

The purpose of these investigations was to estimate the relative potency, receptor affinity, and agonist efficacy of several selective delta opioid agonist peptides of diverse structure, including cyclic [D-Pen2,D-Pen5]enkephalin and its p-Phe4 halogen-substituted analogs, [D-Ser2-O-tBu,Leu5,Thr6]enkephalin, Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH2 (deltorphin I) and Tyr-D-Ala-Phe-Glu-Val-Val-Gly-NH2 (deltorphin II) in functional bioassays. The mouse-isolated vas deferens (MVD) and guinea pig-isolated ileum longitudinal muscle/myenteric plexus bioassay preparations were used; selectivity for delta opioid receptors was quantified by the relative agonist activity of the various peptides in the guinea pig-isolated ileum and MVD assays; agonist affinity and efficacy were determined using the technique of partial irreversible receptor inactivation in the MVD. Data from these experiments were analyzed both by the traditional null method and by use of the operational model of pharmacologic agonism; a comparison of these two methods, which were found to be similar, was performed. Potency determinations in MVD for the various peptides essentially matched those determined in other investigations; the relative affinity of the peptides correlated with the results of radioligand binding studies performed in other laboratories. The relative efficacies of the peptides studied were indistinguishable except for the peptide deltorphin I, which demonstrated efficacy several-fold lower than the remaining seven. All peptides were sufficiently efficacious to appear as full agonists under control conditions. These results suggest that the principle factor determining increases in potency of novel delta receptor ligands to date is an increase in receptor affinity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗