Characterization of aminoalkylindole binding: selective displacement by cannabinoids.
Explore the source record for details and available documents.
Amines↗
Biomedical subjects
S J Ward
Publications and source records attributed to S J Ward.
Aminoalkylindoles (AAIs): structurally novel cannabinoid-mimetics.
Explore the source record for details and available documents.
Amines↗
Aminoalkylindoles (AAIs): a new route to the cannabinoid receptor?
Explore the source record for details and available documents.
Amines↗
Pravadoline: profile in isolated tissue preparations.
Pravadoline is a novel cyclooxygenase-inhibiting analgesic with a preclinical profile of activity in vivo clearly distinct from that of other cyclooxygenase inhibitors. The purpose of the present study was to assess the possibility that pravadoline possesses pharmacologic actions in addition to inhibition of cyclooxygenase. The data demonstrate that pravadoline inhibits neuronally stimulated contractions of the guinea pig ileum and mouse vas deferens preparations. These actions of pravadoline are not shared by known cyclooxygenase inhibitors, but are mimicked by close structural analogs of pravadoline devoid of the ability to inhibit prostaglandin formation. Some structural analogs were inhibitory also in the rat vas deferens preparation. The inhibitory effects of pravadoline and a representative noncyclooxygenase-inhibiting analog in isolated tissue preparations are not mediated by an interaction with muscarinic cholinergic, adrenergic (alpha-1 or alpha-2), serotonin (5-hydroxytryptamine2 or 5-hydroxytryptamine3), opioid (mu, kappa or delta), purinergic (P1), neurokinin-1, bradykinin (B2) or prostaglandin (E2) receptors. It is concluded that pravadoline and aminoalkylinodole analogs are inhibitory in several bioassay systems via a presynaptic mechanism which does not involve inhibition of cyclooxygenase, or the activation or inhibition of several known receptors. The relevance of this mechanism to aminoalkyindole actions in vivo is the subject of future studies.
Animals↗
Pharmacology of pravadoline: a new analgesic agent.
Pravadoline is a new chemical entity with analgesic activity in humans. This report describes the pharmacology of pravadoline and compares the activity of pravadoline with that of two major classes of analgesics, the opioids and the nonsteroidal anti-inflammatory drugs (NSAIDs). Like the NSAIDs, pravadoline inhibited the synthesis of prostaglandins (PGs) in mouse brain both in vitro (IC50, 4.9 microM) and ex vivo (ED50, 20 mg/kg p.o.) and displayed antinociceptive activity in rodents subjected to a variety of chemical, thermal and mechanical nociceptive stimuli. Administration of pravadoline prevented the writhing response induced by i.p. administration of acetylcholine (ED50, 41 mg/kg p.o.) or PGE2 (ED50, 24 mg/kg p.o.) and prolonged the response latency induced by tail immersion in hot water at a temperature of 55 degrees C (minimum effective dose, 100 mg/kg s.c.). In the rat, treatment with pravadoline prevented acetic acid-induced writhing (ED50, 15 mg/kg p.o.), brewer's yeast-induced hyperalgesia (Randall-Selitto test) (minimum effective dose, 1 mg/kg p.o.), the nociceptive response induced by paw flexion in the adjuvant-arthritic rat (ED50, 41 mg/kg p.o.) and bradykinin-induced head and forepaw flexion (ED50, 78 mg/kg, p.o.). The antinociceptive activity of pravadoline cannot be explained by an opioid mechanism, because pravadoline-induced antinociception was not antagonized by naloxone (1 mg/kg s.c.) and pravadoline did not bind to opioid receptors at concentrations up to 10 microM. However, like the opioid analgesics, pravadoline diminished the electrically induced twitch response of mouse vas deferens preparations, but, in contrast to opioids, this action of pravadoline was not attenuated by naloxone. The possibility is discussed that this effect of pravadoline upon isolated tissues may contribute to its antinociceptive activity. In contrast to NSAIDs, pravadoline was more potent ex vivo as an inhibitor of the formation of PGs in brain vs. stomach. In addition, pravadoline failed to produce gastrointestinal lesions when administered p.o. to rats or mice, and did not possess significant anti-inflammatory activity at antinociceptive doses. Also unlike NSAIDs, pravadoline inhibited rat gastrointestinal transit when administered at doses similar to those which were antinociceptive. The overall pharmacologic profile of pravadoline suggests that the compound may be capable of managing more diverse or more severe pain than is achieved by anti-inflammatory analgesics, without producing side effects commonly associated with either the opioid or the nonopioid analgesics.
Analgesics↗
Evaluation of adenosine agonists as potential analgesics.
Adenosine agonists, N6-cyclohexyladenosine (CHA), N6-cyclopentyladenosine (CPA), N6-phenylisopropyladenosine (PIA), 5'-N-ethylcarboxamidoadenosine (NECA), 5'-N-methylcarboxamidoadenosine (MECA) and 2-chloroadenosine (CADO), produced a dose-related inhibition of acetylcholine (ACh)-induced writhing in mice. The antinociceptive potency of adenosine agonists was comparable to that of morphine. Adenosine agonists were 10-1000 times more potent when given i.c.v. than p.o., suggesting a central site of action. Theophylline antagonized the antinociceptive activity of R-PIA in the writhing assay, suggestive of an adenosine receptor-mediated event. The sedative/ataxic properties of adenosine agonists were evaluated using a rotorod assay. Adenosine agonists impaired performance on the rotorod in doses comparable to and in some cases lower than those active in the ACh writhing assay. The results of the present study suggest that adenosine agonists attenuate nociceptive responding to a chemical stimulus through a central purinergic mechanism. The ability of adenosine agonists to inhibit ACh-induced writhing may be secondary to their sedative/ataxic properties.
Adenosine↗
A role for histamine and H2-receptors in opioid antinociception.
To investigate the role of brain H2-receptors in opioid antinociceptive mechanisms, the effects of several antagonists of histamine H2-receptors were determined on morphine (MOR)-induced antinociception, opioid-mediated footshock-induced antinociception (FSIA) and on other opiate effects in rats. Zolantidine dimaleate (ZOL), the first brain-penetrating H2 antagonist (0.03-1.6 mumol/kg s.c.) caused a dose-related inhibition of MOR antinociception in both the tail-flick and hot-plate tests, with no effect on base-line responding. ZOL also inhibited opioid FISA with a similar potency. MOR-induced locomotor activity was also reduced by ZOL, but no effect was seen on MOR-induced hyperthermia, catalepsy or lethality. ZOL (10(-5) M) was inactive at mu, delta or kappa opioid receptors and showed at least 35-fold higher affinity at the H2-receptor than at receptors for serotonin, dopamine, norepinephrine or acetylcholine in brain. To clarify further the role of H2-receptors in ZOL's antiopiate activity, the potencies of seven structural congeners of ZOL were determined on the H2-receptor and on MOR antinociception. Over 3 orders of magnitude, the rank order of potencies of the compounds for inhibiting MOR antinociception was highly correlated with their potencies as H2 antagonists. Cimetidine, unlike other H2 antagonists, potentiated MOR antinociception, potentiated opioid FSIA and increased brain MOR levels, actions that are not likely to be due to blockade of H2-receptors. These findings strongly suggest that stimulation of opioid receptors leads to antinociception by mechanisms that include activation of brain H2-receptors.
Analgesia↗
Pravadoline and aminoalkylindole (AAI) analogues: actions which suggest a receptor interaction.
Explore the source record for details and available documents.
Adenylyl Cyclase Inhibitors↗
Alpha 2-adrenergic agonists/antagonists: the synthesis and structure-activity relationships of a series of indolin-2-yl and tetrahydroquinolin-2-yl imidazolines.
The synthesis and alpha 2-adrenergic activity of a series of indolin-2-yl and tetrahydroquinolin-2-yl imidazolines are described. The indolin-2-yl imidazoline 4b was found to possess potent alpha 2-adrenergic agonist and antagonist activity. The modification of the substituents on the indoline ring of 4b has led to the separation of these activities. Substitution on the aromatic ring of 4b with halogen or increasing the size of the N-alkyl substituent of 4b gave alpha 2-adrenergic antagonists without agonist activity. The N-allylindoline 4d is more potent than idazoxan in vitro and is equipotent in vivo, but is less receptor selective (alpha 2 vs. alpha 1) than idazoxan. The cis-1,3-dimethylindolin-2-yl imidazoline 6a is an alpha 2-adrenergic agonist equal in potency to clonidine in vitro, while the trans-1,3-dimethylindolin-2-yl imidazoline 6b is a moderately potent alpha 2-adrenergic antagonist.
Adrenergic alpha-Agonists↗
Activity of mu- and delta-selective opioid agonists in the guinea pig ileum preparation: differentiation into peptide and nonpeptide classes with beta-funaltrexamine.
Previous studies have demonstrated that pretreatment of guinea pig longitudinal muscle-myenteric plexus ileal preparations with the highly selective noncompetitive mu antagonist beta-funaltrexamine (beta-FNA) causes an increase in the Ke value for the interaction of morphine with naloxone, suggesting that beta-FNA inactivates those receptors at which morphine interacts in the guinea pig ileum. The effect is selective for mu receptors since beta-FNA has no effect upon the interaction of naloxone with the kappa agonist nalorphine. In the present study, it was found that although beta-FNA attenuated the effects of morphine and other morphine-like agonists at mu receptors in the guinea pig longitudinal muscle-myenteric plexus ileal preparation, the mu-mediated actions of delta-selective peptide agonists and mu-selective peptide agonists were not completely attenuated by beta-FNA pretreatment. These data suggest that morphine-like mu agonists and other mu-selective and delta-selective peptide agonists in the guinea-pig ileum preparation either interact with similar opioid receptors but in a distinguishable manner or interact with different populations of opioid receptors or the peptides studied had greater intrinsic activity than the nonpeptides.
Animals↗
Opioid receptor binding characteristics of the non-equilibrium mu antagonist, beta-funaltrexamine (beta-FNA).
beta-Funaltrexamine (beta-FNA) bound to mouse brain membranes in a reversible and an irreversible (not removed by washing of the membrane) manner, and a portion of each type of binding was opioid-specific. Addition of 100 mM NaCl to the incubating medium enhanced the binding of beta-FNA to membranes. Using membranes preincubated with beta-FNA (1 microM) and then washed three times, the maximum number of binding sites available to [3H]morphine was markedly diminished whereas the affinity of morphine for binding sites was not significantly altered. The binding of [3H]naltrexone was also reduced markedly by beta-FNA pretreatment. In similarly pretreated membranes, the binding of [3H]methionine enkephalin [3H][D-Ala2,D-Leu5]enkephalin (DADLE) or [3H]ethylketazocine was reduced to a smaller extent. Using brain membranes from mice pretreated with a single subcutaneous injection of beta-FNA (100 mg/kg) 48 h prior to use, the binding of [3H]methionine enkephalin was unaffected whereas the number of binding sites available to [3H]morphine was significantly reduced. The inhibition by various ligands of the reversible binding of [3H] beta-FNA resembled the relative ability of the same ligands to inhibit the binding of [3H]ethylketazocine. It was concluded that the irreversible portion of the binding of beta-FNA demonstrates a selectivity for mu over delta binding sites, and that the reversible portion of the binding of beta-FNA demonstrates a selectivity for kappa binding sites over mu or delta binding sites. As such, the binding characteristics of beta-FNA are consistent with its profile in vivo and in isolated tissue studies in vitro.
Animals↗
Pharmacological profiles of tonazocine (Win 42156) and zenazocine (Win 42964).
The effects of tonazocine and zenazocine, two mixed agonist/antagonist analgesics, have been evaluated in a range of antinociceptive assays and in isolated tissue preparations in vitro. Both tonazocine and zenazocine were antinociceptive in writhing tests and in the i.a. bradykinin test, and were antagonists in the rat tail flick test. Additionally, zenazocine demonstrated some antinociceptive activity in the rat tail flick test. In vitro, both tonazocine and zenazocine demonstrated agonist and antagonist properties at mu receptors in the GPI and agonist properties at delta receptors in the MVD. In general, the agonist properties of zenazocine were more marked than those of tonazocine, and the antagonist properties of tonazocine were more marked than those of zenazocine.
Analgesics, Opioid↗
The effects of serotonin antagonists in a behavioral despair procedure in mice.
Six serotonin antagonists (pizotifen, mianserin, cyproheptadine, ketanserin, trazodone and methysergide) were tested in mice in a behavioral despair procedure. The behavioral despair procedure detects most antidepressant compounds. Pizotifen, mianserin and cyproheptadine were found to be active and the others were inactive. The serotonin binding potency at serotonin1 or serotonin2 receptors, or the ratio of potency at these receptors did not correlate with activity in the behavioral despair procedure. However, the serotonin antagonists that were active in the behavioral despair procedure were all found to be potent antagonists at histamine1 receptors. It is suggested that the activity of some serotonin antagonists in the behavioral despair procedure is best explained by their antihistaminergic potency.
Animals↗
Determination of the relative involvement of mu-opioid receptors in opioid-induced depression of respiratory rate by use of beta-funaltrexamine.
Using a simple method to measure respiratory rate, it was clearly shown that the depression of respiratory rate caused by morphine, ethylketazocine or [D-Ala2,D-Leu5]enkephalin was not altered by the highly selective, irreversible mu-antagonists, beta-funaltrexamine (beta-FNA) at a dose which produced marked antagonism of morphine antinociception. These results indicated that antinociception and depression of respiratory rate are mediated by different receptor interactions. However using a different method to measure respiratory rate (body plythesmograph), beta-FNA caused substantial antagonism of morphine-induced respiratory depression indicating that the degree to which mu-receptor interactions contribute to the depression of respiratory rate depends on the methodology. Possible explanations for this difference are discussed. It is concluded that careful consideration of the methodology must be given when one measures respiratory rate and caution must be exercised if measurement of rate alone is used to assess opioid-induced respiratory depression.
Analgesics↗
Multiple opioid receptor profile in vitro and activity in vivo of the potent opioid antagonist Win 44,441-3.
Win 44,441-3 is a pure opioid antagonist in rodents in vivo and in isolated tissue preparations in vitro. Win 44,441-3 produced a weak inhibition of electrically-stimulated twitch contractions of the mouse vas deferens (MVD) and guinea-pig ileum (GPI) preparations that was not prevented by naloxone, suggesting that these effects were not mediated through opioid receptors. Similarly, Win 44,441-3 produced a weak, but nonstereoselective antiwrithing effect in the ACh-induced writhing assay. Win 44,441-3 produced a concentration-related antagonism of mu, kappa and delta agonist actions in the MVD and GPI, and was about 10 times more potent than naloxone at each receptor. Also Win 44,441-3 dissociated from mu, kappa and delta receptors more slowly than naloxone. In vivo, Win 44,441-3 produced a dose-related antagonism of morphine and phenazocine-induced antinociception in the tail flick test, and was equipotent with naloxone following s.c. administration. Win 44,441-3 was active orally and demonstrated a significantly longer duration of action than a pharmacologically equivalent oral dose of naloxone vs morphine and phenzaocine in the tail flick test. It can be concluded that Win 44,441-3 is a pure opioid antagonist, 10 times more potent than, with a receptor selectivity profile similar to, that of naloxone in vitro and is of similar potency to, but of longer duration than, naloxone in vivo.
Animals↗
Relative involvement of mu, kappa and delta receptor mechanisms in opiate-mediated antinociception in mice.
The antinociceptive properties of morphine (mu), ethylketazocine (kappa), nalorphine (kappa), [D-Ala2, D-Leu5]enkephalin (delta) and [D-Ala2, Met5]enkephalinamide (mu, delta) were assessed using the radiant heat tail-flick and acetic acid-induced writhing assays in mice. The apparent pA2 values for the interaction of naloxone with morphine were the same regardless of the nociceptive stimulus employed or the route of administration of morphine. The apparent pA2 values for the interactions of naloxone with ethylketazocine and nalorphine in the writhing test differed significantly from that for the interaction of morphine and naloxone. Nalorphine did not produce a consistent antinociceptive effect on the tail-flick test. The apparent pA2 values for the interaction of ethylketazocine (s.c. or i.c.v.) with naloxone were similar to those for morphine-naloxone interactions on the tail-flick assay. The apparent pA2 values for the interactions of naloxone with [D-Ala2, D-Leu5] enkephalin differed from those for morphine-naloxone interactions on the writhing test. The highly selective mu antagonist beta-funaltrexamine antagonized the agonist actions of morphine and [D-Ala2, D-Leu5]enkephalin, and, in a previous study, beta-funaltrexamine antagonized the antinociceptive actions of [D-Ala2, Met5]enkephalinamide, but not those of nalorphine. It was concluded that agonist interaction with mu or kappa receptors can result in antinociceptive effects in the acetic acid-induced writhing test, and that an agonist interaction with mu, but not kappa, receptors results in antinociceptive action on the radiant heat tail-flick test, and furthermore, that a possible combination of mu and delta receptor interaction can result in antinociceptive activity in both tests.
Acetates↗
Relative involvement of receptor subtypes in opioid-induced inhibition of gastrointestinal transit in mice.
Explore the source record for details and available documents.
Animals↗
Improved assays for the assessment of kappa- and delta-properties of opioid ligands.
The highly selective non-equilibrium mu-antagonist beta-funaltrexamine (beta-FNA) produced a maximal 20-fold shift in the IC50 for the mu-agonist morphine on the guinea-pig ileum preparation, whilst producing no significant change in the IC50 for the kappa-agonist ethylketazocine. On preparations pretreated with beta-FNA, the pA2 values for the interaction of morphine and ethylketazocine with naloxone were similar. These values were similar to the pA2 value for the interaction of ethylketazocine and naloxone determined on control tissues, but significantly different from the pA2 value for morphine-naloxone on control tissues, indicating that the agonist actions of morphine on preparations pretreated with high concentrations of beta-FNA are mediated by kappa-, rather than mu-receptor interaction. On the mouse vas deferens preparation, co-incubation with the highly selective delta-agonist Tyr-D-Ser-Gly-Phe-Leu-Thr (DSLET) and the non-selective non-equilibrium opiate antagonist beta-chlornaltrexamine (beta-CNA) resulted in marked inhibition of the agonist actions of morphine but had no effect upon the agonist actions of the delta-agonist leucine-enkephalin. The pA2 values for the interactions of naloxone with leucine-enkephalin and etorphine were unaltered by pretreatment with beta-CNA and DSLET. In similarly pretreated tissues, the agonist actions of ethylketazocine were markedly inhibited. It is concluded that manipulation of the guinea-pig ileum and mouse vas deferens preparations in the described manner results in assay systems that possess a largely homogeneous receptor population, and as such are valuable tools with which to evaluate opioid activity.
Animals↗