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At least 217 records · Page 12Linked to original sources
PubMed1984

Interactions of lindane, toxaphene and cyclodienes with brain-specific t-butylbicyclophosphorothionate receptor.

Three major classes of chlorinated hydrocarbon insecticides, i.e., the lindane/hexachlorocyclohexane, toxaphene and aldrin/dieldrin types, are potent, competitive, and stereospecific inhibitors of t-butylbicyclophosphorothionate (TBPS) binding to brain-specific sites, thereby indicating an action at the gamma-aminobutyric acid (GABA)-regulated chloride channel. The most inhibitory and toxic of four isomers of hexachlorocyclohexane is lindane and of greater than 188 components of toxaphene is 2,2,5-endo, 6-exo,8,9,9,10-octachlorobornane. 12-Ketoendrin (IC50 = 36 nM) is twice as active as the most potent previously known inhibitor of TBPS binding and it is also the most inhibitory and toxic of 22 cyclodienes examined. Within each of these three series of polychlorocycloalkanes the mammalian toxicity is closely related to the potency for inhibition of TBPS binding. A modified receptor assay incorporating liver microsomes and reduced nicotinamide-adenine dinucleotide phosphate compensates in part for oxidative detoxification and bioactivation. Specific TBPS binding is reduced in a dose-dependent manner in dieldrin-poisoned rats. DDT, mirex and kepone are not inhibitors of TBPS binding, even at 10 microM.

Animals↗
PubMed1989

The partial opiate receptor agonists, dezocine and ciramadol act as mu receptor antagonists at the feline ileocecal sphincter.

The effects of two novel synthetic narcotic agonist/antagonists dezocine and ciramadol were examined at the ileocecal sphincter (ICS) in the intact anesthetized cat. Changes in blood pressure were seen with higher doses of both dezocine and ciramadol. No ICS pressure changes were seen in the ICS to dezocine and an increase in ICS pressure was seen only to the highest dose of ciramadol examined (10 mg/kg). The antagonist action of the two drugs were examined against submaximal doses of the mu receptor agonist morphine sulfate, delta receptor agonist methionine enkephalin and the k-receptor agonist dynorphin. Both drugs inhibit the ICS response to morphine sulfate. No inhibition of the responses to methionine enkephalin or dynorphin were seen with dezocine and only partial inhibition of the ICS response to dynorphin was seen with ciramadol.

Analgesics↗
PubMed1993

The opioid receptor binding of dezocine, morphine, fentanyl, butorphanol and nalbuphine.

The ability of morphine, fentanyl, butorphanol, nalbuphine, and dezocine to compete with radiolabeled ligands for binding at the mu1, mu2, kappa1, and delta opioid receptors and the sigma receptor was characterized. In the absence of sodium, the potency of opioid receptor competition at each receptor site was found to be: mu1-fentanyl > butorphanol > morphine > or = dezocine = nalbuphine; mu2-butorphanol > fentanyl > nalbuphine > morphine = dezocine; kappa1-butorphanol > nalbuphine >> morphine > or = dezocine > fentanyl; and delta-butorphanol > nalbuphine > or = dezocine > morphine > fentanyl. For all five compounds, competition at the sigma receptor was weak, with nalbuphine and dezocine having Kis of approximately 0.5 microM and the other opioids having Kis of greater than 1 microM. Since the presence of 100 mM NaCl during the competitive binding decreased the K(i), to varying degrees, of all five opioids at the mu1 and delta receptors and of some of the opioids at the mu2 and kappa1 receptors, the five compounds studied appear to differ in efficacy at the five receptor sites.

Analgesics, Opioid↗
PubMed1981

Morphine-like stimulus effects in the monkey: opioids with antagonist properties.

The discriminative stimulus properties of opioids with a wide spectrum of agonist and antagonist properties were evaluated in squirrel monkeys trained to discriminate between morphine and saline in a two-choice discrete-trial avoidance task. Stimulus control was considered to be established when the monkeys reliably completed at least 22 trials of a 25-trial session on the lever appropriate for the drug state. Tests of stimulus generalization were conducted with compounds that were previously shown in the rat to produce discriminative stimulus effects that are: (a) morphine-like (profadol, WY-16,225, pentazocine, butorphanol, nalmexone); (b) cyclazocine-like (cyclazocine, ketocyclazocine, levallorphan); (c) neither morphine-like nor cyclazocine-like (nalbuphine and nalorphine). Profadol and WY-16,225 were equipotent with morphine in producing morphine-like stimulus effects. Naloxone antagonized the morphine-appropriate responding produced by all three compounds, but 10 times more naloxone was needed to block the stimulus effects of WY-16,225 than to block those of either morphine or profadol consistent with the known antagonist properties of WY-16,225. None of the other drugs produced complete morphine-like stimulus control of behavior but, with the exception of nalorphine, the highest dose of each resulted in about half of the trials being completed on the morphine-appropriate choice lever. These results confirm the heterogeneous nature of the discriminative stimulus effects of opioids with mixed agonist and antagonist properties and indicate the importance of interspecies comparisons.

Animals↗
PubMed1984

Characterization of spermidine synthase from Trypanosoma brucei brucei.

Spermidine synthase from Trypanosoma brucei brucei was characterized and found to be similar to spermidine synthase from other sources. The Km for putrescine was found to be 0.2 mM and the Km for decarboxylated S-adenosylmethionine 0.1 microM. The approximate molecular weight of the enzyme was 74 000 as determined by a combination of molecular sieve chromatography and sucrose density gradient centrifugation. Spermidine synthase activity was markedly inhibited in vitro by dicyclohexylamine (50% inhibition at 3 microM) and cyclohexylamine (50% inhibition at 15 microM); both being competitive inhibitors with respect to putrescine. S-Adenosyl-1,8-diamino-3-thiooctane, a nucleoside bisubstrate analog, was also a potent inhibitor of enzyme activity (50% inhibition at 25 microM). Administration of dicyclohexylamine to mice with trypanosomiasis resulted in no increase in survival time probably due to the lack of effect on trypanosome spermidine concentrations. Other possible inhibitors remain to be tested in vivo.

Animals↗
PubMed1989

Increased neuropeptide-converting enzyme activities in cerebrospinal fluid of opiate-tolerant rats.

Rats were given a continuous subcutaneous infusion at constant rate with either morphine, the opioid agonist/antagonist analgesic dezocine or saline. Tolerance to the antinociceptive effect of morphine or dezocine was complete on day 8, when cisterna magnum cerebrospinal fluid (CSF) was sampled under anesthesia. The activity of the enzymes cleaving dynorphin A (DCE) and substance P (SPE) was measured in the CSF. It was found that the animals treated with morphine had a 2- to 3-fold increase in both DCE and SPE activities. The animals treated with dezocine showed a similar increase in the activity of DCE, whereas SPE did not significantly change. These enzymes may therefore play a role in the development of tolerance to opioid analgesic drugs. The experiments show that chronic opioid treatment affects peptidergic mechanisms.

Animals↗
PubMed1987

Pharmacological properties of musk.

The general pharmacological properties of musk were studied. After the application of musk, inhibition of acetic acid-induced writhing, hemolytic effect and excitation of spontaneous uterine motility of rats, inhibition of spontaneous motility in isolated ileum of rabbits, and anti-inflammatory effects and potentiation of beta-adrenergic action in isolated preparations of guinea pig trachea were observed. These effects were not observed after application of muscone or allantoin, constituents of musk.

Allantoin↗
PubMed1983

Loss of hepatic monooxygenase activities, glutathione, and 'green pigment' formation after the administration of vinyl-cyclooctane to mice.

Vinylcyclooctane, when administered to mice at 500 mg/kg, produced reduction of microsomal cytochrome P-450, heme, aminopyrine-N-demethylase and ethoxycoumarin-O-deethylase activities with respect to control values; furthermore the hepatic reduced glutathione level was depleted suggesting that glutathione is involved in the vinylcyclooctane metabolism. The reduction of cytochrome P-450 and monooxygenase activities was accompanied by the formation of abnormal 'green pigments'.

Animals↗