NLX-112, a highly selective 5-HT1A receptor agonist: Effects on body temperature and plasma corticosterone levels in rats.

NLX-112 (a.k.a. F13640 or befiradol), exhibits nanomolar affinity, exceptional selectivity and high agonist efficacy at 5-hydroxytryptamine 5-HT1A receptors. It possesses marked activity in a variety of animal models of depression, pain and L-DOPA-induced dyskinesia. However, its influence on translational biomarkers of central 5-HT1A receptor activation has not been previously described. Here, we report on the activity, in rats, of NLX-112 to increase plasma corticosterone levels and produce hypothermia, two responses which are also elicited by 5-HT1A receptor agonists in humans. NLX-112 elicited dose-dependent hypothermia (minimal effective dose, MED: 0.31mg/kg p.o.) and also increased plasma corticosterone both by oral and intraperitoneal routes (MED: 0.63mg/kg in both cases). The increase in corticosterone induced by NLX-112 (0.63mg/kg p.o.) was abolished by co-administration of the selective 5-HT1A receptor antagonist, WAY100635. Additionally, NLX-112 also dose-dependently induced flat body posture, forepaw treading and lower lip retraction (MEDs 0.31-0.63mg/kg p.o.). The doses of NLX-112 which induce hypothermia or corticosterone release were similar to those inducing serotonergic behaviors but greater than those reported previously in models of therapeutic-like activity (range 0.04 to 0.16mg/kg). Overall, the present study provides information for clinical dose estimations of NLX-112 and suggests that therapeutic effects may occur at doses below those at which biomarker responses are observed.

Profound, non-opioid analgesia produced by the high-efficacy 5-HT(1A) agonist F 13640 in the formalin model of tonic nociceptive pain.

Previously, we have reported that in rat models of chronic pain, in particular, the very-high-efficacy 5-HT(1A) agonist F 13640 induces unprecedented pain relief by novel neuroadaptative mechanisms that involve inverse tolerance and cooperation with nociceptive stimulation in producing analgesia. The present studies detailed the actions of F 13640 and other compounds in the formalin model of tonic nociceptive pain. Intraperitoneal injection of F 13640 (0.01-2.5 mg/kg; t -15 min) caused a dose-dependent and complete inhibition of the paw elevation and paw licking that occurred both early (0-5 min) and late (22.5-27.5 min) after the intraplantar injection of diluted formaldehyde (2.5%) in the rat. The extent to which F 13640 and other 5-HT(1A) receptor ligands inhibited these pain behaviors correlated (p < 0.05) with the extent to which they activated 5-HT(1A) receptors. Under similar conditions, some inhibitory effects were also observed with various agents that are known to produce analgesia by different peripheral and/or central mechanisms (e.g., opioids, NA/5-HT reuptake inhibitors, COX-2 inhibitors and other nonsteroidal anti-inflammatory drugs, gabapentin, and ABT-594). However, with the possible exception of morphine, the effects of all of these agents at nontoxic doses were lower than those of F 13640, in particular in inhibition of early paw elevation. The 5-HT(1A) antagonist WAY 100635, but not naloxone, antagonized the actions of F 13640. These results help to establish large-magnitude 5-HT(1A) receptor activation as a new molecular mechanism of profound, central analgesia and suggest that F 13640 may be particularly effective against pain arising from severe tonic nociceptive stimulation.

Large-amplitude 5-HT1A receptor activation: a new mechanism of profound, central analgesia.

We report the discovery of F 13640 and evidence suggesting this agent to produce powerful, broad-spectrum analgesia by novel molecular and neuroadaptative mechanisms. F 13640 stimulates G(alphaomicron) protein coupling to 5-HT(1A) receptors to an extent unprecedented by selective, non-native 5-HT(1A) ligands. Fifteen minutes after its injection in normal rats, F 13640 (0.01-2.5 mg/kg) decreases the vocalization threshold to paw pressure; 15 min upon injection in rats that are exposed to formalin-induced tonic nociception, F 13640 inhibits pain behavior. The initial hyperalgesia induced by 0.63 mg/kg F 13640 was followed, 8 hrs later, by paradoxical hypo-algesia; 5 mg/kg of morphine produces the opposite effects (i.e., hypo-algesia followed by hyper-algesia). Repeated F 13640 injections cause an increase in the basal vocalization threshold and a reduction of F 13640-produced hyperalgesia; in these conditions, morphine causes basal hyperalgesia and antinociceptive tolerance. Continuous two-week infusion of F 13640 (0.63 mg/day) exerts little effect on the threshold in normal rats, but markedly reduces analgesic self-administration in arthritic rats. F 13640 infusion also decreases allodynic responses to tactile and thermal stimulations in rats sustaining spinal cord or sciatic nerve injury. In these models of chronic nociceptive and neuropathic pain, the analgesia afforded by F 13640 consistently surpasses that of morphine (5 mg/day), imipramine (2.5 mg/day), ketamine (20 mg/day) and gabapentin (10 mg/day). Very-high-efficacy 5-HT(1A) receptor activation constitutes a novel mechanism of central analgesia that grows rather than decays with chronicity, that is amplified by nociceptive stimulation, and that may uniquely relieve persistent nociceptive and neuropathic pains.

Experimental conditions for the continuous subcutaneous infusion of four central analgesics in rats.

For the analysis of pharmacotherapeutic regimens for chronic pain in animals, it is important to establish delivery methods in which analgesics can be administered continuously and at a constant rate for a prolonged period of time. This allows for the assessment of how drug effects may vary over time in the presence of ongoing pain. The present study determined, for four analgesic compounds, the maximal doses that met all of the following criteria: (i) water-soluble, (ii) stable over 14 days at 38 degrees C, and (iii) devoid of undesirable side-effects in normal rats, as assessed by evolution of body weight and temperature after the subcutaneous implantation of an osmotic mini-pump that continuously infused the compounds over a 14-day period. The results showed the maximal doses to be 5 mg/rat/day for morphine hydrochloride, 2.5 mg/rat/day for imipramine hydrochloride, 20 mg/rat/day for ketamine hydrochloride, and 10 mg/rat/day for gabapentin. These doses were further found to be sufficient to express each compound's representative pharmacological activity. The conditions identified here appear appropriate for future studies of these four compounds in rat models of chronic pain and neuropathic allodynia.

In the formalin model of tonic nociceptive pain, 8-OH-DPAT produces 5-HT1A receptor-mediated, behaviorally specific analgesia.

The experiments examined antinociceptive and intrinsic behavioral effects induced by the prototypical 5-HT1A receptor agonist 8-OH-DPAT (8-hydroxy-2-[di-n-propylamino] tetralin) in rats. 8-OH-DPAT (0.01-2.5 mg/kg, subcutaneous (s.c.)) reduced both the paw licking and paw elevation induced by (2.5%) formalin injection into the plantar surface of the right hindpaw; it also produced forepaw treading. All of these effects were completely blocked by pretreatment with WAY 100635 (N-(2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-N-(2-pyridinyl) cyclohexanecarboxamide trihydrochloride) (0.16 mg/kg, s.c.); prazosin (0.63 mg/kg, s.c.) inhibited forepaw treading, but not 8-OH-DPAT's action on paw elevation and paw licking. Repeated injection of 8-OH-DPAT (0.63 mg/kg, s.c.) twice daily for 4 days, markedly reduced 8-OH-DPAT's ability to produce forepaw treading, but exerted only little and inconsistent effects on its paw licking and paw elevation-inhibiting action. The data indicate that 8-OH-DPAT exerts an analgesic action in the formalin model of tonic nociceptive pain; this action is mediated by 5-HT(1A) receptors, and is not confounded by the productive sign (i.e., forepaw treading) of the 5-HT syndrome which 8-OH-DPAT also induces.

Opiate self-administration as a measure of chronic nociceptive pain in arthritic rats.

The study examined the validity of oral fentanyl self-administration (FSA) as a measure of the chronic nociceptive pain that develops in rats with adjuvant arthritis independently of acute noxious challenges. Arthritic rats self-administered more of a 0.008 mg/ml fentanyl solution (up to 3.4 g/rat per day) than non-arthritic controls (0.5 g/rat per day) and did so with a biphasic time course that reached peak during weeks 3 and 4 after inoculation with Mycobacterium butyricum. The time course paralleled both the disease process and the chronic pain. Continuous infusion of dexamethasone during weeks 3 and 4 via subcutaneous osmotic pumps at 0.0025-0.04 mg/rat per day disrupted the arthritic disease and decreased FSA to a level (i.e. by 65%) similar to that observed in non-arthritic rats. Continuous naloxone (2.5 mg/rat per day) decreased FSA (by 55%) in arthritic but not in non-arthritic animals. Continuous, subcutaneous infusion of fentanyl also decreased arthritic FSA in a manner that varied with dose at 0.04-0.16 mg/rat per day doses, but leveled off at 47% of controls with 0.31 mg/rat per day. The effects of continuous fentanyl on arthritic FSA occurred only with those doses and dose-dependent dynamics with which fentanyl also induced dependence in non-arthritic rats. The findings indicate that pain, rather than the rewarding or dependence-inducing action of fentanyl mediates FSA in arthritic rats. Paralleling patient-controlled analgesic drug intake, FSA offers a specific measure allowing the dynamic effects of neurobiological agents to be studied in this unique animal model of persistent nociceptive pain.

Lack of toxic effects of F 12511, a novel potent inhibitor of acyl-coenzyme A: cholesterol O-acyltransferase, on human adrenocortical cells in culture.

Inhibition of acyl-coenzyme A: cholesterol O-acyltransferase (EC 2.3.1.26; ACAT) reduces intracellular cholesteryl esters that are substrates for steroidogenesis in adrenal cells. The adrenal side effects of ACAT inhibitors remain a key point for their development as antiatherosclerotic agents. The aim of this study was to characterize the effects of a novel and powerful ACAT inhibitor, F 12511 (S)-2',3',5'-trimethyl-4'-hydroxy-alpha-dodecylthio-phenylacetanilide, on the NCI-H295R cell line, which has functional properties comparable to those of normal human adrenal cells. F 12511 incubated with cultured cells for 4-72 hr strongly inhibited cholesteryl oleate formation. The concentrations required to produce 50% inhibition (IC50) values) ranged from 20 to 50 nM; in the presence of low-density lipoproteins (LDL), this effect was paralleled by a decrease in cholesteryl ester mass and an increase in intracellular free cholesterol. At concentrations 100-fold larger than the IC(50) value for up to 48 hr, F 12511 reduced neither the basal release of cortisol and aldosterone nor the production of cortisol stimulated by forskolin. F 12511 did not modify the mRNA levels of the steroidogenic enzyme genes cytochrome P450 cholesterol side-chain cleavage (P450scc), cytochrome P450 17alpha-hydroxylase (P450c17), or cytochrome P450 21-hydroxylase (P450c21) or those of the LDL receptor and high-density lipoprotein scavenger receptor class B, type I (SR-BI) genes, either in the presence or absence of adenosine 3',5'-cyclic monophosphate stimulation for 24 hr. Exposure to F 12511 at up to 3 microM for 24 or 48 hr did not result in significant change in morphological and ultrastructural characteristics; the cytoplasm contained large numbers of mitochondria with intact crystae, and the same typical features of secretory activity were observed in NCI-H295R control cells. Exposure to 3 microM of F 12511 for 96 hr also did not affect cell viability. These data demonstrate that reduction of the substrate for steroidogenesis by the ACAT inhibitor F 12511 impairs neither steroid production nor transcription of genes involved in steroidogenesis and lipoprotein uptake in the pluripotent human adrenal cell line NCI-H295R.

F 11356, a novel 5-hydroxytryptamine (5-HT) derivative with potent, selective, and unique high intrinsic activity at 5-HT1B/1D receptors in models relevant to migraine.

F 11356 (4-[4-[2-(2-aminoethyl)-1H-indol-5-yloxyl]acetyl]piperazinyl-1-yl] ben zonitrile) was designed to take advantage of the superior potency and efficacy characteristics of 5-hydroxytryptamine (5-HT) compared with tryptamine at 5-HT1B/1D receptors. F 11356 has subnanomolar affinity for cloned human and nonhuman 5-HT1B and 5-HT1D receptors, and its affinity for 5-HT1A and other 5-HT receptors, including the 5-ht1F subtype, is 50-fold lower and micromolar, respectively. In C6 cells expressing human 5-HT1B or human 5-HT1D receptors, F 11356 was the most potent compound in inhibiting forskolin-induced cyclic AMP formation (pD2 = 8.9 and 9.6), and in contrast to tryptamine and derivatives, it produced maximal enhancement of [35S]guanosine-5'-O-(3-thio)triphosphate-specific binding equivalent to 5-HT. F 11356 was equipotent to 5-HT (pD2 = 7.1 versus 7.2) and more potent than tryptamine derivatives in contracting rabbit isolated saphenous vein. In isolated guinea pig trigeminal ganglion neurons, F 11356 was more potent (pD2 = 7.3 versus 6.7) and induced greater increases in outward hyperpolarizing Ca2+-dependent K+ current than sumatriptan. In anesthetized pigs, F 11356 elicited highly cranioselective, more potent (from 0.16 microgram/kg i.v.) and greater carotid vasoconstriction than tryptamine derivatives. Decreases in carotid blood flow were observed in conscious dogs from 0.63 mg/kg oral F 11356 in the absence of changes in heart rate or behavior. Oral activity was confirmed when hypothermic responses were elicited in guinea pigs (ED50 = 1.6 mg/kg), suggesting that F 11356 also accesses the brain. F 11356 thus is a selective, high-potency agonist at 5-HT1B/1D receptors, which distinguishes itself from tryptamine and derivatives in exerting high intrinsic activity at these receptors in vascular and neuronal models relevant to migraine.

F 11440, a potent, selective, high efficacy 5-HT1A receptor agonist with marked anxiolytic and antidepressant potential.

F 11440 (4-methyl-2-[4-(4-(pyrimidin-2-yl)-piperazino)-butyl]-2H, 4H-1,2,4-triazin-3,5-dione) was the outcome of a research effort guided by the hypothesis that the magnitude of the intrinsic activity of agonists at 5-HT1A receptors determines the magnitude of their antidepressant and anxiolytic-like effects. The affinity of F 11440 for 5-HT1A binding sites (pKi, 8.33) was higher than that of buspirone (pKi, 7.50), and somewhat lower than that of flesinoxan (pKi, 8.91). In vivo, F 11440 was 4- to 20-fold more potent than flesinoxan, and 30- to 60-fold more potent than buspirone, in exerting 5-HT1A agonist activity at pre- and postsynaptic receptors in rats (measured by, for example, its ability to decrease hippocampal extracellular serotonin (5-HT) levels and to increase plasma corticosterone levels, respectively). F 11440 did not have detectable antidopaminergic activity (unlike buspirone, which inhibited all of the directly observable behavioral effects of methylphenidate in rats), showed no evidence of antihistaminergic activity (unlike flesinoxan, which protected against the effects of a histamine aerosol in guinea pigs), and had a 70-fold separation between its 5-HT1A agonist and alpha-1 adrenergic antagonist properties (measured as the ability to inhibit the methoxamineinduced increase in blood pressure in rats), unlike flesinoxan, which showed a <3-fold separation. In HeLa cells expressing human 5-HT1A receptors, F 11440 decreased the forskolin-induced increase in AMP, and, based on its maximal effect, was found to have an intrinsic activity of 1.0 relative to that of 5-HT, which was significantly higher than that of buspirone (0.49), ipsapirone (0.46) and flesinoxan (0.93). Consistent with the aforementioned hypothesis, F 11440 produced anxiolytic- and antidepressant-like effects in animal models (i.e., increased punished responding in a pigeon conflict procedure and decreased immobility in a rat forced swimming test, respectively) that were more substantial than those of buspirone, ipsapirone and flesinoxan. Thus, F 11440, shown here to be a potent, selective, high efficacy 5-HT1A receptor agonist, appears to have the potential to exert marked anxiolytic and antidepressant activity in humans.

Preclinical in vivo antitumor activity of vinflunine, a novel fluorinated Vinca alkaloid.

Vinflunine, or 20',20'-difluoro-3',4'-dihydrovinorelbine, is a novel Vinca alkaloid obtained by hemisynthesis using superacidic chemistry. The most impressive structural modification of this vinorelbine derivative was the selective introduction of two fluorine atoms at the 20' position, a part of the molecule previously inaccessible by classic chemistry. The antitumor activity of vinflunine was evaluated against a range of transplantable murine and human tumors. Vinflunine exhibited marked activity against murine P388 leukemia grafted i.v. when given i.p. in single or multiple doses according to various schedules or in single i.v. or p.o. doses. Increases in life span achieved with vinflunine, as assessed by T/C ratios, ranged from 200% to 457% and proved markedly superior to those of 129-186% obtained with the other Vinca alkaloids tested. Against s.c.-implanted B16 melanoma, multiple i.p. administration of vinflunine proved active in terms of both survival prolongation and tumor growth inhibition, with optimal T/C values and relative areas under the tumor growth curves (rAUC) being 24% and 36%, respectively. The extent of this activity was superior to that noted for vinorelbine under the same experimental conditions. Growth inhibition of human tumor xenografts LX-1 (lung) and MX-1 (breast) was also observed following four weekly i.p. injections of vinflunine as reflected by optimal T/C values of 23% and 26%, respectively, and significant differences in the rAUCs noted for treated versus control animals. It was also noticeable that vinflunine induced considerably more prolonged inhibitory effects on tumor growth than did vinorelbine. These results demonstrate that vinflunine is well tolerated and is definitively active against a range of experimental animal tumor models. Vinflunine activity has been documented in terms of both survival prolongation and tumor growth inhibition, with definite superiority over vinorelbine being shown in each tumor model evaluated.

Model of bronchial allergic inflammation in the brown Norway rat. Pharmacological modulation.

Exposure of non-sensitized Brown Norway (BN) rats to a 10%-ovalbumin aerosol induced an increase in the number of neutrophils in the broncho-alveolar lavage (BAL) fluid 3 and 6 h later but with no change in number of cells at 24 h. When the BN rats were actively sensitized (i.m. injection of 10 mg/kg ovalbumin and i.p. injection of killed Bordetella pertussis) and exposed 12-14 days later to a 10%-ovalbumin aerosol there was an increase in the number of eosinophils in the BAL fluid, maximal 24-48 h after the anaphylactic reaction. The increase in the number of neutrophils in the bronchial lumen 3 and 6 h after the anaphylactic reaction was larger than that obtained in non-specific inflammation and in contrast to this was still present 24-48 h after ovalbumin exposure. In passively sensitized BN rats exposed to ovalbumin aerosol, no inflammation appeared in the BAL fluid 24 h after the anaphylactic reaction. Various drugs, administered twice, 5 min and 5 h after the anaphylactic reaction, have been evaluated for their effects on the 24-h inflammation obtained in actively sensitized rats. Dexamethasone acetate (0.08 mg/kg i.p.) and theophylline (50 mg/kg i.p.) decreased the number of eosinophils and neutrophils. Ketotifen fumarate (12.5 mg/kg), cetirizine dihydrochloride (12.5 mg/kg), salbutamol (2 mg/kg), disodium cromoglycate (50 mg/kg) all given intraperitoneally, reduced the number of eosinophils. Tioxamast decreased the number of eosinophils at 12.5 mg/kg i.p. and by the oral route.(ABSTRACT TRUNCATED AT 250 WORDS)

Theophylline reduces pulmonary eosinophilia after various types of active anaphylactic shock in guinea-pigs.

The action of theophylline was studied on the inflammatory reaction obtained in bronchoalveolar lavage fluid 24 h after an active anaphylactic shock had been induced by ovalbumin inhalation in conscious sensitized guinea-pigs. The compound was administered twice by intraperitoneal administration after the anaphylactic reaction at a dose of 50 mg kg-1. When the guinea-pigs were sensitized by intramuscular injection of 30 mg kg-1 ovalbumin or by ovalbumin aerosol, theophylline reduced the number of eosinophils and mononuclear cells in the fluid. When animals were sensitized by intramuscular injection of 30 mg kg-1 ovalbumin mixed with Freund's complete adjuvant, treatment with the xanthine derivative decreased only the number of eosinophils. In the three models theophylline did not modify significantly the number of neutrophils. Thus theophylline always reduced pulmonary eosinophilia irrespective of the mode of sensitization used to induce anaphylactic shock.

Bronchial inflammation and hyperreactivity after anaphylactic shock in guinea pigs actively sensitized by systemic or aerosol route.

Hyperreactivity and bronchial inflammation resulting from active anaphylactic shock induced by aerosol have been studied in guinea pigs after sensitization by intramuscular injection of large-dose ovalbumin or aerosol ovalbumin. When animals were sensitized by i.m. injection of 30 mg/kg ovalbumin, hyperreactivity to inhalation of histamine was obtained 1-3 h after shock. In bronchoalveolar lavage (BAL) fluid an increase in the number of eosinophils (6-48 h after shock) and neutrophils (6-24 h) was observed. When guinea pigs were sensitized by aerosol route, the hyperreactivity to histamine inhalation appeared 1-6 h after shock. In BAL fluid the number of mononuclear cells dropped (1-3 h) and then increased (24-48 h); the number of neutrophils (6-48 h) and eosinophils (24-48 h) increased. The results observed during these two types of sensitization were compared to those obtained after sensitization by injection of a large dose of ovalbumin mixed with Freund's complete adjuvant.

Action of tioxamast on various models of anaphylactic shock, hyperreactivity and bronchial inflammation in guinea-pigs.

Tioxamast, an anti-allergic compound inhibiting the release and synthesis of certain mediators of allergy and having no major antagonist effect towards such mediators, was experimented on various models of anaphylactic shock, hyperreactivity and bronchial inflammation in guinea-pigs. Tioxamast does not reduce passive pulmonary anaphylactic shocks induced in anaesthetized or conscious guinea-pigs by i.v. challenge of antigen. Likewise, the compound has no effect on systemic hyperreactivity towards i.v. histamine induced in anaesthetized guinea-pigs after a passive anaphylactic shock caused by i.v. challenge of antigen. On the other hand, tioxamast inhibits passive pulmonary anaphylactic shock induced in guinea-pigs by antigen aerosol in conscious guinea-pigs. Likewise, tioxamast decreases hyperreactivity to inhalation of histamine or carbamylcholine obtained after an active or passive anaphylactic shock by aerosol in conscious guinea-pigs. The oxamate derivative attenuates the increase in number of eosinophils and mononuclear cells obtained in the bronchoalveolar lavage fluid 24 hr after an active anaphylactic shock induced by aerosol. The anti-allergic activity of tioxamast on the various models carried out in guinea-pigs thus appears when these models are induced by a challenge of antigen or mediator by inhalation.

Pharmacological modulation of a model of bronchial inflammation after aerosol-induced active anaphylactic shock in conscious guinea pigs.

Twenty-four hours after an active anaphylactic shock induced by inhalation of antigen in conscious guinea pigs sensitized by a large dose of ovalbumin in complete Freund's adjuvant, a noteworthy bronchial inflammation, characterized by increased numbers of neutrophils, mononuclear cells and eosinophils in the bronchoalveolar lavage fluid, was observed. Some drugs administered after the anaphylactic shock were investigated using this model. Disodium cromoglycate primarily reduced the number of mononuclear cells and eosinophils. Dexamethasone and theophylline decreased the number of eosinophils. Salbutamol and mepyramine increased neutrophils. Indomethacin did not give rise to any significant effect. This test appears to be of use for the investigation of anti-inflammatory compounds in the prophylactic treatment of asthma.

Comparative actions of immunosuppressants, glucocorticoids and non-steroidal anti-inflammatory drugs on various models of delayed hypersensitivity and on a non-immune inflammation in mice.

Various models of delayed hypersensitivity (DH) were used in mice: contact hypersensitivity reactions to picryl chloride and oxazolone and reactions to methylated bovine serum albumin (MBSA) and sheep red blood cells (SRBC). Drugs of different classes were tested in these models by systemic treatment around the challenge period: non-steroidal anti-inflammatory drugs (cyclooxygenase inhibitors, and inhibitors of both cyclooxygenase and lipoxygenase); glucocorticoids and immunosuppressants (cyclosporin A. CsA; cyclophosphamide, Cy; methotrexate, Mtx; azathioprine, Aza). These compounds were also studied and compared for their effects on the 3-h and 24-h phase of the carrageenin mouse-paw edema (in which inflammation is maximal after 24 h). Non-steroidal anti-inflammatory drugs (including double inhibitors of cyclooxygenase and lipoxygenase) had little or no effect on DH models, except indometacin. Glucocorticoids inhibited all immune reactions except that to MBSA. Of the immunosuppressants, CsA reduced all the DH reactions while Aza mainly reduced the reaction to SRBC; Cy and Mtx were mainly active on SBRC and MBSA inflammations. On another hand CsA, Cy and Mtx were inactive on the 3-h phase but decreased the 24-h phase of carrageenin edema. At doses active on the DH models and on carrageenin inflammation, Cy induced a lasting blood leukopenia, but CsA and Mtx did not. This combination of tests in the mouse seems to be of interest to demonstrate any action on DH and any anti-inflammatory effect and to suggest whether these activities are related to a possible leukopenic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Model of bronchial hyperreactivity after active anaphylactic shock in conscious guinea pigs.

A model of bronchial hyperreactivity at various times after an active anaphylactic shock in conscious guinea pigs is described. The bronchial inflammation was quantified in parallel by determination of the number of mononuclear cells, neutrophils, and eosinophils in bronchoalveolar lavage (BAL) fluids. The guinea pigs were sensitized by an intramuscular (i.m.) injection of a large dose of ovalbumin in Freund's complete adjuvant. The administration of ovalbumin (to induce anaphylactic shock) and of histamine to investigate bronchial hyperreactivity was by aerosol. The bronchial hyperreactivity to histamine was observed 3-6 hr after the anaphylactic shock. In the BAL fluid a decrease (1-3 hr) and then an increase (24-48 hr) in the number of mononuclear cells was found as well as an increase in neutrophils (3-48 hr) and in eosinophils (6-48 hr). The hyperreactivity was not correlated with changes in one category of cell in the BAL fluid. This model constitutes one simple test for investigating bronchial hyperreactivity in conscious guinea pigs. Further work is needed to try to determine the possible inflammatory parameters responsible for the hyperreactivity.

Antiallergic and anti-inflammatory action of tioxamast in rats. II. Anti-inflammatory action in vivo.

Tioxamast is an antiallergic drug that inhibits anaphylaxis in various models in rats, and it inhibits the release and synthesis of certain mediators of inflammation [see Tarayre et al., this issue]. Here we report that the drug also has an anti-inflammatory effect in vivo in various nonimmunological models in rats. It reduces zymosan-induced inflammation in the paw and pleural cavity, starting at doses from 1.5625 to 3.125 mg/kg given intraperitoneally. In pleurisy, tioxamast lowers the concentration of leukotriene B4 (LTB4) in the exudate, at doses from 50 mg/kg i.p. Also, at doses from 12.5 mg/kg i.p., the compound reduced PAF-acether-induced pleurisy and the concentrations of LTB4 and peptidoleukotrienes in the exudate. An anti-inflammatory action against carrageenin-induced edema of the paw was seen only at doses of 50 mg/kg i.p. or more. The anti-inflammatory and antiallergic effect of tioxamast makes it a potentially useful drug in the treatment of allergies in humans.

Antiallergic and anti-inflammatory action of tioxamast in rats. I. Antiallergic activity in vivo and in vitro.

Tioxamast (F 1865) is an antiallergic drug that, administered systemically, reduces anaphylaxis in various models in rats. This action is due mainly to the inhibition of the synthesis and release of certain mediators. Orally or intraduodenally administered tioxamast inhibits IgE-dependent passive cutaneous anaphylaxis (ED50 = 0.8 mg/kg), IgE-dependent passive pulmonary anaphylaxis (ED50 = 0.5 mg/kg), and IgG-dependent passive cutaneous anaphylaxis (ED50 = 0.6 mg/kg). It has little or not effect on the increase of cutaneous capillary permeability induced by various mediators. In IgE-dependent passive peritoneal anaphylaxis in rats, tioxamast reduces the release of histamine (IC50 = 0.024 micrograms/ml) and of beta-glucuronidase (IC50 = 0.102 micrograms/ml). Also, histamine release is inhibited in IgG-dependent peritoneal anaphylaxis (IC50 = 0.103 micrograms/ml). The antiallergic compound has less effect on the release of histamine induced by the compound 48/80 in the peritoneal cavity of rats (IC50 = 1.67 micrograms/ml). Tioxamast inhibits the synthesis in vitro of leukotriene B4 (LTB4) by peritoneal neutrophils from rats stimulated by A23187 (IC50 = 8.88 micrograms/ml). At higher tioxamast concentrations, metabolites of the cyclo-oxygenase pathway are inhibited at concentrations of the same order of magnitude as those that inhibit Naja naja phospholipase A2 (IC50 = 144 micrograms/ml). Tioxamast also reduces the production of free radicals by leukocytes from the pleural cavity of rats which had phagocytosed opsonized zymosan (IC50 = 5.21 micrograms/ml).

Pharmacological studies on zymosan inflammation in rats and mice. 1: Zymosan-induced paw oedema in rats and mice.

Injections of zymosan in mouse and rat paws provoke inflammatory reactions, the kinetics of which are different. In both models, inflammation occurs at an early stage but oedema is maximal at 30 min in rat paw and 6 h in mouse paw. In this study the two reactions have been studied up to 6 h. The reduction of oedema by anti-H1 compounds, as well as by disodium cromoglycate, proves the active role played by histamine in rat paw oedema. In mouse its role appears to be minor or non-existent. Serotonin seems to be clearly implicated in the early stages of the oedema in mouse, somewhat less in rat. In the two species, non-steroidal anti-inflammatory compounds only reduce the 4-6 h phase. BW755C and phenidone reduce the early and late phase of paw oedema in both species, with the exception of phenidone which is inactive on the 4-6 h phase in the mouse. We can hypothesize that in the two species some leukotrienes seem to be implicated principally in the early phases, while derivatives of cyclooxygenase play a more important role in the late phases. Theophylline reduces inflammation in the two models, hydrocortisone acetate, however, is only active on the late phases. These results indicate that there are important differences in the participation of the various mediators studied in the two models.