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The present study has been designed to pharmacologically investigate the effect of Montelukast sodium, a leukotriene D(4) receptor antagonist, and 1,2,3,4, tetrahydroisoquinoline, a leukotriene D(4) synthetic pathway inhibitor, on the pathophysiological progression of seizures using mouse models of kindled epilepsy and status epilepticus induced spontaneous recurrent seizures. Pentylenetetrazole (40 mg kg(-1)) (PTZ) administration every second day for a period of 15 d was used to elicit chemically induced kindled seizure activity in mice. In a separate set of groups, fifty consecutive electroshocks were delivered to mice using corneal electrodes with continuously increasing intensity with an inter-shock interval of 40s. Severity of kindled seizures was assessed in terms of a composite kindled seizure severity score (KSSS). Pilocarpine (100 mg kg(-1)) was injected every twenty minutes until the onset of status epilepticus. A spontaneous recurrent seizure severity score (SRSSS) was recorded as a measure of quantitative assessment of the progressive development of spontaneous recurrent seizures induced after pilocarpine status epilepticus. Sub-acute PTZ administration and electroshock induced the development of severe form of kindled seizures in mice. Severity of kindled seizures was assessed in terms of a composite kindled seizure severity score. Further, pharmacological status epilepticus elicited a progressive evolution of spontaneous recurrent seizures in the animals. However, Montelukast sodium, a leukotriene D(4) receptor antagonist, as well as 1,2,3,4, tetrahydroisoquinoline, a leukotriene D(4) synthetic pathway inhibitor, markedly and dose dependently suppressed the development of kindled seizures as well as pilocarpine induced spontaneous recurrent seizures. Therefore, leukotriene D(4) may be implicated in the pathogenesis of seizures., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Cysteinyl leukotrienes are potent inflammatory molecules playing a major role in asthma. The involvement of these mediators in hypersensitivity in mice is not well known. This study aimed at elucidating their implication by using MK-571, a cysLT(1)receptor antagonist. Mice were sensitized with a suspension of ovalbumin (8 microg) adsorbed to alum (2 mg) and were challenged with an aerosolized ovalbumin solution (0.5%). Inflammatory cell infiltration in the bronchoalveolar lavage (mostly eosinophils) following antigen challenge was inhibited by dexamethasone (0.1, 1 and 5 mg kg(-1)s.c.) and MK-571 (1, 10, 100 mg kg(-1)i.v.) in a dose-dependent manner. Maximal inhibition was 95% with 5 mg kg(-1)dexamethasone and 90% with 100 mg kg(-1)MK-571. When injected together they showed an additive inhibitory effect on eosinophil infiltration. Bronchial hyperreactivity, measured by the increased pulmonary insufflation pressure to carbachol injections, was also inhibited dose-dependently by MK-571. The EC(50)values for carbachol were of 22.39+/-1.12 microg kg(-1)in sensitized and challenged animals that did not receive MK-571 and increased to 43.65+/-1.10, 50.12+/-1.15 and 83.18+/-1.16 microg kg(-1)in animals treated with 1, 10 and 100 mg kg(-1)MK-571 respectively. Lung microvascular leakage (as measured by Evans blue extravasation) induced by antigen bronchoprovocation was reduced by 22% after treatment with 10 mg kg(-1)MK-571. All these inhibitory effects of MK-571 suggest a role for leukotriene D(4)in this animal model of allergic asthma., (Copyright 2000 Harcourt Publishers Ltd.)

The i.v. administration of leukotriene (LT)D4 to anesthetized guinea pigs produced dose-dependent increases in pulmonary microvascular permeability, as measured by extravasation of Evans blue dye into the trachea, main bronchi, and small airways, with an ED50 of approximately 0.05 microgram/kg. When LTD4 was administered at 0.3 microgram/kg, the resulting plasma extravasation into all three airway sections was markedly reduced by pretreatment with a cyclooxygenase inhibitor, meclofenamic acid (2.5 mg/kg, i.v.), a thromboxane (TX) receptor antagonist, SQ 29,548 (0.1 or 1 mg/kg, i.v.), or a peptidoleukotriene receptor antagonist, pranlukast (SB 205312) (0.1 or 1 mg/kg, i.v.), but not by the H1 histamine receptor antagonist, pyrilamine. When LTD4 was administered at 1.0 microgram/kg, meclofenamate (2.5 or 5 mg/kg, i.v.) or SQ 29,548 slightly attenuated plasma extravasation only in the small airway, whereas pranlukast was effective in all three airway segments. Administration of the 5-lipoxygenase inhibitor, zileuton (10 mg/kg, i.v.), or the PAF antagonist, L-659,989 (5 mg/kg, i.v.), did not affect the microvascular leakage response to 1.0 microgram/kg LTD4. In addition, i.v.-administered LTD4 (0.3 or 1.0 microgram/kg) or the prostaglandin (PG)/TXA2 receptor agonist, U-46619 (3.0 micrograms/kg), produced significant bronchoconstriction as measured by increases in pulmonary insufflation pressure. The bronchoconstrictor responses to LTD4 were markedly attenuated by the same inhibitors, namely meclofenamic acid, SQ 29,548, and pranlukast, that reduced the 0.3 microgram/kg LTD4-induced plasma extravasation throughout the airways and the 1.0 microgram/kg LTD4-induced extravasation into the small airways. U-46619-induced bronchoconstriction was blocked only by SQ 29,548.(ABSTRACT TRUNCATED AT 250 WORDS)

We investigated the effects of ONO-1078, a newly synthesized peptide leukotriene (p-LT antagonist, on the specific binding of radiolabelled [3H]-LTC4, [3H]-LTD4 and [3H]-LTE4 to a human lung crude membrane fraction (HLMF). The binding assay was performed under conditions in which [3H]-LTC4 and [3H]-LTD4 were not metabolized by HLMF; that is, the metabolism of LTC4 to LTD4 or LTE4 was almost completely prevented by pretreating HLMF with 5 mM acivicin at 37 degrees C for 180 min, and metabolism of LTD4 to LTE4 was inhibited by including 5 mM L-cysteine and 5 mM glycine in the assay. [3H]-LTD4 specific binding was potently and concentration-dependently dissociated by ONO-1078. Its potency was 180-fold stronger than that of FPL 55712, a standardized p-LT antagonist, whereas high concentrations of ONO-1078 similar to those of FPL 55712 were required to inhibit [3H]-LTC4 specific binding. The rank order of the inhibitory potencies of p-LT agonists and antagonists for [3H]-LTD4 specific binding was LTD4 > ONO-1078 > LTE4 > LTC4 > FPI 55712. On the other hand, not only high concentrations of ONO-1078 and FPL 55712 but also more than a 100-fold excess of unlabelled LTE4 was required to inhibit [3H]-LTE4 specific binding, indicating that the binding sites do not appear to be receptors of LTE4. From these results, it is suggested that ONO-1078 is a highly potent LTD4 antagonist which is expected to be very effective on bronchial asthma.