cp-99994 and Bronchial-Spasm

The major pulmonary effects of tachykinins, including bronchoconstriction, are mediated by activation of both neurokinin-1 (NK(1)) and neurokinin-2 (NK(2)) receptors. In guinea-pigs NK(1)and NK(2)receptor antagonists interact synergistically to inhibit the bronchoconstriction induced by neurokinin-A (NKA). However, the effect of combined NK(1)and NK(2)receptor antagonists on tachykinin-induced bronchoconstriction in most other species has not been evaluated. In this study, the interactive effects of CP 99994, an NK(1)receptor antagonist and SR 48968, an NK(2)receptor antagonist, were evaluated against NKA-induced brochospasm in dogs. Pulmonary resistance (R(L)) and dynamic lung compliance (C(Dyn)) were measured in anesthetized, spontaneously breathing dogs to measure the bronchoconstrictor response to aerosolized NKA (1%). Mean arterial blood pressure (MAP) and minute volume (MV) were also measured to assess the NK(1)receptor mediated cardiorespiratory response to substance P (100 ng/kg, iv). Pretreatment with SR 48968 (0.3-3 mg/kg, po) in the presence of an NK(1)antagonist dose of CP 99994 (10 mg/kg, po) inhibited the NKA-induced bronchospasm. However, the inhibition produced by SR 48968 plus CP 99994 was no greater than that previously shown for SR 48968 alone. Therefore, dual NK(1)/NK(2)receptor antagonists do not interact synergistically against NKA-induced bronchospasm in dogs. This may relate to the fact that dogs, like humans, have the NK(2)receptor as the predominant receptor subtype producing bronchoconstriction.

Topics: Animals; Benzamides; Bronchial Spasm; Bronchoconstriction; Disease Models, Animal; Dogs; Male; Neurokinin-1 Receptor Antagonists; Piperidines; Receptors, Neurokinin-1; Receptors, Neurokinin-2; Tachykinins

The present study characterized neurokinin receptor-mediated bronchoconstrictor responses in anesthetized guinea pigs. Thus, we have compared the actions of the selective neurokinin 1 (NK1) (CP-99,994) and neurokinin 2 (NK2) (SR-48,968) receptor antagonists against dose-response curves (DRC) induced by intravenously administered substance P (SP), neurokinin A (NKA), neurokinin B (NKB), beta Ala8-NKA (4-10),Sar9-Met(O2)11SP, and single dose (intravenous) challenge with resiniferatoxin (RTX), a capsaicin-like sensory neurotoxin, leukotriene D4 (LTD4) and antigen. The rank order of potency of the neurokinins for inducing bronchoconstriction was beta Ala8-NKA(4-10) > NKA > Sar9-Met(O2)11Sp > SP >> NKB. The DRC to the selective NK1 agonist Sar9-Met(O2)11SP was shifted to the right 10-fold by the selective NK1 antagonist, CP-99,994 (1 mg/kg, intravenously), but was not shifted by SR-48,968 (3 mg/kg, intravenously). The DRC to the selective NK2 agonist beta-Ala8-NKA(4-10) was shifted to the right 82-fold by the NK2 antagonist, SR-48,968 (1 mg/kg), but was not shifted by CP-99,994 (3 mg/kg, intravenously). SR-48,968 (1 mg/kg) also blocked NKA (3-fold shift) but did not block SP. CP-99,994 failed to produce a significant rightward shift of the DRC to either SP or NKA. However, the combination of 1 mg/kg CP-99,994 and 1 mg/kg SR-48,968 produced significant shifts of the DRCs to SP (> 5-fold) and NKA (> 300-fold). Hypotension induced by NKA and SP was also blocked by this combination.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Benzamides; Bronchial Spasm; Bronchoconstriction; Diterpenes; Dose-Response Relationship, Drug; Drug Interactions; Guinea Pigs; Male; Neurokinin A; Peptide Fragments; Piperidines; Receptors, Neurokinin-1; Receptors, Neurokinin-2; Substance P; Tachykinins