Increased blocking activity of combined tachykinin NK1- and NK2-receptor antagonists on tachykinergic bronchomotor responses in the guinea-pig.
1. The present study compared the effect of the administration of tachykinin NK1- and NK2-receptor antagonists alone and in combination on exogenous and endogenous tachykinin-induced contractions using three different guinea-pig airway preparations: isolated bronchus, isolated perfused lung and in vivo. 2. In the isolated bronchi, the tachykinin NK1-receptor antagonist CP 99994 (0.01-1 microM) produced concentration-dependent inhibition of contractions induced the tachykinin NK1-receptor agonists substance P (SP) and [Met-OMe11] SP ([Met-OMe11]SP), whereas the tachykinin NK2-receptor antagonist SR 48968 (0.1 microM) had no effect. SR 48968 (0.001-0.01 microM) concentration-dependently inhibited contractions induced by the tachykinin NK2-receptor agonists neurokinin A (NKA) and [beta-Ala8]-neurokinin A (4-10) ([betaAla8]-NKA) whereas CP 99994 (0.1 microM) did not inhibit the contractions. The contractile activity of capsaicin, an agent that releases endogenous tachykinins from sensory C-fibres, was inhibited in a concentration dependent manner by SR 48968 (0.001-0.03 microM) but not by CP 99994 (0.1 microM). Combination of CP 99994 and SR 48968 caused increased inhibitory effects on the concentration-response curves to SP, [Met-OMe1l]SP, NKA, [beta-Ala8]-NKA and capsaicin. 3. In isolated perfused lungs, SR 48968 concentration (0.01-10 microM) dependently inhibited NKA-, [beta-Ala8]-NKA- and capsaicin-induced bronchoconstriction whereas CP 99994 (30 microM) had no effect on SP-, NKA-, [beta-Ala8]-NKA- and capsaicin-induced bronchoconstriction. Combination of inactive concentrations of CP 99994 and SR 48968 produced an increased inhibitory effect on all previous stimuli-induced bronchoconstriction. 4. In in vivo guinea-pig studies, intravenous and oral pretreatment with SR 48968 (0.01-1 mg kg(-1) i.v. and 0.1-3 mg kg(-1) p.o., respectively), but not with CP 99994 (1 mg kg(-1) i.v. and 0.3-30 mg kg(-1) p.o., respectively), produced a dose-dependent inhibition of the bronchoconstrictor responses induced by NKA, [beta-Ala8]-NKA and capsaicin. CP 99994 intravenously (0.3 mg kg(-1)) and orally (3-10 mg kg(-1)) inhibited SP-induced bronchoconstriction only. Intravenous and oral low dose combinations of CP 99994 and SR 48968 produced an increased inhibition of SP-, NKA-, [beta-Ala8]-NKA- and capsaicin-induced bronchoconstriction, respectively. The present data indicate that combined tachykinin NK1- and NK2-receptor antagonist treatment compared with single antagonist treatment, using CP 99994 and SR 48968, produced an augmented blockade of tachykinin NK1-, NK2- and capsaicin-mediated contractions in guinea pig airways. These findings support the hypothesis that a dual NK1- and NK2-receptor antagonist may provide an advantage over single activity tachykinin NK1- or NK2-receptor antagonists in pulmonary obstructive diseases.
Corboz
M R
MR
Allergy, Schering-Plough Research Institute, Kenilworth, NJ 07033, USA.
Fernandez
X
X
Rizzo
C A
CA
Tozzi
S
S
Monahan
M E
ME
Hey
J A
JA
D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D001980:Bronchi / Q000187:drug effects* / Q000502:physiology; D016084:Bronchoconstriction / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D064729:Neurokinin-1 Receptor Antagonists; D010880:Piperidines / Q000494:pharmacology; D018040:Receptors, Neurokinin-1 / Q000502:physiology; D018041:Receptors, Neurokinin-2 / Q000037:antagonists & inhibitors* / Q000502:physiology
D001549:Benzamides; D004338:Drug Combinations; D064729:Neurokinin-1 Receptor Antagonists; D010880:Piperidines; D018040:Receptors, Neurokinin-1; D018041:Receptors, Neurokinin-2; C080755:3-(2-methoxybenzylamino)-2-phenylpiperidine; C073839:SR 48968