Characterization of substance P-induced bronchoconstriction in the guinea-pig: a comparison with acetylcholine

Mast cell mediators in citric acid-induced airway constriction of guinea pigs

We demonstrated previously that mast cells play an important role in citric acid (CA)-induced airway constriction. In this study, we further investigated the underlying mediator(s) for this type of airway constriction. At first, to examine effects caused by blocking agents, 67 young Hartley guinea pigs were divided into 7 groups: saline + CA; methysergide (serotonin receptor antagonist) + CA; MK-886 (leukotriene synthesis inhibitor) + CA; mepyramine (histamine H1 receptor antagonist) + CA; indomethacin (cyclooxygenase inhibitor) + CA; cromolyn sodium (mast cell stabilizer) + CA; and compound 48/80 (mast cell degranulating agent) + CA. Then, we tested whether leukotriene C4 (LTC4) or histamine enhances CA-induced airway constriction in compound 48/80-pretreated guinea pigs. We measured dynamic respiratory compliance (Crs) and forced expiratory volume in 0.1 s (FEV0.1) during either baseline or recovery period. In addition, we detected histamine level, an index of pulmonary mast cell degranulation, in bronchoalveolar lavage (BAL) samples. Citric acid aerosol inhalation caused decreases in Crs and FEV0.1, indicating airway constriction in the control group. This airway constriction was significantly attenuated by MK-886, mepyramine, cromolyn sodium, and compound 48/80, but not by either methysergide or indomethacin. Both LTC4 and histamine infusion significantly increased the magnitude of CA-induced airway constriction in compound 48/80-pretreated guinea pigs. Citric acid inhalation caused significant increase in histamine level in the BAL sample, which was significantly suppressed by compound 48/80. These results suggest that leukotrienes and histamine originating from mast cells play an important role in CA inhalation-induced noncholinergic airway constriction.

NK1 and NK2 receptors mediate tachykinin and resiniferatoxin-induced bronchospasm in guinea pigs

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)

Tachykinin-induced dyspnea in conscious guinea pigs

Aerosol administration of neurokinin A (NKA) or substance P (SP) to conscious guinea pigs produced labored abdominal breathing (dyspnea). Time to onset of dyspnea was inversely related to tachykinin concentration. Aerosol administration of the neutral endopeptidase inhibitor thiorphan significantly potentiated tachykinin-induced dyspnea without affecting responses to leukotriene D4 (LTD4), carbachol, histamine, platelet activating factor or serotonin (5-HT), indicating selectivity for tachykinins rather than a nonspecific effect on agonist reactivity. The rank order of potency for producing dyspnea was LTD4 greater than or equal to NKA (with thiorphan) much greater than SP (with thiorphan) greater than 5-HT = carbachol greater than histamine greater than platelet-activating factor. Pretreatment with propranolol, phentolamine, methysergide, pyrilamine or the peptide leukotriene antagonist, ICI 198,165, did not alter dyspnea induced by NKA or SP. The dose-response curves for NKA and SP were shifted to small degrees (less than 3-fold) to the right by atropine and to the left by indomethacin. Also, pretreatment with capsaicin did not affect responses to NKA or SP, indicating that they do not cause dyspnea by activating capsaicin sensitive C-fibers. These results suggest primarily direct effects of NKA and SP. This model may be useful for in vivo evaluation of tachykinin antagonists.

Substance P-like immunoreactive nerve fibers of the human laryngeal mucosa--preliminary report

Substance P (SP) is considered a primary sensory transmitter and is widely distributed within the autonomic nervous system. This study is concerned with the distribution of SP-like immunoreactive nerve fibers in the human larynx. Individual SP-like immunoreactive nerve fibers were detected in the subepithelial connective tissue of the laryngeal mucosa, in the ventricular and subglottic glandular regions and in a few nervous ganglia in the deep connective tissue. No intraepithelial SP-like immunoreactive fibers were present in our material.

The mechanism of tachykinin-induced bronchoconstriction in the rat

The mammalian tachykinins substance P (SP) and neurokinin A (NKA) are known to be present in sensory airway nerves of animals and humans. We studied the effect of mammalian and nonmammalian tachykinins on the conducting airways of anesthetized, mechanically ventilated Fisher 344 rats. Dose-dependent increases in lung resistance and decreases in dynamic compliance occurred after the intravenous administration of eledoisin (E), kassinin (K), NKA, and SP. E, K, and NKA were more potent bronchoconstrictors than was SP. Neurokinin B (NKB) caused a similar decrease in dynamic compliance, but had no effect on lung resistance. This order of potency suggests a predominance of NK-2 receptors in the rat airways. Both atropine and the 5-hydroxytryptamine antagonist methysergide largely reduced the bronchoconstriction induced by E and SP. Vagotomy did not change this reaction, whereas pretreatment with the ganglion blocker hexamethonium slightly enhanced the bronchoconstrictor action of E and SP. Sodium cromoglycate and nedocromil sodium, 2 drugs that can inhibit mediator release from inflammatory cells, significantly reduced the bronchoconstrictor action of NKA. Ketotifen, an antihistamine with mast-cell-stabilizing properties, significantly reduced the bronchoconstriction induced by E, whereas the H1-receptor antagonist clemastine had no effect. We conclude that tachykinins cause bronchoconstriction in rats largely by an indirect mechanism, involving both acetylcholine and 5-hydroxytryptamine. We suggest that tachykinins cause bronchoconstriction by stimulation of postganglionic vagal nerve endings and mast cells.