The role of tachykinins in air ventilation-induced bronchoconstriction in postmortem guinea pigs.
To investigate the relationship between tachykinins and air ventilation-induced airway constriction after heart ligation, 26 guinea pigs were divided into three groups: Group 1, control (n = 15); Group 2, tachykinin depletion via pretreatment with capsaicin (n = 7); and Group 3, isocapnic ventilation (n = 4). To examine the age effect, the first two groups were further separated into two subgroups: young (n = 12) and mature (n = 10). Animals were anesthetized with pentobarbital, sternotomized and artificially ventilated with room air or with 5% CO2 gas mixture. Before (baseline) and after heart ligation, tidal volume and transpulmonary pressure (Ptp) were recorded during ventilation, and the maximal expiratory flow-volume curve was periodically obtained. Minimal volume (lung volume at Ptp = 0) was determined by neon dilution. Within 30 min after heart ligation in the control group, air ventilation significantly decreased dynamic compliance, vital capacity, peak maximal expiratory flow, maximal expiratory flow at 50% total lung capacity, and forced expiratory volume in 0.2 sec. Tachykinin depletion significantly prevented, whereas isocapnic (5% CO2) ventilation failed to alter, the above changes. Young and mature subgroups showed similar results. Our data indicate that air ventilation after heart ligation induced severe airway constriction and that this bronchoconstriction can be prevented by tachykinin depletion.