[The role of parasympathetic nerve on hyperventilation-induced bronchoconstriction in sensitized rabbits]

We have demonstrated that hyperventilation-induced bronchoconstriction (HIB) is observed in sensitized rabbits, and that histamine may play a role in HIB. To investigate the role of parasympathetic neurotransmission in HIB, the effects of atropine and vagotomy on HIB were examined. Japanese white rabbits were sensitized with ovalbumin. They were then anesthetized and paralyzed with pancuronium, and then mechanically ventilated (TV: 7 ml/kg, RR: 40/min). The rabbits were divided into the following three groups: I) control group (n = 7), II) atropine-treated group (n = 6), III) bilateral vagotomy group (n = 6). Hyperventilation was performed at TV: 7 ml/kg, RR: 120/min for 15 min in dry room air containing 5% CO2. Total lung resistance (RL) and dynamic compliance (Cdyn) were measured before and at 0, 5, 15 and 30 minutes after hyperventilation. RL increases significantly at 5 minutes in group 1, but this change was significantly less marked in groups 2 and 3. However Cdyn was not significant change in each group. We conclude that parasympathetic neurotransmission may play an important role in HIB of sensitized rabbits.