1. The bronchial response to an anaesthetic aerosol of 4% bupivacaine hydrochloride has been investigated in normal and asthmatic subjects.
2. No significant changes in specific conductance were seen in normal subjects. In asthmatic subjects a significant fall in specific conductance occurred which was significantly reduced by prior treatment with ipratropium bromide.
3. Aerosols of bupivacaine, sodium cromoglycate and saline were tested on the cough reflex elicited by citric acid aerosol in normal and asthmatic subjects. Bupivacaine, but not the other agents, abolished the cough reflex in both groups of subjects.
4. Ipratropium bromide and bupivacaine were tested on methacholine-induced bronchoconstriction in normal and asthmatic subjects. Ipratropium bromide significantly prevented the fall in specific conductance in both groups of subjects whereas bupivacaine (normal subjects only tested) had no protective effect.
5. Ipratropium bromide, bupivacaine and sodium cromoglycate were tested on histamine-induced bronchoconstriction in normal subjects. Half the normal subjects had an upper respiratory tract infection. Ipratropium bromide significantly reduced the fall in specific conductance at 1 min after histamine but not at 5 or 10 min. Bupivacaine and sodium cromoglycate had no protective effect on histamine-induced bronchoconstriction at 1, 5 and 10 min.
6. Ipratropium bromide and bupivacaine were tested on prostaglandin F2α-induced bronchoconstriction in normal subjects. Neither drug prevented the change in specific conductance after prostaglandin F2α.
7. The possible significance of these results is discussed in relation to vagal mechanisms in the control of airways calibre in normal and asthmatic subjects.