Local anaesthesia of the trachea and mucus secretion.

We have tested whether two local anaesthetics, in the lumen of cat trachea in vivo, would block the stimulation of mucus secretion by parasympathetic nerves without altering its stimulation by a cholinergic drug. Lignocaine, 4.3-43 mM (0.1-1%) in Krebs-Henseleit, increased the output of mucus macromolecules. It abolished secretion in response to vagus nerve stimulation, but also diminished the effect of 5 microM pilocarpine. Tetrodotoxin, 50 microM, abolished vagal control of secretion without inhibiting pilocarpine's action or changing resting secretion. Though lignocaine blocks nerve-mediated secretion, its action is not simply on nerve conduction. In contrast, the effect of tetrodotoxin may be restricted to the blocking of nerves.