Cholinergic nerves stimulate mucociliary transport, ciliary activity, and mucus secretion in the frog palate

Mucociliary transport, ciliary activity, and mucus secretion were studied in the palate of the frog Rana pipiens by direct observation, stroboscopic synchronization of ciliary beating, and histochemistry. Excised palates were studied in vitro, and intact palates were studied in vivo. Electrical stimulation of the glossopharyngeal nerve in vivo or of the palatine nerve in vitro stimulated all three activities. The effect was mimicked by acetylcholine and pilocarpine, enhanced by physostigmine, and blocked by atropine but unaffected by d-tubocurarine. Stimulation increased the number of cilia beating and their rate of beating, the number of goblet cells secreting and, for small acidic cells, the amount of mucus secreted, and the rate and extent of particle transport. The response to tactile stimulation was locally restricted in vitro but widespread in vivo. It was concluded that, although there is a low basal rate of mucus secretion and ciliary activity that is independent of nervous control, stimulation of these activities in the intact animal is mediated through the central nervous system and cholinergic nerves to the palate.