Effects of hormones and nucleotides on ciliary beating in frog esophagus and guinea pig trachea

Ciliary beating frequency of frog palate and rat trachea explants under continuous perfusion

Rat trachea and frog palate explants were continuously perfused for 2 hr with 199 tissue culture medium. The ciliary beating frequency of the frog palate exhibited fluctuations twice as large as compared to the rat trachea. The rat trachea model should be preferred to the frog palate for long-term studies on ciliary beat frequency.

The role of serotonin in mucociliary transport system in the ciliated epithelium of frog palatine mucosa

The effects of serotonin (5-hydroxytryptamine, 5-HT) on mucociliary transport and mucus secretion were investigated pharmacologically. The presence of 5-HT in the ciliated epithelium of frog palatine mucosa was examined chromatographically. Mucociliary transport was accelerated by the application of 10(-6) M 5-HT. Mucus secretion was also stimulated significantly by 5-HT (30 mg/kg). 5-HT in the mucosa was detected by a chromatographic technique when a large amount of 5-HT precursor, 5-hydroxytryptophan (5-HTP), was given previously. Phenylhydrazine was used as MAO inhibitor. When phenylhydrazine (20 mg/kg) was given before 5-HTP, 5-HT was markedly concentrated in the mucosa. Radioactive 5-HT was also detected in the mucosa after incubation with [14C]5-HTP. One hour after systemic administration of [3H]5-HTP, a large number of silver grains appeared in the autoradiograms of some epithelial cells. These results suggest the possibility that epithelial cells with the ability to synthesize 5-HT from 5-HTP exist in ciliated epithelium. A possible functional relationship is proposed between the regulation of mucociliary transport with mucus secretion and 5-HT-containing cells.

Dopaminergic innervation and inhibition of ciliary movement in the ciliated epithelium of frog palatine mucosa

The effect of dopamine on ciliary movement and the existence of dopamine-containing cells in the ciliated epithelium of frog palatine mucosa were investigated pharmacologically and by means of electron and fluorescence microscopy, respectively. Ciliary movement was suppressed markedly when the perfusion medium contained 10(-6) M dopamine, thereby indicating that dopamine has a suppressive effect on ciliary movement. Electron microscopy revealed at least two types of granule-containing (GC) cells, type 1 cells containing small spherical granular vesicles (about 100-150 nm in diameter) and type 2 cells containing elongated dense granules (about 150 X 250 nm in diameter). One hour after systemic administration of dihydroxyphenylalanine-[3H(G)] [( 3H]DOPA), a large number of silver grains appeared only in type 2 GC cells, thus indicating that type 2 cells are catecholamine-storing. Blue-green fluorescent cells were detected in the ciliated epithelium. On microspectrofluorometry, catecholamine fluorescence in the cells showed a main excitation and emission maxima at 415 and 480 nm, respectively. When the fluorescent cells were exposed to HCl vapor for several s, the excitation peak shifted to 380 nm and this peak was unchanged after treatment for an additional 5 min. It may be considered that these fluorescent cells contain dopamine and correspond to type 2 GC cells. A possible functional relationship between regulation of ciliary movement and dopamine-containing cells was also discussed.

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.