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

Abstract

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 150×250 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 the 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 emisson 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.