NEUROTRANSMITTER-INDUCED EXOCYTOSIS IN GOBLET AND ACINAR-CELLS OF RATNASAL-MUCOSA STUDIED BY VIDEO MICROSCOPY

To investigate the mechanism and neural control of the nasal secretion , we observed the isolated rat nasal mucosa by video-enhanced differen tial interference contrast microscopy. This technique allowed us to vi sualize abrupt changes of the individual granules leading to degranula tion in the acinar cells and in epithelial goblet cells during secreto ry stimulation. This image provided evidence that exocytosis is the ma jor mode for regulated secretion in the nasal acinar cells and goblet cells. Acetylcholine (ACh, 0.1-100 muM), substance P (SP, 0.1-10 muM), and vasoactive intestinal peptide (VIP, 0.1-1 muM) induced exocytotic responses and shrinkage of the acinus in a concentration-dependent ma nner. The effects of ACh (10 muM) on the acinus were clearly inhibited by atropine (5 muM), but the effects of SP (1 muM) and VIP (1 muM) we re not. The acinar shrinkage always started before exocytosis, suggest ing that the fluid secretion precedes the mucus release. In goblet cel ls, SP (1 muM) and ACh (10 muM) increased the frequency of exocytotic responses significantly, suggesting that these substances truly play t he role of a neurotransmitter for nasal secretion. Histamine (HIST) in duced no visible response. The effect of HIST on secretory cells may b e neuronally mediated in vivo.