Abstract
1. Electrophysiological study disclosed that chloroform and some other odours generate long-lasting positive potentials in the olfactory epithelium of the bullfrog, while electron microscopical study showed that they elicit vigorous protrusion of the distal cytoplasmic portion of the supporting cell containing the secretory granules.2. The secretory process of the supporting cell is as follows: The first detectable indication is the protrusion of the apical portion of the supporting cell (Pls. 3 and 4); the protruded part detaches from its maternal supporting cell (Pl. 7 B), floats as a droplet in the mucus (Pl. 5), and finally the secretory granules inside the droplet disintegrate into the mucus (Pls. 6 and 7 A).3. The secretion was not elicited by the odours which elicit the negative potentials.4. In Cl(-)-free Ringer solution, neither the positive potential nor the protrusion and secretion occurred.5. When 1-2 mM-Ba(2+) in Ringer solution was dripped on the epithelium, both the positive potential and the protrusion and secretion resulted. Subsequent application of chloroform vapour only advanced further disintegration of the secretory granules, but it elicited neither a new protrusion of the granules nor the positive potential.6. In the olfactory epithelium in which the olfactory cells had degenerated but the supporting cells survived, both the positive potential and the protrusion and secretion occurred, but the negative potential did not.7. It is concluded that Cl(-) entry which mainly generates the longlasting positive potential triggers the secretion of the supporting cell.