NEW STRUCTURE, THE OLFACTORY PIT, IN HUMAN OLFACTORY MUCOSA

A whole-mount immunocytochemical method was devised to study the olfac tory receptor neurons on the surface of the human olfactory mucosal sh eet. Antibodies to neuron-specific tubulin and/or microtubule-associat ed protein 5 and phosphorylated neurofilament protein were used. Speci mens taken at autopsy from 56 patients ranging in age from 2 days to 9 2 years revealed a structure not previously described, an olfactory pi t. Round or oval openings with a diameter of 50 to 500 mu m were obser ved on the surface of the olfactory epithelium in the whole-mount spec imen. The morphology, number, and distribution of these openings varie d among the different individuals. A detailed analysis of these struct ures was carried out by rehydrating and sectioning the whole-mount spe cimens. The olfactory pit (OP) is a blind pouch lined with olfactory e pithelium (OE), which appears as an invagination of OE into the connec tive tissue, with a depth varying between 150 and 200 mu m. In some se ctions through an OP, a thick axon bundle emerging from the bottom of the pouch was visible. The extension and termination of this axon bund le in the central nervous system has not been explored. We have found OPs in monkey olfactory mucosa, but none in rodents. The function of t he pit specialization is unclear, but it appears to be a feature of no rmal, young epithelium. The configuration of the blind pouch may prolo ng odorant association with the olfactory receptor neurons, or the OP may contain specialized neurons that have not yet been recognized by m orphological, biochemical, or functional techniques. (C) 1997 Wiley-Li ss, Inc.