C. structures is labeled. Here we examined the morphology and immunocytochemical properties of these microvillous-like cells using immunocytochemical methods. == Results == We show that the GFP-positive microvillous cells were morphologically diversified and scattered throughout the entire MOE. These cells immunoreacted to an antibody against TRPM5, confirming the expression of this ion channel in these cells. In addition, they showed a Ca2+-activated non-selective cation current in electrophysiological recordings. They did not immunoreact to antibodies that label cell markers and elements NU6300 of the transduction pathways from olfactory sensory neurons and solitary chemosensory cells of the nasal cavity. Further, the TRPM5-expressing cells did not display axon-like processes and were not labeled with a neuronal marker nor did trigeminal peptidergic nerve fibers innervate these cells. == Conclusion == We provide morphological and immunocytochemical characterization of the TRPM5-expressing microvillous cells in the main olfactory epithelium. Our data demonstrate that these cells are non-neuronal and in terms of chemosensory transduction do not resemble the TRPM5-expressing olfactory sensory neurons and nasal solitary chemosensory cells. == Background == The peripheral olfactory epithelium in mammal is made up of four types of cells, ciliated olfactory sensory neurons (OSNs), basal cells, supporting cells and microvillious cells, which together NU6300 form a pseudostratified epithelium [1-3]. The olfactory sensory neurons are specialized in detecting diverse odor molecules and transmitting information to the olfactory bulb through their axonal projections [4-6]. Mature OSNs are ciliated bipolar neurons, with cell bodies that are located in the middle layers of the epithelium[1,7-9]. Each of the mature OSNs sends an apical dendrite to the luminal surface where the dendrite terminates in an oval structure, the olfactory knob, bearing approximately 20 cilia where olfactory receptor proteins and the elements of the olfactory transduction cascade are localized [10-12]. A single axon protruding from the basal end of the soma of the OSN penetrates the basal lamina and projects to the olfactory bulb[12]. The supporting cells and basal cells are not sensory cells. The supporting cells also called sustentacular cells are columnar in shape. Their cell bodies span the NU6300 entire basal to apical extent of the epithelium. Their apical end is covered with long or short microvilli and their somata are located in the superficial layer of the epithelium[2,13-15]. Sustentacular cells are thought to serve a supporting role akin to that of glial cells in the brain. The basal cells, including both globose and horizontal cells, reside basally just above the basal lamina. Amongst these there are olfactory stem cells, capable of regenerating other types of cells in the epithelium throughout life [16-18]. Thus, OSNs, assisting cells and basal cells are distinct in function and morphology. On the other hand, the function of microvillous cells from the mammalian NEU OE isn’t well understood plus they look like morphologically varied. Electron microscopic research have exposed that their apical microvilli may take different styles, measures, and diameters while their cytoplasm could be either electro-lucent or opaque[14,19-22]. Some microvillar cells have already been reported to task thin axons towards the olfactory light bulb, suggesting another course of bipolar sensory neurons in the olfactory mucosa[1,20,22]. Nevertheless, the current presence of axonal procedures can be questioned in additional studies where studies with epithelial markers indicate that at least some microvillar cells in the OE aren’t of neuronal source and don’t bear axonal procedures[21,23]. One probability growing from these scholarly research can be that we now have a number of different types of microvillar cells, some neuronal while others epithelial in character. Arguably the very NU6300 best characterized microvillous cells are those within the OE of seafood where they become sensory receptors that react to water-borne smells[24,25]. Latest studies possess indicated that some microvillous cells in the olfactory epithelium of mammals are chemosensitive aswell. Elsaesser et al [26]reported a subset of microvillar cells express the transient.