Cholinergic microvillous cells in the mouse main olfactory epithelium and effect of acetylcholine on olfactory sensory neurons and supporting cells

Abstract

The mammalian olfactory epithelium is made up of ciliated olfactory sensory neurons (OSNs), supporting cells, basal cells, and microvillous cells. Previously, we reported that a population of nonneuronal microvillous cells expresses transient receptor potential channel M5 (TRPM5). Using transgenic mice and immunocytochemical labeling, we identify that these cells are cholinergic, expressing the signature markers of choline acetyltransferase (ChAT) and the vesicular acetylcholine transporter. This result suggests that acetylcholine (ACh) can be synthesized and released locally to modulate activities of neighboring supporting cells and OSNs. In Ca(2+) imaging experiments, ACh induced increases in intracellular Ca(2+) levels in 78% of isolated supporting cells tested in a concentration-dependent manner. Atropine, a muscarinic ACh receptor (mAChR) antagonist suppressed the ACh responses. In contrast, ACh did not induce or potentiate Ca(2+) increases in OSNs. Instead ACh suppressed the Ca(2+) increases induced by the adenylyl cyclase activator forskolin in some OSNs. Supporting these results, we found differential expression of mAChR subtypes in supporting cells and OSNs using subtype-specific antibodies against M(1) through M(5) mAChRs. Furthermore, we found that various chemicals, bacterial lysate, and cold saline induced Ca(2+) increases in TRPM5/ChAT-expressing microvillous cells. Taken together, our data suggest that TRPM5/ChAT-expressing microvillous cells react to certain chemical or thermal stimuli and release ACh to modulate activities of neighboring supporting cells and OSNs via mAChRs. Our studies reveal an intrinsic and potentially potent mechanism linking external stimulation to cholinergic modulation of activities in the olfactory epithelium.

Identification of cholinergic chemosensory cells in mouse tracheal and laryngeal glandular ducts

“…These cells may represent a population of stem cells [46,47]. Non-neuronal ACh released in their vicinity might modulate their activity as it was shown for cells of the olfactory epithelium [48].…”

Deconstructing Olfactory Stem Cell Trajectories at Single-Cell Resolution

“…In support of this prediction, nine of ten clones containing microvillous cells also contain neurons (Figure 4E). Microvillous cells are rare in comparison to olfactory sensory neurons (Hansen and Finger, 2008; Jia et al, 2013; Ogura et al, 2011; Yamaguchi et al, 2014); this difference is reflected by the small number of microvillous cell-containing clones detected (12% of neuron-containing clones), as well as the low number of microvillous cells present in any given microvillous-containing clone (1.2 +/− 0.1; Figure 4H). These clonal lineage tracing results are complemented by a similar, non-clonal lineage tracing analysis using a knockin Ascl1-CreER driver (Kim et al, 2011), which recapitulates Ascl1’s expression in postnatal GBCs (Figure S4) (Manglapus et al, 2004).…”

Spontaneous and sensory-evoked activity in mouse olfactory sensory neurons with defined odorant receptors

“…A previous report from dissociated OSNs suggests that this is the case, as I7 and M71 neurons exhibited higher rates of spontaneous activity than mOR-EG neurons (Reisert 2010). In addition to potential damage to the cilia and axons, dissociation of OSNs also removes olfactory cells from the surrounding sustentacular and microvillar cells, which potentially influence OSN firing rates (Hegg et al 2009(Hegg et al , 2010Ogura et al 2011). We therefore examined OSNs situated in their natural configuration in the intact olfactory epithelia (Fig.…”

“…The discrepancy in overall firing rates is likely attributed to the different preparations and recording configurations. In the intact olfactory epithelial preparations OSN cilia and axons remain relatively undisturbed in their natural configuration, whereas in dissociated preparations OSNs are isolated from surrounding sustentacular and microvillar cells, which may affect firing (Hegg et al 2009(Hegg et al , 2010Ogura et al 2011). It has been shown in perforated-patch recordings that OSNs in intact epithelium respond to their respective ligands 100% of the time (Grosmaitre et al 2006), while the yield in dissociated OSNs is appreciably lower, suggesting that the intact epithelial preparation keeps OSNs healthier and is more physiologically relevant.…”