Ionic conductances in sustentacular cells of the mouse olfactory epithelium

Abstract

The electrical properties of sustentacular cells (SCs) in the olfactory epithelium (OE) were investigated in tissue slices taken from neonatal mice (P0–P4). Conventional whole-cell recordings were obtained from SCs and also from olfactory receptor neurones (ORNs) insitu. SCs had a larger apparent cell capacitance (C_cell) (18.6 ± 0.5 pF) than ORNs (4.4 ± 0.4 pF) and a lower apparent membrane resistance (R_m) (160 ± 11 MΩversus 664 ± 195 MΩ, respectively). When corrected for a seal resistance of 1 GΩ, these mean R_m values were increased to 190 MΩ and 2 GΩ in SCs and ORNs, respectively. SCs generated a TTX (1 μm)-resistant voltage-activated Na⁺ current (I_Na) that had a peak density at −38 mV of −44 pA pF⁻¹ and supported action potential firing. Peak current density of I_Na in neurones was 510 ± 96 pA pF⁻¹. The outward K⁺ current in SCs was composed (> 70%) of a TEA (2 mm)-sensitive component that was mediated by the opening of large-conductance (237 ± 10 pS; BK) channels. The resting leak conductance (g_L) of SCs was permeable to monovalent cations and anions and was largely inhibited by substitution of external Na⁺ with NMDG and by internal F⁻ with gluconate. g_L deactivated up to 50% at potentials negative of −70 mV and was inhibited by 18β-glycyrrhetinic acid (20 μm). SCs were identified using fluorescent dyes (Lucifer Yellow and Alexa Fluor 488) in the whole-cell patch pipette-filling solution. Our findings indicate that SCs in the OE of neonates are electrically excitable and are distinguishable from neurones by a having a resting g_L.