Responses of Xenopus laevis Water Nose to Water-Soluble and Volatile Odorants

Abstract

Using the whole-cell mode of the patch-clamp technique, we recorded action potentials, voltage-activated cationic currents, and inward currents in response to water-soluble and volatile odorants from receptor neurons in the lateral diverticulum (water nose) of the olfactory sensory epithelium of Xenopus laevis. The resting membrane potential was −46.5 ± 1.2 mV \documentclass[10pt]{article} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{pmc} \usepackage[Euler]{upgreek} \pagestyle{empty} \oddsidemargin -1.0in \begin{document} \begin{equation*}({\mathrm{mean}}\;{\pm}\;{\mathrm{SEM}},\;n\;=\;68)\end{equation*}\end{document}, and a current injection of 1–3 pA induced overshooting action potentials. Under voltage-clamp conditions, a voltage-dependent Na+ inward current, a sustained outward K+ current, and a Ca2+-activated K+ current were identified. Application of an amino acid cocktail induced inward currents in 32 of 238 olfactory neurons in the lateral diverticulum under voltage-clamp conditions. Application of volatile odorant cocktails also induced current responses in 23 of 238 olfactory neurons. These results suggest that the olfactory neurons respond to both water-soluble and volatile odorants. The application of alanine or arginine induced inward currents in a dose-dependent manner. More than 50% of the single olfactory neurons responded to multiple types of amino acids, including acidic, neutral, and basic amino acids applied at 100 μM or 1 mM. These results suggest that olfactory neurons in the lateral diverticulum have receptors for amino acids and volatile odorants.

Olfactory metamorphosis in the coastal tailed frog Ascaphus truei (Amphibia, Anura, Leiopelmatidae)

“…This has been confirmed by vital staining (Iida and Kashiwayanagi, 1999). The olfactory system is thus tripartite, with both the VN and AC epithelium functioning in aquatic olfaction, the PC epithelium in aerial olfaction.…”

“…In X. laevis, which has become the ''model'' amphibian for olfactory studies, Altner (1962) first provided evidence that the adult principal cavity (PC) retains air and the accessory cavity (AC) retains water at all times. This has been confirmed by vital staining (Iida and Kashiwayanagi, 1999). The olfactory system is thus tripartite, with both the VN and AC epithelium functioning in aquatic olfaction, the PC epithelium in aerial olfaction.…”

Exotic Models May Offer Unique Opportunities to Decipher Specific Scientific Question: The Case of Xenopus Olfactory System

“…However, the specificity of the different elements of the tripartite olfactory system needs to be discussed as they do not appear to be as strict as could be thought. First, though the PC is exclusively involved in the detection of volatile odorants, the MC is able to detect both volatile and soluble odorants (Iida and Kashiwayanagi, 1999). Second, though Class I ORs are mainly expressed in the MC and Class II ORs in the PC, some class I ORs have also been shown to be present in the PC (Amano and Gascuel, 2012).…”

“…Olfactory marker proteins (OMPs) (Rossler et al, 1998), lectins (Key and Giorgy, 1986;Suzuki et al, 1999;Saito and Tanigushi, 2000), G protein in MC and PC have been found to be different. Third, physiological experiments have shown that PC ORNs detect volatile odorants (Lischka and Schild, 1993;Schild and Lischka, 1994), whereas MC neurons detect soluble odorants, even though they also detect some volatile odorants (Iida and Kashiwayanagi, 1999). Fourth, Freitag et al (1995Freitag et al ( , 1998 showed that class I (fish like) and class II (mammalian like) OR genes were expressed in the MC and the PC, respectively.…”

Whole‐cell recording from honeybee olfactory receptor neurons: ionic currents, membrane excitability and odourant response in developing workerbee and drone

“…Calcium‐activated potassium currents are also commonly found except for rat ORNs in culture (Trombley & Westbrook, 1991), which lack the latter. Most of the ORNs have in addition a transient A‐like current similar to ORNs in insects (Zufall et al ., 1991), squid (Lucero & Chen, 1997) and some vertebrates (Firestein & Werblin, 1987; Schild, 1989; Miyamoto et al ., 1992; Corotto et al ., 1996; Ma et al ., 1999) with the exception of lobster, frog and toad (Delgado & Labarca, 1993; McClintock & Ache, 1989; Iida & Kashiwayanagi, 1999). In our conditions we were unable to detect an A‐like potassium current although a prominent A current is present in cultured honeybee Kenyon cells from mushroom bodies (involved in odour processing in insect brain; Schäfer et al ., 1994) and antennal motoneurons from adult honeybee (Kloppenburg et al ., 1999).…”