Inhibitory and excitatory responses of olfactory receptor neurons of xenopus laevis tadpoles to stimulation with amino acids

1999 ◽  
Vol 202 (8) ◽  
pp. 997-1003 ◽  
Author(s):  
C. Vogler ◽  
D. Schild
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Xenopus Laevis ◽  
Olfactory Receptor ◽  
Olfactory Receptor Neurons ◽  
Patch Clamp Technique ◽  
Olfactory Neurons ◽  
Receptor Neurons ◽  
Patch Configuration ◽  
Excitatory Responses

Recordings were made from olfactory receptor neurons of Xenopus laevis tadpoles using the patch-clamp technique to investigate the responses of these cells to odorants. Four amino acids (glutamate, methionine, arginine and alanine) both individually and as a mixture were used as stimuli. Of the 156 olfactory neurons tested, 43 showed a response to at least one of the stimuli. Of the cells tested, 19 % responded to glutamate, 16 % to methionine, 12 % to arginine and 10 % to alanine. Each amino acid was able to induce both excitatory and inhibitory responses, although these occurred in different cells. Each amino acid produced approximately equal numbers of inhibitory and excitatory responses. Inhibitory responses could best be observed in the perforated-patch configuration using gramicidin as an ionophore and a recording configuration that is a current-clamp for fast signals and a voltage-clamp for slow signals. The diversity of the odorant responses, in particular the existence of excitatory and inhibitory responses, is not consistent with a single transduction pathway in olfactory neurons of Xenopus laevis tadpoles.

scholarly journals Classes and Narrowing Selectivity of Olfactory Receptor Neurons of Xenopus laevis Tadpoles

2004 ◽  
Vol 123 (2) ◽  
pp. 99-107 ◽  
Author(s):  
Ivan Manzini ◽  
Detlev Schild
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Xenopus Laevis ◽  
Olfactory Receptor ◽  
Developmental Stages ◽  
Olfactory Receptors ◽  
Response Spectra ◽  
Olfactory Receptor Neurons ◽  
Receptor Neurons ◽  
Response Profiles

In olfactory receptor neurons (ORNs) of aquatic animals amino acids have been shown to be potent stimuli. Here we report on calcium imaging experiments in slices of the olfactory mucosa of Xenopus laevis tadpoles. We were able to determine the response profiles of 283 ORNs to 19 amino acids, where one profile comprises the responses of one ORN to 19 amino acids. 204 out of the 283 response profiles differed from each other. 36 response spectra occurred more than once, i.e., there were 36 classes of ORNs identically responding to the 19 amino acids. The number of ORNs that formed a class ranged from 2 to 13. Shape and duration of amino acid-elicited [Ca2+]i transients showed a high degree of similarity upon repeated stimulation with the same amino acid. Different amino acids, however, in some cases led to clearly distinguishable calcium responses in individual ORNs. Furthermore, ORNs clearly appeared to gain selectivity over time, i.e., ORNs of later developmental stages responded to less amino acids than ORNs of earlier stages. We discuss the narrowing of ORN selectivity over stages in the context of expression of olfactory receptors.

Highly Specific Olfactory Receptor Neurons for Types of Amino Acids in the Channel Catfish

2007 ◽  
Vol 98 (4) ◽  
pp. 1909-1918 ◽  
Author(s):  
Alexander A. Nikonov ◽  
John Caprio
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Olfactory Bulb ◽  
Olfactory Receptor ◽  
Neutral Amino Acid ◽  
Olfactory Receptor Neurons ◽  
Side Chain ◽  
Single Group ◽  
Group I ◽  
Receptor Neurons

Odorant specificity to l-α-amino acids was determined electrophysiologically for 93 single catfish olfactory receptor neurons (ORNs) selected for their narrow excitatory molecular response range (EMRR) to only one type of amino acid (i.e., Group I units). These units were excited by either a basic amino acid, a neutral amino acid with a long side chain, or a neutral amino acid with a short side chain when tested at 10−7 to 10−5 M. Stimulus-induced inhibition, likely for contrast enhancement, was primarily observed in response to the types of amino acid stimuli different from that which activated a specific ORN. The high specificity of single Group I ORNs to type of amino acid was also previously observed for single Group I neurons in both the olfactory bulb and forebrain of the same species. These results indicate that for Group I neurons olfactory information concerning specific types of amino acids is processed from receptor neurons through mitral cells of the olfactory bulb to higher forebrain neurons without significant alteration in unit odorant specificity.

In Vivo Responses of Single Olfactory Receptor Neurons of Channel Catfish to Binary Mixtures of Amino Acids

1997 ◽  
Vol 77 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Jiesheng Kang ◽  
John Caprio
Keyword(s):  
Amino Acids ◽  
Binary Mixtures ◽  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Olfactory Receptor ◽  
Olfactory Receptor Neurons ◽  
Electrophysiological Response ◽  
Receptor Neurons ◽  
First Time

Kang, Jiesheng and John Caprio. In vivo response of single olfactory receptor neurons of channel catfish to binary mixtures of amino acids. J. Neurophysiol. 77: 1–8, 1997. For the first time in any vertebrate, in vivo responses of single olfactory receptor neurons to odorant mixtures were studied quantitatively. Extracellular electrophysiological response of 54 single olfactory receptor neurons from 23 channel catfish, Ictalurus punctatus, to binary mixtures of amino acids and to their components were recorded simultaneously with the electroolfactogram (EOG). For 57% (73 of 128) of the tests, no significant change (N) from spontaneous activity occurred. Responses to the remaining 55 tests of binary mixtures were excitatory (E; 13%) or suppressive (S; 30%). No response type was associated with any specific mixture across the neurons sampled. Eighty-six percent of the responses of catfish olfactory receptor neurons to binary mixtures were classifed similar to at least one of the component responses, a percentage comparable (i.e., 89%) with that observed for single olfactory bulb neurons in the same species to equivalent binary mixtures. The responses of single olfactory receptor neurons to component-similar binary mixtures (i.e., component responses were both E, both S, and both N, respectively) were generally (80% of 59 tests) classified similar to the responses to the components. For E+N and S+N binary mixtures, the N component often (66% of 58 tests) reduced or concealed (i.e., “masked”) the excitatory and suppressive responses, respectively. For the majority (6 of 11 tests) of E+S binary mixtures, null activity resulted. Responses to the remaining five tests were either excitatory ( n = 3) or suppressive ( n = 2).

In vivo responses of single olfactory receptor neurons in the channel catfish, Ictalurus punctatus

1995 ◽  
Vol 73 (1) ◽  
pp. 172-177 ◽  
Author(s):  
J. Kang ◽  
J. Caprio
Keyword(s):  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Olfactory Receptor ◽  
Action Potentials ◽  
Olfactory Receptor Neurons ◽  
Receptor Neurons ◽  
Spontaneous Frequency ◽  
Excitatory Responses ◽  
First Time

1. We report for the first time in any teleost, a quantitative in vivo study of recordings from single olfactory receptor neurons (ORNs) in the channel catfish, Ictalurus punctatus, with odorant stimuli. 2. Responses of 69 spontaneously active single ORNs were recorded simultaneously with the electroolfactogram (EOG). Recording times ranged from 10 to 72 min per receptor cell with an average of 24 +/- 15 (SD) min/cell. The averaged spontaneous frequency ranged from < 1 to 12 action potentials/s with a mean frequency of 4.7 +/- 2.5 action potentials/s. 3. Catfish ORNs responded to the odorant stimuli (amino acids, bile salts, and ATP) with either an excitation or suppression of the background neural activity. Suppressive responses were encountered more frequently than excitatory responses, suggesting that suppressive responses also play an important role in olfactory coding. 4. Excitatory and suppressive responses to the different odorants were elicited from the same ORN, suggesting that different olfactory receptor molecules and different transduction pathways exist in the same ORN.

scholarly journals Odorant receptors activated by amino acids in sensory neurons of the channel catfish Ictalurus punctatus.

1993 ◽  
Vol 102 (6) ◽  
pp. 1085-1105 ◽  
Author(s):  
T T Ivanova ◽  
J Caprio
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Olfactory Receptor ◽  
Action Potentials ◽  
Single Channel ◽  
Odorant Receptors ◽  
Olfactory Neurons ◽  
Whole Cell

Odorant receptors activated by amino acids were investigated with patch-clamp techniques in olfactory receptor neurons of the channel catfish, Ictalurus punctatus. The L-isomers of alanine, norvaline, arginine, and glutamate, known to act predominantly on different olfactory receptor sites, activated nondesensitizing inward currents with amplitudes of -2.5 to -280 pA in olfactory neurons voltage-clamped at membrane potentials of -72 or -82 mV. Different amino acids were shown to induce responses in the same sensory neurons; however, the amplitude and the kinetics of the observed whole cell currents differed among the stimuli and may therefore reflect activation of different amino acid receptor types or combinations of receptor types in these cells. Amino acid-induced currents appeared to have diverse voltage dependence and could also be classified according to the amplitude of the spontaneous channel fluctuations underlying the macroscopic currents. A mean single-channel conductance (gamma) of 360 fS was estimated from small noise whole-cell currents evoked by arginine within the same olfactory neuron in which a mean gamma value of 23.6 pS was estimated from 'large noise' response to norvaline. Quiescent olfactory neurons fired bursts of action potentials in response to either amino acid stimulation or application of 8-Br-cyclic GMP (100 microM), and voltage-gated channels underlying generation of action potentials were similar in these neurons. However, in whole-cell voltage-clamp, 8-Br-cyclic GMP evoked large rectangular current pulses, and single-channel conductances of 275, 220, and 110 pS were obtained from the discrete current levels. These results suggest that in addition to the cyclic nucleotide-gated transduction channels, olfactory neurons of the channel catfish possess a variety of odor receptors coupled to different types of transduction channels.

scholarly journals Standing calcium gradients in olfactory receptor neurons can be abolished by amiloride or ruthenium red.

1993 ◽  
Vol 102 (5) ◽  
pp. 817-831 ◽  
Author(s):  
F W Lischka ◽  
D Schild
Keyword(s):  
Spatial Distribution ◽  
Intracellular Calcium ◽  
Olfactory Receptor ◽  
Ruthenium Red ◽  
Olfactory Receptor Neurons ◽  
Patch Clamp Technique ◽  
Pipette Solution ◽  
Fura 2 ◽  
Receptor Neurons ◽  
In Cells

Digital imaging and the patch clamp technique were used to investigate the intracellular calcium concentration in olfactory receptor neurons using the Ca2+ indicator dyes fura-2 and fura-2/AM. The spatial distribution of Cai2+ as well as its modification by the drugs Amiloride and Ruthenium Red were studied. Resting calcium concentrations in cells loaded with fura-2/AM were between 10 and 200 nM. In cells that were loaded with the pentapotassium salt of fura-2 through the patch pipette, calcium concentrations were in the same range if ATP was added to the pipette solution. Otherwise, Ca2+ reached concentrations of approximately 500 nM. Most of the observed cells showed a standing gradient of calcium, the calcium concentrations in the distal dendritic end of the cell being higher than in the soma. In some cells, the gradient was markedly reduced or abolished by adding either Amiloride or Ruthenium Red to the bath solution. In a few cells, neither drug had any effect upon the gradient. It is suggested that the inhomogenous spatial distribution of intracellular calcium in olfactory cells of Xenopus laevis is brought about by an influx of calcium ions through two different calcium permeable conductances in the peripheral compartments of the cells. The fact that only either Ruthenium Red or Amiloride abolished the standing calcium gradient further suggested that the two conductances blocked were presumably not coexpressed in the same cells.

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