scholarly journals Electro-olfactogram and multiunit olfactory receptor responses to binary and trinary mixtures of amino acids in the channel catfish, Ictalurus punctatus.

1989 ◽  
Vol 93 (2) ◽  
pp. 245-262 ◽  
Author(s):  
J Caprio ◽  
J Dudek ◽  
J J Robinson
Keyword(s):  
Amino Acids ◽  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Olfactory Receptor ◽  
Receptor Site ◽  
Sensory Stimulation ◽  
Cross Reactivity ◽  
Electrophysiological Recordings ◽  
Cross Adaptation

In vivo electrophysiological recordings from populations of olfactory receptor neurons in the channel catfish, Ictalurus punctatus, clearly showed that responses to binary and trinary mixtures of amino acids were predictable with knowledge obtained from previous cross-adaptation studies of the relative independence of the respective binding sites of the component stimuli. All component stimuli, from which equal aliquots were drawn to form the mixtures, were adjusted in concentration to provide for approximately equal response magnitudes. The magnitude of the response to a mixture whose component amino acids showed significant cross-reactivity was equivalent to the response to any single component used to form that mixture. A mixture whose component amino acids showed minimal cross-adaptation produced a significantly larger relative response than a mixture whose components exhibited considerable cross-reactivity. This larger response approached the sum of the responses to the individual component amino acids tested at the resulting concentrations in the mixture, even though olfactory receptor dose-response functions for amino acids in this species are characterized by extreme sensory compression (i.e., successive concentration increments produce progressively smaller physiological responses). Thus, the present study indicates that the response to sensory stimulation of olfactory receptor sites is more enhanced by the activation of different receptor site types than by stimulus interaction at a single site type.

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 Electro-olfactogram and multiunit olfactory receptor responses to complex mixtures of amino acids in the channel catfish, Ictalurus punctatus.

1991 ◽  
Vol 98 (4) ◽  
pp. 699-721 ◽  
Author(s):  
J S Kang ◽  
J Caprio
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Binary Mixtures ◽  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Olfactory Receptor ◽  
Complex Mixtures ◽  
Neutral Amino Acids ◽  
Acidic Amino Acids ◽  
Receptor Sites

In vivo electrophysiological recordings from populations of olfactory receptor neurons in the channel catfish, Ictalurus punctatus, clearly showed that both electro-olfactogram and integrated neural responses of olfactory receptor cells to complex mixtures consisting of up to 10 different amino acids were predictable with knowledge of (a) the responses to the individual components in the mixture and (b) the relative independence of the respective receptor sites for the component stimuli. All amino acid stimuli used to form the various mixtures were initially adjusted in concentration to provide approximately equal response magnitudes. Olfactory receptor responses to both multimixtures and binary mixtures were recorded. Multimixtures were formed by mixing equal aliquots of 3-10 different amino acids. Binary mixtures were formed by mixing equal aliquots of two equally stimulatory solutions. Solution 1 contained either one to nine different neutral amino acids with long side-chains (LCNs) or one to five different neutral amino acids with short side-chains (SCNs). Solution 2, comprising the binary mixture, consisted of only a single stimulus, either a LCN, SCN, basic, or acidic amino acid. The increasing magnitude of the olfactory receptor responses to mixtures consisting of an increasing number of neutral amino acids indicated that multiple receptor site types with highly overlapping specificities exist to these compounds. For both binary mixtures and multimixtures composed of neutral and basic or neutral and acidic amino acids, the receptor responses were significantly enhanced compared with those mixtures consisting of an equal number of only neutral amino acids. These results demonstrate that receptor sites for the basic and acidic amino acids, respectively, are highly independent of those for the neutral amino acids, and suggest that a mechanism for synergism is the simultaneous activation of relatively independent receptor sites by the components in the mixture. In contrast, there was no evidence for the occurrence of mixture suppression.

Electrophysiological responses of single olfactory bulb neurons to amino acids in the channel catfish, Ictalurus punctatus

1995 ◽  
Vol 74 (4) ◽  
pp. 1421-1434 ◽  
Author(s):  
J. Kang ◽  
J. Caprio
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Olfactory Bulb ◽  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Action Potentials ◽  
Recording Time ◽  
Over Time ◽  
Olfactory Bulb Neurons

1. Responses of 89 single olfactory bulb neurons from 43 channel catfish, Ictalurus punctatus, to amino acid odorants were recorded in vivo simultaneously with the electro-olfactogram (EOG). Recording time for individual neurons ranged from 16 to 344 min. The averaged spontaneous frequency ranged from x003C; 1 to 16 action potentials/s with a mean frequency of 5.2 +/- 3.6 (SD) action potentials/s. 2. Histological examinations of carbocyanine dye 1,1'diocadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-labeled olfactory bulbs and electrical stimulation of the olfactory tracts in a subset of experiments suggested that the majority of the recorded olfactory bulb neurons in this study were mitral cells. 3. Olfactory bulb neurons responded to amino acids with either an excitation or suppression of the background neural activity. Of the 337 stimulus applications, 28% of the responses were excitatory, and 33% were suppressive. The approximately 1:1 ratio of excitatory to suppressive responses for all stimulus applications suggests that suppressive responses also play important roles in the coding of odorant information in the channel catfish. 4. Responses of single olfactory bulb neurons were highly reproducible over time (up to 5 h). Responses to any amino acid never changed from excitation to suppression, or vice versa over time. 5. Single olfactory bulb neurons responded with excitation or suppression to more than one amino acid previously indicated to bind to independent receptors. 6. Estimated threshold concentrations for activation of an olfactory bulb neuron ranged from 10(-7) to 10(-3) M and were different from neuron to neuron for a particular stimulus and from stimulus to stimulus for a particular neuron. Responses of single olfactory bulb neurons to a given amino acid did not change from excitation to suppression, or vice versa, across different suprathreshold concentrations.

Citrate Enhances Olfactory Receptor Responses and Triggers Oscillatory Receptor Activity in the Channel Catfish

2000 ◽  
Vol 83 (5) ◽  
pp. 2676-2681 ◽  
Author(s):  
James M. Parker ◽  
Qinhui Chang ◽  
John Caprio
Keyword(s):  
Amino Acid ◽  
Binary Mixture ◽  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Olfactory Receptor ◽  
Barium Chloride ◽  
Strontium Chloride ◽  
Olfactory Responses ◽  
Receptor Neurons ◽  
High Concentrations

Citrate, a normal constituent of cellular metabolism, in a binary mixture with an amino acid enhanced asynchronous olfactory receptor responses in the channel catfish, Ictalurus punctatus. In addition, high concentrations of either citrate (≥3 mM) alone or an amino acid (≥0.1 mM) in a binary mixture with citrate (≥1 mM) triggered synchronized voltage oscillations of olfactory receptor neurons (ORNs) known as “peripheral waves” (PWs). Binary mixtures containing lower concentrations of an amino acid also triggered PW activity if the concentration of citrate in the mixture was increased. Both the enhancement of asynchronous activity and the generation of PW activity were the result of citrate chelating calcium, which lowers the surface potential of ORNs making them hyperexcitable. These effects of citrate are replicated by EGTA. Inactivation of the chelating ability of citrate and EGTA with 1 mM calcium chloride, barium chloride, or strontium chloride abolished both the enhancement of asynchronous olfactory responses and PW activity, while not affecting olfactory receptor responses to the amino acids alone.

scholarly journals Electrophysiological evidence for acidic, basic, and neutral amino acid olfactory receptor sites in the catfish.

1984 ◽  
Vol 84 (3) ◽  
pp. 403-422 ◽  
Author(s):  
J Caprio ◽  
R P Byrd
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Ictalurus Punctatus ◽  
Olfactory Receptor ◽  
Olfactory Receptors ◽  
Receptor Potential ◽  
Side Chains ◽  
Short Side ◽  
Neutral Amino Acids ◽  
Receptor Sites

Electrophysiological experiments indicate that olfactory receptors of the channel catfish, Ictalurus punctatus, contain different receptor sites for the acidic (A), basic (B), and neutral amino acids; further, at least two partially interacting neutral sites exist, one for the hydrophilic neutral amino acids containing short side chains (SCN), and the second for the hydrophobic amino acids containing long side chains (LCN). The extent of cross-adaptation was determined by comparing the electro-olfactogram (EOG) responses to 20 "test" amino acids during continuous bathing of the olfactory mucosa with water only (control) to those during each of the eight "adapting" amino acid regimes. Both the adapting and test amino acids were adjusted in concentrations to provide approximately equal response magnitudes in the unadapted state. Under all eight adapting regimes, the test EOG responses were reduced from those obtained in the unadapted state, but substantial quantitative differences resulted, depending upon the molecular structure of the adapting stimulus. Analyses of the patterns of EOG responses to the test stimuli identified and characterized the respective "transduction processes," a term used to describe membrane events initiated by a particular subset of amino acid stimuli that are intricately linked to the origin of the olfactory receptor potential. Only when the stimulus compounds interact with different transduction processes are the stimuli assumed to bind to different membrane "sites." Four relatively independent L-alpha-amino acid transduction processes (and thus at least four binding sites) identified in this report include: (a) the A process for aspartic and glutamic acids; (b) the B process for arginine and lysine; (c) the SCN process for glycine, alanine, serine, glutamine, and possibly cysteine; (d) the LCN process for methionine, ethionine, valine, norvaline, leucine, norleucine, glutamic acid-gamma-methyl ester, histidine, phenylalanine, and also possibly cysteine. The specificities of these olfactory transduction processes in the catfish are similar to those for the biochemically determined receptor sites for amino acids in other species of fishes and to amino acid transport specificities in tissues of a variety of organisms.

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