scholarly journals Odorant Specificity of Single Olfactory Bulb Neurons to Amino Acids in the Channel Catfish

2004 ◽  
Vol 92 (1) ◽  
pp. 123-134 ◽  
Author(s):  
Alexander A. Nikonov ◽  
John Caprio
Keyword(s):  
Amino Acids ◽  
Olfactory Bulb ◽  
Channel Catfish ◽  
Monosodium Glutamate ◽  
Side Chains ◽  
Low Concentration ◽  
Receptor Sites ◽  
Group I ◽  
Methylene Groups ◽  
Guanidinium Group

Odorant specificity to l-α-amino acids was determined for 245 olfactory bulb (OB) neurons recorded from 121 channel catfish. The initial tests included 4 amino acids representing acidic [monosodium glutamate (Glu)], basic [arginine (Arg)], and neutral [possessing short: alanine (Ala) and long: methionine (Met) side chains] amino acids that were previously indicated to bind to independent olfactory receptor sites. Ninety-one (37%) units (Group I) tested at 1, 10, and 100 μM showed high selectivity and were excited by only one of the 4 amino acids. Odorant specificity for the vast majority of Group I units did not change over the 3 s of response time analyzed. A total of 154 OB units (63%) (Group II) were excited by a second amino acid, but only at ≥10× odorant concentration. An additional 69 Group I units were tested with related amino acids and derivatives from 10−9 to 10−5 M to determine their excitatory odorant thresholds and selectivities. Two groups of units originally selective for Met were evident: those most sensitive to neutral amino acids having branched and linear side chains, respectively. OB units originally selective for Ala responded at low concentration to other similar amino acids. Units originally selective for Arg were excited at low concentration by amino acids possessing in their side chains at least 3 methylene groups and a terminal amide or guanidinium group. The specificities of the OB units determined electrophysiologically are sufficient to account for many of the previous results of behavioral discrimination of amino acids in this and related species.

Facial Taste Responses of the Channel Catfish to Binary Mixtures of Amino Acids

1999 ◽  
Vol 82 (2) ◽  
pp. 564-569 ◽  
Author(s):  
K. Ogawa ◽  
J. Caprio
Keyword(s):  
Amino Acids ◽  
Binary Mixture ◽  
Binary Mixtures ◽  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Taste Receptor ◽  
Single Fiber ◽  
Receptor Sites ◽  
Group I ◽  
Group Ii

We investigated the neural processing of binary gustatory mixtures of amino acids by the facial taste system of the channel catfish, Ictalurus punctatus. In vivo electrophysiological recordings indicated that the magnitude of both integrated and single-unit facial taste responses to binary mixtures of amino acids was greatest if the components bound to independent receptor sites. Facial taste responses were obtained from 32 multiunit and 55 single taste fiber preparations to binary mixtures of amino acids whose components bind to independent taste receptor sites (group I) or to the same or highly cross-reactive taste receptor sites (group II). All component stimuli were adjusted in concentration to provide approximately equal response magnitude as determined by either the height of the integrated multiunit taste response or by the number of action potentials generated/3 s of response time/single taste fiber. The mixture discrimination index (MDI), defined as the response to the mixture divided by the average of the responses to the component stimuli, was calculated for each test of a binary mixture. MDIs of group I binary mixtures for both the integrated multiunit and single fiber data were significantly greater than those for either the control or group II binary mixtures. In a subset of multiunit recordings, the MDIs of a group I binary mixture across three log units of stimulus concentration were similar and significantly greater than those of a group II binary mixture. Analysis of the single fiber data also indicated that the MDIs of group I binary mixtures were significantly larger than those of group II binary mixtures for both alanine-best and arginine-best taste fibers; however, the MDIs of group I binary mixtures calculated from recordings from arginine-best taste fibers were significantly greater than those recorded from alanine-best taste fibers.

Responses of Olfactory Forebrain Units to Amino Acids in the Channel Catfish

2007 ◽  
Vol 97 (3) ◽  
pp. 2490-2498 ◽  
Author(s):  
Alexander A. Nikonov ◽  
John Caprio
Keyword(s):  
Amino Acids ◽  
Channel Catfish ◽  
Side Chains ◽  
Single Neurons ◽  
Short Side ◽  
Biologically Relevant ◽  
Acidic Amino Acids ◽  
Group I ◽  
Group Ii ◽  
The Many

A paucity of information exists concerning the processing of odorant information by single neurons in any vertebrate above the level of the olfactory bulb (OB). In this report, odorant specificity to four types of L-α-amino acids (neutral with long side-chains, neutral with short side-chains, basic and acidic), known biologically relevant odorants for teleosts, was determined for 217 spontaneously active forebrain (FB) neurons in the channel catfish. Group I FB units were identified that were excited by only one of four types of amino acids; no Group I unit was encountered that was excited by an acidic amino acid. The Group I FB units exhibited similar preferences as described previously for OB neurons, suggesting that no major modifications of olfactory information for at least some of these units occurred between the OB and FB. Evidence, however, for the convergence of odor information between the OB and FB was suggested by Group II FB units that exhibited a broader excitatory molecular receptive range (EMRR) than those of previously recorded types of OB units or the Group I FB units. Group II FB units were excited by both neutral and basic amino acids and a few also by acidic amino acids, EMRRs not observed previously in OB units. Stimulus-induced inhibition, likely for contrast enhancement, was also often observed for the many of the FB units encountered. The observed EMRRs of the FB units presently identified and those of the OB units previously studied are consistent with the ability of catfish to behaviorally discriminate these compounds.

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.

Electrophysiological Evidence for a Chemotopy of Biologically Relevant Odors in the Olfactory Bulb of the Channel Catfish

2001 ◽  
Vol 86 (4) ◽  
pp. 1869-1876 ◽  
Author(s):  
Alexander A. Nikonov ◽  
John Caprio
Keyword(s):  
Amino Acids ◽  
Olfactory Bulb ◽  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Bile Salts ◽  
Spatial Organization ◽  
Field Potential ◽  
Specific Class ◽  
Biologically Relevant ◽  
Excitatory Responses

Extracellular electrophysiological recordings from single olfactory bulb (OB) neurons in the channel catfish, Ictalurus punctatus, indicated that the OB is divided into different functional zones, each processing a specific class of biologically relevant odor. Different OB regions responded preferentially at slightly above threshold to either a mixture of 1) bile salts (10–7 to 10−5 M Na+ salts of taurocholic, lithocholic, and taurolithocholic acids), 2) nucleotides [10–6 to 10–4 M adenosine-5′-triphosphate (ATP), inosine-5′-monophosphate (IMP), and inosine-5′-triphosphate (ITP)], or 3) amino acids (10–6 to 10–4M l-alanine,l-methionine, l-arginine, andl-glutamate). Excitatory responses to bile salts were observed primarily in a thin, medial strip in both the dorsal (100–450 μm) and ventral (900–1,200 μm) OB. Excitatory responses to nucleotides were obtained primarily from dorsal, caudolateral OB, whereas excitatory responses to amino acids occurred more rostrally in the dorsolateral OB, but continued more medially in the ventral OB. The chemotopy within the channel catfish OB is more comparable to that previously described by optical imaging studies in zebrafish than by field potential studies in salmonids. The present results are consistent with recent studies, suggesting that the specific spatial organization of output neurons in the OB is necessary for the quality coding/decoding of olfactory information.

scholarly journals Selective incorporation of proteinaceous over nonproteinaceous cationic amino acids in model prebiotic oligomerization reactions

2019 ◽  
Vol 116 (33) ◽  
pp. 16338-16346 ◽  
Author(s):  
Moran Frenkel-Pinter ◽  
Jay W. Haynes ◽  
Martin C ◽  
Anton S. Petrov ◽  
Bradley T. Burcar ◽  
...  
Keyword(s):  
Amino Acids ◽  
Side Chains ◽  
Protein Dna Interactions ◽  
Selective Incorporation ◽  
Methylene Groups ◽  
Cationic Amino Acids ◽  
History Of ◽  
Dry Down ◽  
Polypeptide Backbone ◽  
Diaminopropionic Acid

Numerous long-standing questions in origins-of-life research center on the history of biopolymers. For example, how and why did nature select the polypeptide backbone and proteinaceous side chains? Depsipeptides, containing both ester and amide linkages, have been proposed as ancestors of polypeptides. In this paper, we investigate cationic depsipeptides that form under mild dry-down reactions. We compare the oligomerization of various cationic amino acids, including the cationic proteinaceous amino acids (lysine, Lys; arginine, Arg; and histidine, His), along with nonproteinaceous analogs of Lys harboring fewer methylene groups in their side chains. These analogs, which have been discussed as potential prebiotic alternatives to Lys, are ornithine, 2,4-diaminobutyric acid, and 2,3-diaminopropionic acid (Orn, Dab, and Dpr). We observe that the proteinaceous amino acids condense more extensively than these nonproteinaceous amino acids. Orn and Dab readily cyclize into lactams, while Dab and Dpr condense less efficiently. Furthermore, the proteinaceous amino acids exhibit more selective oligomerization through their α-amines relative to their side-chain groups. This selectivity results in predominantly linear depsipeptides in which the amino acids are α-amine−linked, analogous to today’s proteins. These results suggest a chemical basis for the selection of Lys, Arg, and His over other cationic amino acids for incorporation into proto-proteins on the early Earth. Given that electrostatics are key elements of protein−RNA and protein−DNA interactions in extant life, we hypothesize that cationic side chains incorporated into proto-peptides, as reported in this study, served in a variety of functions with ancestral nucleic acid polymers in the early stages of life.

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.

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 binary mixtures of amino acids in the channel catfish, Ictalurus punctatus

1995 ◽  
Vol 74 (4) ◽  
pp. 1435-1443 ◽  
Author(s):  
J. Kang ◽  
J. Caprio
Keyword(s):  
Amino Acids ◽  
Olfactory Bulb ◽  
Binary Mixtures ◽  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Electrophysiological Responses ◽  
Excitatory Responses ◽  
The Individual ◽  
First Time ◽  
Olfactory Bulb Neurons

1. For the first time in any vertebrate, responses of single olfactory bulb neurons to odorant mixtures were studied quantitatively in the channel catfish, Ictalurus punctatus. 2. Extracellular electrophysiological responses of 61 single olfactory bulb neurons from 36 channel catfish to binary mixtures of amino acids and to their components were recorded simultaneously with the electro-olfactogram (EOG). Tested were a total of 297 mixture trials consisting of 18 different stimulus pairs formed from 8 amino acids. 3. For 42% (126 of the 297) of the tests, no significant change (N) from spontaneous activity occurred. Responses to the remaining 171 tests of binary mixtures were excitatory (E; 29%) or suppressive (S; 29%). No response type was associated with any specific mixture across the neurons sampled. 4. Mixture interactions that changed response types (E or S) from those observed to the individual components were rare, because 89% of the responses of single olfactory bulb neurons to the tested binary mixtures were classified similarly as the responses to at least one of the components. 5. Responses of single olfactory bulb neurons were generally predictable for binary mixtures whose component responses were classified as both E, both S, and both N. For binary mixtures whose component responses were classified differently (e.g., one component evoked excitatory responses and the other evoked suppressive responses), the predictability of the response was dependent on the specific mixture type.

Sign in / Sign up

Export Citation Format

Share Document