Biomedical subjects

A Koce

Publications and source records attributed to A Koce.

4 recordsLinked to original sources

PubMed2000

The behavioral detection of binary mixtures of amino acids and their individual components by catfish.

The question of whether a binary mixture of amino acids is detected by fish as a unique odor or whether the qualities of the individual components are retained within the mixture was investigated in channel (Ictalurus punctatus) and brown bullhead (Ameiurus nebulosus) catfish, species that are highly similar in their olfactory receptor and behavioral responses to amino acid odorants. Catfish respond with greater appetitive food-searching (swimming) behavior to amino-acid-conditioned olfactory stimuli than to non-conditioned amino acids. In the present study, appetitive food-searching behavior was measured by counting the number of turns of the fish greater than 90 degrees within 90 s of stimulus onset and, in some tests, by video tracking. The two methods yielded highly correlated results. Channel catfish conditioned to a binary mixture composed of equimolar amino acids responded with searching behavior to the amino acid that produced the larger-amplitude electro-olfactogram (EOG) response as they did to the conditioned stimulus. In further studies, bullhead catfish were conditioned either to a binary mixture or to a single amino acid and tested to determine whether a binary mixture was detected as the component evoking the larger EOG response. In all initial tests (trials 1-3), the more stimulatory component of a binary mixture was not discriminated from the binary mixture; however, the less stimulatory component and all other amino acids tested were discriminated from the mixture. By increasing the concentration of the originally less potent component in a binary mixture, making it the more stimulatory compound, it was now detected as not significantly different from the binary mixture; however, the original more potent component (i.e. now the less potent stimulus) was detected as significantly different from the mixture. However, with 5-10 additional discrimination training trials, the less stimulatory component in a binary mixture influenced the perception of the binary mixture because the binary mixture was no longer detected only as its more stimulatory component. The data suggest that a two-step learning process occurs within the olfactory bulb and possibly higher-order telencephalic nuclei.

Amino Acids↗

PubMed2000

The amplitude of the electroolfactogram in catfish correlates with the proportion of responding ORNs.

We recorded simultaneously the electrophysiological responses of the olfactory organ [the electroolfactogram (EOG)] and action potential activity of single olfactory receptor neurons (ORNs) to amino acid stimuli in the brown bullhead catfish, Ameiurus nebulosus. To determine whether the amplitude of the EOG depends upon the number of responding ORNs, we tested two highly stimulatory (based on EOG recordings) amino acids [L-norvaline (L-nVal) and L-cysteine (L-Cys)], two amino acids of intermediate potency [L-arginine (L-Arg) and L-isoleucine (L-Ile)], and a poorly stimulatory amino acid [L-proline (L-Pro)]. Forty-nine percent of the spontaneously active, single ORNs tested (n=142) were either suppressed or excited by amino acid stimuli. Of the ORNs tested with specific amino acids, 61% responded to 1 mM L-nVal (n=49), 57% responded to 1 mM L-Cys (n=30), 45% responded to L-Arg (n=31) and 36% responded to L-Ile (n=22) with either suppression or excitation. Only one ORN responded with suppression to 10(-2) M L-Pro (n=10). These data suggest that the amplitude of the EOG in the brown bullhead catfish is correlated with the number of responsive ORNs (Spearman corr. coef. = 0.9; P<0.05).

Action Potentials↗

PubMed2000

Coding principles in fish olfaction as revealed by single unit, EOG and behavioral studies.

At present, the principles of coding and codes for individual odorants are not known; however, several coding properties and their limitations emerged. The olfactory code for different odorants must be different to enable olfactory discrimination. We studied elements of the olfactory code that are accessible to combined microelectrode and behavioral techniques. A random sample of spontaneously active olfactory receptor neurons (ORNs) responded to a 15 component mixture of amino acids with suppression, excitation and no change in their activity in the ratio of 6:1:8; ORNs responded to L-arginine (L-Arg) in the ratio of 5:5:60 and to L-cysteine (L-Cys) in the ratio of 10:1:27. ORNs provide information that enables nearly an unlimited behavioral discrimination of single odorants. Underwater electro-olfactogram (EOG) recordings from the olfactory organ measure the odorant-induced summed dc potential change from all the olfactory receptor neurons. In behavioral studies, the more (most) stimulatory component of the binary (ternary) mixture determined in EOG recordings was its better-perceived component; however, discrimination conditioning--repeated presentation of the conditioned mixture and its more stimulatory component alone--enabled the discrimination of the conditioned binary and ternary mixtures from their more (most) stimulatory components. In large multimixtures (13 components), where one amino acid is the more potent EOG stimulus than the other less stimulatory but equipotent components, catfish discriminated all single components from the conditioned multimixture. These results indicate that the multi-mixture is not detected as its most stimulatory component. Catfish also do not learn to discriminate a 13 component multimixture from a 12 component multimixture comprising 12 of the same components. Taken together, these findings indicate that the capacity for parallel transfer of mixture component information is limited in the catfish olfactory system. The finding of a limited capacity of multimixture component detection in catfish also supports the hypothesis of across nerve pattern coding of odorants and eliminates the sole existence of entirely specialized olfactory receptor neurons and labeled lines.

Amino Acids↗

PubMed1996

Learned olfactory discrimination of amino acids and their binary mixtures in bullhead catfish (Ameiurus nebulosus).

The question of whether bullhead catfish can discriminate binary mixtures of amino acids from the individual components of the mixture was investigated. Two groups of catfish were conditioned to different binary mixtures of L-norvaline (NVAL) and L-leucine (LEU). The concentrations of the amino acids in the conditioned mixtures were adjusted so that in different mixtures either NVAL or LEU was the more stimulatory component. Bullhead catfish were unable to discriminate the more stimulatory components, but were able to discriminate the less stimulatory components and other amino acids from the conditioned mixtures. The third group of bullhead catfish was conditioned to L-proline (PRO) and the responses to different mixtures of PRO and NVAL were subsequently evaluated. Behavioral and electrophysiological (EOG) experiments indicated that the difference in relative stimulatory effectiveness levels between NVAL and PRO is > 30,000 times. For subsequent tests, the concentrations of PRO and NVAL were adjusted to form binary mixtures in which PRO and NVAL, respectively, were the more stimulatory components. Bullhead catfish conditioned to PRO discriminated the mixture if NVAL was the more stimulatory component, but did not discriminate PRO from the mixture if PRO was the more stimulatory component. These results suggest that binary mixtures of amino acids are initially perceived as the more stimulatory components of the mixture.

Amino Acids↗