What is the difference between l alanine and alanine

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Following recovery, the mice were conditioned once more in the same manner. Amiloride is thought to be undetectable to mice at this concentration Eylam et al. Since mice might be able to respond to odor cues from each amino acid, all conditioning and testing solutions including water only stimuli also had 0. Separate concentration—response experiments were conducted with wild type and knockout mice to identify appropriate concentrations of each L-amino acid to use in subsequent experiments.

The results of this experiment suggested that the T1r3 — mice may detect ALA at 50 mM, a much lower concentration than originally anticipated. These mice were then tested with 0, 2.

These mice were then tested with 0, 10, 25, 50, , , and mM MSG. In these experiments, each concentration was presented twice, once in each of 2 blocks of trials. The order of concentrations within a block was randomized using a latin square procedure. Each stimulus was separated by 1—3 water rinse trials. The mice were given one more recovery day, and then tested again with a different order of presentation.

While rare, if a stimulus was not sampled in the first session, it was presented early in the second session to ensure the mouse responded to all stimuli. Since mM was an effective CS for each amino acid for both mouse genotypes, mM was also used as the CS for the generalization experiments. Using this concentration, rather than a higher concentration, minimized non-taste cues to which the mice might respond at higher concentrations.

Moreover, amiloride uM , added to all solutions, could more effectively antagonize the taste of the sodium ion associated with MSG. For these experiments, each mouse was tested with 0. These concentrations were selected because they were above the minimum concentration for which all mice showed a learned aversion in the intensity generalization experiments and appeared comparable in their ability to induce avoidance behavior within each mouse genotype.

These concentrations are also above behavioral and nerve recording thresholds of mice for each L-amino acid Bachmanov et al. All mice were also tested with 75 mM NaCl to test for avoidance of any new taste. This concentration was selected to ensure that none of the mice would likely have a natural aversion to NaCl alone Finger et al.

The stimulus presentation and trial procedures used during stimulus generalization testing were identical to those used in the intensity generalization experiments. Amiloride was added to all test solutions except 75 mM NaCl. Amyl acetate 0. However, even though 2 stimuli share taste qualities, they may also elicit qualities that make one taste stimulus distinguishable from the other.

Discrimination methods are best suited to test this possibility since correct responding during these tests is dependent upon attending to stimulus differences rather than similarities.

Three sets of experiments, designed to control for the taste of the sodium ion associated with MSG, were conducted to determine if ALA and MSG elicit the same taste sensation, which would be expected if the same taste receptor is responsible for detection of both amino acids, and to determine if the T1r3 receptor is key in identifying each amino acid. These procedures were similar to those used in previous studies Stapleton et al. Eight wild type and 8 T1r3 — mice were used in the discrimination experiments.

The mouse had to identify the test stimulus and alter its responding by the last 0. Four response-consequence outcomes were possible. Three: If the mouse failed to identify the S— and continued to lick the spout during the last 0. Tongue contact with the lick spout during the 2-s resulted in a weak shock sensation. Shock intensity was titrated by beginning below detection and increasing it until it was just detectable for each mouse and caused the mouse to stop licking briefly.

Four: A correct detection was counted if the mouse did not lick during the last 0. This was followed by a delay of 3 s and then completion of a second variable ratio of 10—30 licks to initiate the next stimulus presentation. Water for reinforcement was stored in the ninth syringe barrel. The order of presentation of the 8 syringe barrels was determined from a latin square using a randomize block procedure.

To help control odor cues, all solutions were mixed with 0. Three discrimination experiments were designed to control for the sodium taste associated with MSG. The combination of amiloride and matching of sodium concentration neutralizes any cue functions that the residual taste of sodium might contribute when the stimulus is MSG Stapleton et al.

Each experiment was conducted for at least 5 consecutive days. Before any statistical analyses were applied to the CTA data, lick counts for each 5-s trial were normalized to reduce the variability due to individual differences in basal lick rates and motivational states. Lick rates for each taste stimulus were first averaged over the 2 test days. The mean lick rate of a solution was then divided by the average lick rate for all water trials, and multiplied by Although rare, any trial in which the lick count was zero was dropped from the data set.

Genotype 2 , CS 2 , and injection 2 conditions were treated as between-subject factors and test stimuli 6 were treated as a within-subject factor in these analyses.

To characterize the contribution of each factor to the interaction, these data were then partitioned to compare normalized lick rates of groups for strength of conditioning to their respective CS and the degree of generalization using univariant ANOVA and Bonferroni-corrected t -test procedures Howell Data for mice of each genotype were evaluated separately and against each other.

As reported in previous studies Stapleton et al. Genotype 2 was treated as a between-subject factor while Amiloride condition 3 and stimulus concentration 4 were treated as within-subject factors in these analyses. The primary purpose of these experiments was to identify the lowest concentration of MSG and ALA that mice of each genotype, especially T1r3 — mice, would show a learned aversion compared to control mice within the parameters of the CTA paradigm.

The normalized lick rates for the wild-type mice were The data for the subsequent intensity gradient experiment in which mice were conditioned with mM ALA were analyzed using an ANOVA treating mouse genotype wild type, T1r3 — and injection condition saline, LiCl as between-subject factors and concentration 8 levels as a within-subject factor. Wild-type mice were able to recognize and avoid each L-amino acid at much lower concentrations than the T1r3 — mice.

T -tests found the lowest concentration in which the LiCl-inject mice had significantly lower lick rates compared to control mice was 2. For simplicity, the lowest concentration that each genotype showed conditioned avoidance will hereafter be referred to as their recognition thresholds.

T-tests indicated that the lowest concentration at which wild-type mice showed avoidance of MSG was 10 mM whereas the T1r3 — mice did not significantly avoid MSG unless the concentration was 50 mM or greater. However, there were no detectable differences in lick rates between genotypes in either analysis. The left side of each panel shows the lick rates for 50 and mM L-ALA of saline-injected solid line and LiCl-injected dashed line mice after conditioning.

The right side of each panel shows the lick rates for the 50 and mM of MSG. Lick rates for 75 mM NaCl no amiloride were unaffected by conditioning with saline solid bar or LiCl open bar. The left side of each panel shows the lick rates of saline-injected solid line and LiCl-injected dashed line mice for 50 and mM MSG after conditioning.

The right side of each panel shows the lick rates for the 50 and mM of ALA. Previous research Stapleton et al. The correct detection data were initially analyzed using a 3-way ANOVA for mixed designs to examine the effects of mouse genotype 2 levels , amiloride condition 3 levels , and concentration 4 levels.

To evaluate these data more thoroughly, simple effects tests were used to examine differences in detect rates for each mouse genotype in the 3 amiloride conditions at each concentration. No differences in correct detections of wild type and T1r3 could be detected at these concentrations. Performances of wild type and knockout mice did not differ statistically. While the effects of the amiloride condition and concentration were significant as reported above, no effect of mouse genotype or amino acid was detected.

In general, these analyses indicated that both mouse genotypes were better at discriminating between ALA and MSG as the concentrations increased. However, the discrimination responses of the 2 mouse genotypes were not statistically different at any concentration or amiloride condition. If these L-amino acids are detected by the same receptor, then one would expect the 2 amino acids to elicit similar, if not identical, tastes.

However, taste discrimination experiments indicated that rats can distinguish between the tastes of ALA and MSG, even when the taste of sodium was neutralized. These findings suggest that although ALA and MSG appear to share some taste qualities, at least one of the compounds elicits taste qualities not shared by the other. In general the results of the experiments in this study suggest that ALA and MSG elicit similar but not identical tastes in both mouse genotypes, and since the T1r3 — mice were able to discriminate between these substances at a level similar to wild-type mice, it appears likely that each amino acid may be detected by more than one receptor.

Differences in taste sensitivity between wild type and T1r3 — mice were detected with the intensity generalization experiments. Wild-type mice were able to detect ALA at 2. Although the concentrations tested were not identical, ALA thresholds are similar to recognition thresholds for MSG in wild type and T1r3 — mice, respectively.

Besides a higher recognition threshold, the T1r3 — mice never showed the same degree of avoidance as wild-type mice, even when conditioned with a high concentration of ALA, suggesting that the intensity of either L-amino acid was not as salient for the T1r3 — mice as for the wild-type mice. The results of the present experiments indicate that T1r3 has an important role in recognizing the taste qualities of both L-amino acids, particularly at lower concentrations, and that other taste receptors are capable of detecting these L-amino acids.

The latter conclusion was further supported by the generalization experiments. Generalization of a CTA from one substance to another occurs when 2 substances elicit similar taste qualities Spector et al. The bi-directionality of CTA generalization indicates that both L-amino acids share common taste qualities. Interestingly, similar bidirectional generalization was also seen in the T1r3 — mice, suggesting that receptors besides T1R heterodimeric receptors may be responding to both L-amino acids, and generating afferent signals for each L-amino acid that are similar enough to elicit comparable tastes.

Even though 2 substances may share similar taste qualities, one or both substances may also elicit qualities that are not shared by the other substance, making the taste of each substance quite distinguishable from the other.

In contrast to CTA methods, the discrete trial discrimination methods used in this study, similar to methods used with rats Taylor-Burds et al. Surprisingly, the T1r3 — mice could discriminate between the 2 substances with an accuracy nearly identical to that of wild-type mice.

Both genotypes were readily able to distinguish between the tastes of MSG and ALA when tested without any controls for the sodium ion associated with MSG at all concentrations tested.

When amiloride was added to all solutions to reduce the intensity of the sodium ion, both genotypes were still able to make the discrimination but their accuracy was reduced, especially at the lowest concentration.

Adding isomolar concentrations of NaCl to ALA to match the concentrations of MSG both amino acids also had amiloride added did not impact discrimination accuracy of either genotype any more than amiloride alone at and mM, but had a small, significant detrimental effect at the 2 lower concentrations.

These data suggest that at lower concentrations these L-amino acids elicit quite similar sensations, but as concentrations increase, differences in taste qualities begin to emerge which are detectable by both mouse genotypes.

In the discrimination experiments, weak shock was used as a punisher and avoidance of the shock served as a negative reinforcer. Shock has the advantage of being clearly identified salient and in this study it is detectable in close temporal and spatial proximity with the stimulus presentation Bouton ; Fowler and Wischer ; Yerkes and Dodson ; Smith It has been suggested that the use of shock as a punisher might alter the sensitivity of the taste system in some manner Smith and Spector However, shock intensity was set just above detection threshold for each mouse, ensuring that shock sensation was weak but attention attracting.

Moreover, the mouse experienced shock only when the tongue was in contact with the lick spout if it failed to identify an S— solution. Once shock is detect, the mouse stops licking immediately, thereby limiting exposure to shock while still maintaining good stimulus control Brosvic and Slotnick ; Stapleton et al. In addition, the interval between shock and the next stimulus presentation was minimally 25 s and generally longer, which should allow any potential effects of very brief, weak shock to dissipate.

In our experience, weak shock facilitates acquisition of the taste discrimination compared to less salient cues such as a time-out i. Thus, the shock procedure used in this study to motivate accurate responding in the discrimination experiment should have had minimal impact on the taste system of mice. The combined findings of CTA and discrimination experiments suggest that while ALA and MSG elicit some of the same taste qualities in mice, one or both L-amino acids also elicit one or more taste qualities not shared by the other.

Moreover, these taste qualities are detectable by receptors independent of T1r3, a key dimer of the primary candidate taste receptor thought to be essential for detection of L-amino acids Nelson et al. The absence of the T1r3 receptor had little effect on discrimination performance, and reduced but did not eliminate the ability of T1r3 — mice to detect taste qualities to which the mice responded during the CTA experiments.

Deletion of the T1r3 receptor may alter or eliminate taste qualities elicited by one or both L-amino acids compared to the perceptions experienced by wild-type mice, but the continued ability of the T1r3 — mice to detect and perceive taste qualities of each amino acid, and to discriminate between both L-amino acids suggests that additional receptors are involved in sensing both L-amino acids.

In humans, ALA elicits a sweet sensation and in rodents, 2-bottle and brief access preference tests generally suggest that ALA and MSG also elicit taste sensations that are similar to other substances that elicit sweet sensations in humans Schiffman et al. It is possible that the mice were able to detect ALA and MSG through other glutamate taste receptors expressed in taste epithelium.

The most likely candidates are the brain and taste variants of mGluR1 and mGluR4 receptors. Therefore, the quantitation of undesirable enantiomers in drug raw material is the challenging task for pharmacists and chemists. Present study demonstrates the differential recognition of l -alanine amino acid by 5,11,17,tetrakis-[ N,N-dimethylamino methyl],26,27,tetrahydroxy-calix[4]arene 3. Another characteristic feature of this study is the use of methyl orange as a UV—visible spectrophotometric probe for the determination of stability constant of host—guest inclusion complexes by adopting competitive inclusion method and complexation ratio was confirmed by Benesi-Hildebrand equation.

Thermodynamics of the recognition have been evaluated that provided the significant distinction for both isomers, i. Thus, the study provides a broad spectrum of its applications in varying fields of analytical and pharmaceutical science.

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