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Dietary salt levels affect salt preference and learning in larval Drosophila.

Russell C, Wessnitzer J, Young JM, Armstrong JD, Webb B - PLoS ONE (2011)

Bottom Line: Drosophila larvae change from exhibiting attraction to aversion as the concentration of salt in a substrate is increased.However, some aversive concentrations appear to act as positive reinforcers, increasing attraction to an odour with which they have been paired.Testing larvae using a substrate 0.025 M above the NaCl concentration on which the larvae were reared consistently results in aversive choice behaviour but appetitive reinforcement effects.

View Article: PubMed Central - PubMed

Affiliation: Institute for Perception, Action, and Behaviour, University of Edinburgh, Edinburgh, United Kingdom.

ABSTRACT
Drosophila larvae change from exhibiting attraction to aversion as the concentration of salt in a substrate is increased. However, some aversive concentrations appear to act as positive reinforcers, increasing attraction to an odour with which they have been paired. We test whether this surprising dissociation between the unconditioned and conditioned response depends on the larvae's experience of salt concentration in their food. We find that although the point at which a NaCl concentration becomes aversive shifts with different rearing experience, the dissociation remains evident. Testing larvae using a substrate 0.025 M above the NaCl concentration on which the larvae were reared consistently results in aversive choice behaviour but appetitive reinforcement effects.

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Related in: MedlinePlus

Preference scores for NaCl vs. Pure substrate as the NaCl concentration at test is increased, as a function of NaCl concentration in the food on which the larvae were reared (from top to bottom, food with no added salt, food containing 0.25 M NACl, 0.275 M NaCl, 0.3 M NaCl, or 0.43 M NaCl).Each boxplot represents ten trials, and * denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/8) does not include 0). The blue line indicates the lowest NaCl level for which significant aversion occurs, and the start of the shaded area the highest significantly attractive level. The lowest aversive level increases when the NaCl concentration in the food is increased.
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pone-0020100-g001: Preference scores for NaCl vs. Pure substrate as the NaCl concentration at test is increased, as a function of NaCl concentration in the food on which the larvae were reared (from top to bottom, food with no added salt, food containing 0.25 M NACl, 0.275 M NaCl, 0.3 M NaCl, or 0.43 M NaCl).Each boxplot represents ten trials, and * denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/8) does not include 0). The blue line indicates the lowest NaCl level for which significant aversion occurs, and the start of the shaded area the highest significantly attractive level. The lowest aversive level increases when the NaCl concentration in the food is increased.

Mentions: We first tested choice behaviours for different rearing conditions as shown in Figure 1. Positive scores indicate attraction to the NaCl substrate, and negative scores indicate aversion. We indicate the concentration value above which the first statistically significant negative score (99.375% C.I. falls entirely below zero) is obtained with a blue line. We find that this crossover point between attraction and aversion increases with the concentration of salt in the food on which the larvae were reared. In general, positive scores are observed up to the level of salt on which the animals were reared, and negative scores are found at higher levels. This suggests the larvae have adapted in some way to the level of salt in their diet. Adaptation is also suggested by the tendency for the attractive response to lower salt levels to become weaker, often not significantly different from zero, as rearing concentration increases, i.e., low concentrations might no longer be detectable. Animals raised on the highest level (0.43 M) show neither clear attraction or aversion, but it is possible this level of salt is compromising to the health of the larvae.


Dietary salt levels affect salt preference and learning in larval Drosophila.

Russell C, Wessnitzer J, Young JM, Armstrong JD, Webb B - PLoS ONE (2011)

Preference scores for NaCl vs. Pure substrate as the NaCl concentration at test is increased, as a function of NaCl concentration in the food on which the larvae were reared (from top to bottom, food with no added salt, food containing 0.25 M NACl, 0.275 M NaCl, 0.3 M NaCl, or 0.43 M NaCl).Each boxplot represents ten trials, and * denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/8) does not include 0). The blue line indicates the lowest NaCl level for which significant aversion occurs, and the start of the shaded area the highest significantly attractive level. The lowest aversive level increases when the NaCl concentration in the food is increased.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105986&req=5

pone-0020100-g001: Preference scores for NaCl vs. Pure substrate as the NaCl concentration at test is increased, as a function of NaCl concentration in the food on which the larvae were reared (from top to bottom, food with no added salt, food containing 0.25 M NACl, 0.275 M NaCl, 0.3 M NaCl, or 0.43 M NaCl).Each boxplot represents ten trials, and * denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/8) does not include 0). The blue line indicates the lowest NaCl level for which significant aversion occurs, and the start of the shaded area the highest significantly attractive level. The lowest aversive level increases when the NaCl concentration in the food is increased.
Mentions: We first tested choice behaviours for different rearing conditions as shown in Figure 1. Positive scores indicate attraction to the NaCl substrate, and negative scores indicate aversion. We indicate the concentration value above which the first statistically significant negative score (99.375% C.I. falls entirely below zero) is obtained with a blue line. We find that this crossover point between attraction and aversion increases with the concentration of salt in the food on which the larvae were reared. In general, positive scores are observed up to the level of salt on which the animals were reared, and negative scores are found at higher levels. This suggests the larvae have adapted in some way to the level of salt in their diet. Adaptation is also suggested by the tendency for the attractive response to lower salt levels to become weaker, often not significantly different from zero, as rearing concentration increases, i.e., low concentrations might no longer be detectable. Animals raised on the highest level (0.43 M) show neither clear attraction or aversion, but it is possible this level of salt is compromising to the health of the larvae.

Bottom Line: Drosophila larvae change from exhibiting attraction to aversion as the concentration of salt in a substrate is increased.However, some aversive concentrations appear to act as positive reinforcers, increasing attraction to an odour with which they have been paired.Testing larvae using a substrate 0.025 M above the NaCl concentration on which the larvae were reared consistently results in aversive choice behaviour but appetitive reinforcement effects.

View Article: PubMed Central - PubMed

Affiliation: Institute for Perception, Action, and Behaviour, University of Edinburgh, Edinburgh, United Kingdom.

ABSTRACT
Drosophila larvae change from exhibiting attraction to aversion as the concentration of salt in a substrate is increased. However, some aversive concentrations appear to act as positive reinforcers, increasing attraction to an odour with which they have been paired. We test whether this surprising dissociation between the unconditioned and conditioned response depends on the larvae's experience of salt concentration in their food. We find that although the point at which a NaCl concentration becomes aversive shifts with different rearing experience, the dissociation remains evident. Testing larvae using a substrate 0.025 M above the NaCl concentration on which the larvae were reared consistently results in aversive choice behaviour but appetitive reinforcement effects.

Show MeSH
Related in: MedlinePlus