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Comments on William M Nuttley et al. (2001) International C. elegans Meeting "Characterization of the E. coli-induced suppression of olfactory habituation" (0)
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William M Nuttley, Karen Atkinson-Leadbeater, & Derek van der Kooy (2001). Characterization of the E. coli-induced suppression of olfactory habituation presented in International C. elegans Meeting. Unpublished information; cite only with author permission.
Food is an important motivator for animals. In C. elegans , the presence of E. coli causes changes in locomotion, egg laying, pharyngeal pumping and thermotaxis. We have been investigating the effect that food has on olfactory behavior and found that the presence of E. coli suppresses both the approach to and the habituation to 100% benzaldehyde. Control experiments demonstrated that this suppression is not caused by an inability to sense odorants in the presence of E. coli . Both of these activities (the suppression of chemotaxis and the suppression of habituation) are inactivated by heating the E. coli to 95degC for 15 minutes. As with other food-induced behavioral modulations in C. elegans , these effects can be mimicked by the addition of exogenous serotonin and are dependent on the tph-1 and cat-4 gene products. We will present a further genetic characterization of this behavior. We are also exploring the behavioral characteristics of olfactory habituation. Associative learning involves the association between a conditioned stimulus (CS) and an unconditioned stimulus (US). With food acting as a US while benzaldehyde represents the CS, exposures to benzaldehyde in the absence of food during habituation training would result in the worms learning that benzaldehyde predicts the absence of food, and they no longer approach benzaldehyde on subsequent tests. The lack of habituation observed in the presence of E. coli therefore would occur because these conditions indicate that benzaldehyde is a good predictor of food. Experiments which increase the exposure to benzaldehyde while varying the exposure to food indicate that the degree of habituation is not determined simply by the time of exposure to benzaldehyde, as non-associative (single-stimulus learning) accounts of habituation would predict. Rather, the amount of habituation is dependent on both the duration of the benzaldehyde exposure and the amount of time that food is present during that exposure, revealing an associative component of benzaldehyde habituation. Supported by NSERC.
