Retention time of attenuated response to diacetyl after pre‐exposure to diacetyl in Caenorhabditis elegans

Abstract

The retention time of attenuated chemotactic response to continuous presentation of odorant diacetyl was investigated in the nematode Caenorhabditis elegans. The level of chemotactic response of nematodes pre-exposed to diacetyl for 90 min was significantly smaller than that of nonexposed control nematodes. In this study, wild-type (N2) nematodes were maintained at 15, 20 and 25 degrees C after pre-exposure to diacetyl. At 20 degrees C, there was a decrease in response to diacetyl continuing for up to 6 hr after pre-exposure to the chemical, but not up to 12 hr. Interestingly, the decrease in response to diacetyl did not continue up to 2 hr in nematodes bred at 15 degrees C, although it continued beyond 12 hr in nematodes bred at 25 degrees C. These results indicate that the retention time of attenuated chemotactic response to diacetyl is dependent on the environmental breeding temperature of nematodes. The breeding temperature correlated with aging speed of nematodes, suggesting that a short life span (higher aging speed) prolongs the retention time of attenuated chemotactic response to diacetyl after pre-exposure to diacetyl. In the long-lived daf-2, age-1, clk-1 and isp-1 mutants, the effect of diacetyl did not continue up to 2 hr. The short-lived daf-16, daf-18, mev-1 and gas-1 mutants showed a longer duration of decrease in response to diacetyl, that is, the retention time of attenuated chemotactic response to diacetyl continued beyond 12 hr. There is a possibility that the duration of decrease in response to diacetyl after pre-exposure to diacetyl was inversely related to the length of nematodes' life span.

Enhancement of Chemotactic Response to Sodium Acetate in the NematodeCaenorhabditis elegans

“…When the animals were maintained at 20°C after being pre-exposed to an odorant diacetyl, the chemotaxis index for diacetyl of the pre-exposed animals was smaller than that of the control animals up to 6 hr (p < 0.05), but not at 12 hr (Matsuura et al, 2009). In this study, the enhancement of the chemotactic response to sodium acetate was also maintained beyond 6 hr, but not at 12 hr (Fig.…”

“…When sodium azide is spotted on the attractant location of the assay plate, the leaving behavior of animals during chemotactic assay cannot be observed (Matsuura et al, 2009). Therefore, we did not use sodium azide to observe the behavior of C. elegans under natural conditions in the present study.…”

“…To evaluate the chemotactic response during the assay, the integral chemotaxis index was also calculated (Matsuura et al, 2009). The index indicated the approximate total number of animals for a 90-min assay.…”

“…In contrast, non-associative learning processes such as sensitization, habituation, and dishabituation involve behavioral modification mediated by the presentation of a single cue (Carew and Sahley, 1986;Brown, 1998). In C. elegans, the continuous presentation of chemical and mechanical stimuli causes a decrease in the level of response to the same stimuli (Bargmann et al, 1993;Colbert and Bargmann, 1995;Rankin, 2000;Matsuura et al, 2009).…”

Extension of the established period of diacetyl adaptation by oxygen intermediates in the nematode Caenorhabditis elegans

“…The nematode shows chemotactic responses to the odorant diacetyl (Matsuura et al, 2005(Matsuura et al, , 2007(Matsuura et al, , 2009Nishino et al, 2013), which is produced by food bacteria. The chemotactic response to diacetyl of young adult (YA) nematodes pre-exposed to this odorant in the absence of food was significantly smaller than that of unexposed control nematodes.…”