Extension of the established period of diacetyl adaptation by oxygen intermediates in the nematode Caenorhabditis elegans Part A Molecular & integrative physiology

After pre-exposure to the odorant diacetyl, the nematode Caenorhabditis elegans showed a decline in chemotactic responses to diacetyl, a phenomenon known as diacetyl adaptation. In the present study, we found that the established period of diacetyl adaptation in nematodes increased with the breeding temperature. When wild-type (N2) nematodes were bred at 15°C, adaptation was observed from the young adult (YA) to the 3-day-old adult that is reached 3days after the YA stage. On breeding nematodes at 20°C and 25°C, adaptation was observed between the YA and 5-day-old adult and between the YA and the 7-day-old adult, respectively. Breeding temperature has been shown to correlate with the rate of aging in nematodes, which is related to the level of oxygen consumption. Accordingly, long-lived isp-1 and clk-1 mutants that demonstrate decreased levels of oxygen consumption showed a shorter established period of adaptation than N2 nematodes, whereas short-lived gas-1 and mev-1 mutants that have a hypersensitive response to oxygen showed a longer period of adaptation than the N2. Moreover, the established period of diacetyl adaptation in N2 nematodes was shortened by the antioxidant α-lipoic acid. These results suggest that oxygen intermediates, which are produced by oxygen consumption, play a significant role in diacetyl adaptation. Although this is only one of many factors that regulate diacetyl adaptation, such as the release of neurotransmitters and changes in intracellular conditions, the acquisition of this adaptation requires an increase in the intensity of moderate oxygen signals.