Excitation of central neurons by dieldrin and picrotoxinin in susceptible and resistant Drosophila melanogaster (meigen)
1991
Bloomquist, J.R. | Ffrench-Constant, R.H. | Roush, R.T.
Neurological studies were used to characterize the resistance mechanism in a new cyclodiene-resistant strain of Drosophila melanogaster. Suction electrode recordings were taken from the peripheral nerves of transected larval central nervous systems. Treatment of nerve preparations with 1 millimole GABA reduced the spontaneous firing of peripheral nerves. This inhibition was effectively reversed within 10 min by exposing preparations from susceptible insects (Oregon-R wild type) to 10 micromoles dieldrin. In contrast, 30 min incubations with 10 micromoles dieldrin had no effect on preparations from resistant individuals. At 10 micromoles, picrotoxinin was also effective in antagonizing the action of GABA in susceptible nerve preparations. In recordings from resistant insects (n = 3), picrotoxinin displayed either no antagonism of GABA-dependent inhibitions, weak antagonism of GABA, or hyperexcitation indistinguishable form those of susceptible preparations. These results demonstrate that cyclodiene resistance in the Maryland strain of D. melanogaster is present at the level of the nerve, and that the resistance extends to picrotoxinin, albeit at a reduced level. The possible role of an altered GABA receptor in this resistance is discussed.
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