Strain differences in minimum anesthetic concentrations in Drosophila melanogaster

An ether-resistant strain of Drosophila melanogaster has been maintained at this laboratory since the appearance of one female mutant in 1961. Sensitivity was defined using mortality as an endpoint when exposed to a high concentration of diethylether; this does not necessarily mean that anesthetic requirements are higher in the resistant strain. The present study was undertaken to determine the difference in anesthetic potency between the ether-resistant strain (Eth-29) and one of the sensitive strains (bw;st;svn). The median effective dose (ED50) for halothane was 0.0096 atm in females and 0.0091 atm in males of the bw;st;svn strain, while in the Eth-29 strain the ED50 was 0.0148 atm in both sexes. The ED50 values for chloroform anesthesia were 0.0051 atm in females and 0.0050 atm in males of the bw;st;svn strain and 0.0100 atm in the Eth-29 strain in both sexes. Strain differences in response to the two anesthetics were statistically significant. Thus the Eth-29 strain shows a cross-resistance to both halothane and chloroform anesthesia. Reciprocal crosses between the two strains revealed that the resistance to halothane anesthesia was a sex-linked recessive trait and that the resistance to chloroform anesthesia was an autosomal incompletely dominant trait.