Abstract:
Mode of action of DDT.
The precise mode of action of DDT has not yet been elucidated. A number of theories, more notably Mullins’ (1955) theory of the fit of the DDT molecule into a hypothetical molecular lattice on the nerve axon, has yet to be substantiated with conclusive evidence. Mullins’ theory received indirect support from Holan (1969) who considered the projected stereochemistry of DDT and analogues, and showed that the insecticidal activities of the analogues were in some way quantitatively related to their fit into a hypothetical hole in the axon derived from the fit required for DDT. A cyclopropane derivative of DDT was shown to be similar to DDT in both steric structure and insecticidal activity. DDE (1,1-bis-(p-chlorophenyl)dichloro-ethylene) has considerable differences in steric structure compared to DDT and no insecticidal activity. Nervous interference is the ultimate cause of death. Yamasaki & Narahashi (1959) reported that DDT prolongs the negative after-potential of the action potential of the cockroach crural nerve. The effect is profound, especially in the absence of potassium ions, and also occurs in vivo.
