Uptake of DDT by the American cockroach central nervous system.

Abstract

Experiments using C14-DDT to relate the DDT content of the central nervous system (CNS) to frequency of appearance of DDT-induced trains indicate that the DDT content of the CNS is not directly related to the levels of nerve activity observed. After either small injected dosages of C14-DDT or large topical dosages of C14-DDT applied to the cerci, a larger number of DDT-induced trains appear in the abdominal CNS of the topically treated cockroaches. In contrast, the C14DDT content of the abdominal CNS of the topically treated American cockroach, Periplaneta americana (L.), is actually less than the amount in the abdominal CNS of the cockroaches treated by injection. Thus, it seems that high levels of afferent activity are more important than the amount of DDT in the abdominal CNS for the production of high levels of activity in the abdominal CNS. When 0.107 ng of DDT in suspension is injected into the sixth abdominal ganglion no DDT trains are produced. When 10 times this dosage is injected into the sixth abdominal ganglion DDT trains are produced in the abdominal CNS. Observation of the frequency of appearance of DDT-induced trains at different temperatures reveals a relationship identical to that found in sensory nerves. That is, as temperature is increased, the frequency of appearance of DDT-induced trains in the abdominal CNS is also increased. Thus when the effect of DDT in the abdominal CNS is studied in the absence of high levels of afferent input, the relationship between the effect of DDT on nerve and temperature is the direct relationship which is obtained with sensory nerve, and not the inverse relation to temperature found in vivo with afferent input intact but subject to the action of DDT.