LONG-TERM EFFECTS OF DDT ON THE BEHAVIOR AND CENTRAL NERVOUS-SYSTEM ACTIVITY IN PERIPLANETA-AMERICANA

The effects of p,p,''-DDT and 4 of its analogs in electrical activity in the CNS of the cockroach, P. americana (L.), were investigated. Cockroaches were injected intraabdominally with an organochlorine compound at LD50 96-h doses (except for p,p''-DDE). Extracellular recordings were made from the CNS at 1 h, 24 h or 3 wk postinjection. p,p''-DDT, methoxychlor, and p,p''-DDD induced behavioral changes (tremors, jitters, hyperexcitability) and repetitive firing in the CNS prior to 1 h postinjection. By 24 h postinjection, most behavioral signs of poisoning had disappeared, though repetitive firing could still be readily elicited in the CNS. Cockroaches injected with o,p''-DDT usually required about 48 h before overt signs of poisoning became apparent. Cockroaches treated with p,p''-DDT or o,p''-DDT behaved normally at 3 wk postinjection but still displayed a significant occurrence of repetitive firing in the CNS. A mechanism is proposed to explain how a cockroach might recover behaviorally from a sublethal dose of an organochlorine compound but still display repetitive firing in its CNS. A direct cause and effect relationship between repetitive firing in the CNS and mortality (and external signs of poisoning) is, therefore, questioned.