SUPPRESSION OF DDT-INDUCED REPETITIVE FIRING BY THE METATHORACIC GANGLION OF THE COCKROACH PERIPLANETA-AMERICANA (L)

The effects of sublethal doses of DDT on the central nervous system of Periplaneta americana (L.) were examined by simultaneously recording from the abdominal ventral nerve cord, metathoracic dorsal unpaired median neurons, and nerves 5rl and 6Br4. When DDT was injected into animals prior to experimentation, exaggerated responses to wind puffs were recorded in the abdominal ventral nerve cord and motor nerves. However, DDT-induced abdominal ventral nerve cord repetitive firing was not transmitted to the motor nerves if DDT treatment was limited to the fifth abdominal ganglion. DDT appeared not to alter the response characteristics of an identifiable dorsal unpaired median neuron. Also, wind puff-induced dorsal unpaired median neuron activity did not occur prior to motor output in nerve 5rl, even after treatment with DDT. The results suggest that filtering of DDT-induced afferent activity can occur in the metathoracic ganglion, although this may not be the only site. Dorsal unpaired median neurons do not appear to be directly involved in the DDT-poisoning syndrome. © 1990.