Toxicology and Pharmacology of Neuroactive Agents in the Cockroach

The American cockroach, Periplaneta americana, has long provided a useful model for studies of both insect neurophysiology ¹ and insect neurotoxicology. ² As a result of studies conducted over the last 50 years, the neuropharmacology of the cockroach is better understood than that of any other insect ³ - ⁶ and, on occasion, phenomena with pharmacological relevance have been described in the cockroach which have only subsequently been found in vertebrates, e.g., the demonstration of cholinesterase in the nerve sheath (or blood-brain barrier) of the cockroach central nervous system (CNS). ⁷ In this chapter will be discussed the mode of action of most of the important classes of insecticide, not by chemical class, but instead from the standpoint of target site. Several sites which are apparently not insecticidal or else have not yet been exploited will also be discussed. Although some of the work to be described has not utilized the cockroach, its role as a model will nevertheless become clear. In Section IV the relative importance of the various targets in causing insect toxicity will be addressed.