A recent investigation by Enan et al. (1998) using the
American cockroach points to the octopaminergic nervous
system as the site-of-action in insects. The binding
of 3H-octopamine in a cockroach nerve cord protein
preparation was signi"cantly a!ected in the presence of
a number of essential oil constituents. The lack of octopamine
receptors in vertebrates likely accounts for the
profound mammalian selectivity of essential oils as insecticides
(i.e. they are toxic to insects but not to mammals),
and thus the octopaminergic system of insects represents
a biorational target for insect control. Investigation of
the formamidine insecticides revealed interesting and potentially
important sublethal behavioral and physiological
e!ects, presumably mediated by the octopaminergic
nervous system (Matsumura and Beeman, 1982). Sublethal
e!ects observed with some of the essential oil
compounds (viz., feeding deterrence, repellency) may be
consistant with this mode-of-action