Insect acetylcholine receptors as a site of insecticide action

Abstract

ACETYLCHOLINE is thought to be an excitatory neurotransmitter at synapses in the insect central nervous system (CNS) and does not seem to be involved in insect neuromuscular transmission1,2. Most of the current generation of insecticides are inhibitors of the enzyme acetylcholinesterase which hydrolyses acetylcholine, terminating its synaptic actions3. Far less attention has been given to other components of cholinergic synapses which might constitute potential sites of action of insecticidally active molecules. These include the presynaptic synthesis of acetylcholine involving the enzyme choline acetyltransferase, the mechanism of transmitter release and the post-synaptically located acetylcholine receptor molecules. The present study demonstrates that an isothiocyanate compound and nicotine, both of which show insecticidal activity, are agonists for an acetylcholine receptor in the CNS of the cockroach Periplaneta americana.