How does fly spray kill flies?
Fly spray contains chemicals (including many organophosphate compounds) that bind to and permanently block the action of an enzyme called acetylcholinesterase. Acetyl choline (ACh) is the nerve transmitter substance released by motor neurones (at a site called the neuromuscular junction) to stimulate muscle contraction. The muscles relax (stops contracting) when the ACh is removed from the neuromuscular junction (NMJ) by the action of acetylcholinesterase. By inhibiting the cholinesterase the fly can no longer break down ACh in the NMJ and so its muscles lock up in a state of tetany (continuous contraction) making flying and respiration impossible. The South American indians used a similar approach to kill animals for food using poison-tipped blow-darts. They discovered the natural chemical curare which blocks the sites on the muscles where ACh usually locks on to activate muscle contraction. Because the ACh cannot activate the muscle the individual becomes paralysed and can then easil
