Involvement of cholinergic mechanism in the action of allethrin in insect CNS.

Allethrin had a stimulating action on spontaneous discharges in the cockroach sixth abdominal ganglion superfused with an insect saline solution. This action at a low concentration (5 X 10(-8) M) of allethrin was abolished by either of d-tubocurarine, hexamethonium or atropine at 5 X 10(-4) M. It was also abolished by the treatment of ganglia with hemicholinium-3 or by low-calcium-high magnesium insect saline solution. However, treatment of these blocked ganglia with allethrin at more than 5 X 10(-7) M overcame the block, producing increased spontaneous activity. Allethrin had no effect on insect cholinesterase activity. These results may suggest that the stimulating action at a low concentration of allethrin may be mediated by the release of ACh from cholinergic terminals in ganglia.