Effects of the pyrethroids bioallethrin, deltamethrin and RU‐15525 on the electrical activity of a cuticular mechanoreceptor of the cockroach Periplaneta americana
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Media type:
E-Article
Title:
Effects of the pyrethroids bioallethrin, deltamethrin and RU‐15525 on the electrical activity of a cuticular mechanoreceptor of the cockroach Periplaneta americana
Description:
<jats:title>Abstract</jats:title><jats:p>A study has been made of the effects of bioallethrin, RU‐15525 [5‐benzyl‐3‐furylmethyl (1<jats:italic>R</jats:italic>)‐<jats:italic>cis</jats:italic>‐2,2‐dimethyl‐3‐(tetrahydro‐2‐oxo‐3‐thienylidenemethyl)‐cyclopropanecarboxylate, ‘Kadethrin’], and deltamethrin on the electrical activity, measured <jats:italic>in vivo</jats:italic>, of a cuticular mechanoreceptor of <jats:italic>Periplaneta americana</jats:italic>. The modifications induced by these pyrethroids on the membrane excitability can be classified into two groups: Type I effects (bioallethrin) are characterised by a substantial increase in the number of action potentials triggered at the initiation site by a given mechanical stimulation, by an electrical activity persisting after mechanical stimulus has been stopped (repetitive activity), and possibly, by an inhibition of excitability of the cell membrane. Type II effects (RU‐15525 and deltamethrin), are characterised by an inhibition of the excitability of the initiation site. In the case of RU‐15525, there was a transient spontaneous electrical activity. Both types of effects have been linked to an action on the sodium channel, particularly at the initiation site. The preparation studied, which possessed no synapses, was shown to be more sensitive to deltamethrin (which is also the most insecticidal of the three pyrethroids) than to either allethrin or RU‐15525. These results suggest that it is unnecessary to envisage a main target (sodium channel) that is different for the two types of pyrethroid.</jats:p>