TOWARDS THE DEVELOPMENT OF RYANOID INSECTICIDES WITH LOW MAMMALIAN TOXICITY

The effects of ryanodine and 9,21-didehydroryanodol on mammalian and i nsect muscles have been compared. Whereas ryanodine markedly affected the functioning of insect and mammalian muscles, the action of 9,21-di dehydroryanodol was mainly restricted to the insect muscles. Unlike ry anodine, 9,21-didehydroryanodol did not elicit a contracture from inse ct muscles, yet it inhibited muscle contractions. This inhibition is a ssociated with changes in the ion selectivities of potassium channels located in the muscle plasma membrane. These changes lead to a decline in muscle resting potential and loss of excitability.