THE EFFECT OF CATECHOLAMINES AND CATECHOLAMINE ANTAGONISTS ON THE 3RD LARVAL MOLT OF DIROFILARIA-IMMITIS INVITRO

Various catecholamines and catecholamine antagonists have been examined for their effects on the third larval moult of the parasitic nematode, Dirofilaria immitis, cultured in vitro. The non-selective alpha and beta agonist, noradrenaline, and the beta agonist, isoprenaline, had no effect on the timing of the third stage moult when used at a concentration of 10(-5)M. The alpha-adrenergic antagonist, phentolamine, resulted in worm mortality at 10(-5)M. At 10(-7)M, both phentolamine and the beta-antagonist, propranolol caused a significant reduction in the numbers of larvae capable of completing the third stage moult. Idazoxan, an alpha2-antagonist, at 10(-5)M did not affect worm mortality but did completely prevent ecdysis. The potential of these compounds as possible filaricides is discussed.