The effect of catecholamines and catecholamine antagonists on the third larval moult of Dirofilaria immitis in vitro.

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 alpha 2-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.