AMITRAZ DEPRESSES CARDIOVASCULAR-RESPONSES TO BILATERAL CAROTID OCCLUSION

The ectoparasiticide amitraz stimulates alpha(2)-adrenoceptors to prod uce side-effects such as bradycardia and hypotension. The actions of a mitraz on baroreceptor reflex responses were evaluated in mongrel dogs by occlusion of both carotid arteries for 30-s periods, Incremental d oses of amitraz given intravenously showed that doses of 60 mu g/kg an d above significantly depressed presser responses to carotid occlusion . By comparison, 2 mu g/kg amitraz given by intracisterna magna (i,c,m ,) injection significantly depressed both blood pressure and heart rat e responses, Pretreatment of dogs with i.c.m, yohimbine (30 mu g/kg) p revented the depressant effects of amitraz on the reflex, but prazosin (20 mu g/kg), in separate experiments, had no effect.