Effects of verapamil on blood pressure and heart rate in neurogenic hypertensive rats.
The effects of verapamil (220 micrograms/kg per min i.v.) on blood pressure and heart rate were studied in sinoaortic baroreceptor denervated and sham-operated rats. In the conscious animals the verapamil-induced hypotension was accompanied by a significant heart rate increase in the first group (from 352 +/- 7 to 422 +/- 10 beats/min) and a decrease in the second group (from 485 +/- 13 to 400 +/- 9 beats/min). The verapamil-induced tachycardia observed in sham-operated rats was prevented by atropine plus propranolol but not by adrenal demedullation. Tachycardia was present in urethane-anesthetized sham-operated rats, similar to the sinoaortic baroreceptor-denervated rats. After verapamil a significant heart rate reduction was observed in sham-operated but not in sinoaortic baroreceptor-denervated rats. The results in conscious rats suggest that the direct inhibitory action of this drug on sinus node automaticity is suppressed by baroreflex tachycardia and that anesthesia masks this response.
D000758:Anesthesia; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D011311:Pressoreceptors / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D012018:Reflex / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology*
D014700:Verapamil