EFFECT OF LARGE DOSES OF ATROPINE SULFATE ON HEART-RATE AND BLOOD-PRESSURE IN RATS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 25  (1) , 13-22
Abstract
Anticholinergic doses of atropine sulfate produce tachycardia, while larger doses produce bradycardia. The effects of large doses of atropine sulfate on heart rate and systemic blood pressure in rats were evaluated. Six groups of urethane-anesthetized, male, Sprague Dawley rats (200-450 g body wt.) were injected with varying doses of atropine via the jugular vein. Groups 1, 2, 3 and 4 received 5, 20, 40 and 80 mg/kg, respectively. Group 5 was bilaterally vagotomized before the injection of 80 mg/kg of atropine. Animals in Group 6 bilaterally vagotomized and pretreated with propranolol-HCl before injection of 40 mg/kg of atropine. Atropine caused a significant (P < 0.005) dose-dependent reduction in both heart rate and blood pressure. The negative chronotropic property of atropine agrees with results of recent in vitro and in vivo studies. The mechanism of bradycardia in these doses appears to be related to the mode of action of atropine rather than centrally mediated. Possible direct action by atropine on peripheral vascular resistance is discussed.