Development of autonomic control of heart rate in genetically hypertensive and normotensive rats

of autonomic control of heart rate in genetically hypertensive and normotensive rats. Am. J. Physiol. 246 (Regulatory Inte-grative Comp. Physiol. 15): R570-R577, 1984.-The present study describes developmental changes in autonomic controls of heart rate in a strain of rats genetically predisposed to hypertension (spontaneously hypertensive rats or SHR) and in a normotensive strain of rats (Wistar-Kyoto rats or WKY). Rat pups were tested at 4,8,12, and 16 days to determine heart rate changes after selective pharmacological treatments. Spe-cifically, freely moving pups were treated with selective,& adrenergic and muscarinic receptor blockers (i.e., atenolol and atropine methylnitrate), using procedures designed to produce minimal pain or discomfort. The results indicated that by 4 days of age there is a substantial sympathetic acceleratory influence on heart rate. Comparison of inferred autonomi