Contribution of neurogenic mechanisms to control of intrinsic heart rate.
Altered autonomic tone as well as humoral factors can change the intrinsic rate of the cardiac pacemaker. To study the relationships of neurogenic and humoral factors on intrinsic heart rate (IHR) we used sinoaortic deafferentation (SAD) to increase sympathetic activity, lesion of nucleus ambiguus to reduce central parasympathetic activity, and one-kidney, one-clip (1K1C) renal hypertension to transiently increase the activity of the renin-angiotensin system and the combination of 1K1C hypertension with SAD. In conscious rats, IHR was determined using combined blockade with atropine and propranolol. Rats with 1K1C hypertension (7th day) showed increased mean arterial pressure (MAP), heart rate (HR), and IHR. Rats with SAD (4th day) demonstrated increased MAP and HR, but in contrast, had decreased IHR. Lesion of nucleus ambiguus increased HR and decreased IHR. When 1K1C hypertension was combined with SAD an additional increase in MAP and HR occurred, whereas IHR was reduced compared with renal hypertension alone. These data suggest that IHR is influenced greatly by autonomic tone and that the tachycardia in renal hypertension is linked to increased IHR that is dependent on integrity of the baroreflex.
Machado
B H
BH
Department of Pharmacology, College of Medicine, University of Iowa, Iowa City 52242.
Brody
M J
MJ
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D006339:Heart Rate; D006977:Hypertension, Renal / Q000503:physiopathology; D008297:Male; D010275:Parasympathetic Nervous System / Q000503:physiopathology; D011311:Pressoreceptors / Q000502:physiology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012084:Renin-Angiotensin System; D013564:Sympathetic Nervous System / Q000503:physiopathology
D001285:Atropine; D011433:Propranolol