title: Baroreflex dysfunction in diabetes mellitus. I. Selective impairment of parasympathetic control of heart rate.
abstract: The purpose of this study was to determine the effect of diabetes mellitus on baroreflex control of heart rate. Diabetes (blood glucose = 378 +/- 21 mg/dl) was induced in rabbits by alloxan (n = 9). Alloxan-treated rabbits that remained normoglycemic (n = 9) and rabbits given saline instead of alloxan (n = 5) served as controls. Baroreflex control of heart rate was evaluated in conscious rabbits by measuring changes in heart rate during phenylephrine-induced increases and nitroglycerin-induced decreases in arterial pressure. In diabetic rabbits, the gain of the baroreflex-mediated bradycardia in response to increased pressure decreased significantly from -1.8 +/- 0.3 beats.min-1 x mmHg-1 before alloxan (n = 9) to -0.9 +/- 0.1 and -0.9 +/- 0.3 beats.min-1 x mmHg-1 after 12 and 24 wk of diabetes, respectively (n = 8; P < 0.05). There was no significant change in baroreflex gain in either alloxan-treated or saline-treated normoglycemic rabbits. Baroreflex-mediated bradycardia was not influenced significantly after beta-adrenergic blockade with propranolol (1 mg/kg) and was still impaired in diabetic vs. control rabbits after propranolol. The gain of the baroreflex-mediated tachycardia in response to decreased pressure was not altered in any of the three groups. Propranolol significantly decreased but did not abolish baroreflex-mediated tachycardia. Neither the vagal nor the sympathetic component of the tachycardia was altered significantly by diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Cardiovascular Center, University of Iowa, Iowa City.
authors.forename: T S
authors.initials: TS
authors.lastname: McDowell
authors.forename: M W
authors.initials: MW
authors.lastname: Chapleau
authors.forename: G
authors.initials: G
authors.lastname: Hajduczok
authors.forename: F M
authors.initials: FM
authors.lastname: Abboud
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D008297:Male; D010275:Parasympathetic Nervous System / Q000503:physiopathology*; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000503:physiopathology