Age-related reduction of reflex bradycardia in conscious rats by catecholaminergic nucleus tractus solitarius lesions.
To determine whether catecholaminergic lesions in the nucleus tractus solitarius (NTS) have age-related baroreflex effects, we compared conscious 3-month- and 14-month-old rats pretreated with either 6-hydroxydopamine (6-OHDA) or vehicle injected into the NTS. Body weights fell immediately in both age groups, but after 2 weeks the weight loss persisted only in 14-month-old rats. Mean pressures and heart rates, though diminished after 3 days, were later elevated slightly in 3-month- but not in 14-month-old rats. Two weeks after 6-OHDA pretreatment, reflex tachycardia was reduced in both age groups, but reflex bradycardia was reduced only in 3-month-old and not in 14-month-old rats. Corresponding changes in vehicle-treated rats were not significant. Because 6-OHDA induced lesions in the NTS inhibited reflex bradycardia selectively at 3 but not at 14 months of age, our results suggest that catecholaminergic mechanisms in the NTS for regulating reflex bradycardia become impaired with age.
Itoh
H
H
Department of Pharmacology, College of Health Sciences and Hospital University of Kansas Medical Center, Kansas City 66103.
Buñag
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RD
D000375:Aging / Q000502:physiology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001919:Bradycardia / Q000209:etiology / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000293:injuries / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D016627:Oxidopamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D012018:Reflex / Q000502:physiology*; D015431:Weight Loss / Q000187:drug effects
D009599:Nitroprusside; D010656:Phenylephrine; D016627:Oxidopamine