title: Role of baroreflex and central alpha2-adrenergic receptor systems in the diurnal variation of blood pressure and heart rate in normotensive and hypertensive rats.
abstract: 1. To elucidate whether baroreflex could contribute to manifest the diurnal blood pressure variations (DBPV) in normotension and hypertension, DBPV were recorded continuously via a femoral artery in awake normotensive (NT) rats and spontaneously hypertensive rats (SHR) with and without sinoaortic denervation (SAD). To determine the role of central alpha2-adrenergic receptor system in DBPV in hypertension, guanabentz (0.5-1.0 mu g/kg per min) was infused in SHR. 2. There were no differences in mean arterial pressure (MAP) variability (SD) of MAP of 24 h (MAP -- SD/MAP) and SD of 24 h heart rate (HR -- SD/HR) between SHR and NT. SAD did not elevate MAP and HR in both SHR and NT. 3. However, in SAD rats, MAP -- SD/MAP was significantly greater than those in sham-operated rats in both SHR and NT, while MAP -- SD/MAP and HR -- SD/HR did not show any difference between the two groups even after SAD. On the other hand, SAD did not augment HR -- SD/HR in either strain. 4. During guanabentz infusion, MAP was significantly lowered in sham-operated and SAD -- SHR. Moreover, MAP -- SD/MAP was significantly reduced in sham-operated, but it was not in SAD -- SHR. 5. These findings suggest that baroreflex could suppress tonically the diurnal change of blood pressure in NT and SHR. The regulation of diurnal blood pressure by baroreflex via a central alpha-adrenergic receptor system may be altered in SHR.
authors.affiliation: Second Department of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yoneda
authors.forename: K
authors.initials: K
authors.lastname: Takeda
authors.forename: K
authors.initials: K
authors.lastname: Nakamura
authors.forename: H
authors.initials: H
authors.lastname: Fujita
authors.forename: A
authors.initials: A
authors.lastname: Uchida
authors.forename: T
authors.initials: T
authors.lastname: Yoshitomi
authors.forename: K
authors.initials: K
authors.lastname: Takenaka
authors.forename: H
authors.initials: H
authors.lastname: Itoh
authors.forename: T
authors.initials: T
authors.lastname: Nakata
authors.forename: S
authors.initials: S
authors.lastname: Sasaki
mesh_terms: D058669:Adrenergic alpha-2 Receptor Antagonists; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D003714:Denervation; D006143:Guanabenz / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006973:Hypertension / Q000235:genetics / Q000503:physiopathology*; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects / Q000502:physiology*; D012849:Sinoatrial Node / Q000502:physiology
chemical_list: D058669:Adrenergic alpha-2 Receptor Antagonists; D000316:Adrenergic alpha-Agonists; D018341:Receptors, Adrenergic, alpha-2; D006143:Guanabenz