Effects of angiotensins on day-night fluctuations and stress-induced changes in blood pressure.
In this study we evaluated by telemetry the effects of ANG II and ANG-(1-7) infusion on the circadian rhythms of blood pressure (BP) and heart rate (HR) and on the cardiovascular adjustment resulting from restraint stress in rats. ANG II or ANG-(1-7) or vehicle were infused subcutaneously for 7 days. Restraint stress was carried out before, during, and after infusion at 7-day intervals. Parallel with an increase in MAP, ANG II infusion produced an inversion of MAP circadian rhythm with a significant MAP acrophase inversion. It also produced bradycardia during the first 3 days of infusion. Thereafter, HR progressively increased, reaching values similar to or above those of the control period at the end of the infusion period. HR circadian variation was not changed by ANG II infusion. Strikingly, ANG II significantly attenuated the increase in MAP induced by restraint stress without altering the HR response. ANG-(1-7) infusion produced a slight but significant decrease in MAP restricted to the daytime period. No significant changes in the MAP acrophase were observed. In addition, ANG-(1-7) infusion produced a small but significant sustained bradycardia. ANG-(1-7) did not change cardiovascular responses to restraint stress. These data indicate that ANG II can influence the activity of brain areas involved in the determination of stress-induced or circadian-dependent variations of blood pressure without changing HR fluctuations. A significant modulatory influence of ANG-(1-7) on basal MAP and HR is also suggested.
Braga
Aline Nardoni Gonçalves
AN
Laboratório de Hipertensão, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901, Belo Horizonte, Minas Gerais, Brasil.
da Silva Lemos
Marisa
M
da Silva
José Roberto
JR
Fontes
Walkíria Ramos Peliky
WR
dos Santos
Robson Augusto Souza
RA
D000803:Angiotensin I / Q000008:administration & dosage*; D000804:Angiotensin II / Q000008:administration & dosage*; D000818:Animals; D001341:Autonomic Nervous System / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D002940:Circadian Rhythm / Q000187:drug effects* / Q000502:physiology; D004334:Drug Administration Schedule; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007279:Injections, Subcutaneous; D008297:Male; D010446:Peptide Fragments / Q000008:administration & dosage*; D051381:Rats; D017208:Rats, Wistar; D012149:Restraint, Physical; D013312:Stress, Physiological; D013686:Telemetry
D010446:Peptide Fragments; D000804:Angiotensin II; D000803:Angiotensin I; C118790:angiotensin I (1-7)