Diurnal rhythms of blood pressure, heart rate, and locomotor activity in adult and old male Wistar rats

Author(s): Sannajust, F.

Journal/Book: Physiol Behav. 2000; 70: the Boulevard Langford Lane, Kidlington, Oxford Ox5 1GB, England. Pergamon-Elsevier Science Ltd. 375-380.

Abstract: The diurnal rhythms of systolic blood pressure (SBP), diastolic BP (DBP), heart rate (HR), and spontaneous locomotor activity (SLA) were determined in adult (6-month-old) and old (24-month-old) male Wistar rats by using radiotelemetry. The rhythm parameters (mesor, amplitude, acrophase, and percent rhythm) were analyzed by Fast-Fourier Transform and Cosinor methods. We found that the 12-h mean values of SEP, DBP, HR, and SLA were significantly (p < 0.001) higher in the dark phase than in the light phase in both adult and old rats. The nocturnal 12-h mean value of HR was significantly (p < 0.01) lower in old than in adult rats. In addition, the differences between diurnal and nocturnal 12-h mean values of SEP and HR were reduced in old rats. There was no significant difference in the 12-h mean values of SEP, DBP, and SLA between old and adult rats. Otherwise, the diurnal HR rhythm amplitude was significantly (p < 0.01) reduced in old rats (32 +/- 2 vs. 46 +/- 2 bpm). A nearly l-h delay in SEP and DBP acrophases (03h55 +/- 00h19 vs. 02h57 +/- 00h14 and 03h17 +/- 00h13 vs. 01h53 +/- 00h22, respectively) was found in old rats comparing to adult rats. No significant change in SLA diurnal rhythm was observed in old rats. In conclusion, these results show a decrease in the nocturnal 12-h mean value of HR and an alteration in cardiovascular diurnal rhythms by a l-h delay of SEP and DBP acrophases and a reduction of HR rhythm amplitude in old Wistar rats.

Note: Article Zhang BL, Fac Pharm Tours, Equipe Accueil 2641, Dept Neuropharmacol, 31 Ave Monge, F-37200 Tours, FRANCE

Keyword(s): aging; blood pressure; circadian rhythms; heart rate; radiotelemetry; rats; SPONTANEOUSLY HYPERTENSIVE RATS; AGE-RELATED-CHANGES; CIRCADIAN-RHYTHMS; SUPRACHIASMATIC NUCLEUS; BODY-TEMPERATURE; PINEAL-GLAND; MELATONIN; YOUNG; LIGHT; RADIOTELEMETRY

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