Article
Diurnal alterations in cerebral blood flow: studies in normotensive and transgenic hypertensive rats
Circadiane Periodik der Gehirndurchblutung: Untersuchungen an normotensiven und transgenen hypertensiven Ratten
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Authors
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C. Wauschkuhn
- Abteilung Neurochirurgische Forschung, Neurochirurgische Universitätsklinik Mannheim, Universität Heidelberg
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K. Witte
- Institut für Pharmakologie und Toxikologie, Fakultät für Klinische Medizin Mannheim, Universität Heidelberg
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S. Gorbey
- Institut für Pharmakologie und Toxikologie, Fakultät für Klinische Medizin Mannheim, Universität Heidelberg
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B. Lemmer
- Institut für Pharmakologie und Toxikologie, Fakultät für Klinische Medizin Mannheim, Universität Heidelberg
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L. Schilling
- Abteilung Neurochirurgische Forschung, Neurochirurgische Universitätsklinik Mannheim, Universität Heidelberg
| Published: | May 4, 2005 |
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Outline
Text
Objective
Cardiovascular parameters such as arterial blood pressure (BP) and heart rate display pronounced circadian variation. Similarly, evidence has been presented in favor of diurnal changes of perfusion in the heart, skin, kidney, and skeletal muscle. The present study was performed to detect whether there is a circadian periodicity in the regulation of cerebral perfusion.
Methods
Normotensive Sprague Dawley rats (SDR, appr. 15 weeks old) and hypertensive (mREN2) 27 transgenic rats (TGR, appr. 12 weeks old) were equipped in the abdominal aorta with a blood pressure sensor coupled to a telemetry system for continuous recording of arterial blood pressure, heart rate, and locomotor activity. Five to twelve days later, a laser-Doppler flow (LDF) probe was attached to the skull by means of a guiding device to measure changes of cerebral blood flow (CBF). After recovery from anesthesia, continuous measurements were taken for 3 - 5 days. The time series were analyzed with respect to the mesor (ie.e midline estimating statistic of rhythm), amplitude, and acrophase of the 24h period.
Results
A pronounced circadian rhythm was obtained for systolic and diastolic ABP, heart rate, and acitivity in both, SDR and TGR. In the latter strain the arterial BP signal showed its typical inverse pattern with the maximum of the ABP occurring during light on (systolic BP, 09:42; diastolic BP, 09:18), i.e. during the subjective resting phase. The LDF signal displayed a significant circadian rhythm. The peak of the LDF periodicity occurred around midnight in both, SDR (22:30) and TGR (00:42), i.e. during the subjective activity period of the animals. Furthermore, the acrophase of the LDF was consistently found prior to that of the activity (SDR, 1:42; TGR: 2:42).
Conclusions
The present data suggest the presence of a circadian periodicity in the regulation of cerebral perfusion. This periodicity is independent from circadian changes of arterial BP since it did not follow the inverse periodicity in TGR. It is probably also independent from locomotor activity since its peak occurred consistently prior to that of the activity. The presence of a circadian periodicity in the CBF may have implications for the occurrence of diurnal alterations of cerebrovascular events with a morning peak observed in humans.
