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Circadian Rhythms in Autonomic Cardiac Function in Mice
Author(s) -
Graham Cathy D,
Morris Mariana
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1262-b
Subject(s) - circadian rhythm , rhythm , baroreflex , medicine , autonomic function , endocrinology , analysis of variance , blood pressure , heart rate , biology , heart rate variability
Circadian rhythms in cardiovascular function are critical in health maintenance. The purpose was to determine time‐specific patterns in blood pressure (BP), pulse interval (PI) and autonomic balance in C57Bl mice (n = 5, light/dark; 0500/1700h). 24 hr radiotelemetric BP recordings were made. Recordings were divided into 8 periods (4 light/4 dark) and analysis performed on 30‐min segments. BP (mmHg) and PI (ms 2 ) oscillations were characterized in time and frequency domains (low and high) using autoregressive spectral analysis. As expected, there was a light/dark rhythm in BP and PI, higher levels in the dark phase (p < 0.02). For PI variance and its LF component, there was a rhythm (ANOVA, p < 0.05 and < 0.01, variance and LF, respectively). There was no day/night rhythm in systolic BP variance. There was a marked decrease in PI variance (~ 2 fold) and PI‐LF (~ 3 fold), with onset of the dark phase. PI variance was 75 ± 10 vs. 40 ± 5 ms 2 and PI‐LF was 36 ± 5 vs. 11 ± 1 (light vs dark). There was no change in HF for either PI or SBP. There was a day/night rhythm in baroreflex. Results demonstrate differences in the circadian autonomic rhythm for PI and BP. For the cardiac axis, there was a clear day/night rhythm which was not seen for the vasculature. The changes in variance and its LF component suggest that there are rhythmic alterations in sympathetic/parasympathetic balance. This study provides important information on the nature of normal autonomic rhythms in mice.