Autonomic Modulation of Altered Diurnal Hemodynamic Profiles in Ethanol-Fed Hypertensive Rats

Apr 19, 2005Alcoholism, clinical and experimental research

Nervous system control of daily blood flow changes in alcohol-fed high blood pressure rats

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Abstract

Chronic ethanol feeding resulted in 3-fold greater hypotension in spontaneously hypertensive rats compared to age-matched Wistar-Kyoto rats.

Control Wistar-Kyoto rats maintained normal circadian rhythms in blood pressure and heart rate over the study period.
Circadian rhythms in spontaneously hypertensive rats were disrupted, with blood pressure rhythms abolished and heart rate rhythms inverted.
Ethanol feeding led to sustained lower blood pressure in both light and dark cycles, with more pronounced effects in spontaneously hypertensive rats.
Variability of blood pressure was reduced during light times in spontaneously hypertensive rats but remained unchanged in Wistar-Kyoto rats after ethanol exposure.
Heart rate increased significantly in spontaneously hypertensive rats during dark periods following ethanol consumption, suggesting reduced cardiac vagal activity.

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BACKGROUND: A recent report from the authors' laboratory showed that circadian hemodynamic rhythms are altered in hypertension due partly to irregularities in cardiovascular autonomic control. This study investigated the long-term effects of chronic ethanol feeding (5% w/v, 12 weeks) on the circadian profiles of blood pressure (BP), heart rate (HR), and their variability in spontaneously hypertensive rats (SHRs) and age-matched Wistar-Kyoto (WKY) rats.

METHODS: Radiotelemetry was used for hemodynamic monitoring. The time-domain measures of the variability of BP (standard deviation of mean arterial pressure [SDMAP]) and HR (standard deviation of R-R intervals [SDRR] and root mean square of successive differences in R-R intervals [rMSSD]) were taken as indices of cardiovascular autonomic activity.

RESULTS: Control WKY rats displayed normal circadian rhythms (i.e., higher dark-time compared with light-time values) of BP, HR, and their variability indices during weeks 6 through 12 of the study. These circadian rhythms were abolished (BP), inverted (HR, SDMAP), or enhanced (SDRR, rMSSD) in SHRs. Ethanol feeding produced sustained hypotension during both light and dark cycles that was 3-fold greater in SHRs than in WKY rats. SDMAP was not affected by ethanol in WKY rats and showed reductions, mostly during light times, in SHRs. Ethanol also caused significant increases in HR in SHRs only during dark periods, probably because of the inhibition of cardiac vagal activity as indicated by temporal reductions in rMSSD.

CONCLUSIONS: These results implicate autonomic factors in the altered diurnal hemodynamic profile by ethanol in SHRs and highlight the possibility of increased risk of cardiac events in hypertensive patients due to alcohol use.

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Autonomic Modulation of Altered Diurnal Hemodynamic Profiles in Ethanol-Fed Hypertensive Rats

Abstract

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