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Baroreflex modulation of muscle sympathetic nerve activity at rest does not differ between morning and afternoon.

Hissen SL, Macefield VG, Brown R, Witter T, Taylor CE - Front Neurosci (2015)

Bottom Line: Similarly, vascular sympathetic BRStotal did not differ significantly between the morning (-3.0±0.5 AU/beat/mmHg) and afternoon (-2.9 ± 0.4 AU/beat/mmHg; P = 0.89).It is concluded that in healthy, young individuals baroreflex modulation of MSNA at rest does not differ between the morning and afternoon.The results indicate that recording MSNA at different times of the day is a valid means of assessing sympathetic function.

View Article: PubMed Central - PubMed

Affiliation: School of Science and Health, University of Western Sydney Sydney, NSW, Australia.

ABSTRACT
The incidence of cardiovascular events is significantly higher in the morning than other times of day. This has previously been associated with poor blood pressure control via the cardiac baroreflex. However, it is not known whether diurnal variation exists in vascular sympathetic baroreflex function, in which blood pressure is regulated via muscle sympathetic nerve activity (MSNA). The aim of this study was to compare vascular sympathetic baroreflex sensitivity (BRS) in the same participants between the morning and afternoon. In 10 participants (mean age 22 ± 2.9 years), continuous measurements of blood pressure, heart rate and MSNA were made during 10 min of rest in the morning (between 0900 and 1000 h) and afternoon (between 1400 and 1500 h). Spontaneous vascular sympathetic BRS was quantified by plotting MSNA burst incidence against diastolic pressure (vascular sympathetic BRSinc), and by plotting total MSNA against diastolic pressure (vascular sympathetic BRStotal). Significant vascular sympathetic BRSinc and vascular sympathetic BRStotal slopes were obtained for 10 participants at both times of day. There was no significant difference in vascular sympathetic BRSinc between morning (-2.2 ± 0.6% bursts/mmHg) and afternoon (-2.5 ± 0.2% bursts/mmHg; P = 0.68) sessions. Similarly, vascular sympathetic BRStotal did not differ significantly between the morning (-3.0±0.5 AU/beat/mmHg) and afternoon (-2.9 ± 0.4 AU/beat/mmHg; P = 0.89). It is concluded that in healthy, young individuals baroreflex modulation of MSNA at rest does not differ between the morning and afternoon. The results indicate that recording MSNA at different times of the day is a valid means of assessing sympathetic function.

No MeSH data available.


Vascular sympathetic baroreflex slopes for a 21-year old male in the morning (closed circles) and afternoon (open circles) using (A) the vascular sympathetic BRSinc method, and (B) the vascular sympathetic BRStotal method.
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Figure 2: Vascular sympathetic baroreflex slopes for a 21-year old male in the morning (closed circles) and afternoon (open circles) using (A) the vascular sympathetic BRSinc method, and (B) the vascular sympathetic BRStotal method.

Mentions: There was no significant difference in vascular sympathetic BRSinc between the morning and afternoon sessions (P = 0.68). Similarly, there was no significant difference in vascular sympathetic BRStotal between the morning and afternoon (P = 0.89). These results are summarized in Table 2. Figure 2 illustrates vascular sympathetic baroreflex slopes in one individual, studied in the morning and in the afternoon on separate days.


Baroreflex modulation of muscle sympathetic nerve activity at rest does not differ between morning and afternoon.

Hissen SL, Macefield VG, Brown R, Witter T, Taylor CE - Front Neurosci (2015)

Vascular sympathetic baroreflex slopes for a 21-year old male in the morning (closed circles) and afternoon (open circles) using (A) the vascular sympathetic BRSinc method, and (B) the vascular sympathetic BRStotal method.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557114&req=5

Figure 2: Vascular sympathetic baroreflex slopes for a 21-year old male in the morning (closed circles) and afternoon (open circles) using (A) the vascular sympathetic BRSinc method, and (B) the vascular sympathetic BRStotal method.
Mentions: There was no significant difference in vascular sympathetic BRSinc between the morning and afternoon sessions (P = 0.68). Similarly, there was no significant difference in vascular sympathetic BRStotal between the morning and afternoon (P = 0.89). These results are summarized in Table 2. Figure 2 illustrates vascular sympathetic baroreflex slopes in one individual, studied in the morning and in the afternoon on separate days.

Bottom Line: Similarly, vascular sympathetic BRStotal did not differ significantly between the morning (-3.0±0.5 AU/beat/mmHg) and afternoon (-2.9 ± 0.4 AU/beat/mmHg; P = 0.89).It is concluded that in healthy, young individuals baroreflex modulation of MSNA at rest does not differ between the morning and afternoon.The results indicate that recording MSNA at different times of the day is a valid means of assessing sympathetic function.

View Article: PubMed Central - PubMed

Affiliation: School of Science and Health, University of Western Sydney Sydney, NSW, Australia.

ABSTRACT
The incidence of cardiovascular events is significantly higher in the morning than other times of day. This has previously been associated with poor blood pressure control via the cardiac baroreflex. However, it is not known whether diurnal variation exists in vascular sympathetic baroreflex function, in which blood pressure is regulated via muscle sympathetic nerve activity (MSNA). The aim of this study was to compare vascular sympathetic baroreflex sensitivity (BRS) in the same participants between the morning and afternoon. In 10 participants (mean age 22 ± 2.9 years), continuous measurements of blood pressure, heart rate and MSNA were made during 10 min of rest in the morning (between 0900 and 1000 h) and afternoon (between 1400 and 1500 h). Spontaneous vascular sympathetic BRS was quantified by plotting MSNA burst incidence against diastolic pressure (vascular sympathetic BRSinc), and by plotting total MSNA against diastolic pressure (vascular sympathetic BRStotal). Significant vascular sympathetic BRSinc and vascular sympathetic BRStotal slopes were obtained for 10 participants at both times of day. There was no significant difference in vascular sympathetic BRSinc between morning (-2.2 ± 0.6% bursts/mmHg) and afternoon (-2.5 ± 0.2% bursts/mmHg; P = 0.68) sessions. Similarly, vascular sympathetic BRStotal did not differ significantly between the morning (-3.0±0.5 AU/beat/mmHg) and afternoon (-2.9 ± 0.4 AU/beat/mmHg; P = 0.89). It is concluded that in healthy, young individuals baroreflex modulation of MSNA at rest does not differ between the morning and afternoon. The results indicate that recording MSNA at different times of the day is a valid means of assessing sympathetic function.

No MeSH data available.