TY - JOUR
T1 - Hysteresis in the sympathetic baroreflex
T2 - Role of baseline nerve activity
AU - Hart, Emma C.
AU - Wallin, B. Gunnar
AU - Curry, Timothy B.
AU - Joyner, Michael J.
AU - Karlsson, Tomas
AU - Charkoudian, Nisha
PY - 2011/7
Y1 - 2011/7
N2 - Sympathetic baroreflex sensitivity (BRS) is greater during decreasing compared to increasing diastolic blood pressure (DBP) in young men and women. In older men and women there is no difference in sympathetic BRS to increasing and decreasing DBP. We investigated whether the sensitivity of the central nervous system to increasing and decreasing DBP is dependent upon baseline muscle sympathetic nerve activity (MSNA). We hypothesised that the difference in sympathetic BRS between falling and rising segments of DBP would be positively related to baseline MSNA in 30 young men, 21 young women, 14 older men and 14 postmenopausal women. MSNA was measured using peroneal microneurography and BRS was measured using the spontaneous baroreflex threshold technique. On average, sympathetic BRS was greater during decreasing compared to increasing DBP in young men (P < 0.05) and women (P < 0.05). In older men and women, mean sympathetic BRS was similar in response to increasing and decreasing DBP. The difference (delta) between the falling and rising BRS correlated with baseline MSNA in young (r= 0.58, P < 0.05) and older men (r= 0.66, P < 0.05) and postmenopausal women (r= 0.74, P < 0.05). Thus, all men, and older women, with higher BRS to falling DBP had lower baseline MSNA. This relationship was not observed in young women (r= 0.14, P > 0.05). In summary, baseline MSNA plays a role in determining sympathetic BRS to falling and rising DBP in young and older men and postmenopausal women, but not in young women. This relationship is consistent with a decreased potential for sympathoexcitation in people with higher resting MSNA. Furthermore, the lack of relationship in young women suggests important contributions of sex hormones to differential responses of MSNA to falling and rising pressures.
AB - Sympathetic baroreflex sensitivity (BRS) is greater during decreasing compared to increasing diastolic blood pressure (DBP) in young men and women. In older men and women there is no difference in sympathetic BRS to increasing and decreasing DBP. We investigated whether the sensitivity of the central nervous system to increasing and decreasing DBP is dependent upon baseline muscle sympathetic nerve activity (MSNA). We hypothesised that the difference in sympathetic BRS between falling and rising segments of DBP would be positively related to baseline MSNA in 30 young men, 21 young women, 14 older men and 14 postmenopausal women. MSNA was measured using peroneal microneurography and BRS was measured using the spontaneous baroreflex threshold technique. On average, sympathetic BRS was greater during decreasing compared to increasing DBP in young men (P < 0.05) and women (P < 0.05). In older men and women, mean sympathetic BRS was similar in response to increasing and decreasing DBP. The difference (delta) between the falling and rising BRS correlated with baseline MSNA in young (r= 0.58, P < 0.05) and older men (r= 0.66, P < 0.05) and postmenopausal women (r= 0.74, P < 0.05). Thus, all men, and older women, with higher BRS to falling DBP had lower baseline MSNA. This relationship was not observed in young women (r= 0.14, P > 0.05). In summary, baseline MSNA plays a role in determining sympathetic BRS to falling and rising DBP in young and older men and postmenopausal women, but not in young women. This relationship is consistent with a decreased potential for sympathoexcitation in people with higher resting MSNA. Furthermore, the lack of relationship in young women suggests important contributions of sex hormones to differential responses of MSNA to falling and rising pressures.
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U2 - 10.1113/jphysiol.2011.208538
DO - 10.1113/jphysiol.2011.208538
M3 - Article
C2 - 21540345
AN - SCOPUS:79959726451
SN - 0022-3751
VL - 589
SP - 3395
EP - 3404
JO - Journal of Physiology
JF - Journal of Physiology
IS - 13
ER -