The neural interaction between the arterial baroreflex and muscle metaboreflex is preserved in older men

New Findings: • What is the central question of this study? Sympathetic baroreflex sensitivity increases during isolated skeletal muscle metaboreflex activation in young adults, but whether this neural interaction between the arterial baroreflex and the muscle metaboreflex is altered in healthy ageing remains unclear. • What is the main finding and its importance? The collective findings indicate that the neural interaction between the arterial baroreflex and the skeletal muscle metaboreflex in the regulation of muscle sympathetic nerve activity is preserved in healthy ageing. This has potential implications for the regulation of blood pressure during exercise in older adults. Sympathetic baroreflex sensitivity is increased during selective activation of the skeletal muscle metaboreflex with postexercise ischaemia (PEI) in young adults. However, to date, there are no data demonstrating this neural interaction between the arterial baroreflex and the muscle metaboreflex in healthy older adults. Therefore, the goal of the present study was to examine the influence of healthy ageing on the metabolic component of the exercise pressor reflex and its interaction with the arterial baroreflex in the control of sympathetic outflow. Postexercise ischaemia following static hand grip performed at 30% maximal voluntary contraction was used to isolate muscle metaboreflex activation in young [n= 10; 24 ± 1 years old; resting blood pressure (BP) 116 ± 3/64 ± 3 mmHg] and older men (n= 9; 59 ± 2 years old; resting BP 120 ± 2/77 ± 2 mmHg). Arterial BP (Finometer) and muscle sympathetic nerve activity (MSNA) were measured continuously. Weighted linear regression analysis between MSNA and diastolic BP was used to estimate arterial baroreflex MSNA gain. There were no age-related differences in the increase in mean BP (young, Δ14 ± 3 mmHg versus older, Δ15 ± 2 mmHg; P > 0.05) or MSNA burst frequency (young, Δ11 ± 2 bursts min^-1versus older, Δ9 ± 1 bursts min^-1; P > 0.05) during PEI. Likewise, the gain of arterial baroreflex control of total MSNA increased to a similar extent in both groups during PEI (young, -4.2 ± 0.9 baseline versus-6.3 ± 1.1 PEI a.u. beat^-1 mmHg^-1; and older, -3.7 ± 1.1 baseline versus-6.7 ± 1.4 PEI a.u. beat^-1 mmHg^-1; P < 0.05 for both). Collectively, these findings indicate that the neural interaction between the arterial baroreflex and the skeletal muscle metaboreflex in the regulation of MSNA is preserved in healthy ageing.