Effects of aging on the arterial baroreflex control of muscle sympathetic nerve activity in healthy subjects.

To determine how arterial baroreflex gains for sympathetic nerve activity are affected by aging, muscle sympathetic nerve activity (MSNA) from the tibial nerve was monitored by microneurography, and heart rate and blood pressure were recorded for the pressor or depressor responses to intravenous injections of phenylephrine or nitroglycerin in 22 healthy humans, aged 16 to 57 years old. Although the arterial baroreflex gain for the heart rate showed attenuation by aging, the gain for MSNA was not affected by aging. These data suggest a preservation of the arterial baroreflex control of sympathetic nerve activity despite attenuation of the arterial baroreflex control of the heart rate with aging in humans.