Microneurographic analysis on age-related changes in sympathetic nerve

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In order to clarify the effect of aging on sympathetic nerve activity in humans, we recorded muscle sympathetic nerve activity (MSNA) and skin sympathetic nerve activity (SSNA) by applying microneurography from subjects of various age-groups, and analyzed the age-related changes of in MSNA and SSNA under different environmental conditions. We also anlyzed the effect of aging on gender difference of resting activity and responsiveness to orthostasis of MSNA.1. Effect of aging on resting activity and responsiveness to orthostasis of MSNA.Subjects were 41 Healthy men. The resting activity increased with advancing age, and a linear correlation was found between age and resting activity. The responsiveness to orthostasis decreased with advancing age, and an inverse correlation was observed between age and responsiveness. 2. Effect of aging on gender difference in resting activity and responsiveness to orthostasis of MSAN.Subjects were 40 men and 25 women(age : 21-25 years)for young group, a … More nd 8 men and 7 women(age : 65-78 years)for elderly. The gender difference in resting activity and responsiveness to orthostasis of MSNA observed in young groups disappeared in the elderly. 3. Effect of aging on MSNA suppression induced by water immersion. Subjects were 16 men aged 19 to 67 years. Suppression rate of MSNA induced by head-out water immersion was attenuated with advancing age. 4. MSNA response during sleep apnea in the elderly. Subjects were three elderly men. A remarked enhancement of MSNA was observed during sleep apnea accompanied with an elevation of systemic blood pressure. 5. Effect of aging on SSNA and effector response. The effector response to SSNA including sweating and vasoconstriction was reduced in 70-year-old man as compared with young subjects.MSNA plays an important role in regulation of blood pressure. The increased MSNA with advancing age may be associated with a rise in systemic arterial blood pressure in the elderly. The decreased responsiveness of MSNA to positional change or head-out water immersion with advancing age indicates a reduced neural regulation no compensatory mechanism against body fluid shift induced by these loads. SSNAplays an essential role in thermoregulation. The attenuated effector responses to SSNA suggest a reduced function of effector organs, e.g. sweet glands or presphincter of skin vessels and/or receptors in the effector organs. Less