TY - JOUR
T1 - Baroreflex increases correlation and coherence of muscle sympathetic nerve activity (SNA) with renal and cardiac SNAs
AU - Kamiya, Atsunori
AU - Kawada, Toru
AU - Mizuno, Masaki
AU - Miyamoto, Tadayoshi
AU - Uemura, Kazunori
AU - Seki, Kenjiro
AU - Shimizu, Shuji
AU - Sugimachi, Masaru
PY - 2006/10
Y1 - 2006/10
N2 - Despite accumulating data of muscle sympathetic nerve activity (SNA) measured by human microneurography, whether neural discharges of muscle SNA correlates and coheres with those of other SNAs controlling visceral organs remains unclear. Further, how the baroreflex control of SNA affects the relations between these SNAs remains unknown. In urethane and α-chloralose anesthetized, vagotomized, and aortic-denervated rabbits, we recorded muscle SNA from the tibial nerve using microneurography and simultaneously recorded renal and cardiac SNAs. After isolating the carotid sinuses, we produced a baroreflex closed-loop condition by matching the isolated intracarotid sinus pressure (CSP) with systemic arterial pressure (CLOSE). We also fixed CSP at operating pressure (FIX) or altered CSP widely (WIDE: operating pressure ± 40 mmHg). Under these conditions, we calculated time-domain and frequency-domain measures of the correlation between muscle SNA and renal or cardiac SNAs. At CLOSE, muscle SNA resampled at 1 Hz correlated with both renal (r2 = 0.71 ± 0.04, delay = 0.10 ± 0.004 s) and cardiac SNAs (r2 = 0.58 ± 0.03, delay = 0.13 ± 0.004 s) at optimal delays. Moreover,muscle SNA at CLOSE strongly cohered with renal and cardiac SNAs(coherence >0.8) at the autospectral peak frequencies, and weakly (0.4-0.5) at the remaining frequencies. Increasing the magnitude of CSP change from FIX to CLOSE and further to WIDE resulted in corresponding increases in correlation and coherence functions at nonpeak frequencies, and the coherence functions at peak frequencies remained high (>0.8). In conclusion, muscle SNA correlates and coheres approximately with renal and cardiac SNAs under closed-loop baroreflex conditions. The arterial baroreflex is capable of potently homogenizing neural discharges of these SNAs by modulating SNA at the nonpeak frequencies of SNA autospectra.
AB - Despite accumulating data of muscle sympathetic nerve activity (SNA) measured by human microneurography, whether neural discharges of muscle SNA correlates and coheres with those of other SNAs controlling visceral organs remains unclear. Further, how the baroreflex control of SNA affects the relations between these SNAs remains unknown. In urethane and α-chloralose anesthetized, vagotomized, and aortic-denervated rabbits, we recorded muscle SNA from the tibial nerve using microneurography and simultaneously recorded renal and cardiac SNAs. After isolating the carotid sinuses, we produced a baroreflex closed-loop condition by matching the isolated intracarotid sinus pressure (CSP) with systemic arterial pressure (CLOSE). We also fixed CSP at operating pressure (FIX) or altered CSP widely (WIDE: operating pressure ± 40 mmHg). Under these conditions, we calculated time-domain and frequency-domain measures of the correlation between muscle SNA and renal or cardiac SNAs. At CLOSE, muscle SNA resampled at 1 Hz correlated with both renal (r2 = 0.71 ± 0.04, delay = 0.10 ± 0.004 s) and cardiac SNAs (r2 = 0.58 ± 0.03, delay = 0.13 ± 0.004 s) at optimal delays. Moreover,muscle SNA at CLOSE strongly cohered with renal and cardiac SNAs(coherence >0.8) at the autospectral peak frequencies, and weakly (0.4-0.5) at the remaining frequencies. Increasing the magnitude of CSP change from FIX to CLOSE and further to WIDE resulted in corresponding increases in correlation and coherence functions at nonpeak frequencies, and the coherence functions at peak frequencies remained high (>0.8). In conclusion, muscle SNA correlates and coheres approximately with renal and cardiac SNAs under closed-loop baroreflex conditions. The arterial baroreflex is capable of potently homogenizing neural discharges of these SNAs by modulating SNA at the nonpeak frequencies of SNA autospectra.
KW - Baroreflex
KW - Muscle
KW - Sympathetic nerve activity
UR - http://www.scopus.com/inward/record.url?scp=34347248070&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34347248070&partnerID=8YFLogxK
U2 - 10.2170/physiolsci.RP009006
DO - 10.2170/physiolsci.RP009006
M3 - Article
C2 - 16956421
AN - SCOPUS:34347248070
SN - 1880-6546
VL - 56
SP - 325
EP - 333
JO - Journal of Physiological Sciences
JF - Journal of Physiological Sciences
IS - 5
ER -