Coherence between the sympathetic drives to relaxed and contracting muscles of different limbs of human subjects

B G Wallin, D Burke, S C Gandevia, B G Wallin, D Burke, S C Gandevia

Abstract

1. This study was undertaken to quantify the simultaneous sympathetic drives to muscles in the two legs of human subjects, and to elucidate the extent to which a common drive determines sympathetic outflow to different limbs at rest, during apnoea and during voluntary contractions. 2. Sympathetic efferent activity was recorded simultaneously from fascicles of both peroneal nerves, innervating the pretibial flexor muscles. At rest the similarity was quantified for a sample of records by manual measurement of equivalent bursts in the two recordings, and for all records by cross-correlation and power spectral analysis of the two recordings. During contractions, only the latter method was used. 3. At rest the correlation coefficient for the relationship between the burst amplitudes for the two recordings was 0.72 (S.D. 0.1). For the same sequences, the computed coherence between the two recordings was 85.6% (S.D. 6.7%) at the cardiac period. There was a statistically significant linear relationship between these two measures of similarity, and this was stronger when data from sequences recorded during apnoea were included in the analysis. At rest the mean difference in coherence between consecutive sequences with no intervening manoeuvre (apnoea, contraction, change in recording site) was 4.2% (S.D. 4.3%). In only two of forty-nine such instances was the difference in coherence > 10%. 4. Apnoea at end-expiration increased the amplitude and frequency of sympathetic bursts and increased the similarity between the two recordings. The correlation coefficients increased from a mean of 0.72 at rest to 0.89 during apnoea. Coherence increased from a mean of 82.1% at rest to 91.9% during apnoea. 5. On the right side, graded voluntary contractions were performed at 5, 10, 20 or 30% maximal force using the muscle innervated by the fascicle from which the recording was made. The coherence between the recordings made from the right and left legs decreased by > 10% at each contraction level. Pooling the data for all contractions, there was a significant decrease in power at the cardiac frequency in the sympathetic recording from the contracting leg. Contraction of a synergist or antagonist at 10% maximum produced negligible changes in coherence. 6. It is concluded that, at rest, homologous muscles of the lower limbs are subject to a common drive and that, during apnoea, this common drive can dominate the sympathetic outflow to the virtual exclusion of regional drives. During voluntary activity, the importance of this common drive is lessened, presumably because of regionally specific changes involving the contracting muscle.(ABSTRACT TRUNCATED AT 400 WORDS)

References

    1. Physiol Rev. 1979 Oct;59(4):919-57
    1. J Physiol. 1959 Oct;148:633-47
    1. J Physiol. 1989 Oct;417:437-46
    1. J Appl Physiol (1985). 1989 Jan;66(1):88-95
    1. Annu Rev Physiol. 1988;50:565-76
    1. Eur J Appl Physiol Occup Physiol. 1986;55(5):493-8
    1. Brain Res. 1972 Dec 24;48:394-6
    1. J Neurophysiol. 1981 Oct;46(4):788-96
    1. J Physiol. 1977 Nov;272(2):383-97
    1. Pflugers Arch. 1976 Feb 24;361(3):231-40
    1. Pain. 1992 Mar;48(3):371-5
    1. Circ Res. 1989 Dec;65(6):1710-7
    1. J Appl Physiol (1985). 1989 May;66(5):2472-8
    1. Am J Physiol. 1989 Jan;256(1 Pt 2):H105-10
    1. J Clin Invest. 1988 Oct;82(4):1301-5
    1. J Appl Physiol (1985). 1988 Jul;65(1):434-40
    1. Acta Physiol Scand. 1987 Dec;131(4):507-15
    1. Circ Res. 1985 Sep;57(3):461-9
    1. Acta Physiol Scand. 1972 Jan;84(1):82-94
    1. Am J Physiol. 1990 Sep;259(3 Pt 2):R549-60

Source: PubMed

Подписаться