The activity of a single muscle sympathetic vasoconstrictor nerve unit is affected by physiological stress in humans.
Recording of neural firing from single-unit muscle sympathetic nerve activity (MSNA) is a new strategy offering information about the frequency of pure sympathetic firing. However, it is uncertain whether and when single-unit MSNA would be more useful than multiunit MSNA for analysis of various physiological stresses in humans. In 15 healthy subjects, we measured single-unit and multiunit MSNA before and during handgrip exercise at 30% of maximum voluntary contraction for 3 min and during the Valsalva maneuver at 40 mmHg expiratory pressure for 15 s. Shapes of individual single-unit MSNA were proved to be consistent and suitable for further evaluation. Single-unit and multiunit MSNA exhibited similar responses during handgrip exercise. However, acceleration of neural firing determined from single-unit MSNA became steeper than multiunit MSNA during the Valsalva maneuver. During the Valsalva maneuver, unlike handgrip exercise, the distribution of multiunit burst between 0, 1, 2, 3, and 4 spikes was significantly shifted toward multiple spikes within a given burst (P < 0.05). These results indicated that evaluation of single-unit MSNA could provide more detailed and accurate information concerning the role and responses of neuronal discharges induced by various physiological stresses in humans, especially amid intense sympathetic activity.
Murai
Hisayoshi
H
Dept. of Internal Medicine, Graduate School of Medical Science, Kanazawa Univ., 13-1 Takara-machi, Kanazawa 920-8641, Japan. murai@medf.m.kanazawa-u.ac.jp
Takata
Shigeo
S
Maruyama
Michiro
M
Nakano
Manabu
M
Kobayashi
Daisuke
D
Otowa
Kan-ichi
K
Takamura
Masayuki
M
Yuasa
Toyoshi
T
Sakagami
Satoru
S
Kaneko
Shuichi
S
D000200:Action Potentials; D000328:Adult; D000368:Aged; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000294:innervation*; D013564:Sympathetic Nervous System / Q000502:physiology*; D013997:Time Factors; D014636:Valsalva Maneuver / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology*