title: The activity of a single muscle sympathetic vasoconstrictor nerve unit is affected by physiological stress in humans.
abstract: 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.
authors.affiliation: 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
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Murai
authors.forename: Shigeo
authors.initials: S
authors.lastname: Takata
authors.forename: Michiro
authors.initials: M
authors.lastname: Maruyama
authors.forename: Manabu
authors.initials: M
authors.lastname: Nakano
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kobayashi
authors.forename: Kan-ichi
authors.initials: K
authors.lastname: Otowa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Takamura
authors.forename: Toyoshi
authors.initials: T
authors.lastname: Yuasa
authors.forename: Satoru
authors.initials: S
authors.lastname: Sakagami
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kaneko
mesh_terms: 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*