title: Enhanced corticospinal excitability with physiologically heightened sympathetic nerve activity.
abstract: Corticospinal excitability is modulated differently with norepinephrine and dopamine agonists, although both monoamines are released with heightened sympathetic nerve activity. The purpose of this study was to investigate the influence of physiological heightening of sympathetic nerve activity on corticospinal excitability in healthy humans. Subjects were divided into control and experimental groups. In each participant, motor-evoked potentials (MEPs) were measured from the resting first dorsal interosseous muscle of the right hand with transcranial magnetic stimulation (TMS) in two trials separated by 1 h. In the experimental group, sympathetic nerve activity was physiologically heightened during the second trial by applying lower body negative pressure (LBNP). In the control group, sympathetic nerve activity was not altered between the two trials. MEP peak-to-peak amplitude increased from trial 1 to trial 2 in the experimental group only. This increase was evident at a TMS intensity of 130% resting motor threshold and higher. It was concluded that physiological heightening of sympathetic nerve activity with LBNP enhances corticospinal excitability.
authors.affiliation: School of Applied Physiology, The Georgia Institute of Technology, Atlanta, Georgia 30332-0356, USA.
authors.forename: Vasiliy E
authors.initials: VE
authors.lastname: Buharin
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Butler
authors.forename: Justin K
authors.initials: JK
authors.lastname: Rajendra
authors.forename: Minoru
authors.initials: M
authors.lastname: Shinohara
mesh_terms: D000704:Analysis of Variance; D019054:Evoked Potentials, Motor; D005260:Female; D005845:Georgia; D006439:Hemodynamics; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation*; D011712:Pyramidal Tracts / Q000502:physiology*; D012044:Regression Analysis; D013564:Sympathetic Nervous System / Q000502:physiology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult