title: Oligosynaptic inhibition of group I afferents between the brachioradialis and flexor carpi radialis in humans.
abstract: Spinal reflex arcs mediated by low threshold afferents between the brachioradialis (BR) and flexor carpi radialis (FCR) were studied in eleven healthy human subjects using a post-stimulus time-histogram method. Electrical conditioning stimuli (ES) to the radial nerve branch innervating BR with the intensity below the motor threshold (MT) induced an early and significant trough (inhibition) in 32/85 FCR motor units (MUs) in 9/9 subjects. Such inhibition was never provoked by cutaneous stimulation. The central synaptic delay (CSD) of the inhibition was approximately 1.1ms longer than that of the homonymous FCR facilitation. ES to the median nerve branch innervating FCR with the intensity below MT induced an inhibition in 27/71 BR-MUs in 10/10 subjects. CSD of the inhibition was about 1.1ms longer than that of the homonymous BR facilitation. These findings suggest that inhibition between BR and FCR exists in humans. Group I afferents seem to mediate the inhibition through an oligo(di or tri)-synaptic path.
authors.affiliation: Department of Orthopaedic Surgery, Yamagata University School of Medicine, Yamagata, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Kobayashi
authors.affiliation: Department of Orthopaedic Surgery, Yamagata University School of Medicine, Yamagata, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hayashi
authors.affiliation: Yamagata City Hospital Saiseikan, Yamagata, Japan.
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Shinozaki
authors.affiliation: Department of Anatomy and Structural Science, Yamagata University School of Medicine, Yamagata, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nito
authors.affiliation: Department of Anatomy and Structural Science, Yamagata University School of Medicine, Yamagata, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Hashizume
authors.affiliation: Department of Judo Therapy, Teikyo University Faculty of Medical Technology, Utsunomiya, Japan.
authors.forename: Takuji
authors.initials: T
authors.lastname: Miyasaka
authors.affiliation: Graduate School of Health Sciences, Matsumoto University, Matsumoto, Japan.
authors.forename: Masaomi
authors.initials: M
authors.lastname: Shindo
authors.affiliation: Department of Anatomy and Structural Science, Yamagata University School of Medicine, Yamagata, Japan. Electronic address: anaitoh@med.id.yamagata-u.ac.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Naito
mesh_terms: D000328:Adult; D000344:Afferent Pathways / Q000502:physiology*; D004550:Elbow / Q000294:innervation / Q000502:physiology; D004558:Electric Stimulation; D006801:Humans; D008475:Median Nerve / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology*; D009068:Movement; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D009433:Neural Inhibition; D011826:Radial Nerve / Q000502:physiology; D013569:Synapses / Q000502:physiology*; D014953:Wrist / Q000294:innervation / Q000502:physiology; D055815:Young Adult
keywords: Brachioradialis; Flexor carpi radialis; Group I afferents; Humans; Oligosynaptic inhibition; Post-stimulus time histogram