Axonal pathways and projection levels of anterior semicircular canal nerve-activated vestibulospinal neurons in cats.
Using collision tests of orthodromically and antidromically generated spikes, we studied the axonal pathways, axonal projection levels, and soma location of anterior semicircular canal (AC) nerve-activated vestibulospinal neurons in decerebrate cats. AC nerve-activated vestibulospinal neurons (n=74) were mainly located in the ventral portion of the lateral vestibular nuclei and the rostral portion of the descending vestibular nucleus, which is consistent with previous studies. Of these neurons, 15% projected through the ipsilateral (i-) lateral vestibulospinal tract (LVST), 74% projected through the medial vestibulospinal tract (MVST), and 11% projected through the contralateral (c-) LVST. The vast majority (78%) of AC nerve-activated vestibulospinal neurons were activated antidromically only from the cervical segment of the spinal cord; 15% of neurons were activated from the T1 segment and only one neuron was activated from the L3 segment. AC nerve-activated vestibulospinal neurons may primarily target the neck muscles and thus contribute to the vestibulocollic reflex. Most of the c-LVST neurons were also activated antidromically from the oculomotor nucleus, suggesting that they are closely related to the control of combined eye-head movements.
Kitajima
Naoharu
N
Department of Physiology, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan. medart@js6.so-net.ne.jp
Sugita-Kitajima
Akemi
A
Bai
Rishu
R
Sasaki
Mitsuyoshi
M
Sato
Hitoshi
H
Imagawa
Midori
M
Kawamoto
Eiichi
E
Suzuki
Mamoru
M
Uchino
Yoshio
Y
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001369:Axons / Q000502:physiology*; D002415:Cats; D004525:Efferent Pathways / Q000033:anatomy & histology / Q000502:physiology*; D004558:Electric Stimulation; D004594:Electrophysiology; D005071:Evoked Potentials / Q000502:physiology; D005133:Eye Movements / Q000502:physiology; D019416:Head Movements / Q000502:physiology; D009334:Neck Muscles / Q000502:physiology; D009431:Neural Conduction / Q000502:physiology; D004856:Postural Balance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology; D012665:Semicircular Canals / Q000033:anatomy & histology / Q000502:physiology*; D013116:Spinal Cord / Q000033:anatomy & histology / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology; D014725:Vestibular Nerve / Q000033:anatomy & histology / Q000502:physiology*; D014726:Vestibular Nuclei / Q000033:anatomy & histology / Q000502:physiology*