Morphology of single vestibulospinal collaterals in the upper cervical spinal cord of the cat: III collaterals originating from axons in the ventral funiculus ipsilateral to their cells of origin.
Some vestibulospinal pathways are composed of a homogeneous collection of axons with similar intraspinal collaterals. Other pathways contain axons whose collaterals vary in terms of shape, distribution, and complexity. The purpose of the present study was to extend the study of homogeneity versus heterogeneity of vestibulospinal axons to vestibulospinal axons that travel in the ventral funiculus ipsilateral to their cells of origin. Collaterals of these axons were stained following extracellular injections of Phaseolus vulgaris-leucoagglutinin in rostral parts of the medial and descending vestibular nuclei. All collaterals found in C2 and C3 were reconstructed. Collaterals arising from small diameter (0.5 to 2.9 microns) axons usually consisted of a single main branch with short side branches. The termination zones of most of these collaterals formed a narrow path in lamina VIII, but the location of this pathway was highly variable. Collaterals arising from large-diameter (3.0-6.1 microns) axons were usually more complex and consisted of many branches with en passant and terminal boutons that were located in motoneuron nuclei as well as laminae VIII and VII. Despite a relationship between termination zone and the position of the parent axon in the ventral funiculus, the variability in collaterals from large-diameter axons precluded a simple classification scheme. These results demonstrate that diversity, instead of homogeneity, is a characteristic feature of vestibulospinal axons that originate from the medial and descending vestibular nuclei and travel in the ipsilateral ventral funiculus. This pathway is therefore composed of multiple anatomical subunits that, as individuals, may selectively coordinate the activity of specific combinations of interneurons and motoneurons.
Rose
P K
PK
Department of Physiology, Queen's University, Kingston, Ontario, Canada.
Tourond
J A
JA
Donevan
A H
AH
D000818:Animals; D001369:Axons / Q000648:ultrastructure*; D002415:Cats / Q000502:physiology*; D048429:Cell Size; D002574:Cervical Vertebrae / Q000294:innervation; D006257:Head / Q000294:innervation / Q000502:physiology; D009333:Neck / Q000294:innervation / Q000502:physiology; D009434:Neural Pathways; D009474:Neurons / Q000166:cytology* / Q000648:ultrastructure; D010525:Peripheral Nerves / Q000166:cytology / Q000648:ultrastructure; D010835:Phytohemagglutinins; D017729:Presynaptic Terminals; D013116:Spinal Cord / Q000166:cytology* / Q000502:physiology; D014726:Vestibular Nuclei / Q000166:cytology* / Q000502:physiology
D010835:Phytohemagglutinins; C100156:leukoagglutinins, plants