Evidence for monosynaptic projections from the nucleus retroambiguus to hindlimb motoneurons in the cat.
The nucleus retroambiguus (NRA) is a group of premotor neurons at the transition between brainstem and spinal cord. It projects to certain motoneuronal cell groups, among which is a distinct set of motoneurons in the lumbar enlargement innervating muscles including iliopsoas, adductor longus, and hamstrings. To find out whether these NRA-motoneuronal projections are monosynaptic, injections of wheat germ-agglutinin horseradish peroxidase (WGA-HRP) into the NRA were combined with injections of cholera toxin subunit b (CTb) into the hamstring muscles. Electron microscopical examination revealed that the NRA terminal profiles make monosynaptic contacts with dendrites of motoneurons innervating these muscles. The NRA terminal profiles formed asymmetrical synapses, and contained spherical and a few dense core vesicles. These findings provide evidence of monosynaptic NRA-hindlimb motoneuronal projections which are likely to be excitatory.
VanderHorst
V G
VG
Department of Anatomy, University of Groningen, EZ, The Netherlands. v.g.j.m.van.der.horst@med.rug.nl
de Weerd
H
H
Holstege
G
G
D000818:Animals; D002415:Cats / Q000502:physiology*; D002772:Cholera Toxin; D005260:Female; D006614:Hindlimb / Q000294:innervation*; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D015335:Molecular Probes; D009046:Motor Neurons / Q000502:physiology* / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000294:innervation; D010446:Peptide Fragments; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate
D015335:Molecular Probes; D010446:Peptide Fragments; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; C050310:cholera toxin, B subunit (50-64); D002772:Cholera Toxin