An ultrastructural study of the synaptic contacts of alpha-motoneurone axon collaterals. I. Contacts in lamina IX and with identified alpha-motoneurone dendrites in lamina VII.
Horseradish peroxidase (HRP) was injected intracellularly in triceps surae alpha-motoneurones. The axons and axon collaterals of these neurones were traced light and electron microscopically. Synaptic boutons of collaterals, in Rexed's lamina IX or in synaptic contact with HRP-stained motoneurone dendrites in lamina VII, were studied ultrastructurally. The boutons exhibited spherical synaptic vesicles and made synaptic contacts of two different types with HRP-stained alpha-motoneurone dendrites in lamina IX and VII, dendrites and cell bodies of large neurones in lamina IX, dendrites of unknown origin in lamina IX and with one cell body of a medium size neurone in lamina IX. The observations are discussed in relation to earlier qualitative and quantitative studies on the synaptology of cat spinal alpha-motoneurones.
D000818:Animals; D001369:Axons / Q000648:ultrastructure*; D002415:Cats; D002450:Cell Communication; D003712:Dendrites / Q000648:ultrastructure; D006735:Horseradish Peroxidase; D007395:Interneurons / Q000648:ultrastructure; D008854:Microscopy, Electron; D009046:Motor Neurons / Q000648:ultrastructure*; D009132:Muscles / Q000294:innervation; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure; D013116:Spinal Cord / Q000033:anatomy & histology*; D013569:Synapses / Q000648:ultrastructure*; D013572:Synaptic Vesicles / Q000648:ultrastructure
D006735:Horseradish Peroxidase