Fine structure of spinocervical tract neurones and the synaptic boutons in contact with them.

Acute electrophysiological experiments were performed on 7 adult cats and spinocervical tract (SCT) neurones were identified and injected intracellularly with horseradish peroxidase (HRP). At the conclusion of experiments regions of spinal cord were prepared for light and electron microscopy. SCT neurones were studied in thick sections and areas of interest were prepared from the same material for electron microscopy. The general ultrastructural features of SCT neurones were categorised and particular attention was paid to axon terminals contacting SCT dendrites. These terminals were found to be of two varieties: those containing clear circular vesicles and an occasional granular vesicle (63% of total) and those containing elongated agranular vesicles (37% of total).