Direct synaptic linkage of ventrolateral nucleus of thalamus terminal with cat fast pyramidal tract neuron.

An electron microscopic study on the synaptic connections between neurons of ventrolateral nucleus of thalamus (VL) and pyramidal tract neurons (PTNs) in cat motor cortex was conducted by means of the anterograde degenerating procedure coupled with horseradish peroxidase (HRP) intracellular staining. Following VL lesions, a large majority of the degenerating terminals were found to terminate on dendritic spines and a few on the dendritic shaft. An asymmetric type synapse formed by a VL degenerating terminal and the dendritic shaft of a branch of apical dendrite of a labeled fast pyramidal tract neuron was demonstrated.