Experimental demonstration of intrinsic synapses in cat's caudate nucleus.

The electron microscopic findings in cats after complete interruption of all afferents to caudate nucleus as well as of its efferent fibers, suggest that the type IX synapses, the presynaptic component of which contains large empty round vesicles, are formed by the axon terminals of intrinsic neurons. They make synaptic contacts with the dendrites or soma of the large efferent striatal neurons. All other types of synapses, except many of the pleomorphic type V which are probably formed by axon collaterals of the efferent neurons, degenerated in these experiments.