DEGENERATIVE CHANGES IN ENTOPEDUNCULAR NUCLEUS FOLLOWING LESIONS OF CAUDATE NUCLEUS - AN ELECTRON MICROSCOPIC STUDY

Degenative changes in the entopeduncular nucleus which result from discrete lesions of the head of the caudate were examined by electron microscopy. By the third postoperative day, numerous dense and shrunken boutons make contact with dendritic profiles in the neuropil. Few degenerated axosomatic synaptic contacts are found. Astrocytic processes isolate and presumably phagocytose degenerated boutons during the first week. Later degeneration involves mainly thin myelinated and unmyelinated axons. This is characterized by increased density and granularity of the axoplasm and myelin disruption. Contralateral entopeduncular elements remain intact following unilateral destruction of the caudate nucleus. I suggest that the inhibitory influences of the caudate nucleus on entopeduncular elements are mediated by thin, finely-myelinated and unmyelinated projections which terminate mainly on dendritic profiles in the entopeduncular nucleus. © 1969.