The count of dopamine-containing neurons decreased by 77%, the area of the remaining cells shrank by 75%, and the neuroglia doubled 4 weeks after injection of toxin (6-hydroxydopamine) into the compact part of the substantia nigra of the right cerebral hemisphere of rats, while no changes in the substantia nigra of the left hemisphere were observed. Neurons of the caudate nucleus were virtually unchanged in comparison with the intact control, while the neuroglia was activated: its total volume in the right hemisphere increased by 33% (50% increase in astrocyte count and a 25% increase of the rest neuroglia), while in the left hemisphere only astrocyte count increased by 20%. Astrocyte nuclei in the caudate nuclei of both hemispheres were enlarged by 22-23%. Hence, unilateral destruction of the nigral dopamine-containing neurons stimulated the neuroglia (particularly astroglia) in the caudate nuclei, especially on the side of damage.