Types of neurons of the subthalamic nucleus and zona incerta in the guinea pig--Nissl and Golgi study.

The studies were carried out on the subthalamus of adult guinea pigs. Golgi impregnation, Nissl and Klüver-Barrera methods were used for the study. In Nissl stained sections the subthalamic neuronal population consists of multipolar, fusiform, oval and pear-shaped perikarya. In two studied areas: nucleus subthalamicus (STN) and zona incerta (ZI) three types of neurons were distinguished. Type I, multipolar neurons with quadrangular, triangular or oval perikarya. They have 3-6 primary dendrites which run slightly wavy and spread out in all directions. Type II, bipolar neurons with fusiform or semilunar perikarya, they have two primary dendrites. Type III, pear-shaped neurons with 1-2 dendritic trunks arising from one pole of the neuron. In all types of neurons axon emerges from the perikaryon or initial segment of a dendritic trunk and can be followed at a maximum distance of about 50 microns.