THE GOLGI ARCHITECTURE AND SOME EM OBSERVATIONS ON THE AVIAN NUCLEUS DORSOLATERALIS ANTERIOR THALAMI - CELL-TYPES, FIBERS AND SYNAPSES

In Golgi preparations of the chicken diencephalon, various types of ce lls and fibres were studied in the nucleus dorsolateralis anterior tha lami (DLA). Two groups of neurons were found: projection neurons with long axons and interneurons with locally branching axons. The projecti on neurons varied in the different areas of the DLA. In the medial par t the neurons are large cells with long, moderately spiny dendrites, a nd in the dorsal part there are small cells with short, wavy and moder ately spiny dendrites. These neurons differ completely from those foun d in the rostral and lateral parts, where the neurons have medium-size d cell bodies and curving, spiny dendrites, which branch tuft-like or with bifurcations. In the rostral and lateral parts of the DLA, thick afferent fibres were impregnated which developed their terminal branch ings among the neurons. Owing to their terminal branching pattern and the shape of the terminals they are thought to be optic fibres. The te rminal pattern of these fibres is similar to the optic terminals in th e LGB of the mammalian brain. The interneurons are GABA positive, as a ttested by immunostaining in light microscopic and EM specimens. There are rather few of them. The HRP-filled projection neurons and the sur rounding neuropil were investigated under EM: synaptic connections aro und the large terminals and/or around dendrites were identified, but t his synaptic arrangement does not display the characteristics of a syn aptic glomerulus.