A light microscope study of the cytology and organization of neurons in the simple mammalian nucleus lateralis: columns and swirls.

Abstract

The lateral nucleus in the rat is investigated with several variants of the rapid Golgi method and in Nissl preparations. The neurons are divided into two classes according to their size and the disposition of their axons. The smaller neurons or interneurons have cross sectional areas less than 180 μm2, and short axons that ramify in the vicinity of the cell bodies. Small neurons have also been seen on rare occasions with longer axons that may leave the nucleus. The larger cells (areas greater than 180 μm2) have long axons that leave the nucleus and emit short, beaded, recurrent collaterals. In the rostral and caudal poles of the lateral nucleus, the large projection neurons as well as the small neurons are multipolar with swirled dendritic arborizations. Neurons in the dorsal rim and ventral third of the nucleus have similar dispositions of their dendrites. In the central columnar zone, the projection neurons have dendrites that are arranged in columns directed diagonally across the body of the nucleus in the 4 to 10 o'clock direction in the right lateral nucleus and the 8 to 2 o'clock direction in the left nucleus. A collection of small neurons is generally found in the medial hilus zone. In each part of the lateral nucleus, the neurons are arranged in characteristic ways.