Golgi studies of the neurons in layer II of the dorsal horn of the medulla (trigeminal nucleus caudalis)

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Abstract
The translucent band which lies just beneath the spinal V tract at the lower end of the spinal trigeminal nucleus (nucleus caudalis) can be divided into three layers. These three layers are distinguished by textural differences in their neuropil and by the morphology and laminar distribution of the axons and dendrites of their neurons. Layer II contains four different kinds of interneurons. Stalked cells are named after their short, stalk-like branches. Their cell bodies are found in greatest numbers in the outer half of layer II. Their coneshaped dendritic arbors extend medially across layers II and III and sometimes extend into layer IV. Their axons form extensive, canopy-like arborizations in layer I. Stalked cells are considered to be excitatory interneurons receiving input on their dendritic spines from primary axonal endings in the layers II and III glamour and transferring it to the dendrites of the layer I projection neurons. Layer II contains three kinds of Golgi type II interneurons, i.e., neurons whose axons branch repeatedly within the confines of their dendrite arbors. Islet cells, similar to those found in layer III (Gobble, 1975a), are found in small clusters in layer II. Their dendrites and axons are largely confined in layer II. The dendrites of the arboreal cell burst, in tree-like fashion, into highly focal dendrite arbors confined largely in layer II while the extensive rostral and caudal dendrite arbors of the II-III border cell lie largely in layers II and III with a few branches extending into layer I. The axons of both of these interneurons arborist in layers II and III with a few collaterals extending into layer I. Islet cells, arboreal cells and II-III border cells are considered to be inhibitory interneurons. They are strategically situated to interrupt transmission between primary axonal endings in layers II and III and the layer I projection neurons by altering the output of the stalked cells.