The neurons and their postnatal development in the ventral lateral geniculate nucleus of the rat

The morphology and distribution of neurons in the ventral lateral geniculate nucleus (vLGN) of adult rats, and the postnatal growth and differentiation of these neurons were studied in Golgi-Cox preparations. In the adult, two main cell classes were recognized: class A cells and class B cells. The former are assumed to be projection neurons. The latter closely resemble the class B cells of the dorsal lateral geniculate nucleus and are interpreted as presynaptic dendrite-bearing interneurons. Class A cells predominated and three subtypes were tentatively identified: small--medium size multipolar neurons, with short, branched spiny dendrites (most numerous in dorsolateral vLGN); medium--large fusiform cells with one or two stem dendrites at each pole (most numerous in medial vLGN); large multipolar neurons with long, sparsely branched dendrites (most numerous in ventral vLGN). Class A and B cells were distinguishable at birth and showed parallel cell body size increases up to postnatal day 24. The dendrites of both classes of cell also reached the adult stage of differentiation at about day 24 but the differentiation of class B cell dendrites lags slightly behind that of class A cell dendrites.