The postnatal development of neurons in the dorsal lateral geniculate nucleus of the rat: A Golgi study

Abstract

The postnatal differentiation of neurons in the dorsal lateral geniculate nucleus of the albino rat was studied using the Golgi-Cox technique. At least four animals were used at postnatal ages 12 hours, 2, 4, 6, 8, 10, 11, 12, 13, 14, 15, 16, 18, 20, 24, 28, 35 days and adult. Presumptive thalamo-cortical projection cells (Class A cells of Grossman et al., '73) and non-projection, intrinsic neurons (Class B cells) are distinguishable at 12 hours after birth. At this stage both types of neuron are immature, with prominent growth cones at their dendritic extremities. Dendritic growth and differentiation appear to be complete by 18 days. Relay cells display two apparent "growth spurts" characterized by noticeable enlargement of the perikaryon and a marked increase in dendritic length and complexity. One occurs between days 4 and 6 and coincides with a period of enhanced synaptogenesis and gliogenesis: the second occurs between days 14 and 15, around the time of eye opening (day 14) and may be related to a further phase of increased synaptogenesis and gliogenesis (Karlsson, '67; Biesold et al., '76). Class B cells appear to "lag" behind class A cells in their initial postnatal differentiation, but also reach their mature condition by day 18.

Morphologically Distinct Classes of Relay Cells Exhibit Regional Preferences in the Dorsal Lateral Geniculate Nucleus of the Mouse

“…In contrast as shown in Figure 2 D, soma surface area, although somewhat variable, did not show any significant changes with age. Thus, similar to the observations made in the developing rat dLGN (Parnavelas et al, 1977), relay cells in mouse undergo a rapid growth spurt during early postnatal life. By P7, dendritic branching stabilized and profiles took on a highly stereotypic architecture.…”

“…1). Representative examples are shown in Figure 2 A. Relay cells had type I or class A morphology (Parnavelas et al, 1977) that consists of a thick unbranched axon, relatively large round somata, and multipolar dendritic arbors comprising six to seven primary dendrites. In fact, even cells at early postnatal ages had fairly large somata and complex dendritic trees with a distinct architecture.…”

“…Sections were initially visualized and photographed with an upright epifluorescence microscope (Nikon E6000) to select labeled cells that were suitable for confocal laserscanning microscopy. Relay neurons were readily distinguished from interneurons by the appearance of round somata, radially oriented dendritic trees, and axons that exited the dLGN (Parnavelas et al, 1977).…”

Two types of interneuron in the dorsal lateral geniculate nucleus of the rat: A combined NADPH diaphorase histochemical and GABA immunocytochemical study

“…The light microscopical features of diaphorase-reactive neurons in the rat dLGN (i.e., somatic size and shape, and the morphology and orientation of processes) were similar to the morphological characteristics of class B neurons described in Golgi impregnation studies of the rat dLGN (Grossman et al, 1973;Brauer and Schober, 1973;Kreibel, 1975;Parnavelas et al, 1977;Webster and Rowe, 1984;Gabbott et al, 1986a). We have therefore categorised the diaphorase-reactive neurons as belonging to this class of dLGN neuron.…”

P-Cells and I-Cells in in Vitro Slices of the Lateral Geniculate Nucleus of the Cat

“…According to Daniels, Pettigrew and Norman (1978) surround inhibition was not detected in the LGN neurons of neonatal kittens, but in kittens older than 3 weeks. Histological studies have shown that intrinsic neurons are already distinguishable in the LGN of newborn kittens and rats (Tombol 1966/7;Morest 1969;Parnavelas et al 1977) and that the density of synapses in the LGN observed in newborn kit tens is about 25% of the adult value (Cragg 1975). These physiological and histological data may well be interpreted as showing that intrageniculate inhibition is already functioning to some extent at birth although it is not organized in such a fashion as to support surround inhibition which is detected only by light stimula tion.…”