[Morphometric analysis of the dorsal lateral geniculate body of the laboratory mouse and microphthalmic variants]

The dorsal lateral geniculate nucleus (dLGN) of the mouse (strain 944 with microphthalmus syndrome, P. Hertwig 1942) has been morphometrically investigated. The eyes of the gray littermates develop normally (control animals) while the white littermates show the microphthalmus syndrome (microphthalmic animals). Four male twentyone day old animals were examined. Following perfusion with formaldehyde (diluted 1:4 with H2O) Nissl stained frontal sections were used for classification of neurons. we differentiate between projection neurons (PN) (geniculo-cortical relay neurons) and interneurons (IN). We succeeded in identifying these two cell types using deimpregnated Golgi preparations (Fairén et al. 1977), which were counterstained with methylene blue (0.1%). The neuronal packing density and the ratio PN:IN were conventionally determined using 20 micron thick sections from both control and microphthalmic animals. In both cases this ratio was 12:1 (= 8% IN). Measuring fields distributed in a meander-like manner were selected for estimating the neuronal density. Measuring fields giving equal values were connected. The results show that we can distinguish between 3 regions of dLGN: lateral, medial and caudal. They differ with regard to neuronal packing density, size and structure of the PN. Using 3 micron thick Nissl stained sections from both control and microphthalmic animals the size and structure of PN were automatically determined using the picture processing device "MORPHOQUANT" VEB Carl Zeiss JENA). The distribution pattern of IN is apparently uniform. The microphthalmus syndrome produces a diminished number of pathologically changed retinal fibers. The morphometrically registered findings show that within the dLGN, of the microphthalmus mouse the neuronal packing density increased (diminution of neuropil), the size of PN decreased and their structural density increased (transneuronal dystrophy). Compared with the other parts, the medial part of the dLGN is minimally altered.