The orientation of interneurones in the dorsal lateral geniculate nucleus of the rat: a quantitative study

The orientation of the processes of 60 Golgi-impregnated interneurones in the rat dorsal lateral geniculate nucleus (dLGN) was studied quantitatively. A statistical analysis of the orientation of 238 interneuronal processes (dendrites and axon-like processes) showed that they were aligned preferentially along a dorsoventral axis through the dLGN and were predominantly oriented parallel with the outlying optic tract. Computer reconstructions of two of the Golgi-impregnated dLGN interneurones and their subsequent 3-dimensional computer rotations showed that their processes ramified in long columnar-shaped territories aligned dorsoventrally. There was little extension of these processes along the rostrocaudal axis of the nucleus. The data of this investigation provide evidence that the processes of 'inhibitory' interneurones in the rat dLGN are predominantly aligned along the dorsoventral axis, parallel with both the optic tract and with the afferent and efferent fibre tracts coursing through the nucleus.