NEUN EXPRESSION IN SPINAL NEURONS ORGANIZING PROJECTIONS TO THE CEREBELLUM

We analyzed the peculiarities of the NeuN immunostaining of the cat spinal cord neurons located in four structures organizing projections to the cerebellum: the Clarke’s nucleus and border cells – in the L4 segment, the central cervical nucleus – in the C3 segment, and the Stilling’s nucleus – in the S2 segment. Morphometric and densitometric studies were carried out. It was shown that all neurons of interest have a striking feature: an extremely weak level of the cytoplasmic NeuN-staining, while maintaining a high level of the nuclear NeuN-staining. The soma size of neurons of interest was 1000–1850 mkm², which is comparable to the size of another type of large neurons at slices – motoneurons (1140–1660 mkm²). Thus, we used a motoneuronal population of the corresponding segments to compare the values of optical density. The relative optical density of neurons of interest was several times lower than for the motoneurons (0.060 ± 0.030 vs 0.330 ± 0.127). There were no significant differences in optical density between different structures of interest. Given the morphological uniqueness and similarity of these four cell populations, we believe that the feature of NeuN protein expression can be used as a simple tool for the visualization of cells organizing projections to the cerebellum. It can be valuable both for targeted morphological examination and for histological control after a physiological experiment.