Three-dimensional reconstruction and quantitative morphometric analysis of pyramidal and giant neurons of the rat...

Correct interpretation of functional data obtained from various cell types of the cochlear nucleus (CN), a structure involved in auditory information processing, necessitates reliable cell identification. Our aim was to perform a quantitative morphological characterization of giant and pyramidal cells of the rat CN and identify parameters that are suitable for their adequate classification. Neurons were labeled with biocytin, visualized with a fluorescent marker, and three-dimensionally reconstructed from confocal images. The size and shape of the soma and dendritic tree of each neuron were characterized by 17 morphometric parameters. The variables were subjected to multivariate statistical analysis to determine their importance while discriminating between giant and pyramidal cells. Our results provide a new battery of morphometric data, which could not be obtained earlier, improve the chances of correct cell identification, make modeling experiments easier and more reliable, and help us to understand both the functions of individual CN neurons and the network properties of this nucleus. In addition, we demonstrate that even partial labeling and/or incomplete reconstruction of neurons may be enough for their correct identification if selected parameters describing the cell bodies and the proximal portions of the dendritic trees are utilized. We propose that our findings have specific relevance to studies which attempt cell identification after functional experiments resulting in incomplete labeling of the investigated neurons.