Postnatal Changes in Glia/Neuron Index with a Comparison of Methods of Cell Enumeration in the White Rat

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This chapter presents a study with three different methods of cell enumeration, with particular emphasis on obtaining values for neuroglial packing density and the neuroglia/neuron index at certain post-natal stages of development. The glia/neuron index in rat cerebral cortex increased throughout the periods studied as determined in both fresh and fixed-stained tissues. The index in fixed tissues increased beyond the period at which brain weight became stable (200 days). The chapter compares the results obtained from these methods. Total cell counts were in good agreement in all 3 methods employed. Relating the findings to those of Nurnberger and Gordon, the proportion of non-neural cells appeared to be about equal as determined in both fresh and fixed-stained tissues. Differential counts of neuroglia and neurons in the studies, however, revealed a higher glia/neuron index in fresh tissue than in fixed-stained preparations. As the differential counts of neuroglia and neurons made in fixed-stained tissues are based on more definite morphological criteria than in fresh tissue, the fixed tissue differential counts are considered more accurate. For total cell counts whether in whole brain or specific sites the fresh-tissue method offers the advantages of speed, accuracy, and simplicity.