[8] - Determination of Numerical Density of Perforated and Nonperforated Synapses

Publisher Summary In most of the ultrastructural investigations of central nervous system synapses, synaptic density has been expressed as number of synaptic profiles per unit area of section. Although such a parameter has been widespread, it unfortunately fails to take into account the effects of the size-frequency distribution or shape of the synapses; it also ignores the effects of section thickness on the density estimates. The application of relatively more advanced stereological methods has enabled corrections to be made for these factors and has also made it possible to convert counts of synaptic profiles, made on single sections, into more meaningful numerical density estimates (NVs), expressed as number of synapses per unit volume of tissue studied. However, the use of stereological approaches has itself ushered in an awareness of the limitations of many such approaches. This, in turn, has demonstrated the need to search for more adequate stereological procedures. An understanding of the significance of perforated synapses (PSs) is at the mercy of the stereological procedures employed. This chapter also reviews some previous stereological procedures. Then it provides an overview of the dissector method, which has proved to be extremely successful for the estimation of the numerical density of perforated and non-perforated synapses (NPSs) and has overcome all the problems and difficulties encountered with the stereological procedures.

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