[Determination of the width of the synaptic cleft in PWS-contrasted rat brain material]

Based on a simple model of the synaptic cleft, some of those procedures that render possible an appraisal of the cleft width starting from cuttings as seen in micrographs are described in this paper. The results of the investigation prove that contrary to figures published previously by other authors, the width of the synaptic cleft is not constant, but exhibits a frequency distribution with a maximum - to - minimum ratio of about ten. Relative frequency in per cent can be approximately expressed as follows: p = 7.7 + 4.1 n with n = 1, 2, 5 ordinal class numbers of cleft width and the according class mid-points 7.62n nm Typflying of synapses according to physiological points of view has turned out to be out of reach.