3-DIMENSIONAL MORPHOMETRY OF INTACT DENDRITIC SPINES OBSERVED IN THICK SECTIONS USING AN ELECTRON-MICROSCOPE

An experimental technique is described which allows observation of fix ed neuronal dendrites at magnifications from 10-12 K. The method uses 4-7-mu m-thick sections of Epon-embedded tissue with nerve cells that are first impregnated by the rapid Golgi technique and then stained wi th gold particles/aggregates using a modified gold-toning procedure. A relatively high acceleration voltage (200 kV) is employed to observe in fine detail the dendritic fragments of interest at different angula r positions in space, by using a eucentric goniometer stage with a til t angle of (+/-)45 degrees. Image analysis methodology is proposed whi ch permits estimation of 3-dimensional (3D) lengths and of the volume of observed intact dendritic spines. The advantages of the technique w ith respect to 3D reconstruction methodology are discussed.