Fig. (3) Spine analysis on dentate gyrus neurons. Golgi impregnated granule neurons in the granule cell layer (GCL) of hippocampus at low (A) and high magnification (B) were traced. Spine density and type of spine were analyzed on a distance of 20µm from the end of the dendrite. Thin, mushroom, filopodia, stubby and branched spines could be distinguished (Ziess microscope, 100 x objective with a numerical aperture on 1.4)(B). Running for five weeks increased spine density in the dentate gyrus of hippocampus (C). The increased density was found in the population of thin spines (D). ** p<0.01 and *p<0.05 comparing runners vs non-runners Unpaired two-tailed Student´s t-test.