We used an atomic force microscope, in the repulsive regime of contact mode, to take images of uncoated neurons fixed in glutaraldehyde on a gold covered stainless steel substrate. We observed granule cells and their axons with a resolution better than 20 nm. The good stability of the sample and the mechanical reproducibility of the microscope allowed the imaging of a neuron culture area of several square microns. Modifications induced by glutamate on the neuronal culture resulted in observing a drastic reduction in cell granule height (from 1.5-2.0 mu m for the unperturbed ones down to 0.7-1.0 mu m) and in an increased corrugation of the surface membrane. The atomic force microscope images were very reproducible over repeated scanning acquisition, demonstrating a very good mechanical and thermal stability of the instrument-sample system.