Atomic force microscopic observation of three-dimensional morphological changes of neurons when stimulated by a neurotransmitter

As the first step in the study of morphological changes in neurons associated with their functional changes, we applied atomic force microscopy (AFM) for the observation of fine three-dimensional morphological changes in rat cerebellar granule cells stimulated by an agonist of glutamate receptors, N-methyl-D-aspartate (NMDA). The AFM revealed that NMDA changed the cross-sections of cell bodies from a trapezoid-like form to a triangle-like form within a minute. The fine hill-like structures on the top surfaces of the cell bodies became wider during the same period. These results were suggested to be induced by the depolymerization of filamentous actin triggered by the entry of Ca²⁺ via cation channels complexed with the activated NMDA receptors.