Cytoplasmic calcium elevation in hippocampal granule cell induced by perforant path stimulation and L-glutamate application.

Calcium-dependent fluorescence of a Ca2+ indicator (fura-2) loaded in the slice of guinea pig hippocampus was measured by a microscope/video-camera/photometry system. Tetanic stimulation of the perforant path (PP) or application of L-glutamate caused increment of the fluorescence from the dendritic and somatic layers of the granule cells in the dentate gyrus. Magnitude of the increment depended on the frequency and intensity of the PP-stimulation or on the dose of L-glutamate. 2-Aminophosphonovaleric acid, a glutamate-receptor antagonist, suppressed both PP-stimulus-induced and L-glutamate-evoked responses, while tetrodotoxin blocked the former only. Thus the fluorescence increment should represent an elevation of Ca2+ concentration in the postsynaptic cytoplasm of the granule cells.