Precisely localized LTD in the neocortex revealed by infrared-guided laserstimulation

In a direct approach to elucidate the origin of long-term depression (LTD), glutamate was applied onto dendrites of neurons in rat neocortical slices. An infrared-guided laser stimulation was used to release glutamate from ca ged glutamate in the focal spot df an ultraviolet laser. A burst of light f lashes caused an LTD-like depression of glutamate receptor responses, which was highly confined to the region of "tetanic" stimulation (<10 micrometer s). A similar depression of glutamate receptor responses was observed durin g LTD of synaptic transmission. A spatially highly specific postsynaptic me chanism tan account for the LTD induced by glutamate release.