Fig. 2.

Characterization of infrared-guided laser stimulation. A, B, Caged glutamate does not desensitize glutamate receptors by spontaneous hydrolyzation. Neither the rise time nor the amplitude of evoked EPSPs changed significantly when caged glutamate (caged glu) was added to the extracellular medium. In A, single sweeps are shown. B, Statistical evaluation. The respective values of 15 EPSPs under control conditions (c) and in the presence of caged glutamate were averaged for six neurons. C, D, Spatial specificity of infrared-guided laser stimulation. The laser point was moved laterally away from the dendrite in increments of 2.5 μm. The decrease in glutamate response amplitude is plotted as a function of this distance. In C, a single experiment is shown.D, Only the data of one side were pooled (n = 6 neurons), because the typical Gaussian shape of the other side was sometimes distorted. This may be an effect of invisible dendritic branches.