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. 2002 Sep 1;22(17):7558–7568. doi: 10.1523/JNEUROSCI.22-17-07558.2002

Fig. 3.

Fig. 3.

Tetanic release of glutamate causes a decrease in the glutamate response amplitude (photo-LTD). A, Focal photolysis of caged glutamate with a frequency of 5 Hz for 1 min duration (arrow with flash symbol) reliably elicited photo-LTD. For control stimulation, glutamate was released every 20 sec. The data shown are averages for every minute. The 100% value (dashed line) represents the mean of the last 5 min before the onset of the 5 Hz train in all figures. Thetraces show single glutamate responses before (black) and after (gray) 5 Hz stimulation. B, Photo-LTD is not caused by damage to the neuron attributable to the UV radiation. The glutamate responses were not affected by the 5 Hz train when applied in the absence of caged glutamate. In contrast, a second application of the 5 Hz stimulation in the presence of caged glutamate reliably induces photo-LTD. A single experiment is shown. C, Photo-LTD is not induced by the photolytically released caging group. The amplitudes of GABA responses, elicited by photolysis of caged GABA, were not affected by the 5 Hz stimulation. Because the caged glutamate and caged GABA used are protected by the same caging group, photo-LTD cannot be caused by the photolytically released caging group. The traces show single GABA responses before (black), and after (gray) the 5 Hz stimulation.