BRAIN-DERIVED NEUROTROPHIC FACTOR BLOCKS LONG-TERM DEPRESSION IN RAT VISUAL-CORTEX

1. Brain-derived neurotrophic factor (BDNF) has been reported to play a role in long-term potentiation (LTP) in hippocampus, but whether it is involved also in long-term depression (LTD) is not yet known. In th is study, we tested whether BDNF and its gene family, nerve growth fac tor (NGF), have any effect on synaptic transmission and LTD in visual cortical slices of young rats. 2. An application of BDNF at the concen tration of 20 ng/ml did not significantly change layer II/III field re sponses evoked by layer IV stimulation at 0.1 Hz, although at 200 ng/m l it enhanced responses. BDNF at 20 ng/ml prevented LTD of field respo nses from being induced by low-frequency stimulation (1 Hz for 15 min) of layer IV. NGF did not have such effects in the same concentration range as that of BDNF. 3. The action of BDNF was antagonized by K252a, an inhibitor of receptor tyrosine kinases. When K252a alone was appli ed to slices, LTD of stronger magnitude than in control slices was ind uced by low-frequency stimulation. 4. These results suggest that endog eneous BDNF may prevent synapses from being depressed by low-frequency inputs in the developing visual cortex.