Figure 4. Effect of GABA_A receptor block (bicuculline) on LTD induced by HFS at the early stage of development.

A, time courses of the effects of bicuculline applied before (• and ▪) and after (^) HFS in different experiments at P8. Note that in the presence of bicuculline, HFS only induces LTP (•) or null effect (▪), while bicuculline applied after HFS, when depression is induced has no effect. The arrow shows the time of delivery of HFS, and the bars show the infusion period of bicuculline before HFS (▪) and after HFS (□). B, percentage occurrence of LTP (dark grey bar), null effect (light grey bar) and LTD (open bar) after HFS applied alone (□) and during bicuculline infusion () in P7-P10 and P21 slices.