Figure 3. Intra-hippocampal NaB injections selectively cause persistent extinction enhancements only in the presence of weak extinction and repeated testing.
A) During Reversal, mice receiving either NaB or Veh following conditioning (n=9 NaB and Veh groups) or retrieval (NaB n=9; Veh n=8) did not differ. Mice receiving post-extinction NaB injections showed a significant extinction enhancement relative to controls when test 1D later. This extinction enhancement persisted to 14 D only when mice were retested (14DR). No conditioning enhancement was seen on any test. B) NaB (n=9) infused into the hippocampus immediately after weak (1 shk) conditioning did not result in a significant difference in freezing from Veh (n=9) when test 1 and 14 D later. C) Strong (24 min) extinction led to persistent decreases in freezing 1 and 14D later. Post-extinction NaB (n=10) hippocampal infusions was not able to induce any change in freezing relative to Veh (n = 12). D) Infusion of NaB (n=5) into the hippocampus 4 hr following 3 min extinction had no significant effect on freezing relative to Veh (n=8) when tested 1D later.