Figure 4.

Conditioned fear and extinction in mice with amygdala GAD67 knockdown. (a) Acquisition of conditioned fear to auditory conditioned stimulus (CS)+ shock pairing as measured by freezing. There was no difference in acquisition of fear in animals receiving bilateral amygdala injections of LV-SCR or LV-siGAD67. (b) Animals were tested 24 h after training to examine the retention of conditioned fear (session 1 extinction). There was no difference between the groups on level of conditioned fear. (c) Percent conditioned freezing is graphed for sessions 1–6 of extinction tests. Mice infected with LV-SCR demonstrate significant greater decreases in their level of conditioned fear, compared with LV-siGAD67-infected mice. Impaired extinction of fear, measured by percentage of freezing, is evident across multiple testing sessions. Error bars denote 1 standard error of the mean (s.e.m.). Star indicates that the difference between virus groups was statistically significant (P<0.05).