Figure 7
Pcdh19 hemizygous male and heterozygous female mutants show differential fear responses. Fear conditioning tests with male (a–f) and female (g–l) mice. For fear conditioning, a cue signal (CS) of 30 sec followed by 2-sec unconditioned stimulus (UCS, foot shock) was applied at 2, 4 and 6 mins after starting the test. (a,b,g,h) In both wild-type and Pcdh19 mutant males, the extent of freezing (a) and travel distance (b) induced by unconditioned stimuli (three footshocks) was increased. (c,d) Context-dependent (c) and cued (d) fear responses did not differ between wild-type and Pcdh19 hemizygous mutant males. (e,f) Retention test held 28 days after the training for contextual (e) and cued (f) fear responses in male mice. There were no significant differences between wild-type and Pcdh19 hemizygous mutant males. (g,h) In both wild-type and Pcdh19 heterozygous mutant females, the extent of freezing (g) and travel distance (h) induced by unconditioned stimuli (three footshocks) was increased, but with a significantly reduced freezing response in the mutants. (i,j) Contextual (i) and cued (j) fear responses significantly decreased in Pcdh19 heterozygous mutant females. (k,l) Retention test held 28 days after the training for contextual (k) and cued (l) fear responses. There was a significant decrease in both responses in Pcdh19 heterozygous mutant females compared to wild-type mice. In the experiments in (c and i), mice were put in the same box as used for the conditioning, whereas in (d and j), mice were put in a box different from the one used for the conditioning. The cue signal was applied at 4 mins after starting the test and lasted for 2 mins.
