IL EphB2 mRNA and protein is downregulated after fear extinction. A, C, Percentage of time that rats spent freezing to the tone during fear conditioning (day 1, 1 habituation tone plus 3 tone–shock pairings) and extinction (day 2, 15 tones). B, EphB2 mRNA expressed by each group (COND group, n = 7; CR group, n = 4; EXT group, n = 6). All values are relative to B-actin and GAPDH. D, EphB2 protein expression by each group (COND group, n = 5; CR group, n = 5; EXT group, n = 6). E, Sample gels for each group. No EphB2 band was found after immunoprecipitation with beads lacking EphB2 antibody (beads). Last lane shows immunostaining for the NR1 subunit of NMDA receptors after EphB2 immunoprecipitation. Mouse anti-NR1 antibody (catalog 556308, BD Biosciences) does not detect heavy chain of rabbit anti-EphB2 antibody. Red arrow indicates the time point of euthanasia. **p < 0.01, *p < 0.05. Numbers of samples are indicated in parentheses.