nNOS knockout mice show reduced freezing responses during an odor cued test 24 h and 7 d after training. Animals received six pairings of odor and foot shock during the training session. (A) Percent freezing per minute across successive trials on acquisition in males and (B) in females. The amount of the freezing increases during the session in wild-type (•), heterozygous (▪), and nNOS knockout (▴) mice. (C) Mean time spent freezing across the trained odor for each group. nNOS knockout mice show reduced freezing to the odor 24 h and (D) 7 d after the training. (*) Significant difference from the control wild-type group, (#) significant difference from the pre-CS to post-CS presentation, P < 0.05.
