Neuronal nitric-oxide synthase deficiency impairs the long-term memory of olfactory fear learning and increases odor generalization

Pretraining nitric oxide donor molsidomine in nNOS knockout mice increases the freezing response during the test. Mice received molsidomine or saline 20 min before the training with odor and foot shock. (A) Mean time spent freezing across the trained odor for each group 24 h and (B) 7 d after the training. (*) Significant difference from the control wild-type group, P < 0.05.