Acute stress produces dendritic retraction in the right basolateral amygdala (BLA), whereas fear conditioning and extinction produces dendritic retraction in the left BLA. (A) Total branch number [mean ± standard error of the mean (SEM)] for right and left BLA pyramidal neurons in unstressed (black bars) vs. stressed (gray bars) rats that were either non-conditioned or underwent fear conditioning and extinction. *P < 0.05 relative to unstressed within the learning condition. †P < 0.05 relative to untested within the stress condition. (B) Total branch length (mean ± SEM) for right and left BLA pyramidal neurons in unstressed (black bars) vs. stressed (gray bars) rats that were either non-conditioned or underwent fear conditioning and extinction. *P < 0.05 relative to unstressed within the learning condition. †P < 0.05 relative to untested within the stress condition. Unstressed, no conditioning, n = 5. Stressed, no conditioning, n = 4. Unstressed, conditioning and extinction, n = 8. Stressed, conditioning and extinction, n = 10.