Differential response of two subdivisions of lateral amygdala to aversive conditioning as revealed by c-Fos and P-ERK mapping.

Rats were subjected to two aversive learning protocols: either classical (fear conditioning) or instrumental (two-way active avoidance training). Next, immunocytochemical mapping of phosphorylated extracellular signal-regulated kinase (P-ERK) and c-Fos transcription factor protein was performed, and the expression pattern of both markers within the dorsal nucleus of lateral amygdala (LaD) was analyzed. As immunocytochemical studies revealed, aversive training induced ERK phosphorylation and c-Fos expression specifically in ventral but not dorsal tip of LaD. These data show for the first time molecular distinction between subdivisions of LaD as well as they also strengthen the idea of Repa that the neurons in the ventral tip of LaD are involved in storage of long-lasting changes associated with formation of fear memories.