*L. W. MASSIE, N. HARRANHALLI, J. P. LITTLE, L. R. JOHNSON, J. E. LEDOUX;
Ctr. for Neural Sci., New York Univ., New York, NY

The amygdala and especially the lateral amygdala (LA) is a key nucleus for the formation of associative emotional memories. In Pavlovian fear conditioning a previously neutral stimulus such as a tone is paired with an unconditioned stimulus such as a mild shock. As a result of associative memory formation the previously neutral stimulus becomes a conditioned stimulus (CS) capable of eliciting defensive responses. Evidence indicates plastic changes in lateral amygdala neurons, which includes activation of the mitogen activated protein kinase (MAPK) signalling cascade leads to regulation of protein synthesis, underlies memory formation (Schafe, et al 2000). Human studies have demonstrated differential involvement of the left and right lateral amygdalae (LA) in the representation of fear, suggesting unique roles for each hemisphere in fear memory storage. Emerging research has indicated that this hemispheric disparity may be conserved in the rat (Baker et al., 2004). We explored the rat amygdala to see whether the right or left amygdala has a different increase in cellular activation in response to fear learning. Rats were habituated and subject to either 5 paired or unpaired presentations of the CS (20sec, 5kHz, 75db tone) and US (0.5sec, 1.0mA foot shock). Animals were then studied behaviorally or anatomically. In the behavioral study rats that received paired training exhibited significantly higher levels of conditioned fear (freezing) to the CS in a novel context. In the anatomical study brains were prepared for immunocytochemical detection of phosphorylated mitogen activated kinase (pMAPK). pMAPK activated neurons were mapped and quantified using Neurolucida (Microbrightfield, VT). We find no significant difference in pMAPK immunoreactive neurons number between the right and left lateral amygdala, in either the paired or unpaired rats. We conclude that under these learning conditions, amygdala in both hemispheres participate equally to acquisition of auditory fear memory in rats.

Support Contributed By: R01 MH46516, R37 MH38774, K05 MH067048, P50 MH58911

Program No. 307.11/BBB24
Poster presentation:Sunday, Nov 04, 2007, 3:00 PM - 4:00 PM
Location: San Diego Convention Center: Halls B-H