LeDoux Lab 2010 SfN Abstracts

Program#/Poster#:	914.19/MMM35
Title:	Changes in presynaptic structure with fear and safety conditioning
Location:	Halls B-H
Presentation Time:	Wednesday, Nov 17, 2010, 3:00 PM - 4:00 PM
Authors:	*L. OSTROFF1, C. K. CAIN1,2, N. JINDAL1, N. DAR1, J. E. LEDOUX1,2; 1Ctr. for Neural Sci., New York Univ., New York, NY; 2Emotional Brain Inst., Nathan S. Kline Inst. for Psychiatry Res., Orangeburg, NY
Abstract:	Classical fear conditioning depends on synaptic changes in the lateral amygdala (LA), and we have previously shown that LA dendritic spine structure changes after fear learning. Synaptic plasticity in the LA involves both presynaptic and postsynaptic mechanisms, but presynaptic structure has not been examined. We used serial section transmission electron microscopy to reconstruct presynaptic boutons and axonal segments from the adult rat LA after either fear or safety conditioning. We found that relative to naïve controls, fear conditioning increased the number of spine synapses per bouton, while both fear and safety conditioning increased the number of boutons lacking postsynaptic partners. The largest spines had a higher ratio of postsynaptic density (PSD) area to docked vesicle number relative to small spines. Fear conditioning increased the number of synapses with a high ratio of PSD per docked vesicle, suggesting that the relationship between the presynaptic and postsynaptic elements is altered by learning. We measured vesicle pools in boutons along the length of individual axonal segments, and found that in naïve animals there was coherence in vesicle pool size among boutons on the same axon. After fear conditioning the average size of the vesicle pools was smaller and the distribution of vesicle pool size along each axon was random, indicating rearrangement of vesicle pools with learning. Overall, our data show that learning induces structural changes on both sides of the synapse.
Support:	NIH R01-MH046516 NIH P50-MH058911 NIH F32-MH083583 NIH F32-MH077458