LeDoux Lab 2006 SfN Abstracts
 
Short-term plasticity differentially regulates long-term plasticity at thalamic and cortical auditory inputs to the lateral amygdala in vivo

*T. SIGURDSSON1, C. K. CAIN1, V. DOYERE1,2, J. E. LEDOUX1;
1Ctr Neural Sci, NYU, New York, NY, 2Namc, umr8620, Univ Paris-Sud, Orsay, FRANCE.

Several lines of evidence suggest that auditory fear conditioning is mediated by synaptic plasticity at auditory inputs to the lateral amygdala (LA). One outstanding question, however, is the relative contribution of long-term plasticity at the thalamic and cortical auditory inputs to the LA. We have previously shown that the magnitude of long-term potentiation (LTP) is greater at cortical compared to thalamic inputs in vivo. Here we ask whether this difference is due to a more fundamental difference in the synaptic properties of the two inputs. In urethane-anesthetized rats, the two inputs were examined by recording field potential responses in the LA evoked by electrical stimulation of the auditory thalamus (MGm/PIN) and auditory association cortex (TE3). Extending our previous findings, we first show that high-frequency stimulation (HFS) induces LTP of much greater magnitude at cortical compared to thalamic inputs across a range of induction frequencies and stimulation protocols. We next show that the integrated field potential response during HFS is greater during stimulation of cortical inputs, suggesting that these inputs are more effective at depolarizing postsynaptic LA neurons during HFS. Finally, we asked whether this might reflect differences in short-term plasticity at the two inputs. Using paired-pulse stimulation, we found that thalamic inputs display primarily depression whereas cortical inputs show more facilitation. This difference was seen in both evoked field potential and single-unit responses. These results suggest that short-term plasticity, by affecting responses during HFS, may differentially regulate the induction of LTP at thalamic and cortical auditory inputs to the LA. In particular, the induction of LTP at thalamic inputs may be constrained by the short-term depression observed at these inputs. Possible pharmacological mechanisms underlying the differences in short-term and long-term plasticity at the thalamic and cortical inputs are currently being investigated.
Support Contributed By: R01 MH046516;R37 MH38774 ;K05 MH067048 ;CNRS-PICS

Program No. 370.1/KK19
Poster presentation:
Monday, Oct 16, 2006, 8:00 AM - 9:00 AM
Location: Georgia World Congress Center: Halls B3-B5