LeDoux Lab 2004 SfN Abstracts

BLOCKADE OF RECONSOLIDATION BUT NOT CONSOLIDATION OF AUDITORY FEAR CONDITIONING BY PROPRANOLOL INFUSION INTO THE LATERAL AMYGDALA IN RATS
J.Debiec*; J.E.LeDoux
Ctr for Neural Sci, New York Univ, New York, NY, USA
Recent evidence suggests that consolidated auditory fear memories, when reactivated through retrieval, undergo reconsolidation in the lateral amygdala (LA). Previous studies indicate the involvement of noradrenergic system in the amygdala in memory consolidation. We therefore asked whether the noradrenergic system is involved in the consolidation (study 1) and reconsolidation (study 2) of auditory fear conditioning. Study 1 (consolidation): Rats were placed in a chamber and given a 30 s 5 kHZ tone (CS) that terminated with 1, 1.0 mA, 1 s shock. Immediately after, rats received intra-peritoneal (i.p.) injections of either the beta-adrenergic receptor antagonist propranolol or saline. Two days later when freezing responses to the CS were assessed the two groups did not differ. Similar results were found when conditioning was immediately followed by bilateral infusion of propranolol or cerebro-spinal fluid in the LA. Study 2 (reconsolidation): On the day following auditory fear conditioning, rats were presented with a single CS to reactivate the memory. Immediately after, they received i.p. injections of propranolol or saline. Propranolol injected rats, tested 48 hrs later, showed impaired freezing to the CS as compared to the saline controls. Propranolol injections without memory reactivation did not produce the deficit. Similar findings were obtained when propranolol was infused directly in the LA immediately after reactivation. Infusions of propranolol 2mm above the LA following memory reactivation did not produce a freezing deficit. Our results suggest that blockade of beta-adrenergic receptors in the lateral amygdala has different effects on consolidation and reconsolidation of fear conditioning. Because propranolol is safe for human use, our results pave the way for using propranolol as a means of blocking reconsolidation in studies of humans, including patients with PTSD.
Support Contributed By: MH38774, MH58911, MH067048, I/77376, HSF-RGP0094
Program No. 208.3
Poster presentation:Sunday, Oct. 24, 10:00 AM - 11:00 AM
Location: NN18