Plasticity of inhibitory synaptic network interactions in the lateral amygdala upon fear conditioning in mice.
After fear conditioning, plastic changes of excitatory synaptic transmission occur in the amygdala. Fear-related memory also involves the GABAergic system, although no influence on inhibitory synaptic transmission is known. In the present study we assessed the influence of Pavlovian fear conditioning on the plasticity of GABAergic synaptic interactions in the lateral amygdala (LA) in brain slices prepared from fear-conditioned, pseudo-trained and naïve adult mice. Theta-burst tetanization of thalamic afferent inputs to the LA evoked an input-specific potentiation of inhibitory postsynaptic responses in projection neurons; the cortical input was unaffected. Philanthotoxin (10 microM), an antagonist of Ca2+-permeable AMPA receptors, disabled this plastic phenomenon. Surgical isolation of the LA, extracellular application of a GABA(B) receptor antagonist (CGP 55845A, 10 microM) or an NMDA receptor antagonist (APV, 50 microM), or intracellular application of BAPTA (10 mM), did not influence the plasticity. The plasticity also showed as a potentiation of monosynaptic excitatory responses in putative GABAergic interneurons. Pavlovian fear conditioning, but not pseudo-conditioning, resulted in a significant reduction in this potentiation that was evident 24 h after training. Two weeks after training, the potentiation returned to control levels. In conclusion, a reduction in potentiation of inhibitory synaptic interactions occurs in the LA and may contribute to a shift in synaptic balance towards excitatory signal flow during the processes of fear-memory acquisition or consolidation.
Szinyei
Csaba
C
Institut für Physiologie I, Westfälische Wilhelms-Universität Münster, Robert-Koch-Str. 27a, D-48149 Münster, Germany.
Narayanan
Rajeevan T
RT
Pape
Hans-Christian
HC
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000679:Amygdala / Q000166:cytology / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal; D003214:Conditioning, Classical / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005239:Fear; D018756:GABA Antagonists / Q000494:pharmacology; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D007395:Interneurons / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009434:Neural Pathways / Q000502:physiology* / Q000528:radiation effects; D018733:Nicotinic Antagonists / Q000494:pharmacology; D010721:Phosphinic Acids / Q000494:pharmacology; D011073:Polyamines / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D018709:Statistics, Nonparametric; D009435:Synaptic Transmission / Q000502:physiology*
D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D018733:Nicotinic Antagonists; D010721:Phosphinic Acids; D011073:Polyamines; D011412:Propanolamines; C085075:CGP 55845A; D015763:2-Amino-5-phosphonovalerate; C034092:delta-philanthotoxin