Differential dynamics of amino acid release in the amygdala and olfactory cortex during odor fear acquisition as revealed with simultaneous high temporal resolution microdialysis.
Although the amygdala seems to be essential to the formation and storage of fear memories, it might store only some aspects of the aversive event and facilitate the storage of more specific sensory aspects in cortical areas. We addressed the time course of amygdala and cortical activation in the context of odor fear conditioning in rats. Using high temporal resolution (1-min sampling) intracerebral microdialysis, we investigated the dynamics of glutamate and GABA fluctuations simultaneously in basolateral amygdala (BLA) and posterior piriform cortex (pPCx) during the course of the acquisition session, which consisted of six odor (conditioned stimulus)-footshock (unconditioned stimulus) pairings. In BLA, we observed a transient increase in amino acid concentrations following the first odor-shock pairing, after which concentrations returned to baseline levels or slightly below. In pPCx, transient increases were seen after each pairing and were also observed after the last odor-shock pairing, corresponding to the predicted times of anticipated trials. Furthermore, we observed that for the first pairing, the increase in BLA occurred earlier than the increase in pPCx. These data suggest that the amygdala is engaged early during acquisition and precedes the activation of the olfactory cortex, which is maintained until the end of the session. In addition, our data raise the challenging idea that the olfactory cortex might store certain aspects of fear conditioning related to the timing of the associations.
Neurosciences Sensorielles, Comportement, Cognition, CNRS-UMR 5020, Université de Lyon, Lyon, France.
Chloé
C
Hegoburu
Yannick
Y
Sevelinges
Marc
M
Thévenet
Rémi
R
Gervais
Sandrine
S
Parrot
Anne-Marie
AM
Mouly
D000596:Amino Acids / Q000378:metabolism*; D000679:Amygdala / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D003214:Conditioning, Classical / Q000502:physiology*; D004597:Electroshock / Q000009:adverse effects; D005239:Fear / Q000502:physiology*; D046352:Freezing Reaction, Cataleptic / Q000502:physiology; D008297:Male; D017551:Microdialysis / Q000379:methods; D009448:Neurochemistry; D017711:Nonlinear Dynamics; D009812:Odorants; D009833:Olfactory Pathways / Q000378:metabolism*; D051381:Rats; D020318:Rats, Long-Evans; D013997:Time Factors
D000596:Amino Acids