Pre-Training Reversible Inactivation of the Basal Amygdala (BA) Disrupts Contextual, but Not Auditory, Fear Conditioning, in Rats.
The basolateral amygdala complex (BLA), including the lateral (LA), basal (BA) and accessory basal (AB) nuclei, is involved in acquisition of contextual and auditory fear conditioning. The BA is one of the main targets for hippocampal information, a brain structure critical for contextual learning, which integrates several discrete stimuli into a single configural representation. Congruent with the hodology, selective neurotoxic damage to the BA results in impairments in contextual, but not auditory, fear conditioning, similarly to the behavioral impairments found after hippocampal damage. This study evaluated the effects of muscimol-induced reversible inactivation of the BA during a simultaneous contextual and auditory fear conditioning training on later fear responses to both the context and the tone, tested separately, without muscimol administration. As compared to control rats micro-infused with vehicle, subjects micro-infused with muscimol before training exhibited, during testing without muscimol, significant reduction of freezing responses to the conditioned context, but not to the conditioned tone. Therefore, reversible inactivation of the BA during training impaired contextual, but not auditory fear conditioning, thus confirming and extending similar behavioral observations following selective neurotoxic damage to the BA and, in addition, revealing that this effect is not related to the lack of a functional BA during testing.
Department of Physiology, Biosciences Institute, University of São Paulo, São Paulo, SP, Brasil.
Elisa Mari
EM
Akagi Jordão
Department of Physiology, Biosciences Institute, University of São Paulo, São Paulo, SP, Brasil.
Barbara Kazue Amaral
BK
Onishi
Department of Physiology, Biosciences Institute, University of São Paulo, São Paulo, SP, Brasil.
Gilberto Fernando
GF
Xavier
D000818:Animals; D066272:Basolateral Nuclear Complex / Q000187:drug effects / Q000502:physiology*; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology*; D005239:Fear / Q000187:drug effects / Q000502:physiology*; D007649:Ketamine / Q000494:pharmacology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D014991:Xylazine / Q000494:pharmacology
D014991:Xylazine; D007649:Ketamine