title: Conditioned and unconditioned fear organized in the inferior colliculus are differentially sensitive to injections of muscimol into the basolateral nucleus of the amygdala.
abstract: Chemical stimulation of the inferior colliculus (IC) with semicarbazide--an inhibitor of the gamma aminobutyric acid synthesizing enzyme--functions as an unconditioned stimulus in the conditioned place aversion test (CPA), and electrolytic lesions of the basolateral amygdala (BLA) enhance the aversiveness of the IC stimulation. This study examined the effects of inactivation of the BLA with muscimol on the conditioned and unconditioned fear using semicarbazide injections into the IC of rats subjected to conditioned (CPA) or unconditioned (open field) fear tests. In both tests, the rats were injected with semicarbazide or saline into the IC and muscimol or saline into the BLA. Muscimol decreased the CPA and increased the unconditioned fear elicited by IC injections of semicarbazide. These findings indicate that distinct modulatory mechanisms in the BLA are recruited during the conditioned and unconditioned fear triggered by IC activation.
authors.affiliation: Laboratório de Psicobiologia, Faculdade Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Carlos Eduardo
authors.initials: CE
authors.lastname: Macedo
authors.forename: Raquel Chacon Ruiz
authors.initials: RC
authors.lastname: Martinez
authors.forename: Marcus Lira
authors.initials: ML
authors.lastname: Brandão
mesh_terms: D000679:Amygdala / Q000187:drug effects* / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005106:Exploratory Behavior / Q000187:drug effects; D005239:Fear / Q000187:drug effects / Q000502:physiology*; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects / Q000502:physiology; D018755:GABA Agonists / Q000494:pharmacology*; D007245:Inferior Colliculi / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009118:Muscimol / Q000494:pharmacology*; D051381:Rats; D012663:Semicarbazides / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D018755:GABA Agonists; D012663:Semicarbazides; D009118:Muscimol; C010059:carbamylhydrazine