title: Gabaergic regulation of the neural organization of fear in the midbrain tectum.
abstract: In midbrain tectum (MT) structures, such as the dorsal periaqueductal gray (dPAG), the superior colliculus (SC) and the inferior colliculus (IC) GABAergic neurons exert a tonic control on the neural substrates involved in the expression of defensive reactions. In this review, we summarize behavioral, immunohistochemical (brain Fos distribution) and electrophysiological (auditory evoked potentials) data obtained with the reduction of GABA transmission by local injections of a GABA receptor blocker (bicuculline, BIC) or a glutamic acid decarboxylase inhibitor (semicarbazide, SMC) into the MT. Distinct patterns of Fos distribution were obtained following the freezing and escape reactions induced by MT injections of SMC and BIC, respectively. While only the laterodorsal nucleus of the thalamus was labeled after SMC-induced freezing, a widespread increase in Fos expression in the brain occurred after BIC-induced escape. Also, injections of SMC into the IC increased the auditory evoked potentials recorded from this structure. It is suggested that GABAergic mechanisms of MT are also called into play when sensory gating of the MT is activated during different emotional states.
authors.affiliation: Laboratório de Psicobiologia, FFCLRP, University of Sao Paulo, Campus USP, Av. Bandeirantes 3900, 14049-901 Ribeirão Preto, SP, Brazil. mbrandao@usp.br
authors.forename: Marcus Lira
authors.initials: ML
authors.lastname: Brandão
authors.forename: Karina Genaro
authors.initials: KG
authors.lastname: Borelli
authors.forename: Manoel Jorge
authors.initials: MJ
authors.lastname: Nobre
authors.forename: Julia Maria
authors.initials: JM
authors.lastname: Santos
authors.forename: Lucas
authors.initials: L
authors.lastname: Albrechet-Souza
authors.forename: Amanda Ribeiro
authors.initials: AR
authors.lastname: Oliveira
authors.forename: Raquel Chacon
authors.initials: RC
authors.lastname: Martinez
mesh_terms: D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D001931:Brain Mapping; D004924:Escape Reaction / Q000187:drug effects / Q000502:physiology; D005239:Fear / Q000502:physiology*; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects / Q000502:physiology*; D018756:GABA Antagonists / Q000494:pharmacology; D007245:Inferior Colliculi / Q000187:drug effects / Q000502:physiology*; D008959:Models, Neurological; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D010487:Periaqueductal Gray / Q000187:drug effects / Q000502:physiology*; D012663:Semicarbazides / Q000494:pharmacology; D013788:Thalamus / Q000378:metabolism; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D018756:GABA Antagonists; D016761:Oncogene Proteins v-fos; D012663:Semicarbazides; C010059:carbamylhydrazine; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline