Effects of medial amygdala inactivation on a panic-related behavior.

Full Abstract

In the last years, the role played by the medial nucleus of the amygdala (MeA) in the modulation of fear- and anxiety-related behaviors has been increasingly investigated. This nucleus plays an important role in the processing of predator odor-induced defensive reactions, i.e. freezing and risk-assessment behaviors. Immunohistochemical evidence also indicates that the MeA may be involved in the regulation of escape, a defensive behavior related to panic attacks. In this study, we further addressed this question by investigating the effects of the reversible inactivation of the nucleus on escape behavior generated in male Wistar rats by two different aversive stimuli, electrical stimulation of the dorsal periaqueductal gray matter (dPAG) and exposure to one of the open arms of the elevated T-maze. Results showed that intra-MeA administration of either the reversible sodium channel blocker lidocaine (34 nmol/0.2 microl) or the GABA(A) receptor agonist muscimol (0.22 nmol/0.2 microl) raised the threshold of aversive electrical stimulation, increasing the amount of current that applied to the dPAG evokes escape, an antiaversive effect. Local microinjection of muscimol (0.22 nmol/0.2 microl) inhibited escape behavior in the elevated T-maze, also suggesting an antiaversive effect. In this latter test, muscimol did not affect inhibitory avoidance, a behavior associated with generalized anxiety disorder. Muscimol effect in the elevated T-maze was independent of changes in general exploratory activity as measured in an open-field. Taken together, our data corroborate previous evidences suggesting that the MeA is involved in the modulation of escape. Dysfunction of this regulatory mechanism may be of relevance in the genesis/maintenance of panic disorder.

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Author information

Author/s: Herdade, Karina Costa Paes (KC); Strauss, Christiana Villela de Andrade (CV); Zangrossi Júnior, Hélio (H); Viana, Milena de Barros (MB);

Affiliation: Laboratório de Psicofarmacologia, FFCLRP, Universidade de São Paulo, 14040-901 Ribeirão Preto, Brazil.

Journal and publication information

Publication Type: Comparative Study; Journal Article

Journal: Behavioural brain research (Behav Brain Res), published in Netherlands. (Language: eng)

Reference: 2006-Sep; vol 172 (issue 2) : pp 316-23

Dates: Created 2006/08/07; Completed 2006/12/28; Revised 2007/02/23;

PMID: 16806522, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Amygdala - drug effects; physiology
Animals
Avoidance Learning - drug effects; physiology
Electric Stimulation
Escape Reaction - drug effects; physiology
Exploratory Behavior - drug effects; physiology
GABA Agonists - administration & dosage
Male
Microinjections

Microinjections
Muscimol
Panic - drug effects; physiology
Periaqueductal Gray - physiology
Rats
Rats, Wistar
Sodium Channel Blockers - administration & dosage
Spatial Behavior - drug effects; physiology
Statistics, Nonparametric

Associated Chemicals: GABA Agonists (0) ; Sodium Channel Blockers (0) ; Muscimol (2763-96-4)

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