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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Intra-periaqueductal gray matter injections of midazolam fail to alter anxiety in plus-maze experienced mice

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Author(s):
dos Reis, Luciana Maria [1, 2] ; Canto-de-Souza, Azair [1]
Total Authors: 2
Affiliation:
[1] Univ Fed Sao Carlos, CECH, Depto Psicol, Grp Psicobiol, BR-13565905 Sao Carlos, SP - Brazil
[2] Univ Fed Sao Carlos, CCBS, Programa Posgrad Ciencias Fisiol PPG CF, BR-13565905 Sao Carlos, SP - Brazil
Total Affiliations: 2
Document type: Journal article
Source: Brain Research; v. 1231, p. 93-102, SEP 22 2008.
Web of Science Citations: 8
Abstract

It is well known that prior experience to the elevated plus-maze increases the avoidance of rodents to the open arms and impairs the anxiolytic-like effect of benzodiazepines evaluated during a subsequent exposure to the maze, a phenomenon known as ``one-trial tolerance{''}. Centrally injected benzodiazepine drugs attenuate anxiety in some limbic structures, such as hypothalamus, amygdala and the midbrain periaqueductal gray (PAG). This study investigated the effects of intra-PAG infusions of midazolam (MDZ) in maze-naive and maze-experienced mice. The antiaversive effects of MDZ (3.0 nmol and 30 nmol in 0.1 mu l) were evaluated by prior injection of flumazenil (16 nmol/0.1 mu l), a benzodiazepine receptor antagonist, into the same midbrain site. Test videotapes were scored for conventional measures of anxiety and locomotor activity, as well as a range of ethological measures related to risk assessment. In maze-naive mice, intra-PAG infusions of MDZ increased % open arm entries (3.0 nmol) and % open arm time (3.0 and 30 nmol). These effects were observed in the absence of significant changes in locomotor activity, indicating a selective anxiolytic-like effect of MDZ. The antiaversive effects of MDZ were completely blocked by prior injection of flumazenil which in turn did not alter any other behavioral measure. In maze-experienced mice, intra-PAG infusion of MDZ did not modify any behavioral measure. Taken together, present results corroborate previous studies demonstrating that GABA/benzodiazepine receptor complex located within the PAG plays a role on anxiety modulation in maze-naive mice as well as indicate its involvement in the OTT phenomenon. (C) 2008 Elsevier B.V. All rights reserved. (AU)