Effects of angiotensin (5-8) microinfusions into the ventrolateral periaqueductal gray on defensive behaviors in rats

Author(s)

Genaro, Karina ^{[1, 2, 3]} ; Juliano, Maria A. ^[4] ; Prado, Wiliam A. ^[2] ; Brandao, Marcus L. ^{[3, 5]} ; Martins, Antonio R. ^{[1, 2]}

Affiliation

^[1] Univ Fed Triangulo Mineiro, Inst Ciencias Biol, Uberaba, MG - Brazil

^[2] Univ Sao Paulo, Dept Farmacol, BR-14040901 Ribeirao Preto, SP - Brazil

^[3] INeC, Inst Neurociencias & Comportamento, Ribeirao Preto, SP - Brazil

^[4] Univ Fed Sao Paulo, Escola Paulista Med, Dept Biofis, Sao Paulo - Brazil

^[5] Univ Sao Paulo, Dept Psicol, BR-14040901 Ribeirao Preto, SP - Brazil

• Document type: Journal article
• Source: Behavioural Brain Research; v. 256, p. 537-544, NOV 1 2013.
• Web of Science Citations: 2

Abstract

Peptides of the renin-angiotensin system modulate blood pressure and hydro-electrolyte composition. Angiotensin (Ang) receptors are localized in brain areas related to the regulation of autonomic and endocrine control and involved in sensory perception, memory process and behavioral responses. Among these areas, the ventrolateral periaqueductal gray (vlPAG) is one of the most important structures of the neuronal circuitry controlling the autonomic and behavioral components of emotional states. Although Ang II metabolism in the vlPAG forms several Ang-peptides including Ang (5-8), the role of this tetrapeptide in the organization of defensive responses has not yet been described. To address this issue, the purpose of the present study was to determine the effects of intra-vlPAG injections of Ang (5-8) (0.2, 0.4 and 0.8 nmol/0.25 mu L) in rats submitted to the elevated plus-maze (EPM) test. Additionally, it was evaluated the effects of intra-vlPAG Ang (5-8) on the expression of conditioned fear, assessed by the fear-potentiated startle and contextual conditioned freezing tests. The results showed that Ang (5-8) produced an intense, dose-related reduction in the entries into and time spent in the open arms of the EPM, decreased direct exploration and increased risk assessment behaviors. Moreover, intra-vlPAG injections of Ang (5-8) before the test session promoted pro-aversive effects in the FPS and enhanced contextual freezing. Taken together, these results point out to an important anxiogenic-like action for Ang (5-8) in the mediation of defensive behaviors organized in the vlPAG. (C) 2013 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 11/00041-3 - Neurobiology of stress: the sensorimotor gating
• Grantee: Marcus Lira Brandão
• Support Opportunities: Research Projects - Thematic Grants