Psychopharmacology

, Volume 226, Issue 3, pp 579–587

Effects of glutamate NMDA and TRPV1 receptor antagonists on the biphasic responses to anandamide injected into the dorsolateral periaqueductal grey of Wistar rats

  • Manoela V. Fogaça
  • Felipe V. Gomes
  • Fabrício A. Moreira
  • Francisco S. Guimarães
  • Daniele C. Aguiar
Original Investigation

DOI: 10.1007/s00213-012-2927-2

Cite this article as:
Fogaça, M.V., Gomes, F.V., Moreira, F.A. et al. Psychopharmacology (2013) 226: 579. doi:10.1007/s00213-012-2927-2

Abstract

Rationale

The endocannabinoid and endovanniloid anandamide (AEA) exerts biphasic effects when injected into the dorsolateral periaqueductal grey (dlPAG) in rats submitted to threatening situations. Whereas lower doses of AEA induce anxiolytic-like effects by activating cannabinoid CB1 receptors, no effects are observed with higher doses, possibly due to the simultaneous activation of transient receptor potential vanilloid type 1 (TRPV1) receptors. This activation would facilitate glutamatergic neurotransmission.

Objective

Considering that the blockade of TRPV1 or NMDA receptors in the dlPAG induces anxiolytic-like effects, we tested the hypothesis that facilitation of glutamate transmission through TRPV1 is responsible for the lack of anxiolytic-like effect observed with high AEA doses.

Methods

Male Wistar rats with a unilateral cannula aimed at the dlPAG received injections of an ineffective dose of AP7 (an NMDA antagonist, 1 nmol) or capsazepine (CPZ, a TRPV1 antagonist, 10 nmol), followed by a high dose of AEA (50 and 200 pmol) and were exposed to the elevated plus maze (EPM) or the Vogel conflict test (VCT).

Results

AP7, CPZ, or AEA did not induce any significant effects when administered alone. However, AP7 or CPZ prior to AEA significantly increased the percentage of entries and time spent in the open arms of EPM and the number of punished licks in the VCT suggesting an anxiolytic-like effect.

Conclusions

These results suggest that the lack of anxiolytic-like effect of higher AEA doses is due to facilitation of glutamate release in the dlPAG, probably via activation of TRPV1 receptors in this structure.

Keywords

GlutamateEndovanilloidsAnxietyDefensive behavior

Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Manoela V. Fogaça
    • 1
    • 3
  • Felipe V. Gomes
    • 1
    • 3
  • Fabrício A. Moreira
    • 2
  • Francisco S. Guimarães
    • 1
    • 3
  • Daniele C. Aguiar
    • 2
  1. 1.Department of Pharmacology, School of Medicine of Ribeirão PretoUniversity of São PauloRibeirão PretoBrazil
  2. 2.Department of Pharmacology, Institute of Biological SciencesUniversidade Federal de Minas GeraisBelo HorizonteBrazil
  3. 3.Center for Interdisciplinary Research on Applied Neurosciences (NAPNA)University of São PauloSão PauloBrazil