[Abstract Title]. - Society for Neuroscience

Topic: C.15.h. Affective disorders: Animal models
Support: Fapesp
CNPQ
Title: Stress influence on anxiety modulatory role of the endocannabinoid system in the ventral
hippocampus
Authors: *A. C. CAMPOS, J. I. LEMOS, F. R. FERREIRA, F. S. GUIMARAES;
Dept. of Pharmacol., Sch. Med. Ribeirao-USP, Ribeirão Preto, Brazil
Abstract: Introduction: Several studies have suggested that the endocannabinoid system
modulates anxiety and stress adaptation. There is, however, a paucity of data regarding the
involvement of endocannabinoids such as anandamide (AEA) on brain sites related to these
effects. The ventral hippocampus (VHC) has been related to anxiety behaviors and has a high
expression of cannabinoid-1 (CB1) receptors. Moreover, endocannabinoid signaling in the
hippocampus is proposed to regulate stress adaptation. Thus, the aim of this study was to
investigate the effects of AM404, an AEA uptake inhibitor, and AM251, a CB1 receptor
antagonist, microinjected into the VHC of stressed and non-stressed rats.
Methods: Male Wistar rats (240-270g) with cannulae aimed at the VHC were submitted to
restraint stress for 2h. Non-stressed animals remained in their home cages. Twenty four hours
later they received bilateral injections of vehicle (V, 0.5 microL), AM-404 (5 or 50 pmol, N=8-
11) or AM251 (1-100 pmol; N= 5-11) and 10 minutes later were submitted to the elevated plus
maze (EPM).
Results: Restraint stress induced a significant decrease in the percent of entries and time spent in
the open arms. AM-404 (50 pmol) reduced the percentage of entries and time spent in the open
arms in non-stressed animals. On the other hand, AM404 (5 pmol) increased the open arm
exploration in previously stressed animals. AM251 (1 pmol) tended to increase the time spent in
the open arms of the non stressed animals but did not change EPM exploration of stressed
animals.
Discussion: The results suggest that the endocannabinoid system in the VHC modulates anxietylike
behavior depending on previous stressful experience of the animal.
REFERENCES: Hill et al., Neuropsychopharmacology, 2005; Rubino et al.
Neuropharmacology, 2008. Financial support: FAPESP, CNPQ
Disclosures: A.C. Campos, None; J.I. Lemos, None; F.R. Ferreira, None; F.S. Guimaraes,
None.
Poster
255. Mood Disorders: Animal Models and Treatment Effects II