Anxiolytic-like effects induced by blockade of transient receptor potential vanilloid type 1 (TRPV1) channels in the medial prefrontal cortex of rats.
BACKGROUND
The endocannabinoid anandamide, in addition to activating cannabinoid type 1 receptors (CB1), may act as an agonist at transient receptor potential vanilloid type 1 (TRPV1) channels. In the periaqueductal gray, CB1 activation inhibits, whereas TRPV1 increases, anxiety-like behavior. In the medial prefrontal cortex (mPFC), another brain region related to defensive responses, CB1 activation induces anxiolytic-like effects. However, a possible involvement of TRPV1 is still unclear.


OBJECTIVE
In the present study, we tested the hypothesis that TRPV1 channel contributes to the modulation of anxiety-like behavior in the mPFC.


METHODS
Male Wistar rats (n = 5-7 per group) received microinjections of the TRPV1 antagonist capsazepine (1-60 nmol) in the ventral portion of the mPFC and were exposed to the elevated plus maze (EPM) or to the Vogel conflict test.


RESULTS
Capsazepine increased exploration of open arms in the EPM as well as the number of punished licks in the Vogel conflict test, suggesting anxiolytic-like effects. No changes in the number of entries into the enclosed arms were observed in the EPM, indicating that there were no changes in motor activity. Moreover, capsazepine did not interfere with water consumption or nociceptive threshold, discarding potential confounding factors for the Vogel conflict test.


CONCLUSIONS
These data suggest that TRPV1 in the ventral mPFC tonically inhibits anxiety-like behavior. TRPV1 could facilitate defensive responses opposing, therefore, the anxiolytic-like effects reported after local activation of CB1 receptors.
Aguiar
Daniele C
DC
Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP 14049-900, Brazil.
Terzian
Ana Luisa B
AL
Guimarães
Francisco S
FS
Moreira
Fabrício A
FA
D000704:Analysis of Variance; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001007:Anxiety / Q000473:pathology*; D001522:Behavior, Animal / Q000187:drug effects; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D009020:Morphine / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects; D017397:Prefrontal Cortex / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors* / Q000502:physiology*; D014868:Water Deprivation
D014151:Anti-Anxiety Agents; D009294:Narcotics; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; D009020:Morphine; C071423:capsazepine; D002211:Capsaicin