Involvement of the prelimbic prefrontal cortex on cannabidiol-induced attenuation of contextual conditioned fear in rats.
BACKGROUND
Systemic administration of cannabidiol (CBD), a non-psychotomimetic component of Cannabis sativa, is able to attenuate cardiovascular and behavioral (freezing) changes induced by re-exposure to a context that had been previously paired with footshocks. The brain sites mediating this effect, however, remain unknown. The medial prefrontal cortex (mPFC) has been related to contextual fear conditioning.


OBJECTIVE
(1) To verify, using c-Fos immunocytochemistry, if the mPFC is involved in the attenuation of contextual fear induced by systemic administration of CBD; (2) to investigate if direct microinjections of CBD into mPFC regions would also attenuate contextual fear.


RESULTS
Confirming previous results systemic administration of CBD (10mg/kg) decreased contextual fear and associated c-Fos expression in the prefrontal cortex (prelimbic and infralimbic regions). The drug also attenuated c-Fos expression in the bed nucleus of the stria terminalis (BNST). Direct CBD (30 nmol) microinjection into the PL prefrontal cortex reduced freezing induced by re-exposure to the aversively conditioned context. In the infralimbic (IL) prefrontal cortex, however, CBD (30 nmol) produced an opposite result, increasing the expression of contextual fear conditioning. This result was confirmed by an additional experiment where the conditioning session was performed under a less aversive protocol.


CONCLUSIONS
These results suggest that the PL prefrontal cortex may be involved in the attenuation of contextual fear induced by systemic injection of CBD. They also support the proposition that the IL and PL play opposite roles in fear conditioning. A possible involvement of the BNST in CBD effects needs to be further investigated.
Department of Pharmacology, School of Medicine of Ribeirão Preto, Campus USP, Av. Bandeirantes 3900, Monte Alegre, Ribeirão Preto, SP, Brazil.
José Inácio
JI
Lemos
Leonardo Barbosa
LB
Resstel
Francisco Silveira
FS
Guimarães
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002185:Cannabidiol / Q000494:pharmacology*; D003214:Conditioning, Classical / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004597:Electroshock; D005106:Exploratory Behavior / Q000187:drug effects; D005239:Fear / Q000187:drug effects*; D007031:Hypothalamus / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000378:metabolism; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013037:Spatial Behavior / Q000187:drug effects
D016760:Proto-Oncogene Proteins c-fos; D002185:Cannabidiol