Involvement of serotonin-mediated neurotransmission in the dorsal periaqueductal gray matter on cannabidiol chronic effects in panic-like responses in rats

• Published in: Psychopharmacology 2013-03, Vol.226 (1), p.13-24
• Main Authors: Campos, Alline Cristina, de Paula Soares, Vanessa, Carvalho, Milene C, Ferreira, Frederico Rogerio, Vicente, Maria Adrielle, Brandão, Marcus Lira, Zuardi, Antonio Waldo, Zangrossi, Hélio, Guimarães, Francisco Silveira
• Format: Article
• Language: English
• Subjects: Animals; Behavior, Animal - drug effects; Biomedical and Life Sciences; Biomedicine; Brain Mapping; Cannabidiol - administration & dosage; Cannabidiol - pharmacology; Cannabidiol - therapeutic use; Cannabinoids; Cannabis sativa; Dose-Response Relationship, Drug; Drug therapy; Genetic aspects; Male; Maze Learning - drug effects; Microdialysis; Neural transmission; Neurosciences; Original Investigation; Panic attacks; Panic Disorder - physiopathology; Panic Disorder - prevention & control; Panic Disorder - psychology; Periaqueductal Gray - drug effects; Periaqueductal Gray - metabolism; Periaqueductal Gray - physiopathology; Pharmacology/Toxicology; Physiological aspects; Polymerase Chain Reaction; Psychiatry; Psychopharmacology; Rats, Wistar; Receptor, Serotonin, 5-HT1A - metabolism; Rodents; Serotonin; Serotonin - metabolism; Synaptic Transmission - drug effects
• ISSN: 0033-3158; 1432-2072
• DOI: 10.1007/s00213-012-2878-7

Rationale Cannabidiol (CBD) is a non-psychotomimetic constituent of Cannabis sativa plant that promotes antianxiety and anti-panic effects in animal models after acute systemic or intra-dorsal periaqueductal gray (DPAG) administration. However, the effects of CBD repeated administration, and the possible mechanisms involved, in animal models of anxiety- and panic-related responses remain poorly understood. Objective The present study evaluates the role of the serotonergic neurotransmission within the DPAG in the modulation of escape responses of rats chronically treated with CBD. Methods Male Wistar rats received acute or repeated (5 mg/Kg/daily/21 days) administration of CBD and were submitted to the elevated T-maze (ETM). We also investigated if CBD effects on the ETM depend on facilitation of 5-HT1A-mediated neurotransmission in the DPAG. To this latter aim, we verified if these effects would be prevented by intra-DPAG injection of the 5-HT1A receptor antagonist WAY100635 (0.37 nmol/0.2 μL). Also, we verified, by in vivo microdialysis, if CBD chronic treatment increases serotonin (5-HT) release and, by quantitative polymerase chain reaction, if there are changes in 5HT-1A or 5HT-2C mRNA expression in DPAG. Results The results showed that repeated but not acute peripheral administration of CBD decreases escape responses in the ETM, suggesting a panicolytic effect. This treatment did not change 5HT-1A or 5-HT-2C receptor mRNA expression nor modify serotonin extracellular concentrations in the DPAG. CBD effects were prevented by DPAG injection of the 5-HT1A receptor antagonist. Conclusions Together, these findings suggest that repeated treatment with CBD induces anti-panic effects by acting on 5-HT1A receptors in DPAG.