A new animal study published by Psychopharmacology found that cannabidiol (CBD) administered into a specific region of the brain reduced neuropathic pain, as well as anxiety- and depression-like behaviors associated with the condition.

For the study, researchers from multiple colleges and institutions in Brazil examined whether CBD could influence chronic neuropathic pain by targeting the anterior insular cortex, a brain region involved in processing both the sensory and emotional aspects of pain. Chronic neuropathic pain is often accompanied by anxiety and depression, which researchers say may reflect maladaptive interactions between pain-processing and emotion-related brain networks.

Researchers used male Wistar rats subjected to chronic constriction injury of the sciatic nerve, a commonly used model of neuropathic pain. Twenty-one days after the injury, the animals received microinjections of CBD directly into the anterior insular cortex at doses of 15, 30 or 60 nmol, or received a vehicle treatment.

The animals were then evaluated using multiple behavioral tests, including the von Frey test for mechanical allodynia, the acetone test for cold allodynia, open field and elevated plus maze tests for anxiety-like behavior, and forced swim and sucrose spray tests for depression-like behavior.

Researchers found that CBD reduced both mechanical and cold allodynia in a dose-dependent manner, while also reducing anxiety- and depression-like behaviors. The strongest effects were observed at the highest dose tested, 60 nmol.

The study also examined whether CBD’s effects depended on cannabinoid CB1 receptors or serotonin 5-HT1A receptors. To test this, researchers pretreated some animals with either AM251, a CB1 receptor antagonist, or WAY-100,635, a 5-HT1A receptor antagonist. In both cases, the pretreatment blocked CBD’s effects, suggesting that both receptor systems were involved.

Researchers concluded that CBD administration within the anterior insular cortex produced “integrated analgesic, anxiolytic, and antidepressant-like effects” in the neuropathic pain model.

The findings add to growing preclinical evidence that CBD may influence both pain and the emotional symptoms that can accompany chronic pain conditions. However, because the study was conducted in rats and involved direct administration into the brain, further research would be needed to determine whether the findings translate to human patients or more conventional CBD delivery methods.