What happens in the brain when cannabis generates anxiety?
For the first time, Northwestern scientists have identified a set of neurons that play a role in generating anxiety after exposure to cannabinoid drugs, especially under stressful conditions. Cannabinoids are a class of substances that includes THC, the main psychoactive ingredient in cannabis.
Researchers from Northwestern University have pinpointed a group of brain cells that trigger anxiety when exposed to cannabis, particularly under stressful situations. Cannabinoids, including THC, are the primary psychoactive components in cannabis. The study involved exposing mice to a fox urine scent, a known stressor, after administering either a placebo or a synthetic cannabinoid drug.
The mice that received the drug exhibited more frequent freezing and less investigation into the scent, indicating anxious behavior. This anxiety was linked to the activation of somatostatin neurons in the central amygdala, a region responsible for processing fear and stress. When these neurons were genetically silenced, the mice avoided the predator scent more readily, suggesting their crucial role in cannabinoid-induced anxiety.
Dr. Sachin Patel, the study's senior author, explained that the findings could help explain why cannabis use sometimes leads to heightened anxiety, especially when combined with other stressful conditions. The research, published in Nature Communications, tested various doses of the synthetic cannabinoid on mice and monitored their interaction with the predator odor, both in terms of proximity and behavioral responses such as freezing or fleeing.
By implanting small microscopes in the mice's brains, the team was able to record brain activity and analyze how cannabinoids affected neural interactions. The drugs weakened the brain's natural "brake" on somatostatin neurons, leading to increased activity and excessive anxiety. The research also revealed that higher doses of cannabinoids, in combination with environmental stress, synergistically suppressed the brake on the central amygdala, amplifying anxiety.
Increasing rates of cannabis use in the U.S., coupled with rising emergency department visits due to adverse effects, and the global surge in anxiety and mood disorders, underscore the importance of understanding how cannabis impacts brain function. Patel noted that these findings could potentially lead to new strategies for mitigating negative consequences of cannabis use, including its impact on anxiety.
Moreover, the insights gained could have broader implications beyond cannabis, as suppressing somatostatin neurons in the central amygdala might offer a pathway to alleviate anxiety symptoms in general.
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