The amygdala is a key emotional center in the brain that helps regulate anxiety and the flight-or-fight response, and this finding may help explain why many marijuana users say they take the drug to reduce anxiety.
The study also showed for the first time how nerve cells in this part of the brain make and release their own natural “endocannabinoids.”
The study “could be highly important for understanding how cannabis exerts its behavioral effects,” said Sachin Patel, M.D., Ph.D., the paper’s senior author and professor of Psychiatry and of Molecular Physiology and Biophysics.
As the legalization of marijuana spreads across the country, more people — and especially young people whose brains are still developing — are gaining access to and being exposed to the drug.
Previous studies at Vanderbilt and elsewhere, Patel said, have suggested the following:
- The body’s natural endocannabinoid system regulates anxiety and our response to stress by cooling down excitatory signals that involve the neurotransmitter glutamate;
- Chronic stress or severe emotional pain can trigger a reduction in both the production of endocannabinoids and the responsiveness of the receptors. Without this “buffering” effect, anxiety runs wild;
- And finally, chronic use of the drug down-regulates the receptors, paradoxically increasing anxiety. This can trigger a cycle of increasing marijuana use that in some cases can lead to addiction.
In the current study, scientists used high-affinity antibodies to “label” the cannabinoid receptors so they could be seen using various microscopy techniques. This enabled researchers to see what was happening at individual synapses, or gaps between nerve cells.
“We know where the receptors are, we know their function, we know how these neurons make their own cannabinoids,” Patel said. “Now can we see how that system is affected by … stress and chronic (marijuana) use? It might fundamentally change our understanding of cellular communication in the amygdala.”
The study, published in the journal Neuron, was led by first author Teniel Ramikie, a graduate student in Patel’s lab. The research team included scientists from Hokkaido University in Sapporo, Japan, the Hungarian Academy of Sciences in Budapest, and Indiana University in Bloomington.
Source: Vanderbilt University