Researchers have found cannabinoid receptors, through which marijuana exerts its effects, in a key emotional hub in the brain involved in regulating anxiety and the flight-or-fight response, according to a recent study.

For the first time, cannabinoid receptors have been identified in the central nucleus of the amygdala in a mouse model by scientists from Vanderbilt University. They said this could explain why some marijuana users take the drug mainly to reduce anxiety.

The study "could be highly important for understanding how cannabis exerts its behavioral effects," Sachin Patel, paper's senior author and professor of Psychiatry and of Molecular Physiology and Biophysics, said in a statement.

In the report, published in the current issue of the journal Neuron, researchers showed for the first time how nerve cells in this part of the brain make and release their own natural "endocannabinoids."

Previous studies at Vanderbilt and elsewhere have suggested that the natural endocannabinoid system regulates anxiety and the response to stress by dampening excitatory signals that involve the neurotransmitter glutamate. They have also suggested that chronic stress or acute, severe emotional trauma can cause a reduction in both the production of endocannabinoids and the responsiveness of the receptors. Without their "buffering" effect, anxiety goes up.

For the recent study, Patel and first author Teniel Ramikie used high-affinity antibodies to "label" the cannabinoid receptors so they could be seen using various microscopy techniques, including electron microscopy, which allowed very detailed visualization 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."