New Drug May Help Treat Symptoms of Depression

A new drug looks to treat depression and other mood disorders that may lie in a group of GABA neurons (gama-aminobutyric acid-the neurotransmitters that inhibit other cells) and which are shown to help contribute to social withdrawal and increased anxiety.

Penn Medicine researchers found that people suffering from depression and other mood disorders often reacted to rejection or bullying simply by pulling themselves socially out of a situation more than the average person.

A preclinical study found that bullying and other social stresses can trigger symptoms of depression in mice by activating GABA neurons in a never-before-seen direct relationship between social stimuli with neural circuitry. Through activation of the neurons, researchers have found that directly inhibited levels of serotonin play a vital role in behavioral responses and whether a depressed individual will choose to interact in a certain social situation.

"This is the first time that GABA neuron activity-found deep in the brainstem-has been shown to play a key role in the cognitive processes associated with social approach or avoidance behavior in mammals," Dr. Berton said, via a press release. "The results help us to understand why current antidepressants may not work for everyone and how to make them work better-by targeting GABA neurons that put the brake on serotonin cells."

Lower levels of serotonin can create a defensive response and cause avoidance or submission. However, higher levels can create the opposite reaction.

For the study, mice were exposed to brief bouts of aggression from trained "bully" mice. When researchers compared gene expression in the brains of resilient and avoidant mice, Berton discovered that from bullying avoidant mice, GABA neurons had become more excitable and the mice exhibited signs of social defeat. Yet resilient mice did not show any changes in neuron levels.

"Our paper provides a novel cellular understanding of how social defensiveness and social withdrawal develop in mice and gives us a stepping stone to better understand the basis of similar social symptoms in humans," said Berton, via the release. "This has important implications for the understanding and treatment of mood disorders."

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More information regarding the study can be found via the Journal of Neuroscience.