Pitt researchers discover brain’s dopamine signal

Have you ever wondered why people become addicted to drugs and sex knowing that it is potentially damaging to them? This question could be answered by understanding the effects of the hormone and neurotransmitter dopamine. Recent research has indicated that dopamine has a significant role in brain pleasure pathways and has led to the understanding of multiple psychological diseases.

Dopamine is a neurotransmitter that plays a crucial role in addiction by operating through the reward-signaling system in the brain. It is a precursor to adrenaline and plays a pivotal role in brain processes that control movement, emotional response, and the ability to experience pleasure and pain. Pleasurable activities like eating, drinking, and having sex are all associated with elevated dopamine levels in the brain.

On the other hand, dopamine levels decrease in an individual’s brain when the person is experiencing anxiety or depression. Many drugs that give “calming” highs, like cocaine and nicotine, appear to work by simulating the effects of dopamine in the brain. Due to this, dopamine is called the “pleasure hormone.” Dopamine secreted in the body also causes schizophrenics to experience hallucinations.

When a person gets a sudden urge for pleasure-related activites, it is actually the dopamine neurons “burst firing.” This so-called burst firing is what channels goal-directed behavior in people.

Research done at the University of Pittsburgh recently attempted to study the cause of the neural burst. “We had a long-standing interest in the dopamine system,” said Anthony Grace, professor of neuroscience, psychiatry, and psychology and head of the project along with Pitt neuroscience research associate Daniel Lodge. “The current treatments for curing schizophrenia and other such related diseases block all the dopamine secreted by the neurons. However, some of this dopamine is necessary for cognition.”

The medicines or drugs used to cure mental disorders like Parkinson’s disease or schizophrenia and addictions block all the dopamine secreted by the brain. However, dopamine is also important for emotions and pain sensations. For this reason, people on medication for psychiatric reasons often appear to be detached and “zombie-like.”

The researchers attempted to study the mechanisms of the brain’s reward-signaling system. Their experimental setup consisted of anesthetized rats, a model used to study what caused the neurons to go into burst mode.

What they found was a chemical responsible for signaling dopamine neurons to start firing. They found this “switch” in a particular area of the brain stem known as the laterodorsal tegmental nucleus. This area of the brain is regulated by the prefrontal cortex, which is also called the “planning” part of the brain. The researchers then found an indirect means to regulate the dopamine secreted by the brain. Thus, dopamine’s functions in normal routine and mental disorders can be controlled.

“We have found the area of the brain that tells [dopamine neurons] to go into communication mode or not,” said Grace. “It could provide potential therapies for major mental disorders. We could develop drugs that control what the dopamine is doing.” Instead of merely blocking all the dopamine secreted and thus having significant personality side affects, researchers could alter when the dopamine is secreted to cure schizophrenia and other diseases while preserving dopamine for other critical brain functions.

This research is a breakthrough in the understanding of neurological pathways.