Addiction Research Articles

How the Brain Responds to Nicotine

Smoking is associated with multiple health risks. Heart disease and several types of cancer are more likely to occur in individuals who smoke. In trying to understand how to help smokers quit, scientists also want to understand how smokers get started in their addiction.

A new neuroscience research study attempted to pinpoint the specific brain activity that occurs within the first few minutes of exposure to nicotine. The study, published inĀ The Journal of Neuroscience, showed that there was a connection formed between neurons within a single 15-minute exposure to nicotine, causing a long-term excitability between the neurons.

The results show that nicotine behaves similarly to cocaine in the brain, changing mechanisms during the very first contact and creating a long-lasting change in the brain.

Danyan Mao, PhD, is a postdoctoral researcher at the University of Chicago Medical Center and lead author of the study. Mao explains that the change in the brain for smokers is a long-term behavioral change, but that the changes begin at the first exposure to nicotine. The researchers wanted to find out what happened in the brain at first exposure to a cigarette that then led the person to choose to have a second cigarette.

The study’s design was based on the understanding that as neurons are repeatedly activated together, they begin to form a strengthening bond. This leads to the neurons having the ability to excite one another.

Previous research has shown that nicotine can promote plasticity in a region of the brain known as the ventral tegmental area (VTA). Mao monitored the electrical activity of VTA dopamine neurons in slices of brain from adult rats. Each section of the rat’s brain was soaked for 15 minutes in a concentration of nicotine comparable to the exposure experienced in the brain during the smoking of a single cigarette.

After several hours, Mao conducted electrophysiology experiments to test for synaptic plasticity and identify receptors involved. Mao found that the nicotine affected a receptor for the neurotransmitter acetylcholine located on the dopamine neurons. But another surprising result showed that the nicotine affected the D5 dopamine receptor, a component associated with cocaine addiction.

The results of the study show how even one cigarette can introduce changes in the brain that mimic those found in cocaine use. The first time a cigarette is used, neurons begin to make connections, encouraging the pleasurable response associated with smoking. Understanding how nicotine affects the brain, even during the first cigarette smoked, may help scientists develop strategies for helping individuals with smoking cessation.

New Insights into the Brain’s Role in Drug Addiction

New animal research is enabling a deeper understanding of the neurobiology of drug addiction in humans, and this knowledge may lead to more effective treatment options to weaken the powerful cravings that cause people to relapse.

The findings were released today at Neuroscience 2009, the Society for Neuroscience’s annual meeting and the world’s largest source of emerging news about brain science and health.

Drug addiction is known to change the structure and function of the brain, affecting a person’s self-control and decision-making ability. According to the Substance Abuse and Mental Health Services Administration’s latest survey, 23.6 million persons aged 12 or older needed treatment for an illicit drug or alcohol abuse problem in 2006.

These new studies have identified brain mechanisms that help explain how addictions form, as well as the cognitive problems associated with them. Additional research findings discussed could also offer hope against addiction relapses.

Today’s new findings show that:
1.) Chronic alcohol consumption reduces the number of new brain cells that form in the hippocampus of primates. The hippocampus plays a key role in memory, perhaps explaining the association between chronic alcoholism and memory problems (Chitra Mandyam, PhD).

2.) After exposure to cocaine, rhesus monkeys developed impairments in learning, cognitive flexibility, and memory. This finding suggests that cognitive problems associated with cocaine addiction in humans result directly from the cocaine abuse (Charles W. Bradberry, PhD).

3.) An amino acid already in the body was found to reduce cravings in addicted rats and appears to restore normal functioning in a brain circuit associated with cocaine addiction (Khaled Moussawi).

Other research findings being discussed at the meeting show that:

1.) Advanced neuroimaging technologies and behavioral research suggest that addiction disrupts the fine balance underlying reward, motivation, memory, and cognitive control. This research has important implications for developing therapies to treat addictive disorders (Nora D. Volkow, MD).

2.) Increasing evidence suggests that chronic drug use may alter the brain’s reward circuits on a genetic level, contributing to addiction. Focusing on the genetic effects of addiction may open new avenues for improved treatment (Eric J. Nestler, MD, PhD).
“The brain is the body’s most complex organ and chemical alterations caused by drug abuse have significant overarching impact on neuroplasticity,” said press conference moderator George F. Koob, PhD, of The Scripps Research Institute, an expert on addiction and stress.

“Today’s findings offer a better understanding of the impacts of this disease and provide a clearer approach toward treating addiction and guarding against relapse.”