Nicotine triggers the same brain reward circuitry as opiates

June 15, 2005

In experiments with mice, researchers have found that nicotine triggers the same neural pathways that give opiates such as heroin their addictively rewarding properties--including associating an environment with the drug's reward. However, unlike opiates, nicotine does not directly activate the brain's opiate receptors, but activates the natural opioid reward pathway in the brain.

The researchers, led by Julie Blendy of the Transdisciplinary Tobacco Use Research Center (TTURC) at the University of Pennsylvania, said their findings suggest more effective ways that opiate blockers could be used to help smokers quit.

In their experiments reported in the June 16, 2005, issue of Neuron, the researchers administered nicotine to mice and analyzed the levels of a protein called CREB--known to control genes involved in the reward pathway of opiates and other abused drugs. They found that not only was CREB activated in the reward regions of the nicotine-treated animal's brains, but also that the drug naloxone, which blocks the opiate receptors, blocked CREB activation. Also, mutant mouse strains lacking the opioid receptor did not show an increase in CREB activity when they received nicotine.

The researchers also studied the relationship among nicotine, the environment, and this reward pathway. They conditioned mice to associate a specific test chamber with receiving nicotine, finding that the mice would prefer to stay in that chamber when given a choice. The researchers found that just placing the conditioned mice in the chamber activated CREB. They also found that naloxone blocked this conditioned increase in CREB, and that mutant mice lacking CREB or pretreated with naloxone did not show any reward response to nicotine.

However, naloxone did not block the chamber choice of mice conditioned with cocaine, found the researchers, indicating that cocaine activates the brain reward pathway in a different way from nicotine and opiates.

"The present results demonstrate that nicotine-associated environmental stimuli can activate the same molecular signal transduction molecules as the drug itself," wrote Blendy and her colleagues. They wrote that the activation of CREB "is evident not only after acute and repeated nicotine administration, but also following exposure to an environment in which the animal has previously received nicotine."

The researchers noted that clinical studies of opioid receptor blockers to relieve cigarette cravings "so far have produced mixed results, ranging from ineffectiveness at smoking cessation to mild reduction in the desire to smoke."

The researchers wrote that their findings "suggest that the timing and context of opioid receptor antagonist administration are critical for determining the effectiveness of blocking nicotine reward . . . . Given the results reported here, clinical studies designed to evaluate administration of opioid antagonists just prior to cues associated with smoking could lead to a more promising treatment regimen."

Source: Cell Press

Explore further: Study discovers a way to control internal clocks

Related Stories

Study discovers a way to control internal clocks

December 23, 2014

Researchers hypothesize that targeting components of the mammalian clock with small molecules like REV-ERB drugs may lead to new treatments for sleep disorders and anxiety disorders. It also is possible that REV-ERB drugs ...

And that is how the desert locust lost its memory

January 14, 2014

The desert locust (a type of grasshopper), much like Dr Jekyll/Mr Hyde, goes from being an innocuous solitary-living individual to become a voracious gregarious animal that destroys everything on its path (and back). These ...

Strategies to prevent tobacco use among teens

December 17, 2010

According to the Center for Disease Control, 21.4 percent of people aged 18 to 24 years smoke tobacco. Today everyone knows smoking is an unhealthy habit, so why do people still smoke? Penn State experts say several factors ...

Recommended for you

Reshaping the solar spectrum to turn light to electricity

July 28, 2015

When it comes to installing solar cells, labor cost and the cost of the land to house them constitute the bulk of the expense. The solar cells—made often of silicon or cadmium telluride—rarely cost more than 20 percent ...

New blow for 'supersymmetry' physics theory

July 27, 2015

In a new blow for the futuristic "supersymmetry" theory of the universe's basic anatomy, experts reported fresh evidence Monday of subatomic activity consistent with the mainstream Standard Model of particle physics.

A cataclysmic event of a certain age

July 27, 2015

At the end of the Pleistocene period, approximately 12,800 years ago—give or take a few centuries—a cosmic impact triggered an abrupt cooling episode that earth scientists refer to as the Younger Dryas.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.