WHY NICOTINE IS AS ADDICTIVE AS HEROIN

Scientists reckon they have solved a puzzle about nicotine addiction: why,
if it gives the brain less of a buzz than drugs like cocaine or heroin, does
it generate comparable withdrawal symptoms?

Now, experiments with rats have shown that nicotine, the active drug in
tobacco, depresses the brain's ability to experience pleasure and respond to
chemical "rewards".

Researchers from the Scripps Research Institute in La Jolla, California,
found that rats suddenly deprived of nicotine had to be given much more of a
pleasurable reward stimulus to get the same buzz they had before.

Using electrodes implanted in the rats' brains, the researchers measured the
levels of "reward" experienced by chemical receptors. Drugs such as cocaine,
heroin, alcohol and nicotine all produce their "high" when parts of their
molecules latch on to chemical receptors in particular nerves in the brain.
Addiction is a reflection of a physical demand by those receptors for more
of the chemical. Getting used to the absence of the "high" produced by those
molecules is part of the process of withdrawal, and varies in severity for
different drugs.

In the experiment, nicotine withdrawal produced a decrease in brain reward
function - meaning that for the same stimulation, the nerve centres
experienced a smaller buzz. The effects lasted four days, during which the
rats showed the classic signs of withdrawal such as anxiety, irritability
and craving.

The scientists wrote in the journal Nature: "The decreased function in brain
reward systems during nicotine withdrawal is comparable in magnitude and
duration to that of other major drugs of abuse and may constitute an
important motivational factor that contributes to craving, relapse and
continued tobacco consumption in humans."

Checked-by: "Rolf Ernst"