ÜDS-Sağlık 2010-1 Soru=69

One can understand from the passage that drug addiction ----.

A study by a group of scientists has resulted in a major
step forward in overcoming drug addiction. As addiction
was known to cause molecular changes in the brains of
addicts, causing their neurons to transmit much stronger
signals of dopamine, a messenger molecule involved in
reward-seeking behaviours, the scientists were hoping to
prove experimentally that certain key proteins in the
dopamine-producing neurons influence drug addiction. It
was an inspired guess, as the study found that mice in
which these key proteins had been selectively switched off
displayed clear addictive behaviour. For instance, mice in
which the CluR1 protein was switched off showed a much
longer period of dependence. Conversely, re-administration
of cocaine after a long break immediately re-ignited the
addiction, but mice whose NR1 protein had been
deactivated resisted relapsing into addictive behaviours.
The ability of these proteins to determine i addictive
behavioural patterns makes them fascinating.