The gene that regulates the body's main biological clock could also play a pivotal role in controlling drug addiction, scientists have said.

The Clock gene regulates the brain's response to drug abuse apart from controlling the body's circadian rhythms, including sleep and wakefulness, body temperature, hormone levels, blood pressure and heart activity, researchers at the University of Texas Southwestern Medical Centre of Dallas said.

In their study on mice, the researchers found that the Clock gene regulates the brain's response to cocaine, suggesting that similar actions take place in humans too.

According to researcher Colleen A. McClung, the gene regulates the brain's response to drug abuse "through its actions on dopamine pathways", the medical centre's website said.

Dopamine is a neurotransmitter associated with the "pleasure system" of the brain, providing feelings of enjoyment from certain activities. Dopamine is released naturally by rewarding experiences like food, sex and use of certain drugs.

In the study, mice that lacked the Clock gene were injected with cocaine. Not only did the mice experience problems with their circadian cycles - not sleeping as much and becoming more hyperactive - they also found cocaine more rewarding than controlling mice, demonstrated by their strong preference for the location where the drug was administered.

"We tracked dopamine cells in the mice brains and found that these cells fired more rapidly and showed a pattern called bursting, which leads to an usually large dopamine release," McClung said.

It was also found that more dopamine is produced and released in these mice under normal conditions and particularly after exposure to cocaine.