Cocaine Acts As Suppressant Not Stimulant In Genetically Altered Mice

Researchers at the Ohio State University have found that cutting off the reward pathway of cocaine on mice by genetically altering a vital target in the brain of the mice makes them shun cocaine.

Howard Gu, the study's lead author and an associate professor of pharmacology and psychiatry at Ohio State University said that the researchers were not suggesting that humans be treated in the same way, but had identified the key protein, which controls cocaine's effects in the body.

'Cocaine blocks dopamine transporters, and this action ultimately is what makes a person feel high,' Gu said. 'We found that cocaine would not produce a high if it could not block the transporters.' The study appears in May 29 issue of the Proceedings of the National Academy of Sciences.

Dopamine is a chemical messenger in the brain, which is vital for the functioning of the nervous system. Cocaine blocks the dopamine transmitter as its principal effect, the researchers altered this gene that codes for the dopamine transporter in the mice.

'By doing so we created a dopamine transporter that resists cocaine but also retains its function of taking up dopamine and carrying it back to the neurons,' Gu said.

Now researchers spilt the mice into two groups, the normal ones and the ones with the altered genes and gave them cocaine injections. 'After the cocaine injections, the normal mice ran all over the place, sniffing and checking everything out in the box over and over again, until we took them out of the box,' Gu said. 'But cocaine seemed to calm the modified mice, as they sat in a corner for long periods of time.'

'Deleting the dopamine transporter itself caused tremendous changes in the mouse brain,' Gu said. 'It's possible that, somehow, the animals' brains rewired themselves and, as a result, the mice still felt the effects of cocaine.'