‘Brain boost' for Down's syndrome?

A drug might alleviate learning disabilities associated with Down's patients, writes Emma Baines

What is the story?
A ‘brain booster’ drug treatment to alleviate the learning difficulties of patients with Down’s syndrome could soon be available, according to media reports.

They said that pentylenetetrazole (PTZ) — a drug that was first tested as a brain enhancer for mentally impaired people 50 years ago — had been found substantially to improve the learning and memory of mice with symptoms of Down’s syndrome.

This has led scientists to believe that a low daily dose of PTZ could also increase the cognitive abilities of patients with Down’s syndrome,  helping them to live more normal lives, the papers added.

What is the research?
The gamma aminolontyric acid (GABAA) antagonist PTZ was first used as a cardiac stimulant in the 1920s, and as an alternative to insulin shock treatment for patients with schizophrenia in the 1940s.

During the 1950s and 1960s,  PTZ at doses of 200 to 800mg, were administered to geriatric patients as a mental stimulant. However, high doses of the drug were found to be the cause of  seizures.

Since then, PTZ has primarily been used for the study of epilepsy in animals.

The current study was designed to see if cognitive deficits found in Down’s could be reversed with GABAA antagonist treatment.

The researchers treated a strain of mice with memory problems similar to those found in Down’s patients (Ts65Dn mice) with non-epileptic oral doses of PTZ daily, for 17 days.

They then tested the performance of the treated mice on an object recognition and maze exploration tasks.

They found the treated mice performed as well on both tests as mice with no cognitive deficit.

The researchers concluded that GABAA antagonists at non-epileptic doses improved the cognitive performance of mice that exhibited Down’s-type symptoms, and that PTZ could potentially produce a similar improvement in patients with Down’s syndrome.

What do the researchers say?
Lead research on the study, Professor Craig Garner, Professor of Psychiatry and Behavioural Sciences at the Down Syndrome Research Center at the Stanford University Medical Center in California, said: ‘Our findings clearly open a new avenue for considering how cognitive dysfunction in individuals with Down’s syndrome might be treated.

‘As you can imagine, measuring cognition in mice is limited, but on all tests the treated mice did as well as the wild-type mice.’

But he warned that the safety of the treatment in human patients had not yet been tested, and that the effects of PTZ on children were largely unknown.

‘Our studies are in mice and although they show a great deal of promise, one really needs to wait for clinical trials on people with Down’s syndrome before using PTZ.

‘Children with Down’s syndrome have a higher incidence of epilepsy. Why this is remains unclear. But since PTZ can induce seizures at high doses, this is a very important question.

‘In our study, the mice did not have seizures, but we do not know how people with Down’s syndrome will respond to drugs like PTZ.

‘We anticipate that clinical trials will be able to identify a safe and efficacious dose and dosing frequency for PTZ in people with Down’s syndrome,’ he concluded.

What do other experts say?
Chief Executive of the Down’s Syndrome Association, Carol Boys welcomed the finding.

‘The Down Syndrome Research Center at Stanford consistently produces highly respected, pioneering work,’ she said.

‘However, we must remember that this research has been conducted with mouse models.

‘At this stage, the compound PTZ is not approved for human use and until extensive further clinical trials with real people have been conducted, it will be impossible to predict how this drug might work.’

Dr Elizabeth Fisher, from the Institute of Neurology in London,  agreed that this study provided good evidence that PTZ could potentially improve the learning and memory of patients with Down’s syndrome.

But she added it was important to remember that it would not be a complete cure for the condition: ‘There is no reason to think it would affect any other cognitive or behavioural problems found in patients with Down’s syndrome,’ she said.

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