Pubdate: Thu,  2 Mar 2000
Source: Times, The (UK)
Copyright: 2000 Times Newspapers Ltd
Contact:  PO Box 496, London E1 9XN, United Kingdom
Fax: +44-(0)171-782 5046
Author: Nigel Hawkes, Science Editor


CANNABIS may ameliorate the symptoms of multiple sclerosis, experiments on
mice have shown.

There have been many anecdotal reports of benefits from MS sufferers who
have taken cannabis illegally but scientific evidence has been lacking. Now
a team led by David Baker of the Institute of Neurology in London has shown
that in a strain of mice which suffer a similar disease, the active agents
in cannabis reduce rigidity and trembling of the muscles.

The team also found that synthetic chemicals mimicking tetrahydrocannabinol
(THC), an active chemical in cannabis, had a similar effect, pointing the
way to new drugs to treat MS.

The results will boost calls to legalise cannabis for medical use. But the
scientists say that their main result may be a move from cannabis to
related synthetic drugs that are even more effective.

The mice were injected with THC and three other compounds: methanandamide,
similar to a cannabinoid produced naturally in the body, and two synthetic
compounds. All reduced both tremor and spasticity (rigidity), but a
synthetic compound called WIN55 proved the best against tremors, halting
uncontrolled limb movements in as little as a minute. Dr Baker said: "The
effect was really startling. It was a question of 'Now you see the tremor,
now you don't'."

The compounds lock on to two receptors in cells of the brain and spinal
cord. Blocking the receptors not only prevented the therapeutic action of
the compounds but made the existing symptoms much worse.

The scientists conclude in Nature that the purpose of the receptors and the
natural chemicals that bind to them is to maintain control of the muscles.
Dr Baker said: "One of their functions is to provide a protective filter
mechanism to limit excess excitation of the nerves. In a normal animal or
human being it provides fine control over motor function."

One implication of the research is that it may be possible to increase
levels of the natural cannabinoid, in the same way that anti-depressant
drugs lift the levels of chemicals in the brain linked to mood.

Additionally, the same receptors are found in the pain centres of the
spinal cord. That may explain the claimed benefits of cannabis for pain

Lorna Layward of the Multiple Sclerosis Society, co-author of the report,
said there was a "crying need" for new drugs for MS because current
treatments were either not very effective or caused severe side-effects.
Tremor was particularly difficult to treat and could be severely disabling,
she said.

A Medical Research Council clinical trial is examining the effect of
cannabis and THC on spasticity in 600 MS patients. It will report in two
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