New cannabis-like drugs could block pain without affecting brain, says study

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New cannabis-like drugs could block pain without affecting brain,

says study

http://www.eurekalert.org/pub_releases/2008-09/icl-ncd091208.php

A new type of drug could alleviate pain in a similar way to cannabis

without affecting the brain, according to a new study published in

the journal Pain on Monday 15 September.

The research demonstrates for the first time that cannabinoid

receptors called CB2, which can be activated by cannabis use, are

present in human sensory nerves in the peripheral nervous system, but

are not present in a normal human brain.

Drugs which activate the CB2 receptors are able to block pain by

stopping pain signals being transmitted in human sensory nerves,

according to the study, led by researchers from Imperial College

London.

Previous studies have mainly focused on the other receptor activated

by cannabis use, known as CB1, which was believed to be the primary

receptor involved in pain relief. However, as CB1 receptors are found

in the brain, taking drugs which activate these receptors can lead to

side-effects, such as drowsiness, dependence and psychosis, and also

recreational abuse.

The new research indicates that drugs targeting CB2 receptors offer a

new way of treating pain in clinical conditions where there are

currently few effective or safe treatments, such as chronic pain

caused by osteoarthritis and pain from nerve damage. It could also

provide an alternative treatment for acute pain, such as that

experienced following surgical operations.

The new study showed that CB2 receptors work to block pain with a

mechanism similar to the one which opiate receptors use when

activated by the powerful painkilling drug morphine. They hope that

drugs which target CB2 might provide an alternative to morphine,

which can have serious side effects such as dependency, nausea and

vomiting.

Praveen Anand, Professor of Clinical Neurology and Principal

Investigator of the study from the Division of Neurosciences and

Mental Health at Imperial College London, said: " Although cannabis is

probably best known as an illegal recreational drug, people have used

it for medicinal purposes for centuries. Queen used it in

tea to help with her period pains, and people with a variety of

conditions say that it helps alleviate their symptoms.

" Our new study is very promising because it suggests that we could

alleviate pain by targeting the cannabinoid receptor CB2 without

causing the kinds of side-effects we associate with people using

cannabis itself. "

The researchers reached their conclusions after studying human

sensory nerve cells in culture with CB2 receptor compounds provided

by GlaxoKline, and also injured nerves from patients with

chronic pain.

The researchers are now planning to conduct clinical trials of drugs

which target CB2 in patients with chronic pain at Imperial College

Healthcare NHS Trust, which has integrated with Imperial College

London to form the UK's first Academic Health Science Centre.