- Susan Greenfield, professor
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT
People have been using drugs to alter brain states since the dawn of time. But the use of specific drugs to combat specific brain problems is a hallmark of this century. In previous eras doctors reached for laudanum to combat hysteria, oblivious to the underlying neurochemistry. However, in Paris the famous neurologist Charcot purposely gave belladonna to patients with Parkinson's disease to combat the constant salivation that accompanies loss of motor control because women of the time who used the drug to dilate their pupils complained of a dry mouth. Surprisingly, this anticholinergic drug proved effective in combating not just the dribbling but the motor symptoms of Parkinson's disease.
Today we owe much to the work of Henry Dale and Otto Loewi, who established that chemicals act as transmitters to relay a signal from one neurone to the next.1 The guiding principle of modern neuropharmacology is to mimic, block, amplify, or reduce the availability of certain transmitters, believed to be pivotal to the disease to be treated. Yet herein lies the problem.
One transmitter may be linked to many disorders, and one disorder to many transmitters
Classic transmitters have non-classic modulatory functions too
Substances such as nitric oxide and acetylcholinesterase have unexpected signalling properties
Neurodegeneration might be an aberrant form of development, so drugs promoting neuronal regeneration should be approached with caution
Drugs in the future could be used as a Rosetta stone for linking brain and mind
The promiscuous transmitter
There is no one to one matching of a single chemical system to a disease. Consider, for example, the well known transmitter dopamine. In Parkinson's disease there is a deficit of dopamine in the substantia nigra, hence prompting administration of the precursor and eventual mimicry of the effects of dopamine …