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Carlsson, Arvid

dopamine brain drugs memory

(1923– ) Swedish pharmacologist: his work led to knowledge of Parkinson’s disease and of schizophrenia at the cellular level, and to new drugs to treat them.

Carlsson qualified in medicine at Lund in 1951, and worked thereafter in pharmacology at Gothenburg in Sweden, studying especially the action of drugs on the brain. Before his work it was known that the human brain contains about 10 11 nerve cells (neurons) each with complex connections; their tree-like shape allows each neuron to connect with thousands of neighbours. These connections or contact points (synapses) allow electrical signals to be passed between neurons, through a chemical transmitter at the synapse. In the 1950s Carlsson examined the action of the plant alkaloid reserpine on brain cells in rabbits: at that time it was used to treat schizophrenia. He found that reserpine reduced the amount of a rather simple brain chemical, dopamine, in one type of neuron. Given a sufficient dose of reserpine, the rabbits became immobile, and Carlsson noted that they showed similarities to human patients with severe Parkinson’s disease. He found that the ‘frozen’ rabbits recovered if they were given the synthetic chemical levodopa, which compensated for their depleted dopamine. Since this work levodopa has been widely used to treat parkinsonism. From Carlsson’s work it seems that the level of the neurotransmitter dopamine in the brain is critical: a deficit leads to the loss of movement control characteristic of parkinsonism, but an excess of dopamine produces the psychotic state of schizophrenia, and drugs useful in treatment of the latter disease are dopamine-inhibitors.

Carlsson later worked on antidepressive drugs, developing the selective serotonin re-uptake blockers, which have largely replaced earlier antidepressants. He was awarded the Nobel Prize for physiology or medicine in 2000, sharing it with Paul Greengard (1925– ) of Rockefeller University, New York, who from the 1960s studied in detail the way in which dopamine initiates a series of changes in neurons. The third sharer of the prize, Eric Kandel (1929– ) of Columbia University in New York also worked in neuroscience. His studies on memory used the sea slug Aplysia . This has few nerve cells (20 000), many of them large. It does not remember much; but if its protective gill reflex is strengthened by a stimulus, this amplified reflex is retained for days or weeks. Kandel showed that a weak stimulus, retained only for hours, is due to increase in the amount of neurotransmitter at some synapses. In contrast to this short-term memory, a strong stimulus whose effect is retained for weeks is linked with increased protein formation at the synapse. If this protein formation is prevented, long-term memory is blocked but not short-term memory. In the 1990s Kandel showed that similar changes could be found in mice, and fairly certainly apply to humans.

Carmen: A Hip Hopera. 2001 [next] [back] Carlos, Wendy (née Walter)

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