Propensity for smoking linked to molecules in specific brain regions, say scientists

Smokers could be predisposed to lighting up because of the make-up of their brain, new research suggests.

A predisposition to smoking may come from the molecular composition of specific regions of the brain, scientists found.

By creating a map of the brain based on post mortem tissue samples, researchers have been able to understand why certain behaviours – including smoking – are linked with certain brain areas.

“We studied the molecular makeup of the brain and isolated thousands of proteins out of the brain, and then we asked what this could tell us about human behaviour,” said Professor Seth Grant, a neuroscientist at the University of Edinburgh who led the Nature Neuroscience study.

“What we found was that we could link behaviours to sets of proteins in different parts of the brain,” he said.

The map was produced by analysing the protein molecules the brain uses to communicate.

These molecules are produced by genes at synapses – connection points between nerve cells in the brain.

Mapping the molecules therefore gave the researchers an idea of where different genes are being expressed in different parts of the brain.

“Smoking was particularly interesting, because when smokers think about smoking they use a part of their frontal lobes, and what we found was that the proteins in this part of the brain are ones controlled by the genes that make people want to smoke,” said Professor Grant.

Certain genes have previously been linked with smoking, so using their new map of gene expression the scientists could identify the regions of the brain where smoking genes were having an influence.

They found that their results matched earlier findings from brain imaging studies.

The researchers say their new study “bridges the gap” between past genetic studies and brain imaging studies.

“There’s about half a million papers on brain imaging, but the big problem with all that literature is that nobody really knows what the signal is really measuring,” said Professor Grant.

“What our evidence shows is that these signals associated with brain imaging are related to the molecular composition of synapses in those parts of the brain. We are offering a new molecular explanation for brain imaging studies.”

It also has implications for a variety of behaviours besides smoking.

Other aspects that can be investigated using this molecular map include language, emotions and memory.

“This is an important step toward understanding the molecular basis of human thought,” said Professor Grant.

By making links between diseases and certain parts of the brain, this mapping technique could also allow scientists to create better treatments for those diseases.

Transcranial stimulation, for example, is a technique that is already being trialled as a means of treatment by targeting a specific area and zapping it with magnetic waves.

Professor Derek Hill, a medical imaging specialist at University College London who was not involved in the study, agreed that the new research showed promise.

“This could help understand molecular basis of behaviour and could lead to new treatments, but it is early research and needs replication,” he said.