Washington: Scientists claim to have for the first time generated a detailed map of human neuroreceptor, a breakthrough that may revolutionise the engineering of drugs used to treat diseases like Alzheimer's and schizophrenia.

A team at the University of Southern California has produced the world's first high-resolution images of the ?7 (Alpha 7) receptor, a molecule responsible for transmitting signals between neurons -- particularly in regions of the brain believed to be associated with learning and memory.

Using the image, the scientists will be better equipped to design pharmaceuticals specifically to interact with the receptor, instead of blindly using a trial-and-error approach.

"A lot of interest in this work will come from pharmaceutical companies. They really have no clear picture of this. They don't know how or why (their drugs) work,"  said team member Prof Lin Chen.

The high-resolution image will also help neuroscience researchers study how these receptors receive and transmit neuronal signals, a question that has puzzled researchers for decades, says the team.

Developing an image of the ?7 receptor was no simple task, which is partly why it has taken until now to achieve this despite the wide interest in the understanding the receptor's structure. Attempts to decipher neuroreceptors have been ongoing for 30 years.

"This has been a longstanding challenge. The challenge is twofold," Chen said.

In the case of ?7, the team engineered a chimera, a Frankenstein molecule sharing about 70 per cent of its structure in common with the ?7 that reacted to stimuli in the same way that natural ?7 does.

The next step was to form crystals with these proteins for high-resolution study. This turns out to be particularly difficult for neuronal receptors because they are flexible -- they need to bind to a neurotransmitter, a small molecule that acts as a messenger in the nervous system, and transmit the signal across the protein body.

Moreover, these receptors are decorated with sugar molecules that add further flexibility to the system.

The crystallisation of ?7 was a painstaking process. For every hundred crystals obtained, only one or two were good enough for structural analysis. Li had to sort through hundreds of crystals to collect enough data for structural analysis.

"In a sense, these crystals are probably among the world's most expensive crystals, certainly more expensive than diamond. But considering the rich information we can get from these crystals about human neuronal receptors, and the potential impact on drug development that can benefit human health, they are worth the effort," Chen said.