Method uses near-infrared light to unravel memory loss conditions

A near-infrared laser technique can bridge the missing links in memory flow, which could lead to treatments for memory loss.

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Researchers at Hiroshima University (Japan) have developed a near-infrared (near-IR) laser-activated technique for bridging missing links in memory flow. The work aims to increase understanding of the mechanisms involved in neurotransmission, which could potentially lead to treatments for memory loss conditions.

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While scientists are aware that stimulation of neurotransmitters such as glutamate is required for functioning memory, where and how these chemical messengers are produced remains a mystery. What is known is that calcium has a critical role to play, as its concentration increases prior to glutamate release—a mechanism that is poorly understood because of calcium's elusiveness in neuron cells where it exists as a dissolved salt, making it difficult to control or detect.

Manabu Abe, a professor in the Department of Chemistry at Hiroshima University, developed the laser technique that, when used, could allow the production sites of chemical messengers within neurons to be sourced, studied, and even rebooted as required to reestablish flows between neurons and boost memory.

The first phase of the method involves synthesized carrier molecules that, when applied to the body via spray, diffuse independently into neuron cells, capturing and holding in place any calcium they encounter by bonding favorably with it. But because calcium suspended in place is of little use in memory experiments unless it can actually be detected, Abe and his research team incorporated chromophores into the carriers to give them light-absorbing properties. When near-IR light is projected at these modified carriers, they break down via two-photon emission. This breakdown, using light capable of penetrating tissue without damaging it, makes it particularly useful for internal use in living organisms via external control using lasers.

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Calcium carriers hold calcium in place and release it upon exposure to near-infrared light.

In Abe's lab, near-IR lasers were projected at neuron cells containing the light-sensitive carriers to see if calcium was released. When the electrical charge at each laser-beam penetration point was recorded, exposure to the electromagnetic wave broke down the light-sensitive calcium-carrier molecules, causing them to shed their electrically charged calcium cation. As calcium only exists at specific neurotransmitter production areas in neurons, a higher charge was detected in these points. Because this only happened in specific areas and at relatively high levels, it could also be deduced that the elusive sites of calcium concentration in neurons had finally been found.

Scientists can now focus on these precise points of neurotransmitter production to develop treatments for memory loss, whether by observing how these areas respond to medication or by introducing outside sourced glutamate to neurons that are not functioning.

Full details of the work appear in the journal ACS Omega; for more information, please visit http://dx.doi.org/10.1021/acsomega.6b00119.

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