AsianScientist (Feb. 8, 2017) – Japanese researchers have successfully synthesized a compound that allowed them to precisely control the release of calcium ions (Ca2+) in mouse brains. Their technique, described in a paper published in ACS Omega, could be extended to other processes where calcium ions plays an important role, such as muscle contractions and blood clotting.
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—its concentration increases prior to the release of glutamate, but again the mechanisms are poorly understood. The main obstacle is detecting and controlling the location of calcium in the neuron, where it exists as a dissolved salt.
To study the flow of calcium ions during neurotransmission, a team of researchers led by Professor Manabu Abe from Hiroshima University developed a calcium-binding compound that can be activated by near-infrared laser light to trap and release calcium ions.
When applied to the body via spray, the carrier molecules diffused independently into neuron cells, capturing and holding in place any calcium they encounter by bonding favorably with it.
However, calcium suspended in place is of little use in memory experiments unless it can actually be detected. To solve this dilemma, chromophores—essentially light sensitive antennae—were incorporated into the carriers giving them light absorbing properties.
When near-infrared light is projected at these modified carriers they break down via two-photon emission. Near-infrared light is capable of penetrating tissue without damaging it, allowing the researchers to externally control the release of calcium without harming the living organism.
The researchers used near-infrared lasers on neuron cells containing these light sensitive carriers to see if calcium was released. As expected, exposure to the laser caused the light-sensitive calcium carrier molecules to break down and release calcium ions, triggering an release of an electrical charge at the point of laser beam penetration.
As this change in electrical charge only happened in specific areas and at relatively high levels, the authors concluded that those locations were where neurotransmitters are located.
Scientists can now focus on these precise points of neurotransmitter production to develop treatments for memory loss, for example by observing how these areas respond to medication or by introducing glutamate to neurons which are not functioning.
The article can be found at: Jakkampudi et al. (2016) Design and Synthesis of a 4-Nitrobromobenzene Derivative Bearing an Ethylene Glycol Tetraacetic Acid Unit for a New Generation of Caged Calcium Compounds with Two-Photon Absorption Properties in the Near-IR Region and Their Application in Vivo.
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Source: Hiroshima University; Photo: Shutterstock.
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