Detection of Glutamate in Optically Trapped Single Nerve Terminals by Raman Spectroscopy

Glutamate is the major excitatory neurotransmitter and is of particular interest in light of current models of memory and learning. The paper describes the first in situ detection of glutamate in single nerve terminals (synaptosomes), which is achieved by using laser trapping Raman spectroscopy. The near-infrared laser light captures a single synaptosome obtained from a Wister rat brain. The release of glutamate in a single laser-trapped synaptosome was detected by subtracting the Raman spectrum before depolarization from that after depolarization with the addition of the K ⁺-channel blocker, 4-aminopyridine. The result indicated that the single synaptosome released ∼3 amol of glutamate and that the release rate depended on the 4-aminopyridine concentration.