hide
Free keywords:
-
Abstract:
The extracellular compartment of the brain is a complex, dynamic microenvironment
containing nutrients, metabolites, and molecules related to neural signaling. Understanding of
brain function requires direct monitoring of neural activity, commonly done by means of
intracortical microelectrode recordings. The existing extracellular recording techniques
provide us with rich information regarding single or multiple neuron activity as well as some
information about subthreshold processes, but fail to reveal the role of inhibition in the
anatomically demonstrated microcircuits. One possible solution to this is simultaneous
extracellular field potential and neurotransmitter recordings. In this study, an in vivo nanosampling
technique was developed, with significantly higher spatial resolution than that
afforded through microdialysis. The technique capitalizes on its ability to directly withdraw
large quantities (several hundreds of nL) of extracellular fluids (ECF) from the monkey brain
at a rate of 1-50 nL min-1. The fluids were stored along a 4 m long, 20 µm I.D., 90 µm O.D.
fused silica capillary loop. The obtained intact ECF sample was then distributed into a series
of micro-vials according the time interval specified by the systems temporal resolution. The
contents of multiple neurotransmitters and signaling molecules in each distributed ECF
sample, including glutamate, GABA, acetylcholine, and asparagine, were determined
simultaneously by capillary HPLC-MS. Hydrophilic interaction chromatography was
employed to separate the highly polar and ionic compounds directly for mass spectrometer
detection.
