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  • Microelectrode array studies of basal and potassium-evoked release of L-glutamate in the anesthetized rat brain.

Microelectrode array studies of basal and potassium-evoked release of L-glutamate in the anesthetized rat brain.

Journal of neurochemistry (2006-01-31)
B K Day, F Pomerleau, J J Burmeister, P Huettl, G A Gerhardt
ABSTRACT

L-glutamate (Glu) is the predominant excitatory neurotransmitter in the mammalian central nervous system. It plays major roles in normal neurophysiology and many brain disorders by binding to membrane-bound Glu receptors. To overcome the spatial and temporal limitations encountered in previous in vivo extracellular Glu studies, we employed enzyme-coated microelectrode arrays to measure both basal and potassium-evoked release of Glu in the anesthetized rat brain. We also addressed the question of signal identity, which is the predominant criticism of these recording technologies. In vivo self-referencing recordings demonstrated that our Glu signals were both enzyme- and voltage-dependent, supporting the identity of L-glutamate. In addition, basal Glu was actively regulated, tetrodotoxin (TTX)-dependent, and measured in the low micromolar range (approximately 2 microm) using multiple self-referencing subtraction approaches for identification of Glu. Moreover, potassium-evoked Glu release exhibited fast kinetics that were concentration-dependent and reproducible. These data support the hypothesis that Glu release is highly regulated, requiring detection technologies that must be very close to the synapse and measure on a second-by-second basis to best characterize the dynamics of the Glu system.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
L-Glutamic acid monosodium salt hydrate, ≥99% (HPLC), powder
Sigma-Aldrich
L-Glutamic acid potassium salt monohydrate, ≥99% (HPLC), powder
Sigma-Aldrich
L-Glutamic acid hydrochloride