Microelectrode array studies of basal and potassium-evoked release of L-glutamate in the anesthetized rat brain.
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.
Day
B K
BK
Center For Sensor Technology, Morris K. Udall Parkinson's Disease Research Center of Excellence, Department of Anatomy and Neurobiology, University of Kentucky, Lexington, Kentucky 40536-0098, USA.
Pomerleau
F
F
Burmeister
J J
JJ
Huettl
P
P
Gerhardt
G A
GA
D000777:Anesthetics / Q000494:pharmacology; D000818:Animals; D016477:Artifacts; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D004594:Electrophysiology / Q000295:instrumentation / Q000379:methods; D045604:Extracellular Fluid / Q000187:drug effects / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008839:Microelectrodes / Q000592:standards; D009448:Neurochemistry / Q000295:instrumentation / Q000379:methods; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D013569:Synapses / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
D000777:Anesthetics; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D018698:Glutamic Acid; D011188:Potassium