Impulse-dependent and tetrodotoxin-sensitive release of GABA in the rat's substantia nigra measured by microdialysis.
gamma-Aminobutyric acid (GABA) release in the rat substantia nigra pars reticulata (SNR) was studied by microdialysis coupled with high-performance liquid chromatography and fluorimetric detection. Electrical stimulation of striatonigral axons in the internal capsule (IC) increased nigral GABA release in conscious and halothane-anaesthetized rats. This was prevented by intranigral infusion of tetrodotoxin (TTX) while basal GABA release was unaffected. Calcium-free, cobalt-containing (2 mM CoCl2) artificial cerebrospinal fluid reduced basal GABA overflow but not that evoked with high K+ (100 mM). Extracellular levels of glutamate (GLU) and taurine (TAU) were not modified by IC stimulation, TTX or 0 Ca2+ although high K+ promoted GABA and TAU release but not that of GLU. These data demonstrate an impulse-and sodium-dependent release of GABA from nigral afferent neurones which contribute little to the extracellular concentration of GABA under steady-state conditions.
Biggs
C S
CS
Department of Pharmacology, School of Pharmacy, London, UK.
Fowler
L J
LJ
Whitton
P S
PS
Starr
M S
MS
D000818:Animals; D004558:Electric Stimulation; D007700:Kinetics; D008297:Male; D017551:Microdialysis; D051381:Rats; D017208:Rats, Wistar; D013378:Substantia Nigra / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology*; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid