Non-exocytotic GABA overflow in rat striatum inhibits gnawing.
The present study tested the hypotheses that spontaneous gamma-aminobutyric acid (GABA) efflux in anterior rat striatum is 1) independent of intra- and extracellular calcium; and 2) is physiologically relevant. Extracellular dopamine (DA) and GABA were sampled from striatum of awake, freely moving rats using in vivo microdialysis. Although dialysate concentrations of DA were 2 to 3 times greater than GABA and were decreased by at least 70% by removal of calcium, GABA was unaffected even in the presence of EGTA or the intracellular calcium chelator APTRA-AM. Functional significance of this non-exocytotic pool of GABA was tested by injecting 3-mercaptopropionic acid (3-MPA), an inhibitor of GABA synthesis, into the striatum via a guide cannula sidled alongside a microdialysis probe and measuring subsequent effects on behavior and perfusate concentrations of GABA. Results show that 3-MPA increases gnawing behavior suggesting that basal, non-exocytotic GABA overflow normally functions to suppress gnawing.
Drew
K L
KL
Institute of Arctic Biology, University of Alaska Fairbanks, 99775-7000, USA. ffkld@aurora.alaska.edu
Fitka
T
T
Hu
Y
Y
Ungerstedt
U
U
D015097:3-Mercaptopropionic Acid / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D005089:Exocytosis; D018756:GABA Antagonists / Q000494:pharmacology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D002614:Chelating Agents; D018756:GABA Antagonists; D005680:gamma-Aminobutyric Acid; D015097:3-Mercaptopropionic Acid; D002118:Calcium; D004298:Dopamine