GABA(A) and GABA(B) receptors modulating basal and footshock-induced nitric oxide releases in rat prefrontal cortex

Using an in vivo brain microdialysis technique, we measured extracellular l evels of nitric oxide (NO) metabolites (NOx-) in the medial prefrontal cort ex (mPFC) upon perfusion of gamma-aminobutyric acid (GABA) receptor antagon ists as well as agonists, and also examined the effects of GABA receptor ag onists on mild intermittent footshock-induced NO releases in the mPFC in co nscious rats. Perfusion of either bicuculline methiodide, a GABA(A) recepto r antagonist, or saclofen, a GABA(B) receptor antagonist, through a microdi alysis probe resulted in dose-dependent increases in NOx- levels. Higher-do se perfusion of either muscimol (50 mu M), a GABA(A) receptor agonist, or b aclofen (250 mu M), a GABA(B) receptor agonist resulted in a significant de crease in NOx- levels. The elevated levels of NOx- after mild intermittent footshock were attenuated by perfusion of either muscimol (10 mu M) or bacl ofen (50 mu M), either of which alone did not affect basal NOx- levels. The se findings are likely to provide helpful clues to our understanding of the inhibitory modulation of basal and footshock-induced NO metabolites releas es by GABA(A) and GABA(B) receptors in the mPFC. (C) 2000 Elsevier Science B.V. All rights reserved.