A quick and dirty Medline search (GABA + BBB) turned up little plain talk. The best I came up with is below:

1: Brain Res Bull. 2002 Jan 15;57(2):231-6.

Evidence that nitric oxide production increases gamma-amino butyric acid
permeability of blood-brain barrier.

Shyamaladevi N, Jayakumar AR, Sujatha R, Paul V, Subramanian EH.

Dept of Biophysics and Crystallography, University of Madras, Chennai, India.

Blood-brain barrier permeability (BBB) to the inhibitory neurotransmitter
gamma-amino butyric acid (GABA) was studied in rats following intraperitoneal
(i.p) injections of GABA alone and in combination with L-Arginine (L-Arg).
Administration of GABA (600 mg/kg body weight [b. wt.]) alone increased brain
GABA concentration (33%, p < 0.01), when compared to untreated rats and
administration of L-Arg (2000 mg/kg b. wt.) alone also increased GABA
concentration (65%, p < 0.01) in the brain. Moreover, GABA + L-Arg treated brains
showed a fourfold increase in GABA level (383.3%, p < 0.01) when compared to
controls. Dose-dependent increase in nitric oxide production was observed 10 min
after i.p injections of L-Arg (400, 800, 1000, and 2000 mg/kg b. wt.) and a peak
nitric oxide (NO) production was observed at the dose level of 2000 mg/kg b. wt.
On the other hand, administration of GABA failed to increase NO production in the
brain. Rats pretreated (10 min) with a nonspecific nitric oxide synthase (NOS)
inhibitor N(omega)-nitro-L-Arginine methyl ester (L-NAME, 50 mg/kg b. wt.)
completely blocked the production of NO induced by L-Arg. In addition, L-NAME
attenuated GABA entry into the brain after the administration of GABA alone or in
combination with L-Arg. We conclude that high NO concentrations in the brain
following L-Arg administration may increase the permeability of BBB to peripheral
GABA.


PMID: 11849830 [PubMed - indexed for MEDLINE]