Hi Girija,
Sorry for delay, only just back from vacation.
I have no information about GABA, which is gamma-aminobutyric acid.
I did a quick search, and came across one statement that " GABA does not cross the normal BBB".
http://content.karger.com/ProdukteDB...asp?Doi=101274
Very interesting that they say "normal" BBB. Implying that it does cross a defective one. However, Wilkipedia says, "it is unknown whether GABA can pass the blood-brain barrier.

I feel there is confusion in the literature about what does and does not pass "the BBB" What is the permeability of a "normal healthy BBB"? Do all healthy people have an exactly identical BBB permeability, say 100? I think not, no more than we are all exactly 6 feet tall. There will be a bell shaped curve in both the heights of a group of people and their BBB permeability.
I believe the normal human rules apply, and healthy people will AVERAGE around say 100. People with PD, and those about to show PD, will be on the high side, say 130 to 150. Remember the permeablity increases with aging, so those on the right hand side of the graph will tend to be older. So when a reference says, X crosses or does not cross the BBB, they should qualify their statement with a permeability measurement.
This explains why there is so much contradiction in the literature on what passes and what does not. As Lurking says,
"For every article I find that says it doesn't easily cross the BBB, I find another that says it does! Aahh!!"

Ron
PS The Dutch scientist Prof.Leenders has shown the BBB's of PWP are defective, high in permeability, ref in my report.