Higher GABA concentrations in fallopian tube than in brain of the rat.

The GABA content was determined simultaneously in two peripheral organs, i.e., ovary and Fallopian tube. Moreover, the effects of inhibitors of glutamate decarboxylase or gamma-aminobutyrate transaminase (GABA-T) on the GABA concentrations of the two organs were examined, to point out similarities and differences between central and peripheral pathways of GABA biosynthesis and degradation. In ovary, GABA concentration was found to be about 30% of that in total brain tissue. Furthermore, isoniazid and thiosemicarbazide caused significant reduction of GABA levels in peripheral organs. In contrast to the CNS, aminooxyacetic acid failed to increase, but even produced a significant diminution in peripheral GABA content. Gabaculine did not change GABA levels. In conclusion, it has been demonstrated for the first time that a peripheral organ, i.e. fallopian tube, contained higher GABA concentrations than the CNS. On the other hand, in the organs examined GABA seemed to be synthesized similarly, but metabolized by a pathway different from that in the brain.