A screen of selected peripheral organs of the rat found that γ-aminobutyric acid (GABA) is generally present outside the central nervous system, and, of those organs examined, GABA was present at the highest concentration in the pancreas (∼40 pmol/mg wet wt). Furthermore, this putative inhibitory neurotransmitter was found to be present at even higher levels in islets of Langerhans tissue isolated from rat pancreas (190 pmol/mg). Administration of streptozotocin, a selective β-cell toxin, decreased pancreatic GABA levels significantly, but had no or only small effects on the GABA content of other organs. Normal teleost (catfish) Brockmann body contains about the same level of GABA as normal rat islet tissue.

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