In vitro activity: γ-Aminobutyric acid (GABA) functions primarily as an inhibitory neurotransmitter in the mature central nervous system. The addition of GABA into the cell culture medium promoted the proliferation of GABRP-expressing PDAC cells, but not GABRP-negative cells, and GABAA receptor antagonists inhibited this growth-promoting effect by GABA. The HEK293 cells constitutively expressing exogenous GABRP revealed the growth-promoting effect of GABA treatment. GABA treatment in GABRP-positive cells increased intracellular Ca2+ levels and activated the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/Erk) cascade. GABA exerts antidiabetic effects by acting on both the islet β-cells and immune system. Unlike in adult brain or islet α-cells in which GABA exerts hyperpolarizing effects, in islet β-cells, GABA produces membrane depolarization and Ca2+ influx, leading to the activation of PI3K/Akt-dependent growth and survival pathways

Kinase Assay:

Cell Assay: GABRP-positive cell lines, KLM-1 and PK-45P, and GABRP-negative cell lines, PK-59 and KP-1N, are incubated with GABA or GABA receptor agonist Muscimol at serial concentration (0, 1, 10, 100 μmol/L) in appropriate medium supplemented with 1% FBS for 6 days. To inhibit the GABA-mediated pathway, cells are incubated with 250 μmol/L of GABAA receptor antagonist bicuculline methiodide or 1 mmol/L of GABAB receptor antagonist CGP-35348. After 6 days of exposure to either of these drugs, cell viability is measured by MTT assay as described above.

Cancer Res. 2007 Oct 15;67(20):9704-12; Proc Natl Acad Sci U S A. 2011 Jul 12;108(28):11692-7; Proc Natl Acad Sci U S A. 2010 Feb 9;107(6):2580-5.