GABA and GABAA agonist isoguvacine stimulate TM3 cell proliferation. Summary graph of 13–36 independent experiments (means+SEMs). TM3 cells were incubated for 24 h with GABA (n = 22), GABA+bicuculline (n = 19), isoguvacine (n = 21) and isoguvacine+bicuculline (n = 13). Both GABA and isoguvacine stimulated TM3 cell proliferation, whereas addition of bicuculline blocked these effects. All results were normalized to proliferation of unstimulated TM3 cells (n = 36), serving as control panel. Columns with different superscripts are significantly different from each other (ANOVA/Newmann-Keuls, p < 0.05).