DISPLACEMENT OF [H-3] GABA BINDING TO BOVINE BRAIN RECEPTORS BY SULFUR-CONTAINING ANALOGS

The displacement of [3H]GABA binding to GABA receptors of bovine brain cortical membranes by some sulfur-containing compounds (homothiotaurine, thiotaurine and carboxymethylcysteamine) was investigated and their potency was compared to that of other known sulfur-containing analogues of GABA, such as homotaurine, homohypotaurine and taurine. Displacement studies showed homotaurine to be more effective as a GABA displacer than homohypotaurine and homothiotaurine (IC50: 3.9 × 10-8, 6.7 × 10-7 and 6.8 × 10-7 M, respectively). Saturation experiments showed that the effect of taurine, homothiotaurine, homotaurine and homohypotaurine was due to a loss of high-affinity GABA sites (Kd = 10.7 nM). Homotaurine seems also to interact with low-affinity sites, decreasing the affinity constant, whereas the number of binding sites remains unchanged. © 1990.