Inhibition of gaba binding by pyridoxal and pyridoxal phosphate

1. 1. GABA exerts its neuroinhibitory effects by binding to a specific receptor on the post-synaptic membrane. 2. 2. Since both GABA and vitamin B 6 have been implicated in convulsion, the effects of B 6 vitamers on Na-independent binding of GABA was investigated by incubating synaptic membrane suspensions for 5 min at 4°C in 1 ml of 50 mM Tris-citrate buffer containing 10 nM [ 3H]GABA in the presence or absence of 1 mM GABA. 3. 3. Pyridoxal (0.1 mM or greater) and pyridoxal phosphate (1 mM or greater), but not pyridoxamine or pyridoxamine phosphate, inhibited specific [ 3H]GABA binding non-competitively. 4. 4. This inhibition, which may involve the interaction between a carbonyl group and a lysine residue, may be used as a probe to further our understanding of the GABA receptor.