Amyloid beta proteins reduce the GABA-induced Cl- current in identified Aplysia neurons

The amyloid beta protein (A beta P) is the major component of the amyloid deposition which characterizes Alzheimer's disease. Effects of extracellularly applied A beta P on the gamma-aminobutyric acid (GABA)-induced Cl- current recorded from identified neurons (R9 and R12) of Aplysia kurodai were investigated with conventional voltage-clamp and pressure ejection techniques. Focal application of 100 nM A beta P (1-40) reduced the GABA-induced hyperpolarization at resting membrane potential and the GABA-induced Cl- current in the neurons held at -50 mV. Bath-applied 100 nM A beta P fragments (1-40) and (25-35) but not A beta P (1-16) inhibited the GABA-induced Cl- current as well as muscimol-induced Cl- currents in the neurons without affecting the resting membrane conductance or holding current. These results suggest that A beta P may increase neuronal excitability by inhibiting GABA-induced Cl- current in the neurons of mammalian central nervous system.