Tumor necrosis factor reduces the ACh-induced outward current in identified Aplysia neurons.

Effects of extracellularly applied recombinant human tumor necrosis factor (rhTNF) on the acetylcholine (ACh)-induced K+ current recorded from identified neurons (R9 and R10) of Aplysia kurodai were investigated with conventional voltage-clamp and pressure ejection techniques. Bath-applied rhTNF (200-500 U/ml) reduced the ACh-induced current in the neurons without affecting the holding current and resting membrane conductance. The suppressing effect of rhTNF on the current was completely reversible. Inhibition by rhTNF was non-competitive. Heat-inactivated rhTNF was without effect. Our results suggest that the immunomodulator TNF can act on the ACh receptor in the nervous system.