Excitotoxicity of Lathyrus sativus neurotoxin in leech retzius neurons

The effects of Lathyrus sativus neurotoxin were studied on the cell membran e potential and cellular cation composition in Retzius nerve cells of the l eech Haemopis sanguisuga, with ion-selective microelectrodes using liquid i on-exchangers. Bath application of 10(-4) mol/l Lathyrus sativus neurotoxin for 3 min depolarized the cell membrane potential and decreased the input resistance of directly polarized membrane in Retzius neurons. At the same t ime the cellular Na+ activity increased and cellular K+ activity decreased with slow but complete recovery, while the intracellular Ca2+ concentration was not changed, Na+-free Ringer solutions inhibited the depolarizing effe ct of the neurotoxin on the cell membrane potential. Zero-Ca2+ Ringer solut ion or Ni2+-Ringer solution had no influence on the depolarizing effect of the neurotoxin on the cell membrane potential. It is obvious that the incre ase in membrane conductance and depolarization of the cell membrane potenti al are due to an influx of Na+ into the cell accompanied by an efflux of K from the cell.