Magnesium effects on nonsynaptic epileptiform activity in leech Retzius neurons

Abstract

© Institute of Systematics and Evolution of Animals, PAS, Kraków, 2015. The effects of Mg2+ on Ni2+-induced epileptiform bursting activity and input membrane resistance during this activity of leech Retzius neurons were examined using intracellular recordings. To induce epileptiform activity, 3 mmol/l NiCl2 was added into superfusing Ringer (Ri) saline. To test for dose-dependence of the effects of Mg2+ on the induced epileptiformactivity,MgCl2was added in concentrations from1mmol/l to 20mmol/lMg2+ to the Ni2+-containing Ri saline. Input membrane resistance (IMR) was measured in standard Ri, Ni2+ Ri and 20 mmol/lMg2+Ni2+ Ri saline. Superfusion with Ni2+Ri induced epileptiform bursting activity characterized by generation of paroxysmal depolarization shifts (PDSs). Parameters of epileptiform activity including PDS frequency, PDS duration, PDS amplitude and the number of spikes/PDS were measured. Magnesium suppressed Ni2+-induced epileptiform activity, significantly reducing values of all parameters observed in a concentration-dependent manner. The highest concentration applied of 20 mmol/l Mg2+ completely eliminated epileptiform activity. To test for the effect of Mg2+ on membrane conductance during bursting, IMR was measured. Magnesium significantly increased IMR during bursting suppression.