Effects of dimethylarsinic and dimethylarsinous acid on evoked synaptic potentials in hippocampal slices of young and adult rats

In this study, the effects of pentavalent dimethylarsinic acid ((CH3)2AsO(OH); DMAV) and trivalent dimethylarsinous acid ((CH3)2As(OH); DMAIII) on synaptic transmission generated by the excitatory Schaffer collateral-CA1 synapse were tested in hippocampal slices of young (14–21 day-old) and adult (2–4 month-old) rats. Both compounds were applied in concentrations of 1 to 100 μmol/l.DMAV had no effect on the amplitudes of evoked fEPSPs or the induction of LTP recorded from the CA1 dendritic region either in adult or in young rats. However, application of DMAIII significantly reduced the amplitudes of evoked fEPSPs in a concentration-dependent manner with a total depression following application of 100 μmol/l DMAIII in adult and 10 μmol/l DMAIII in young rats. Moreover, DMAIII significantly affected the LTP-induction. Application of 10 μmol/l DMAIII resulted in a complete failure of the postsynaptic potentiation of the fEPSP amplitudes in slices taken both from adult and young rats. The depressant effect was not reversible after a 30-min washout of the DMAIII. In slices of young rats, the depressant effects of DMAIII were more pronounced than in those taken from adult ones.Compared to the (absent) effect of DMAV on synaptic transmission, the trivalent compound possesses a considerably higher neurotoxic potential.