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

Abstract

In this study, the effects of pentavalent dimethylarsinic acid ((CH 3) 2AsO(OH); DMA V) and trivalent dimethylarsinous acid ((CH 3) 2As(OH); DMA III) 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. DMA V 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 DMA III significantly reduced the amplitudes of evoked fEPSPs in a concentration-dependent manner with a total depression following application of 100 μmol/l DMA III in adult and 10 μmol/l DMA III in young rats. Moreover, DMA III significantly affected the LTP-induction. Application of 10 μmol/l DMA III 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 DMA III. In slices of young rats, the depressant effects of DMA III were more pronounced than in those taken from adult ones. Compared to the (absent) effect of DMA V on synaptic transmission, the trivalent compound possesses a considerably higher neurotoxic potential.