ZINC INHIBITS CA3 AND DENTATE ORTHODROMIC RESPONSES BUT ENHANCES DENTATE ANTIDROMIC RESPONSES IN RAT HIPPOCAMPAL SLICES

The divalent cation zinc (Zn2+) exerts multiple effects on transmitter receptors and voltage gated ion channels and may act as an endogenous modulator of neuronal function. Most of the specific blocking effects on transmitter-activated ion channels display apparent K-D values in the lower micromolar range. We therefore tested the effect of low conc entrations of Zn2+ (1-25 mu M) on synaptic transmission in adult rat h ippocampal slices using field potential recordings. Zn2+ reduced popul ation spikes in CA3 and in area dentata upon orthodromic stimulation. Interestingly, antidromically evoked population spikes in area dentata were slightly but consistently enhanced by Zn2+. Pahed pulse inhibiti on was unchanged in CA3 and area dentata. The results indicate that Zn 2+ at low concentrations reduces synaptically evoked responses in CA3 and area dentata without selectively affecting paired pulse inhibition .