Effects of copper on viability and functional properties of hippocampal neurons in vitro

Copper (Cu²⁺) is an essential metal presented in the mammalian brain and released from synaptic vesicles following neuronal depolarization. However, the disturbance of Cu²⁺ homeostasis results in neurotoxicity. In our study we performed for the first time a combined functional investigation of cultured hippocampal neurons under Cu²⁺ exposure, its effect on spontaneous spike activity of hippocampal neuronal network cultured on multielectrode array (MEA), and development of long-term potentiation (LTP) in acute hippocampal slices in the presence of Cu²⁺. Application of 0.2mM CuCl₂ for 24h reduced viability of cultured neurons to 40±6%, whereas 0.01mM CuCl₂ did not influence significantly on the neuronal survival. However, exposure to the action of 0.01mM Cu²⁺ resulted in pronounced reduction of network spike activity and abolished LTP induced by high-frequency stimulation of Schaffer's collaterals in CA1 pyramidal neurons of hippocampal slices. Antioxidant Trolox, the hydrosoluble vitamin E analogue, prevented neurotoxic effect and alterations of network activity under Cu²⁺ exposure, but didn't change the impairment of LTP in Cu²⁺-exposured hippocampal slices. We hypothesized that spontaneous network neuronal activity probably is one of the potential targets of Cu²⁺-induced neurotoxicity, in which free radicals can be involved. At the same time, it may be suggested that Cu²⁺-induced alterations of long-lasting trace processes (like LTP) are not mediated by oxidative damage.