Low, but Not High, Doses of Copper Sulfate Impair Synaptic Plasticity in the Hippocampal CA1 Region In Vivo.

Previous studies have shown the inhibitory effect of the in vitro application of copper sulfate on hippocampal long-term potentiation. While in vivo administration of copper did not affect spatial learning and memory. To find possible answers to this controversial issue, we evaluate the effect of different doses of copper sulfate on in vivo long-term potentiation, synaptic transmission, and paired-pulse behavior of CA1 pyramidal cells. Thirty-two male Wistar rats were divided into four groups: control, 5, 10, and 15 mg of copper sulfate. Field excitatory postsynaptic potential from the stratum radiatum of CA1 neurons was recorded following Schaffer collateral stimulation in rats. Spike amplitude, long-term potentiation and paired-pulse index were measured in all groups. The results of this study showed that 5 mg/kg copper sulfate increased synaptic transmission and inhibited long-term potentiation and decreased the hippocampal paired-pulse ratio, while 10 and 15 mg/kg copper sulfate did not affect CA1 synaptic transmission properties. Low, but not high, doses of copper sulfate affect synaptic plasticity. This finding may explain the difference between the effect of copper on synaptic plasticity and spatial learning and memory.