Interference of chronically ingested copper in long-term potentiation (LTP) of rat hippocampus.

The objective of our study was to find the evidence of copper interaction in LTP, motivated by copper involvement in neurodegenerative illness, like Parkinson, Alzheimer and Amyotrophic Lateral Sclerosis, and we initiated the study of this element in the LTP. For this purpose we used hippocampus slices of rats chronically consuming copper dissolved in water (CuDR; n=26) and non-copper-consuming rats (CR; n=20). The CuDR rats received 8--10 mg/day during 20--25 days. Electrophysiological tests showed absence of LTP in CuDR slices, contrary to CR slices. The stimulus-response test applied before and after LTP showed significant increases of synaptic potential in the CR group. This did not occur in the CuDR group, except for the initial values, which probably seem associated to an early action of copper. The paired-pulse (PP) test, applied to CR and CuDR prior to tetanic stimulation, showed a significant reduction in PP, for the 20-, 30- and 50-ms intervals in CuDR. At the end of the experiments, copper concentration was 54.2 times higher in CuDR slices, compared to the concentration present in CR slices. Our results show that copper reduces synaptic sensibility and also the facilitation capability. These effects represent a significant disturbance in the plasticity phenomenon associated with learning and memory.