Administering copper reduces hyper-excitability generated by penicillin G in motor cortex neurons from rat brain slices.

Recording synaptic activity of layer III neurons from motor cortex slices, which was provoked by stimulating layer IV, generated synaptic responses of the field potential (FP) that went from mean 100 μV to 600 μV when the stimulus was increased up to twice the threshold. Administering 100 μM or 200 μM of copper, increased the responses to mean 800 μV and 820 μV, respectively. The response to 200 μM was not significantly greater than that to 100 μM. However, all FP responses were significantly lower to a copper concentration of 500 μM. The basal FP was slowly restored by removing the copper with Krebs-Ringer(K-R), resulting in similar characteristics to those observed before copper administration. Then, neurons were perfused with penicillin (2000 UI) to increase cortical excitability and to assess the depressing effect of high concentrations of copper. Administering 500 μM of copper significantly reduced the activity generated by penicillin, while removing by wash(K-R) penicillin and copper generated FP responses similar to those obtained at baseline. Our data indicate that depending on the concentration, copper can behave as an activating or blocking agent for cortical activity.