Stability of brain neocortical slice seizure-like activity during low-magnesium exposure: Measurement and effect of artificial cerebrospinal fluid temperature.

Low-magnesium perfusion is an established method for inducing seizure-like activity in neocortical slices and is widely utilized as a model of human epilepsy. However, many contentious issues remain around optimizing in vitro cortical slice experimental protocols. In this study we investigated the stability of low-magnesium seizure-like event (SLE) activity at different perfusion temperatures; with an aim towards determining whether time-dependent effects in this preparation could be attributed to a reduction in tissue viability. The results showed that SLE characteristics changed significantly and consistently over a 3h recording period, independent of artificial cerebrospinal fluid temperature; there was a median increase in event frequency of 61% (p<0.001) following 2h of recording which remained elevated after 3h (52%, p<0.001). Event amplitude was significantly reduced after 3h (38% reduction, p<0.001). Similar effects were recorded whether perfusion temperature was maintained at 26°C or 36°C. No evidence was found to implicate a reduction in slice viability in these time-dependent changes in SLE behaviour. The results indicate that low-magnesium-induced SLE activity is not stable for long periods and the likelihood of time-related changes in slice performance must be considered when planning and interpreting experiments utilizing the low-magnesium seizure model.