Physiological and kainate-induced network activity of organotypic hippocampal slices depends on culture medium on...

Organotypic hippocampal slices (OHSs) grown on multielectrode arrays (MEAs) provide unique means to investigate network activity in the same slice over a long period. However, hippocampal activity may not be consistent across different culture media. In this study, we compared two standard culture media with the novel BrainPhys medium to investigate the effect of medium on OHS gross morphological structure and network activity. First, we compared OHS surface area in three different culture media: serum-containing Dulbecco's Modified Eagle Medium (DMEM)-based medium, serum-free Neurobasal-A (NB-A), and serum-free BrainPhys. Our results show that the surface area of the hippocampal slice was well preserved in serum-free culture media, but not in serum-based DMEM. Second, we studied spontaneous network activity in OHS at 7 days in vitro in NB-A and BrainPhys media. In BrainPhys medium, fewer OHS had spontaneous epileptiform activity than in NB-A. Third, we induced epileptic-like activity with 2 µM kainic acid (KA) in OHS cultured either in NB-A or BrainPhys. After 6 h of KA treatment and 24 h recovery period, cultures grown in BrainPhys developed spontaneous epileptiform activity, while activity of OHSs in NB-A did not differ from the activity before KA treatment. We conclude that when cultured on MEA, OHS retain their gross morphological structure better in serum-free culture media than in serum-containing DMEM. Furthermore, BrainPhys supports the physiological network activity of OHSs during the first week in culture and is well suited medium for studies of epileptogenesis in vitro.