A simple innovation to move beyond juvenile brain slices:
the concept of the ‘protective recovery' method
Experienced brain slice electrophysiologists are well aware of the difficulties for preparing healthy brain slices from adult animals, and as such the vast majority of acute brain slice studies have been limited to juvenile or adolescent animals. This is especially true for whole cell patch clamp investigations. To address this serious limitation, we recently undertook a tedious and systematic effort to explore novel variations in the slice preparation procedures in order to search for particular modifications that would be favorable for preparing healthier slices from adult and aging brain. Here we demonstrate a simple but surprising principle that has enabled us to achieve this goal. We find that the majority of the neuronal swelling and damage in the procedure arises from the initial time period following the completion of the slice cutting step, but not from the actual cutting step per se. By applying a ‘protective recovery method’ involving a Na-replacement strategy restricted to the initial brain slice recovery period alone, we demonstrate a dramatic improvement in neuronal preservation in acute brain slices from mature adult animals as compared to the conventional ‘protective cutting method.’ The protective recovery method results in markedly improved preservation of neurons across diverse brain regions and animal ages and is simple and straightforward to implement.