Patch - damping in slices of mammalian CN $ techniques

In light of the proliferation of channels and receptors that are being cloned from the mammalian CNS it is a major challenge to understand their different roles in signalling and synaptic transmission within the brain. The patch-clamp technique developed by Neher, Sakmann and co-workers 1-3 has allowed successful studies of ionic currents and the underlying single-channel activity in the small cells of the CNS. The ability to voltage-clamp these cells, alter the intracellular milieu, and to record single-channel events, has clarified questions that were unapproachable with the traditional CNS electrophysiological techniques of single-unit recording and intracellular recording with conventional microelectrodes. The patch-clamp method requires cells that have clean, smooth membranes, so it has been primarily applied to neurones in culture or to cells acutely dissociated enzymatically. Experiments on neurones within slices of brain tissue were restricted to a few special cases 4-7. Recently, however, an advancement of the technique 8 has allowed the method to be extended to slice preparations of almost any region of the mammalian CNS. A relatively simple 'cleaning' procedure has been developed 8 that allows the exposure of neurones within thin slices 9-11 of tissue. This procedure, which consists of mechanically removing the neuropile from around a neurone, circumvents the use of proteolytic enzymes that alter the properties of membrane proteins 12. In addition, the experimental set-up was modified to allow for the visualization and identification of cells within slices and to provide access for recording and stimulating electrodes 8.