Cutting of living hippocampal slices by a highly pressurised water jet (macromingotome).

Abstract Living brain slices are usually cut with razor blades, which compress a ca. 50-μm-thick layer of tissue. This results in cell debris and lesioned cells which, e.g. form diffusion barriers between the bath and living neurons underneath, thereby prolonging response times of neurons to drugs in the bath saline and impeding the experimental access to intact neurons. To avoid such drawbacks, a macromingotome was developed which cuts nervous tissue with water jets. Physiological saline under pressures of 100–1800 bar was ejected through nozzles of 35–100 μm to cut 300–500-μm-thick hippocampal slices. Systematic variations of pressure and nozzle diameter revealed best results at 400–600 bar and with nozzle diameters of 60–80 μm. Under these conditions, intact CA1- and CA3-neurons as well as granule cells were detected with infrared microscopy at less than 10 μm underneath the surface of the slice. Superficial neurons with intact fine structures were also seen when the slices were studied by light-microscopy. Intra- and extracellular recordings from superficial neurons showed normal membrane- and full action potentials and the development of stable epileptiform discharges in 0 Mg 2+ -saline. These results indicate that the macromingotome offers an alternative way of cutting slices which may facilitate electrophysiological/neuropharmacological or fluorometric studies on superficial neurons.