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

Living brain slices are usually cut with razor blades, which compress a ca. 50-mu m-thick layer of tissue. This results in cell debris and lesioned ce lls which, e.g. form diffusion barriers between the bath and living neurons underneath, thereby prolonging response times of neurons to drugs in the b ath saline and impeding the experimental access to intact neurons. To avoid such drawbacks, a macromingotome was developed which cuts nervous tissue w ith water jets. Physiological saline under pressures of 100-1800 bar was ej ected through nozzles of 35-100 mu m to cut 300-500-mu m-thick hippocampal slices. Systematic Variations of pressure and nozzle diameter revealed best results at 400-600 bar and with nozzle diameters of 60-80 mu m. Under thes e conditions, intact CA1- and GAS-neurons as well as granule cells were det ected with infrared microscopy at less than 10 mu m underneath the surface of the slice. Superficial neurons with intact fine structures were also see n when the slices were studied by light-microscopy. Intra- and extracellula r recordings from superficial neurons showed normal membrane- and full acti on potentials and the development of stable epileptiform discharges in 0 Mg 2+-saline. These results indicate that the macromingotome offers an alterna tive way of cutting slices which may facilitate electrophysiological/neurop harmacologic or fluorometric studies on superficial neurons. (C) 2000 Elsev ier Science B.V. All rights reserved.