| Abstract: | Several studies have examined the activity of neurons in hypothalamic tissue slices. The present experiments studied relationships between neuronal activity (firing rate and thermosensitivity) and tissue survival as a function of time and slice thickness. Rat hypothalamic tissue slices were sectioned at different thicknesses (350, 450, and 600 μm) and maintained in an oxygenated interface chamber which was perfused with artificial cerebrospinal fluid (ACSF). Electron and light microscopy were used to examine tissue morphology at different depths from the slice surfaces, and extracellular recordings were used to measure each cell's spontaneous activity and response to changes in temperature. Tissue damage was most evident at tissue layers nearest the gas-exposed surface. At 9 h in the chamber, 350 μm thick slices showed subtle changes in morphology with little difference between the gas-exposed and ACSF-exposed surfaces. In the 450 and 600 μm thick slices, tissue degeneration became more evident with increased damage at the gas-exposed surface. This damage extended fully into the tissue of the 600 μm section. There were no differences in firing rate or thermosensitivity between 350 and 450 μm slices; but in 600 μm slices, there were fewer spontaneously active neurons, although these neurons had a higher mean thermosensitivity. Based on the incidence of spontaneous activity and morphological integrity, the results suggest that electrophysiological experiments using 350 μm slices are preferable to experiments using thicker slices. |
