SPONTANEOUS SINGLE CELL DISCHARGE IN RAT SOMATOSENSORY CORTICAL SLICES AND ITS RELATIONSHIP TO DISCHARGE IN THE URETHANE-ANESTHETIZED RAT

A slice preparation of rat somatosensory cortex has been used to observe the nature of spontaneous single cell discharge in layer V. On the basis of their discharge pattern, cells recorded using extracellular microelectrodes fell in to one of two categories: 70% of cells discharged single action potentials separated by relatively constant time intervals, while the remainder discharged in bursts of 2-7 action potentials. The firing patterns and the range of discharge frequencies observed were similar to those recorded in the same region and layer of the cortex in urethane-anaesthetized rats. However, unlike cells recorded in vivo, the majority of cells in slices never changed their discharge pattern. This suggests that while these layer V cells in cortical slices have the basic ability to discharge spontaneously, the potential for switching between discharge patterns requires circuitry absent from this isolated preparation. Urethane, over the dose range 6-24 mM, caused a dose-dependent decrease in the discharge frequency of cells with a regular firing pattern but did not affect their basic pattern of discharge. © 1990.