Spindle-like activity appearing during paradoxical sleep in rats with iron-induced cortical focus.

Under barbiturate anesthesia, male Wistar rats weighing 250-300 g were injected with 2.5 microliters of 0.2 M FeCl3 solution into the left sensori-motor cortex to induce an epileptic focus with minimal abnormal activities. Polygraphy started 1 week after the surgery, showed a spindle-like hypersynchronous activity that appeared not only in the slow wave sleep period but also during paradoxical sleep (PS). This activity had a frequency of 8-14 Hz. The amplitude was more than 200 mu v in the right (non-injected side) cortex but very small in the left cortex (injected side). Isolated spike discharges were observed in an ECoG of slow wave sleep. Apart from this activity there was nothing resembling the usual sleep spindles.