Effect of diazepam on the electroencephalographic pattern and vigilance of unanaesthetized and curarized rats with a chronic cobalt-gelatin focus.

The author studied the effect of diazepam in doses of 1 and 3 mg/kg on rats with a chronic cortical cobalt-gelatin focus and implanted cortical and subcortical electrodes. Focal spike activity localized at the site of the focus and hypersynchronous generalized episodes of spikes (and waves) of 8--9/sec frequency were studied in the electroencephalogram and the main phases of vigilance (waking, telencephalic slow waves/SWS/and REM sleep) after diazepam were evaluated. The effect of diazepam on rats temporarily immobilized with tubocurarine was also evaluated. 1. Focal spike activity during sleep was mildly inhibited by diazepam. If present in the waking state, it was markedly inhibited. 2. The number of episodes diminished significantly after diazepam. The maximum decrease occurred 30--45 minutes after administering diazepam and after that they slowly recovered. 3. Diazepam did not inhibit alteration of the phases of vigilance, but there was an increase in the proportion of telencephalic sleep with large numbers of spidles of 12--14/sec frequency and the incidence of REM phases rose by 250--300%. 4. Diazepam brought no renewal of the episodes which disappeared from the waking EEG recording of rats with a chronic focus temporarily immobilized with tubocurarine. Its administration was followed mostly by sleep activity with spindles. 5. Despite certain effects in common (disappearance of episodes), the action of diazepam differs from that of barbiturates in many respects and is effected by different mechanisms.