Effect of kainic acid injected into raphe dorsal nucleus on sleep stages in cats

Early (up to 5 h) and late (up to 65 days) effects of kainic acid (KA) injected into raphe dorsal nucleus (NRD) at two doses, 4 and 12 nmol, on waking-sleep stages in cats were studied. Slow-wave sleep (SWS-1 and SWS-2) and rapid eye movement sleep (REM) were strongly reduced or even completely suppressed, while waking stage, especially quiet waking stage (W-2), was significantly increased during the first 5 h after the injection. The effect was much more pronounced after injection of KA at a dose of 12 nmol. These changes in sleep stages gradually subsided and starting from the first-third day up to the 65th day after injection of KA, sleep was completely normal. The effects were interpreted as reflecting the action of KA first as a strong excitant--when a suppression of sleep was established, and then as a toxic substance with respect to NRD cells--when sleep restored to normal. These results suggest that raphe dorsal nucleus is not essential for triggering or maintenance of sleep.