Awaking effect of PGE2 microinjected into the preoptic area of rats

Abstract We examined the effects of prostaglandin (PG)E 2 on the sleep-wake activity and on body temperature by microinjecting PGE 2 into the preoptic area of rats that had been chronically implanted with guide cannulae and electrodes for the recordings of electroencephalogram and electromyogram. PGE 2 at doses of 2.5 × 10 13 , 2.5 × 10 11 , 2.5 × 10 −9 mol reduced the time of slow wave sleep (SWS) to 75%, 61%, and 59% and that of paradoxical sleep (PS) to 73%, 50%, and 25% of the controls, respectively. The SWS and PS reductions were mainly due to the shortening of the SWS episode and the less frequent occurrence of PS episodes. The sleep reduction was accompanied by increased behavioral movement. The maximum increases of rectal temperature at doses 2.5 × 10 −11 and 2.5 × 10 −9 mol of PGE 2 were 1.3 °C and 2.7 °C, respectively. At a dose of 2.5 × 10 −13 mol of PGE 2 , the time of SWS and that of total sleep (sum of SWS and PS) decreased significantly, but the change in body temperature was negligible. This may imply that the effect of PGE 2 on the sleep-wake activity is not caused by the hyperthermia produced by PGE 2 . Injections of PGE 2 at a dose of 2.5 × 10 −15 mol and saline control induced alteration in neither sleep-wake activity nor body temperature. PGD 2 at a dose of 2.5 × 10 −9 mol slightly elevated the rectal temperature (0.5 °C), but did not produce any change in the sleep-wake activity. On the basis of these findings, we conclude that PGE 2 acts at the preoptic area of rats to increase the wakefulness by inhibiting the maintenance of SWS and consequently decreasing the occurrence of PS.