Modulation by prostaglandins of activity of sleep-related neurons in the preoptic/anterior hypothalamic areas in rats.

Using head-restrained unanesthetized rats, we examined the effects of ionophoretically applied prostaglandin (PG) D2 and PGE2 on the activity of neurons in the preoptic/anterior hypothalamic areas that were classified according to the activity change across sleep-wakefulness cycles. About 24% (84/345) of the neurons had a higher firing rate during slow wave sleep than during wakefulness (S-neurons), and about 14% (47/345) were more active during wakefulness than during slow wave sleep (W-neurons). PGD2 had an excitatory effect on about one-third of the S-neurons examined, while a similar percentage of W-neurons were excited by PGE2. These results suggest that PGD2 and PGE2, influencing sleep-related neurons in the preoptic/anterior hypothalamic areas, are key substances underlying the regulation of sleep and wakefulness.