Effects of prostaglandin and noradrenalin on sleep-related neurons in the preoptic area.

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Electrical stimulation of noradrenergic cells in the locus coeruleus and ventrolateral medulla inhibited sleep-active neurons and excited waking-active neurons in the preoptic area of the rat. Noradrenaline applied through a multibarrel micropipette also inhibited sleep-active neurons and excited waking-active neurons. Application of antagonists and agonists for adrenoceptors revealed that inhibition was mediated by alpha_2-and excitation by alpha_1-receptors.During wakefulness, prostaglandin D_2 (PGD_2) excited sleep-active neurons and inhibited waking-active neurons. Continuous application of PGD_2 attenuated neuron activity during wakefulness. However, PGD_2 was less effective in eliciting a response during sleep. PGD_2 also attenuated noradrenaline-induced responses of sleep-related neurons.These results suggest (1) noradrenaline promotes wakefulness by inhibiting sleep-active neurons through alpha_2-receptors and by exciting waking-active neurons through alpha_1-receptors, (2) PGD_2 promotes sleep by exciting sleep-active neurons and by inhibiting waking-active neurons, (3) most important action of PGD_2 is the attenuation of activity during wakefulness, and (4) PGD_2 attenuates the noradrenaline-mediated arousal influence.