Noradrenergic receptor binding during sleep-waking states in the rat.

It was recently shown that the number of muscarinic receptors in the rat pons undergoes short-term changes which are related to sleep-waking states and may thus play a role in determining their time course. In this study we investigated whether also noradrenergic receptors change in relation to polygraphically documented wakefulness (W), synchronized (S) and desynchronized sleep (D). Brain noradrenergic systems are deeply involved in the control of vigilance states, and a new hypothesis about the function of D has suggested that adrenoceptors would be desensitized or downregulated during W and upregulated during D. We examined the number of alpha 1-, alpha 2- and beta-adrenergic receptors in the forebrain and the cerebellum, and the number and affinity of alpha 2-receptors in a brainstem region including the locus coeruleus. The results indicate that the number of alpha 1-, alpha 2- and beta-adrenergic receptors does not change in relation to sleep-waking states either in the forebrain or in the cerebellum, and that the number and the affinity of alpha 2-adrenergic receptors in the brainstem are stable as well.