Suprachiasmatic nucleus ablation abolishes circadian rhythms in rat brain neurotransmitter receptors

The effect of suprachiasmatic nucleus (SCN) ablation on rhythms in brain neurotransmitter receptors was studied. In control animals, the rhythms in the number of alpha-adrenergic and benzodiazepine receptors were circadian, whereas the rhythms in beta-adrenergic and acetylcholine receptors were ultradian. SCN ablation resulted in loss of circadian, but not ultradian, rhythms, without change in the 24-h mean numbers. SCN ablation appears to cause a selective loss of circadian function in the regulation of brain receptors.