Lithium and rhythms of beta-adrenergic ([3H]CGP-12177) binding in intact rat retina, pineal gland, and hypothalamus
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A new assay technique for the determination of neurotransmitter binding in retinal fragments has been used to characterize and quantify beta-adrenergic receptors with the ligand [3H]CGP-12177. This assay allowed us to quantify beta-adrenergic receptors in the retina, pineal gland, and hypothalamus obtained from individual rats during a 10-hr period around the switch from light to dark under a 12-hr light/12-hr dark lighting cycle. A significant rhythm of beta-adrenergic binding was observed in the retina and pineal gland. These rhythms were abolished by chronic lithium treatment. In contrast to previous observations in whole brain preparations, lithium did not affect beta-adrenergic binding in brain tissue (hypothalamus) using this assay. Our data suggest that lithium may attenuate beta-adrenergic receptor down-regulation in pineal and retinal tissue. To the extent that this mechanism is important for the coding of information about light and dark in the environment, these observations might assist in our understanding of the clinical chronopharmacological properties reported for lithium.
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