Beta-adrenergic ([3H]CGP-12177) binding to brain slices and single intact pineal glands

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Abstract
We have characterized and quantified the binding of [3H]CGP-12177 to β-adrenergic receptor sites in slices (300 microns) of rat cerebral cortex. The receptors are stereospecific, saturable and of high affinity. Binding of [3H]CGP is readily reversible and demonstrates appropriated drug specificty. This assay method allows the demonstration of isoproterenol-induced down-regulation (internalization) of β-adrenoreceptors. Receptor recycling is observed at 37°C in the absence of β-agonist but can be blocked by low temperature (0°C) or by monensin. β-Adrenoreceptors can also be labeled and quantified in intact, single pineal glands of rat, mouse and hamster. Rat pineals contain approximately 10 times more binding sites than do hamster or mouse pineals and up to 8 times more sites than found in rat cerebral cortex. Rat pineal [3H]CGP binding can be up- and down-regulated but not to the same degree as seen in brain slices. This assay method is simple, rapid and provides new opportunities for the study of other receptor types in intact tissue.