Quantitative autoradiography of beta 1- and beta 2-adrenergic receptors in rat brain.

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Abstract
Quantitative autoradiography was used to localize in rat brain .beta.1- and .beta.2-adrenergic receptors. These receptors were labeled in vitro with 125I-labeled pindolol, an antagonist of .beta.-adrenergic receptors that binds nonselectively to both .beta.1 and .beta.2 subtypes. The selective inhibition of 125I-labeled pindolol binding with specific antagonists of .beta.1 and .beta.2 receptors allowed the visualization of .beta.-adrenergic receptor subtypes. High levels of .beta.1 receptors were observed in the cingulate cortex, layers I and II of the cerebral cortex, the hippocampus, the Islands of Calleja and the gelatinosus, mediodorsal, and ventral nuclei of the thalamus. High levels of .beta.2 receptors were found in the molecular layer of the cerebellum, over pia mater and in the central, paraventricular, and caudal lateral posterior thalamic nuclei. Approximately equal levels of .beta.1 and .beta.2 receptors occurred in the substantia nigra, the olfactory tubercle, layer IV of the cerebral cortex, the medial preoptic nucleus and all nuclei of the medulla. The pronounced differences in the ratio of .beta.1 to .beta.2 receptors among brain regions suggests that the subtypes of .beta.-adrenergic receptors may play different roles in neuronal function.