Characteristics of the β‐Adrenoreceptor from Neuronal and Glial Cells in Primary Cultures of Rat Brain

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Abstract
The cellular characteristics of the β‐adrenoreceptor in glial and neuronal cells from the newborn rat brain were determined by (−)‐[125I]iodocyanopindolol binding. In membranes from both cell types, the binding was saturable and from competition assays the potency series of (−)‐isoproterenol > (−)‐epinephrine = (−)‐norepinephrine > (+)‐isoproterenol was observed. 5′‐GuanylyI‐imidodiphosphate reduced the affinity of (−)‐isoproterenol for the β‐adrenoreceptor from glial cells but had no effect on agonist affinity in neuronal cells. Chronic treatment of both cell types with (−)‐isoproterenol reduced the receptor content and the capacity of the agonist to increase the cellular cyclic AMP content. However, the receptor recovery after chronic agonist treatment was faster in glial cells (72 h) than neuronal cells (120 h) and was blocked by cycloheximide. Treatment of both types with the irreversible β‐blocker bromoacetylalprenololmentane (2 μM) reduced the receptor content by 78% but no receptor recovery was observed for 120 h after the initial receptor loss. The data indicated that the majority of β‐adrenoreceptors in both cell types are the β−1 subtype, but show some differences in receptor‐agonist interactions. Furthermore, these CNS cells may be useful models for regulatory studies on the β‐adrenoreceptor.