Abstract
The binding of gastrin-releasing peptide (GRP) to rat brain membranes was characterized. GRP binds specifically to a high affinity site in rat brain membranes, with a Kd equal to 2 nM and Bmax equal to 5 pmol/g wet weight of tissue. The specific binding is saturable, reversible, and dependent on tissue concentration, time of incubation, and the pH of the buffer. Hippocampus, cortex, and striatum contained the highest concentration of high affinity binding sites and the thalamus the lowest. The affinities of GRP, bombesin, and their analogues for the GRP receptor were determined. GRP(14-27) and [Tyr4]bombesin had the greatest affinity, whereas GRP(1-16), which lacks the COOH terminal region, had no affinity for the receptor. GRP, bombesin, and analogues stimulate the breakdown of phosphatidylinositol in rat brain hippocampal minces and potencies correspond to their affinities for the GRP receptor.
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