Neurotensin, a central nervous system peptide: apparent receptor binding in brain membranes

Neurotensin, a tridecapeptide recently isolated from bovine hypothalami, has potent pharmacologic effects in several peripheral systems and a regional distribution in rat brain suggestive of a specialized function. ¹²⁵I-neurotensin binds to membrane preparations from rat brain saturably, reversibly, and with high affinity (apparent K_{D = 3 nM}) under conditions that minimize degradation of the polypeptide. This binding is displaced by neurotensin sequence fragments with relative potencies generally paralleling their potencies in peripheral systems. ¹²⁵I-neurotensin binding is highest in specific thalamic, cerebral cortical, and hypothalamic areas of rat and calf brain. White matter, brain stem and cerebellar regions have substantially lower amounts of binding. Characteristics of this binding suggest an association with a physiologically relevant neurotensin receptor.