[³H]Neurotensin(8–13) Binds in Human Brain to the Same Sites as Does [³H]Neurotensin but with Higher Affinity

Abstract: The binding of [³H]neurotensin(8–13) to membranes from human frontal cortex at 0°C was time dependent, specific, saturable, and reversible. Saturation isotherms provided an equilibrium dissociation constant (K_D) of 0.52 nM, and the maximal number of binding sites (B max) was 3.5 pmol/g original wet weight of tissue. Scat‐chard analysis yielded a straight line, and the Hill coefficient was equal to 1, a result indicating that [³H]‐neurotensin(8–13) bound to single, noncooperative sites. The K_D values of several analogs of neurotensin determined in competition with [³H]neurotensin(8–13) were similar to those previously determined in competition with [³H]‐neurotensin. The regional distribution of binding sites for [³H]neurotensin(8–13) was also similar to that for [³H]‐neurotensin. These results suggest that [³H]neurotensin(8–13) binds to the same sites as [³H]neurotensin and that [³H]neurotensin(8–13) has a higher affinity than [³H]‐neurotensin for these sites in human brain.