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

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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 (KD) 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 KD 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.