Brain somatostatin receptor subpopulation visualized by autoradiography.

[125I-Tyr11]somatostatin-14 as well as iodinated D-Tyr1 and Tyr3 derivatives of the cyclic octapeptide somatostatin analog, SMS 201-995 (H-D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-ol) have been used as radioligands for somatostatin receptor autoradiography in rat brain. Although the cyclic octapeptide ligands label the majority of the regions labeled with [125I-Tyr11]somatostatin, in the cortex and hippocampus only a subpopulation of somatostatin receptors is labeled. Cyclic octapeptide ligands have improved resolution due to their very low non-specific binding.