Inverse relationship between neurotensin receptors and neurotensin-like immunoreactivity in cat striatum.

The adult corpus striatum in mammals is divided into distinct histochemical compartments. If the cat caudate nucleus is stained for acetylcholinesterase a number of macroscopically visible zones appear that have lower acetylcholinesterase activity than the surrounding tissue. These patches, called 'striosomes', correspond to regions of high [Met]-enkephalin-like immunoreactivity and dense opiate receptor binding and are related to the uneven distribution of striatal efferent neurones and cortical afferent terminations. One of the highest concentrations of neurotensin-like immunoreactivity is in the striatum and the immunoreactive material co-elutes with synthetic neurotensin on gel chromatography. Recently, we have found that neurotensin-like immunoreactivity in the cat caudate nucleus coincides with the striosomes. We have now localized neurotensin receptors in the cat caudate nucleus by autoradiography and found low density in the neurotensin-rich striosomes and a high density in the neurotensin-poor surrounding tissue.