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

The adult corpus striatum in mammals is divided into distinct histochemical compartments¹. If the cat caudate nucleus is stained for acetylcholinesterase a number of macroscopically visible zones appear that have lower acetylcholinesterase activity than the surrounding tissue². These patches, called 'striosomes'¹, correspond to regions of high [Met]-enkephalin-like immunoreactivity³ and dense opiate receptor binding⁴ and are related to the uneven distribution of striatal efferent neurones and cortical afferent terminations^5,6. One of the highest concentrations of neurotensin-like immunoreactivity is in the striatum and the immunoreactive material co-elutes with synthetic neurotensin on gel chromatography⁷. Recently, we have found that neurotensin-like immunoreactivity in the cat caudate nucleus coincides with the striosomes ⁸. We have now localized neurotensin receptors in the cat caudate nucleus by autoradiography⁹ and found low density in the neurotensin-rich striosomes and a high density in the neurotensin-poor surrounding tissue.