SPATIAL-ORGANIZATION OF PATCH AND MATRIX COMPARTMENTS IN THE RAT STRIATUM

The visualization of mu opiate receptors by [H-3]naloxone binding was used to determine precisely the spatial organization of the patch comp artment in the rat striatum and its reproducibility in different anima ls. Three-dimensional reconstruction of the patch network was made usi ng maps of autoradiographic data obtained from successive coronal, sag ittal or horizontal sections. The extreme rostral pole of the striatum (A 11) was characterized by a large patch territory exhibiting comple x and tortuous fields with several extensions. In the intermediate par t of the structure (A 9.0-10.0), about 20 serial parallel continuous p atch channels running in a mediolateral axis, obliquely oriented and d isplaying in some cases connecting branches, could be observed. Howeve r, no channels could be distinguished in the rostrocaudal direction. M ore caudally, patches were rare and of small size. In addition, the la terocaudal region of the striatum was almost exclusively represented b y a large matrix field. Finally, a fine discontinuous band of [H-3]nal oxone binding was seen in all sections, bordering and limiting the dor solateral part of the striatum. The topographical and spatial distribu tion of the patch compartment was similar in all animals investigated. However, due to the tortuous shape and the labyrinthine organization of the patches, the precise degree of reproducibility from one animal to another could not be established. Nevertheless, the prominent patch compartment observed in the rostral pole of the striatum, the patch c hannels, oriented in the mediolateral axis as well as the large latero caudal matrix field were observed in all cases. These results were com pared with previous data obtained in the cat in which patch (striosome ) channels oriented along a rostrocaudal axis are also observed.