Spatial organization of patch and matrix compartments in the rat striatum.

The visualization of mu opiate receptors by [3H]naloxone binding was used to determine precisely the spatial organization of the patch compartment in the rat striatum and its reproducibility in different animals. Three-dimensional reconstruction of the patch network was made using maps of autoradiographic data obtained from successive coronal, sagittal or horizontal sections. The extreme rostral pole of the striatum (A 11) was characterized by a large patch territory exhibiting complex and tortuous fields with several extensions. In the intermediate part of the structure (A 9.0-10.0), about 20 serial parallel continuous patch channels running in a mediolateral axis, obliquely oriented and displaying in some cases connecting branches, could be observed. However, no channels could be distinguished in the rostrocaudal direction. More caudally, patches were rare and of small size. In addition, the laterocaudal region of the striatum was almost exclusively represented by a large matrix field. Finally, a fine discontinuous band of [3H]naloxone binding was seen in all sections, bordering and limiting the dorsolateral part of the striatum. The topographical and spatial distribution 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 channels, oriented in the mediolateral axis as well as the large laterocaudal matrix field were observed in all cases. These results were compared with previous data obtained in the cat in which patch (striosome) channels oriented along a rostrocaudal axis are also observed.