Gaba- and serotonin-immunoreactive structures and ca(2+)-binding protein in the neocortex of the reeler mouse mutant.

The transmitter organization of anomalously formed neocortex was studied in reeler mutant mice by immunohistochemical studies of GABA- and serotoninergic structures and Ca(2+)-binding protein. GABAergic structures were identified in terms of the localization of glutamate decarboxylase (GDC) within them, this being an enzyme involved in GABA synthesis. The neocortex of reeler mutant mice was found to contain an unusual distribution of cells morphologically and chemically identical to Cajal-Retzius cells - beneath layer I rather than in its upper third, as seen in normal animals. GDC-immunoreactive label accumulated in the neuropil of the intermediate and deep layers, layer I containing only occasional granules. Serotonin-immunoreactive fibers did not form superficial or deep plexuses, as seen in normal animals, though they did reach their innervation targets. Thus, the anomalously formed neocortex which lacks the typical cytoarchitectonic organization, showed abnormalities in the structure of both intrinsic and projectional transmitter systems.