Contrasting patterns in the localization of glutamic acid decarboxylase and Ca2+ /calmodulin protein kinase gene expression in the rat centrat nervous system

The expression of the genes encoding the alpha subunit of type II calcium calmodulin-dependent protein kinase (CaM II kinase α) and the 67,000 mol. wt form of glutamic acid decarboxylase was examined throughout the rat centrat nervous system.In situ hybridization histochemistry, using cRNA probes, revealed a dense population of CaM II kinase α-expressing cells throughout the telencephalon and diencephalon. CaM II kinase α mRNA was also expressed in the midbrain, cerebellum and medulla oblongata, but at greatly reduced levels. No CaM II kinase α gene expression was detected in nuclei producing monoamines or acetylcholine. By contrast, the glutamic acid decarboxylase gene was moderately to highly expressed throughout the centrat nervous system. In severat regions there was a complementarity in the distributions of cells expressing the glutamic acid decarboxylase or CaM II kinase α genes. Cells in certain nuclei such as the thalamic reticular nucleus or globus pallidus showed glutamic acid decarboxylase gene expression only; others such as the majority of the dorsal thalamic nuclei showed CaM II kinase α gene expression only. Severat regions contained both glutamic acid decarboxylase and CaM II kinase α expressing cells. However, simultaneous immunostaining for both proteins revealed only two regions where CaM II kinase α and glutamic acid decarboxylase immunoreactivity were colocalized: the cerebellar Purkinje cells and the commissurat nucleus of the stria terminalis. The results imply that CaM II kinase α is primarily expressed in non-GABAergic neurons. In severat regions CaM II kinase α mRNA is concentrated in nuclei known to contain populations of neurons that use excitatory amino acid transmitters.