Neuronal expression of leukemia inhibitory factor (LIF) in the rat brain

Very little is known about the action of the leukemia inhibitory factor (LIF) in the central nervous system. To analyze LIF expression in adult rat brain, we used non-radioactive in situ hybridization with digoxigenin-labeled RNA probes, in combination with immunohistochemistry to identify the cell types expressing LIF mRNA. Hippocampal pyramidal cells, hilar interneurons and granule cells of the dentate gyrus display strong hybridization signals, while neurons of the cerebral cortex, cerebellum, cholinergic basal forebrain nuclei, and the striatum are labeled as well. The most prominent expression in cerebral cortex is in layers IV and VI. Glial fibrillary acidic protein-positive astrocytes did not display a detectable LIF hybridization signal suggesting that LIF mRNA is predominantly expressed in neurons in the normal, adult rat brain, although a presence in resting microglial cells cannot be excluded.