EXPRESSION OF CILIARY NEUROTROPHIC FACTOR RECEPTOR-ALPHA MESSENGER-RNA IN NEONATAL AND ADULT-RAT BRAIN - AN IN-SITU HYBRIDIZATION STUDY

Ciliary neurotrophic factor is a pleiotropic molecule thought to have multiple functions in the developing and adult nervous system. To inve stigate the role of ciliary neurotrophic factor in the developing and mature brain by defining putative target cells the expression of the l igand-binding alpha-subunit of the ciliary neurotrophic factor recepto r was studied in neonatal and adult rat brains using a digoxygenin-lab elled probe for bz situ hybridization. Neuronal populations expressing ciliary neurotrophic factor receptor-alpha messenger RNA were found i n many functionally diverse brain areas including the olfactory bulb ( mitral cells and other neurons), neocortex (layer V) and other cortica l areas (pyramidal cell layers in the piriform cortex and hippocampus, granule cell layer of the dentate gyrus) and distinct nuclei in the t halamus, hypothalamus and brainstem. In the latter, reticular nuclei a nd both cranial motor and sensory nerve nuclei showed intense hybridiz ation signals in the neonatal brain. The nucleus ruber, substantia nig ra pars reticularis, deep cerebellar nuclei and a subpopulation of cel ls in the internal granular layer of the cerebellum were also labelled . In many areas (e.g., in thalamic, midbrain and pontine nuclei) cilia ry neurotrophic factor receptor-alpha expression became undetectable w ith maturation; however, there were other areas (e.g., olfactory bulb, cerebral cortex and hypothalamus) where expression was higher in the adult. The neuroepithelium of the neonatal rat displayed a highly sele ctive expression of ciliary neurotrophic factor receptor-alpha in area s which are known to exhibit high rates of postnatal cell proliferatio n in the germinal zones. Generally, neurons which have been reported t o respond to exogenous ciliary neurotrophic factor were labelled by th e ciliary neurotrophic factor receptor-alpha probe. This was not the c ase, however, for striatal and septal neurons. The results of this stu dy suggest that ciliary neurotrophic factor receptor-alpha ligands hav e even broader functions than previously thought, acting on different neuronal populations in the developing and mature brain, respectively. Copyright (C) 1997 IBRO.