DISTRIBUTION OF INSULIN-LIKE GROWTH FACTOR-I RECEPTOR MESSENGER-RNA IN RAT-BRAIN - REGULATION IN THE HYPOTHALAMONEUROHYPOPHYSEAL SYSTEM

The distribution and regulation of mRNA for the IGF-I receptor (IGF-I- R) in the adult rat brain were studied by in-situ hybridization with a S-35-labelled cRNA probe. The pituitary gland showed a strong hybridi zation signal in the pars tuberalis (the surface of the median eminenc e), pars distalis and pars intermedia. Within the brain, a strong hybr idization signal was found in the circumventricular organs, olfactory bulb, hippocampus, cerebellum and hypothalamus. IGF-I-R mRNA was consi stently found in cell bodies of the hypothalamo-neurohypophysial syste m. Six days of intermittent salt-loading resulted in an increase in IG F-I-R gene expression in the supraoptic nucleus. The increase in IGF-I -R mRNA was accompanied by a high expression of c-Fos immunoreactivity in the same cells. The presence and regulation of IGF-I-R mRNA in the hypothalamus suggest that IGF-I may affect the local plasticity or mo dulation of activated magnocellular neurones by an autocrine or paracr ine action through specific receptors in the hypothalamoneurohypophysi al system.