Insulin-like growth factor-I receptors in human brain and pituitary gland: an autoradiographic study

Insulin-like growth factor (IGF)-I receptors were studied in adult human postmortem brain and pituitary gland using quantitative autoradiography with human recombinant [125I]IGF-I. The highest densities were found in the choroid plexus, pituitary gland--where IGF-I receptors were mainly concentrated in the anterior lobe, pineal gland, glomerular layer of the olfactory bulb, and the molecular layer of the cerebellar cortex. Moderate densities were present in cerebral cortex, caudate nucleus, putamen, accumbens, the CA1, CA2, CA3 fields and dentate gyrus of the hippocampus, the dentate nucleus of the cerebellum, amygdala, thalamus, pontine nuclei, and substantia nigra. All other brain areas, including white matter, contained low densities of IGF-I receptors. The finding that several well-defined brain structures are enriched with IGF-I receptors suggests a neurotrophic/survival or neuromodulatory role of insulin-like growth factors on specific neuronal systems. IGF-I receptors observed in the white matter may be associated with oligodendrocytes.