Specific retrograde transport of nerve growth factor (NGF) from neocortex to nucleus basalis in the rat

[125I]labeled NGF injected in very small quantities into the frontal or dorsal anterior occipital cortex of adult rats, was specifically taken up and transported retrogradely to large, presumably cholinergic neurons in the nucleus basalis region (lateral preoptic nucleus, anterior lateral hypothalamic nucleus, substantia innominata, ventral globus pallidus and internal capsule), as revealed by light microscopic autoradiography. Cells projecting to the injection site in the frontal cortex were localized ipsilaterally in the more caudal parts of the nucleus basalis region, whereas cells projecting to the dorsal anterior occipital cortex could be found throughout the entire extent of the nucleus basalis and also in the vertical and horizontal limb of the nucleus of the diagonal band of Broca. Other nuclei known to project to the cortex (locus coeruleus, substantia nigra, nucleus raphe, thalamus) were consistently found to be unlabeled. In contrast to [125I]NGF, injection of [125I]cytochrome C failed to label any cell bodies in the basal forebrain nuclei by retrograde transport. This high selectivity for uptake and retrograde transport of NGF indicates the presence of membrane receptors for NGF or a closely related molecule on these cholinergic neurons of the basal forebrain innervating the cerebral cortex.