| Abstract: | Although beta-nerve growth factor is primarily known for its trophic role in the peripheral nervous system, recent reports have also revealed an inductive effect of beta-nerve growth factor on the cholinergic metabolism of the forebrain. To learn more about the significance and location of beta-nerve growth factor action in the central nervous system, the distribution of 125I]beta-nerve growth factor binding sites was studied by using the method of in situ receptor autoradiography and compared with the distribution of acetylcholinesterase, a sensitive enzyme marker of cholinergic neurons. The autoradiographic studies demonstrated strong, specific and saturable 125I]beta-nerve growth factor binding to several neuronal groupings in the forebrain and brainstem. beta-Nerve growth factor binding sites and strong acetylcholinesterase reactivity were jointly distributed in the forebrain on the medial septal nucleus, the diagonal band of Broca, the magnocellular basal nucleus and in the striatum. In the brainstem, beta-nerve growth factor binding sites were located on a number of neuronal groups in the reticular formation, the dorsolateral lemniscus and the cochlear nuclei. In contrast to the forebrain, less correlation was found with the distribution of acetylcholinesterase; no beta-nerve growth factor receptor expression was recorded on the cholinergic motor nuclei of the brainstem, while specific 125I]beta-nerve growth factor labeling could be located on the non-cholinergic cochlear nuclei. The present autoradiographic studies reveal a variety of tentatively beta-nerve growth factor receptor-positive neurons in the central nervous system. While strong correlation between the cholinergic metabolism and the presence of specific beta-nerve growth factor binding is demonstrated in the forebrain, this observation could not be extended to the brainstem, indicating the chemical diversity of central beta-nerve growth factor receptor-positive neurons. |
