Properties of receptors for nerve growth factor in the mature rat nervous system

The binding properties of receptors for nerve growth factor (NGF) in the adult rat nervous system have been analyzed in membrane fractions from discrete regions and in radioautographs of tissue sections. Steady-state experiments with both preparations revealed specific binding of radioiodinated NGF that was heterogeneous in distribution and affinity. Of the regions in the central nervous system that were sampled, the dorsal spinal cord and basal forebrain were richest in NGF receptor. By 4 independent methods of analysis a high-affinity binding site was detected in the basal forebrain with half-maximal saturation estimated at 20-60 pM NGF. Binding at lower affinity was also seen but difficult to analyze quantitatively. Cross-linking studies followed by electrophoresis showed the NGF receptor in the rat basal forebrain to have an apparent molecular weight of 90 kDa. The binding and molecular properties of NGF receptors on adult mammalian neurons resemble those described on other NGF-responsive cells.