The spatial and temporal pattern of beta NGF receptor expression in the developing chick embryo.

To gain insight into the developmental program of nerve growth factor (NGF) receptor expression, the binding of [125I] beta NGF to frozen chick sections was investigated autorradiographically between embryonic day 3 (E3) and post-hatching day 3. Strong NGF receptor expression was observed as early as E4, throughout embryonic development and in the post-hatching period at the classical NGF target sites: the paravertebral sensory and sympathetic ganglia, the paraaortal sympathetic ganglia as well as the cranial sensory ganglia with neurons of neural crest origin and their respective nerves. Only weak [125I] beta NGF binding was observed during a restricted time span in the parasympathetic ciliary ganglion. Clear differences were observed in the intensity and in the developmental time course of [125I] beta NGF binding to the dorsomedial and ventrolateral aspects of the dorsal root ganglia. NGF receptors were also found to be expressed on central axons of the dorsal root entry zone and the dorsal tract in the spinal cord. A transient expression of specific NGF binding sites of the same high affinity as measured at the classical NGF targets, was detected in the lateral motor column and in muscle at the time of motoneuron synapse formation and elimination.