NGF receptor (p75)-immunoreactivity in the developing primate basal ganglia

The distribution of the p75 nerve growth factor receptor (NGFr) was determined within the developing human basal ganglia in specimens between weeks 16 through 40 of gestation, 5 years of age, and adulthood. Although NGFr-immunoreactive neurons were rarely seen in the caudate nucleus, a few such neurons were seen in the putamen between prenatal weeks 16 and 26 of development. At 26 and 40 weeks of gestation, the putamen also displayed NGFr-immunoreactive fibers of putative basal forebrain origin. Some of these fibers coursed through the putamen en route to the cortex while others appeared to remain within the putamen. The external segment of the globus pallidus contained dense collections of NGFr-immunoreactive neurons between 16 and 26 weeks of gestation, whereas the internal segment was devoid of immunoreactive perikarya. A few NGFr-immunoreactive neurons were observed within the globus pallidus at embryonic week 40. The expression of NGFr-immunoreactive neurons within the external segment of the globus pallidus was paralleled by a dense granular NGFr-immunoreactive terminal-like staining pattern within the subthalamic nucleus. This staining pattern was most intense at midgestation (weeks 21-26) and was not observed at 40 weeks of gestation or in adulthood. Interestingly, a similar NGFr-immunoreactive terminal-like pattern was also observed within the monkey subthalamic nucleus at embryonic day 120. These data indicate that NGF receptor mediated mechanisms may underlie developmental processes within the primate basal ganglia. The absence of NGFr-immunoreactive neurons within the caudate nucleus, and the paucity of such neurons in the putamen, suggests that NGF receptors play a limited role in primate neostriatal development. Alternatively, developmental events mediated through NGF receptors may occur prior to embryonic week 16. Furthermore, an NGFr/trophic interaction appears to underlie the development of the pallidal-subthalamic nucleus pathway.