CALBINDIN D-28K-CONTAINING NEURONS ARE RESTRICTED TO THE MEDIAL SUBSTANTIA-NIGRA IN HUMANS

A controversy exists in the literature as to whether neurons containin g the calcium binding protein calbindin-D-28k are located within the h uman substantia nigra. The point of variance between reports, however, is not the anatomical distribution of these neurons, but rather the d elineation of the dorsal border of the substantia nigra. It has been s uggested that the dense substance P striatonigral innervation delimits the substantia nigra in the human. The aim of the present study is to re-examine the distribution of calbindin-D-28k-positive neurons throu ghout the substantia nigra using substance P to delimit its borders. A lthough a few calbindin-D-28k-positive neurons were found in the media l cell group of the substantia nigra, the vast majority of positive ne urons were located in the adjacent A8 and A10 dopaminergic cell groups . This anatomical location of calbindin-D-28k-positive neurons is cons istent with previous reports, though our results indicate that when th e striatonigral projection is used to define the substantia nigra, cal bindin-D-28k is not a notable feature of these neurons. This questions the neuroprotective role of this protein in Parkinson's disease.