Neurocalcin-immunoreactive neurons in the mammalian dorsal root ganglia, including humans

Neurocalcin (NC) is a recently characterized EF-hand calcium-binding protei n present in a discrete population of sensory neurons and their peripheral mechanoreceptors, but its presence in peripheral nervous system neurons oth er than in the rat is still unknown. The present study was designed to inve stigate the occurrence of NC in the dorsal root ganglia (DRG) of several ma mmalian species (horse, buffalo, cow, sheep, pig, dog, and rat), including humans. DRG were fixed, embedded in paraffin, and processed for immunohisto chemistry using a polyclonal antibody against NC. The size of the immunorea ctive neurons was measured. In all species examined, NC immunoreactivity (T R) was restricted to neurons but the percentage, as well as the size of the immunoreactive neurons, varied among different species. As a rule, small n eurons (diameter <20 mu m) lack NC IR. In some species (pig, dog, buffalo, cow), only the largest neurons showed IR, whereas in others (sheep, horse, rat, and humans) they covered the entire range of neuron sizes. The pattern of immunostaining was cytoplasmic, although in some species (cow and buffa lo), it formed a peripheral "ring." The present results demonstrate that ma mmalian DRG contain a subpopulation of NC-positive neurons, which varies fr om one species to another. Based on the neuron size, the possible function of the NC-containing neurons is discussed. Anat Rec 259:347-352, 2000. (C) 2000 Wiley-Liss, Inc.