CALCIUM-BINDING PROTEINS IN THE SPIRAL GANGLION OF THE MONKEY, CALLITHRIX-JACCHUS

Calcium-binding proteins can act as intermediaries between changing le vels of free intracellular calcium ions and the physiological response of neurons. Some of these proteins, among them calbindin (CB), calret inin (CR) and parvalbumin (PV), can act as calcium buffers. A survey o f previous studies in rodents and human fetuses leads to the impressio n that many spiral ganglion cells co-express CB, CR, and PV. The findi ngs of the present study suggest that, in the adult marmoset, the expr ession of CB is restricted to a small number of cells, most likely typ e II ganglion cells, and that at least some of the numerous type I gan glion cells co-express CR and PV. In the neonate marmoset, large numbe rs of putative type I ganglion cells from the apical cochlear turn tra nsiently expressed a light and granular labeling for CB-like immunorea ctivity, in addition to the cells we believe to be type II ganglion ce lls exhibiting a strong and solid CB-like staining. The spiral ganglio n cells in all developmental stages co-expressed the mitochondrial enz yme cytochrome oxidase. Furthermore, a small population of CB-LI axons of unknown origin was found to terminate near the CB-immunoreactive g anglion cells.