Localization of vitamin D-dependent calcium binding protein in the electrosensory and electromotor system of high frequency gymnotid fish.

Vitamin D-dependent calcium binding protein (D-CaBP) was localized in the brains of high frequency gymnotid fish. In birds and mammals this protein is seen in a variety of cell types including Purkinje cells, inferior olivary cells and CA1 pyramids of the hippocampus. This distribution has led us to speculate that D-CaBP may be important in buffering intracellular calcium, perhaps more specifically that calcium which enters the cell during dendritic calcium spikes. In the gymnotid fish D-CaBP was found in many of the same cell types in which it is also seen in birds and mammals. In addition, D-CaBP is specifically present in neurons which drive the electric organ (pacemaker and relay cells) and neurons within the electrosensory system which are phase-locked to the electric organ discharge (spherical and giant cells). Relay cells and giant cells have exceptionally high concentrations of D-CaBP. These cells do not exhibit calcium spikes and the role of their D-CaBP may be to regulate calcium released from intracellular stores.