ULTRASTRUCTURAL-LOCALIZATION OF THE PLASMALEMMAL CALCIUM-PUMP IN CEREBELLAR NEURONS

In a previous study, fluorescence labeling of a plasmalemmal ATPase pr otein with the 5F10 monoclonal antibody revealed prominent antigen in the cerebellar molecular layer surrounding the somata and dendrites of Purkinje cells. In the present study, this antibody labeled with silv er enhanced nano-sized gold particles on semithin plastic sections rev ealed a clearly demarcated plasma membrane outlining the somata and en tire dendritic arbors of Purkinje cells including their spines. Ultras tructural analysis of horseradish peroxidase preparations showed react ion product along the plasmalemma and extending on to the sub-plasmale mmal endoplasmic reticulum. In the granular layer, somata of granule c ells were reactive, as were their dendritic extensions into glomeruli where reactive claws surrounded voids formed by messy fiber rosettes. Somata and dendrites of cerebellar nuclear cells also had reactive zon es that were limited to the plasma membrane and a narrow zone of the s ub-plasmalemmal endoplasmic reticulum. Comparative labeling of this pr otein and P channel protein revealed similar plasmalemmal locations. T his study shows that a specific calcium ATPase pump protein is located on the plasmalemma of certain types of cerebellar neurons. The ultras tructural distribution of calcium pump and P channel antibodies occurr ed in punctate sites along the plasma membrane of dendrites and spines of Purkinje cells. The close association between P-type calcium chann els and the plasma membrane calcium pump is consistent with rapid extr usion of intracellular calcium from neurons endowed with large numbers of voltage-gated calcium channels.