DISTRIBUTION OF INOSITOL-1,4,5-TRISPHOSPHATE AND RYANODINE RECEPTORS IN RAT NEOSTRIATUM

The distribution of the inositol-1,4,5-trisphosphate (IP3) and the car diac form of the ryanodine receptor, two intracellular calcium channel s, was examined in the rat neostriatum. Both IP3 and ryanodine recepto r labeling occurred within striatal medium spiny cells but only ryanod ine receptor labeling was present in choline acetyltransferase- and pa rvalbumin-positive; interneurons. IP3 receptor labeling was observed w ithin cell bodies, dendrites and spines of spiny striatal neurons, as seen at both the light and electron microscopic levels. Subcellular la beling for the ryanodine receptor was restricted to cell bodies and pr oximal dendrites when a polyclonal antibody raised against a peptide s equence from the dog cardiac ryanodine receptor was employed. More ext ensive dendritic labeling was seen using monoclonal antibody MA3-916, also raised against the canine cardiac ryanodine receptor. At the ultr astructural level, labeled dendritic spines were observed frequently w ith the monoclonal but not the polyclonal antibody. Ryanodine receptor labeling also was present within astrocytic processes surrounding blo od vessels and within the neuropil, regardless of the antibody used. T he results of these studies suggest that the ryanodine receptor plays a general role in intracellular calcium regulation within striatal cel ls while the IP3 receptor plays a specialized role within spiny neuron s.