The activation of inositol phospholipid metabolism as a signal- transducing system for excitatory amino acids in primary cultures of cerebellar granule cells

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Abstract
L-Glutamic, L-aspartic acids and a number of their structural analogs, including quisqualic, kainic, ibotenic, quinolinic, and N-methyl-D- aspartic (NMDA) acids, increase inositol phospholipid hydrolysis when added to primary cultures of cerebellar granule cells, as is reflected by an enhanced formation of 3H-inositolmonophosphate (3H-IP1) in the presence of Li+. L-Glutamic acid also enhances the formation of the initial products of inositol phospholipid hydrolysis, 3H-inositol di- (3H-IP2) and triphosphate (3H-IP3). In the absence of extracellular Ca2+, L-glutamic acid fails to enhance 3H-IP1 formation, but still increases 3H-IP2 and 3H-IP3 formation. The stimulation of 3H-IP1 formation elicited by L-glutamic acid is reduced by DL-2-amino-5- phosphonovaleric acid (APV) and gamma-glutamylglycine and, to a lesser extent, by 2,3-cis-piperidindicarboxylic acid (PDA). The stimulation of 3H-IP1 formation by kainic acid is antagonized by PDA and gamma- glutamylglycine, but it is almost unaffected by APV. The increase in 3H- IP1 formation elicited by quisqualic acid is not reduced by any of the dicarboxylic amino acid receptor antagonists that we have tested. We conclude that different subtypes of excitatory amino acid recognition sites are associated with inositol phospholipid metabolism in primary cultures of cerebellar granule cells.