REDUCTION OF PHOSPHOINOSITIDE HYDROLYSIS BY L-AMINO-3-PHOSPHONOPROPIONATE MAY BE CAUSED BY THE INHIBITION OF SYNTHESIS OF PHOSPHATIDYLINOSITOLS

L-Amino-3-phosphonopropionate (L-AP3), a putative antagonist of metabotropic glutamate receptors, inhibited the formation of [H-3]inositol phosphates induced by (1S,3R)1-aminocyclopentane-1,3-dicarboxylic acid in rat hippocampal slices. The inhibition was accompanied by a decrease in the levels of [H-3]phosphatidylinositols ([H-3]PIs). Preincubation of slices with L-AP3 inhibited the incorporation of [H-3]myo-inositol into PI fractions. The effects of L-AP3 was in contrast with those of a typical receptor antagonist, atropine; atropine inhibited carbachol-induced phosphoinositide hydrolysis, but the levels of [H-3]PIs were not affected. These findings suggest that the inhibition of phosphoinositide hydrolysis by L-AP3 is not due to the receptor antagonism but may be caused by the inhibition of synthesis of PIs.