Serine-O-phosphate, an endogenous metabolite, inhibits the stimulation of inositol phospholipid hydrolysis elicited by ibotenic acid in rat hippocampal slices.

Serine-O-phosphate (PS) inhibits the accumulation of 3H-inositolmonophosphate elicited by ibotenic acid in rat hippocampal slices incubated in the presence of 7 mM Li+. This inhibition is concentration- dependent and stereoselective, L-PS being 5 fold more potent than D-PS. Among different structural analogues of PS, only L-serine weakly antagonizes the action of ibotenic acid, whereas phosphorylcholine, phosphorylethanolamine and phosphothreonine are inactive even at high concentrations. These results are consistent with the hypothesis that L-PS may act as an endogenous regulator of excitatory amino acid receptor function.