Gaba-receptor agonists and noradrenaline: effects on inositol lipid metabolism in the hippocampus.

The effecs of noradrenaline (NA), gamms-aminobutyric acid (GABA) and other GABAreceptor agonists on the metabolism of polyphosphoinositides (PIPS) were studied in rat hippocampal slices prelabelled with I3Hl myo-inositol. The content of inositol phosphates (IPs) and PIPs in the slices was measured. NA (1-100 µM) induced the formation of IPs in a dose-dependent menner: GABA. 3-aminopropanesulphonic acid (3APS) and muscimol did not affect the PIPs metabolism per se, but strongly increased (100%) the PIPs hydrolysis induced by t sM NA. The action of GABA, 3APS and muscimol was blocked by bicuculline, a selective GABA^-receptor antagonist. Baclofen, a GABA6receptor agonist, did not affect the NA-induced PIPs hydrolysis. In conclusion, GABA and GABA^-receptor agonists are considered to potentiate the effect of NA on the melabolism of PIPs. The implicafions of this inleraction for hippocampal neurotmnsmission are discussed.