Ca2(+)-dependence provides evidence for differing mechanisms of GABA-induced inositol phosphate formation and GABA potentiation of inositol phosphate formation induced by noradrenaline in rat cerebral cortex.
[3H]Inositol phosphate formation ([3H]IP) induced by gamma-aminobutyric acid (GABA) in slices of rat cerebral cortex prelabelled with [3H]inositol was abolished in Krebs-Henseleit medium without added Ca2+, but could be restored by addition of Ca2+. In contrast, GABA potentiation of noradrenaline-induced [3H]IP accumulation in the same tissue was still observed in the absence of added Ca2+. This provides evidence (a) that the effect of GABA alone on [3H]IP formation is indirect and (b) that the mechanism of this effect is unlikely to be the same as for the potentiation by GABA of [3H]IP accumulation induced by noradrenaline.
Crawford
M L
ML
Department of Pharmacology, University of Cambridge, U.K.
Young
J M
JM
D000818:Animals; D002118:Calcium / Q000494:pharmacology* / Q000502:physiology; D002540:Cerebral Cortex / Q000187:drug effects* / Q000378:metabolism; D006168:Guinea Pigs; D007295:Inositol Phosphates / Q000378:metabolism*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D015290:Second Messenger Systems / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology* / Q000502:physiology
D007295:Inositol Phosphates; D005680:gamma-Aminobutyric Acid; D002118:Calcium; D009638:Norepinephrine