Ethanol inhibits the peak of muscarinic receptor-stimulated formation of inositol 1,4,5-trisphosphate in neuroblastoma SH-SY5Y cells.
The effect of ethanol on muscarinic receptor-stimulated formation of inositol 1,4,5-trisphosphate was studied in human neuroblastoma SH-SY5Y cells. Stimulation with carbachol induced a biphasic increase of inositol 1,4,5-triphosphate with an initial peak after 10 sec declining to a plateau phase of elevation above basal levels, which was sustained for at least 5 min in the presence of agonist. The peak, but not the plateau phase, was concentration-dependently decreased by exposure to ethanol. Maximal inhibition was obtained within 30 sec of exposure to ethanol. Ethanol caused an increase in the EC50 value of carbachol for the initial rate of inositol 1,4,5-trisphosphate formation, measured after 10 sec of stimulation, from 98 microM in the absence to 196 microM in the presence of 100 mM ethanol. The potencies of pirenzepine and hexahydro-sila-difenidol hydrochloride for inhibiting [3H]quinuclidinyl benzilate binding and inositol 1,4,5-trisphosphate formation suggest that both phases are mediated via the muscarinic M1 receptor. Phorbol 12-myristate 13-acetate inhibited both phases of inositol 1,4,5-trisphosphate formation, whereas okadaic acid and modulators of cAMP-dependent protein kinase were without any effect. There was no inhibitory effect of ethanol when protein kinase C was inhibited by H7 and calphostin C, indicating that the ethanol effect is dependent on protein kinase C activity.
Larsson
C
C
Department of Psychiatry and Neurochemistry, Lund University, Sweden.
Simonsson
P
P
Hoek
J B
JB
Alling
C
C
D002217:Carbachol / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis*; D007700:Kinetics; D018727:Muscarinic Antagonists; D009447:Neuroblastoma; D011493:Protein Kinase C / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000187:drug effects*; D014407:Tumor Cells, Cultured
D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D000431:Ethanol; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; D011493:Protein Kinase C