The effect of ethanol (EtOH) in vitro on norepinephrine-stimulated phosphoinositide (Pl) hydrolysis in cultured astrocytes was investigated
under acute and chronic conditions stimulated by norepinephrine (NE). Using purified astrocytes from neonatal rat brain, the effect of acute and chronic exposure to ethanol on the norepinephrine stimulated PI breakdown was determined. Astrocytes maintained in culture in the presence and absence of ethanol were prelabeled with 3H-inositol, and the accumulation of 3 H-inositol phosphates was measured in the, presence of 10-5 M NE. Acute doses of ethanol (25-200 mM) had little´ effect on NE-stimulated PI breakdown. With astrocytes chronically exposed to the same concentrations for 7 days, significant increases in stimulated breakdown were observed beginning with concentrations of ethanol as low as 50 mM. NE stimulated PI hydrolysis in astrocytes ex-posed to 200 mM ethanol was 3 times that measured in astrocytes grown in the absence of ethanol. When astrocytes were chronically ex-
posed to 100 and 500 mM ethanol for various periods of time up to 7 days, it was found that significant increases in NE-stimulated PI hydrolysis occurred with exposure times as short as 4 hours. After 1 day of exposure to both EtOH concentrations, the observed increase in stimulated hydrolysis began to plateau, reaching the observed maximum values by days 3 to 5. The dose-dependency of PI hydrolysis in astrocytes chronically exposed to 100 mM EtOH was not affected even though; stimulated breakdown at all concentrations of NE tested was greater than that in cells grown in the absence of EtOH. The NE-stimulated PI hydrolysis in astrocytes was markedly inhibited by acute doses of the cyclic nucleotide phosphodiesterase inhibitor, isobutylmethylxanthine (IBMX) as well as dibutyryl CAMP. Chronic exposure. to 0 mM, 100 mM and 500 mM EtOH resulted in an increased sensitivity of PI hydrolysis of inhibition by IBMX in the ethanol treated cultures. The sensitivity of this inhibition was greatest in the 500 mM EtOH-treated cultures and least in the control cultures.
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