Effects of beta-phenylethylamine on polyphosphoinositide turnover in rat cerebral cortex

The effects of the trace amine, beta-phenylethylamine, on the hydrolysis of inositol phospholipids in rat cerebral cortical slices was studied using a direct assay involving prelabeling with [3H]inositol and then examining the production of [3H]inositol phosphates in the presence of lithium. Phenylethylamine exhibited two different effects. Millimolar concentrations of phenylethylamine stimulated the production of [3H]inositol phosphates to about 200% of control, while much smaller concentrations (micromolar) inhibited noradrenaline(NE)-stimulated [3H]inositol phosphate formation dose-dependently. The alpha 1-antagonist, prazosin, inhibited the increases in [3H]polyphosphoinositide turnover stimulated by phenylethylamine and by NE, though it inhibited phenylethylamine to a lesser extent than NE. It appears, therefore, that phenylethylamine affects [3H]inositol phosphate formation by acting as a partial alpha 1-agonist.