Phenylethylamine-induced stereotypies in the rat: a behavioral test system for assessment of MAO-B inhibitors.

Stereotyped sniffing behavior together with forepaw padding--defined as the beta-phenylethylamine (PEA) syndrome--is induced by MAO-B inhibitors in rats injected with 30 mg/kg IP PEA. The comparison of the abilities of the MAO-B inhibitors to induce the syndrome and to inhibit MAO-B in rat brain homogenates indicated that at least 75% of MAO-B activity in rat brain had to be inhibited to induce the PEA syndrome. A good correlation was found between the abilities of MAO-B inhibitors to induce the behavioral syndrome and to increase levels of PEA in rat brain. Specific MAO-A inhibitors potentiated the behavioral effect of the MAO-B inhibitor deprenyl, while they did not induce the syndrome themselves or only at very high doses. Inhibitors of the reuptake of 5-HT or noradrenaline were inactive under the described experimental conditions. This behavioral test system seems to be a useful in vivo screening test in rats for detecting compounds with strong MAO-B inhibiting activity.