Deuterium substitution enhances the effects of beta-phenylethylamine on spontaneous motor activity in the rat.

The effects of beta-phenylethylamine (PEA) and alpha, alpha, beta, beta-tetradeutero-beta-phenylethylamine (deuterated PEA) on spontaneous motor activity and conditioned taste aversion learning in the rat were examined. The intensity and duration of certain behavioural components elicited by PEA, namely, sniffing, headweaving, splayed hindlimbs and hyperreactivity, were significantly increased by deuterium substitution. In contrast, deuteration had no effect on the ability of PEA to elicit a conditioned taste aversion. The potentiation of the amine's effects on activity seemed to be directly related to the longer persistence of PEA in the brain due to the kinetic isotope effect since it appears that tetra-deuterated PEA is a poorer substrate for monoamine oxidase than the protonated amine.