Psychomotor stimulant effects of beta-phenylethylamine in monkeys treated with MAO-B inhibitors

Psychopharmacology (Berl). 2001 Dec;159(1):21-30. doi: 10.1007/s002130100890. Epub 2001 Sep 6.


Rationale and objective: Sufficiently high doses of beta-phenylethylamine (beta-PEA), a trace amine that is rapidly metabolized by monoamine oxidase-type B (MAO-B), can produce effects comparable to those of cocaine or methamphetamine (MA). The present experiments were conducted to study how the discriminative-stimulus (S(D)) and reinforcing-stimulus (S(R)) effects of beta-PEA in monkeys are modified by treatment with inhibitors of MAO-B [R-(-)-deprenyl and MDL 72974].

Methods and results: In studies of its S(D) effects, doses of beta-PEA up to 30 mg/kg engendered only sporadic responding on the drug-associated lever in squirrel monkeys that discriminated intramuscular injections of 0.3 mg/kg MA from vehicle whereas lower doses of 0.3-1.0 mg/kg beta-PEA produced full substitution when administered after either R-(-)-deprenyl or MDL 72974 (0.3 mg/kg). The MA-like S(D) effects of beta-PEA were attenuated by either dopamine D(1) or D(2) receptor blockers. In studies of its S(R) effects, high doses of beta-PEA maintained responding in two of three monkeys under a second-order fixed-interval schedule (3.0 or 10 mg/kg per injection) and two of three monkeys under a simple fixed ratio (FR) schedule (0.3-1.0 mg/kg per injection) of intravenous (i.v.) self-administration. MAO-B inhibition by R-(-)-deprenyl or MDL 72974 enhanced the S(R) effects of beta-PEA in all monkeys and, under the FR schedule, induced a 30-fold or greater leftward shift in the dose-response function for its i.v. self-administration. Based on time-course determinations, the enhanced S(R) effects of beta-PEA under the FR schedule were long-lasting and dissipated gradually over 3-7 days.

Conclusions: These results show that inhibition of MAO-B enhances S(D) and S(R) effects of beta-PEA in monkeys, presumably by delaying its inactivation. MAO-B inhibition leading to increased levels of beta-PEA may be useful, alone or in combination with other therapeutic agents, in the pharmacological management of selected aspects of drug dependence.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Central Nervous System Stimulants / pharmacology
  • Discrimination, Psychological / drug effects
  • Discrimination, Psychological / physiology
  • Dose-Response Relationship, Drug
  • Macaca mulatta
  • Male
  • Monoamine Oxidase Inhibitors* / pharmacology*
  • Monoamine Oxidase* / metabolism
  • Phenethylamines / pharmacology*
  • Psychomotor Performance / drug effects*
  • Psychomotor Performance / physiology
  • Psychotropic Drugs / pharmacology*
  • Reaction Time / drug effects
  • Reaction Time / physiology
  • Saimiri
  • Self Administration / methods


  • Central Nervous System Stimulants
  • Monoamine Oxidase Inhibitors
  • Phenethylamines
  • Psychotropic Drugs
  • phenethylamine
  • Monoamine Oxidase