When a primate is given a single oral dose of 2.5 mg/kg, which is higher than the standard therapeutic dose, there is no neurotoxicity at all. MAPS has contributed seed money to Dr. Ricaurte for a study in which an oral dose of 2.5 mg/kg will be given once every two weeks for four months, for a total of eight administrations. The study will help to determine the neurotoxic risk of multiple doses of 2.5 mg/kg, a dose pattern more similiar to the average therapeutic or recreational than a single dose. This study will be concluded in late 1989.

Degenerated serotonergic nerve terminals experience regeneration. Dr. Ricaurte demonstrated that ten weeks after exposure to very large doses, primates that had 80-90% reductions in their serotonin levels had recovered roughly half of their lost nerve terminals. Currently underway is another study by Dr. Ricaurte, partially assisted by MAPS, which is investigating whether serotonergic nerve terminals will exhibit total recovery after a period of 40 weeks. This study will also be completed in late 1989.

Serotonergic nerve terminal degeneration, even in the range of 80-90%, seems not to result in behavioral or functional consequences. After over 7 million doses of MDMA have been taken in the United States, there are still no cases in the literature of any individual experiencing symptoms of MDMA related neurotoxicity. Nor have any published studies demonstrated that a relationship between repeated high doses of MDMA and long term behavioral effects exists. Dr. Thoms Insel's NIMH study found that even large doses to newborn rats had no long term behavioral effect. The only time that behavioral effects were noted occurred when MDMA was given in large amounts to pregnant rats, with the newborns exhibiting some abnormal behavior.