One human clinical trial (Pacifici et al. 2001), one retrospective study comparing ecstasy users and non-users (Reneman et al. 2001), one report on other characteristics of MDMA or ecstasy users, (Logan 2001), one review (Doyon 2001),and six studies performed in non-human animals (Colado et al. 2001; Hong et al. 2001; Bunzow et al. 2001; Cannon et al. 2001; Mortenson et al. 2001) were located in this time period.

Immunological Effects in Humans
A report describing three clinical trials in men found that a second dose of MDMA can exacerbate or maintain the immunological changes produced after an initial dose (Pacifici et al. 2001).

Imaging: Gender Differences
An imaging study using Beta-CIT, intended to measure serotonin transporter binding found that only female heavy ecstasy users showed less Beta-CIT binding (Reneman et al. 2001) as compared with controls, whereas Beta-CIT binding in male heavy ecstasy users was not significantly different from binding in same-sex controls. The same study found that lowered Beta-CIT binding was no longer significantly lower in abstinent female ecstasy users, and that no differences in binding were seen in moderate (lifetime use of 1-50 tablets) users of either sex.

Impaired Driving
A report reviewing others' work and presenting an original case series found evidence of impaired driving in individuals with MDMA detected in blood (Logan 2001).

Drug Discrimination
A rat drug discrimination study explored the putative entactogenic effects of alpha-ethyltryptamine (Alpha-ET). Anecdotal reports suggest that alpha-ET has entactogenic effects in humans, and previous research in rats suggest that it is also a serotoninergic neurotoxin (Huang et al. 1991).

Mouse Neurotoxicity
A report examining MDMA-induced dopaminergic neurotoxicity in mice indicates that mice and rats are affected by different processes leading up to MDMA neurotoxicity (Colado et al. 2001). This suggests that rats, and not mice, are a better model for MDMA neurotoxicity in humans.

Rats: Biological Clocks, Vascular Tissue
An examination of rat suprachiasmatic nucleus (SCN) slices (Biello et al. 2001) suggests that MDMA can alter circadian rhythm, which supports some claims MDMA may play a role in altering circadian rhythm in humans as well. These changes in circadian rhythm might be associated with altered cognitive function in humans, as has been found in a study of flight attendants (Cho et al. 2000). A study of the effects of MDMA on rat vascular tissue (Cannon et al. 2001) found that MDMA reduced contraction of aortic rings without altering 5-HT uptake in aortic tissue.

General Pharmacology
One in vitro study used MDMA as a probe to study a newly discovered CNS receptor sensitive to tyramine (Bunzow et al. 2001). In another study, MDMA served as one of several probes used to examine differences between human and bovine serotonin transporter (Mortensen et al. 2001).