MDMA and S-(-)-cathinone (one enantiomer, or form, of the active ingredient in khat) were tested for their ability to reduce or eliminate haloperidol-induced catalepsy (rigidity and slow or "frozen" body movement) in rats, often used as a model for testing potential anti-Parkinson’s disease drugs. Rats were either treated with vehicle (no drug), 2.5 mg/kg MDMA or 1 mg/kg S-(-)-cathinone 30 minutes after receiving 0.5 mg/kg haloperidol. The time it took rats to remove their paws from an elevated horizontal bar and from a vertical grid served as measures of catalepsy. Rats underwent assessment of catalepsy for 7 consecutive days to examine short-term effects of MDMA, and again after 18 drug-free days, with the second assessment lasting 5 consecutive days. A within-subjects assessment was also performed by comparing behavior after haloperidol alone on Day 29 with behavior after haloperidol and either S-(+)-cathinone or MDMA. Eight days after assessing catalepsy, the researchers measured the ability of MDMA and S-(-)-cathinone to attenuate haloperidol-induced reduced locomotor activity in an "open field" with a hole-board. Open field behavior was videotaped, and observers coded the video, for entry into new part of open field, rearing, active sitting (grooming, moving), inactive sitting, and head dips into hole board. Both MDMA and S-(-)-cathinone had significant anti-cataleptic activity (reducing time until paws were moved, or "descent latency"), and both drugs continued to reduce descent latency during seven days of treatment, though haloperidol also had less of a cataleptic effect over time. After an 18-day drug-free period, MDMA and S-(-)-cathinone treatment still reduced descent latency. MDMA and S-(-)-cathinone both attenuated haloperidol-induced reductions in rearing and locomotion in the open field, but S-(-)-cathinone attenuated haloperidol effects to a greater degree than MDMA. Both MDMA and S-(-)-cathinone increased active sitting after haloperidol, with both drugs being equally good at increasing active sitting. Possible explanations for the anti-cataleptic effects of MDMA and S-(-)-cathinone include direct effects on dopamine release, release or inhibited uptake of serotonin, or an unexpected and heretofore unexamined effect common to both drugs. The authors do not examine possible serotonin effects on dopamine tone in this paper. The same research team has previously authored a report on the anti-cataleptic activity of MDMA (Schmidt et al. 2002), and another report comparing effects of MDMA, MDA, MDE and MBDB on another rat model of Parkinson’s disease (Lebsanft et al. 2003).