A scientist involved with a television programme featuring public figures taking ecstasy has praised it for offering an "unusual opportunity" for studying the aftereffects of the drug.

Dr Jonathan Roiser, from UCL's Institute of Cognitive Neuroscience, is set to appear in the second installment of Channel 4's "Drugs Live: the Ecstasy Trial" programme.

The show, the first part of which was broadcast after Yom Kippur last night, saw well-known figures including author Lionel Shriver and comedian Keith Allen take pills containing the active ingredient in ecstasy, MDMA.

Dr Roiser, who has been involved in the follow-up aspect of the drug trial, said the nature of the study was hugely beneficial to scientists.

"I don't think that there has been another opportunity in the UK to study the effects of MDMA in this manner," he said, adding that past studies had necessarily relied on field samples; "going out into nightclubs or advertising for people who have taken the drug".

"With those we have to make the assumption that they are actually taking MDMA but they don't know that and we don't know that. Someone might report they've taken it on Saturday night but could have all sorts of drugs mixed in to their ecstasy tablet whereas in this case the study is giving pure MDMA and we can be certain of that," he said. "It makes the science much stronger."

Dr Roiser said the research was important in terms of the potential uses of MDMA in therapy for post-traumatic stress disorder, and also because MDMA is said to be followed by a drop in serotonin levels, which scientists believe has a link to depression.

"After people take MDMA it is reported in literature and anecdotally that in the middle of the next week they feel very low or depressed, but it's quite transient," he said. "Normally if people are going to have aftereffects from taking some kind of substance, alcohol for example, then they won't necessarily feel down three days later. So from the perspective of pharmacology that's very interesting."

He said that the advertising for the programme, which focused on the televised taking of illegal drugs, was "a good way for Channel 4 to market it" but that it was the public health messages about the effects of ecstasy, including the subsequent mid-week low and longer-term effects on the brain, that were important.

"Ecstasy has the risk of being dangerous because it has a huge toxicity - people take it and could die - but it's important that in addition to understanding the risk in [these] terms that people also understand the potential impacts and how serious they are in terms of their mood and cognitive function."

The second part of "Drugs Live" will air this evening.