Monday, May 24, 2010

X-ed Out.

Another look at MDMA and serotonin.

A study by Canada’s Centre for Addiction and Mental Health (CAMH) has confirmed earlier findings that chronic users of ecstasy (MDMA) have abnormally low levels of serotonin transporter molecules in the cerebral cortex.

While a decade of research on the effects of ecstasy on brain serotonin has been controversial and largely inconclusive, the latest study used drug hair analysis to ResearchBlogging.orgconfirm levels of MDMA in 49 users and 50 controls. An additional division was made between chronic X users who also tested positive for methamphetamine, and those who did not. Regular usage of MDMA was defined as two tablets twice a month.

The Canadian study, funded by the U.S. National Institute on Drug Abuse (NIDA) and published in the journal Brain, suggests that the serotonin surge responsible for ecstasy’s effects results in a net depletion in regular X users. That is not a new finding--but the Canadian study goes further, suggesting that the serotonin depletion is localized in one area of the brain.

“We were surprised to discover that SERT was decreased only in the cerebral cortex and not throughout the brain,” said study leader Stephen Kish in a press release, “perhaps because serotonin nerves to the cortex are longer and more susceptible to changes.”

Low serotonin transporter (SERT) levels in the cerebral cortex were found in all X users, with or without amphetamine. Dr. Kish noted that the CAMH findings replicate what Kish referred to as “newer data” from Johns Hopkins University. In 1999, a controversial serotonin study of ecstasy users at Johns Hopkins laboratory was criticized for overestimating the level of danger posed by ecstasy-induced serotonin impairments.

Okay, the finding is becoming more robust. But what does it mean? According to co-author Isabelle Boileau, a low SERT level does “not necessarily” indicate structural brain damage. “There is no way to prove whether low SERT is explained by physical loss of the entire serotonin nerve cell, or by a loss of SERT protein within an intact nerve cell.”

For his part, Dr. Kish indicated that his concerns centered on the connection between lower serotonin measurements and MDMA tolerance levels. “Most of the ecstasy users of our study complained that the first dose is always the best, but then the effects begin to decline and higher doses are needed,” he said. “The need for higher doses, possibly caused by low SERT, could well increase the risk of harm caused by this stimulant drug.” The published study concluded that “behavioural problems in some ecstasy users during abstinence might be related to serotonin transporter changes limited to cortical regions.”

However, in addition to the confounding variable of methamphetamine (see my post, “How Pure is Ecstasy?”), it remains unclear whether the SERT alterations detected in the study are transient or permanent. Moreover, the nature of the link that “might” exist between lower SERT levels and cognitive impairment in the brains of regular ecstasy users remains a subject of dispute in the drug research community, as in this earlier post.  (And just to emphasize that drugs are complicated things, a spate of promising recent research has suggested that ecstasy might be an effective option for treating people with post-traumatic stress disorder).

The CAMH, affiliated with the University of Toronto, is Canada’s largest mental health and addiction teaching hospital.

Kish, S., Lerch, J., Furukawa, Y., Tong, J., McCluskey, T., Wilkins, D., Houle, S., Meyer, J., Mundo, E., Wilson, A., Rusjan, P., Saint-Cyr, J., Guttman, M., Collins, D., Shapiro, C., Warsh, J., & Boileau, I. (2010). Decreased cerebral cortical serotonin transporter binding in ecstasy users: a positron emission tomography/[11C]DASB and structural brain imaging study Brain DOI: 10.1093/brain/awq103

No comments:

Related Posts Plugin for WordPress, Blogger...