Ahluwalia was lead author of the 2003 paper, “Activation of capsaicin-sensitive primary sensory neurones induces anandamide production and release,” while earning his PhD at Imperial College London. It had already been the subject of a June 2010 correction. That correction blamed the paper’s problems on a typo:
The authors wish to draw attention that in spite of several proof readings, regrettably, the unit for the amount of anandamide released from cultured primary sensory neurons was incorrectly entered into the manuscript therefore, it was incorrectly published in Ahluwalia et al. (2003). Further, the authors of this manuscript wish to provide a more-informative legend for Fig. 2.
The correct unit for the amount of anandamide released by cultured primary sensory neurons should be pmol/ml instead of pmol/μl throughout the manuscript.
A millimole is, of course, 1000 times the concentration of a micromole.
In July, we reported that Imperial had finished re-running all of Ahluwalia’s experiments, and was reviewing the results. Now, in a letter obtained by Retraction Watch, senior author Istvan Nagy, of Imperial, tells the Journal of Neurochemistry the data aren’t reliable at all:
In 2003, we reported in the Journal of Neurochemistry (Ahluwalia et al., Activation of capsaicin-sensitive primary sensory neurones induces anandamide production and release. J. Neurochem., 84, 585: 591; 2003) that application of capsaicin (10nM or 100nM) or KCl (50mM) to adult rat cultured primary sensory neurons results in increased anandamide content of the superfusate of the cells. In one of our recent studies, we repeated a part of the experiment we described in that Journal of Neurochemistry paper. While we found that application of capsaicin or KCl indeed results in increased anandamide content of the superfusate, regretfully, I have to inform you that our current data indicate that the concentration of anandamide in the superfusate we reported in the Journal of Neurochemistry paper must be incorrect.
Based on our current data, we can estimate that the superfusate of 500 cultured primary sensory neurons, after incubating the cells in 100nM capsaicin for 5 minutes, could contain ~ 7 fmol/ml anandamide, in average. However, in the paper we reportedthat 250µl superfusate of 500 cultured primary sensory neurons, following 3 minutes incubation in 100nM capsaicin contained 2.07pmol/ml anandamide, in average.
Based on our current data, we can also estimate that 5 minutes incubation of 500 cultured primary sensory neurons in 100nM capsaicin or 50nM KCl results, respectively, in ~47fmol/ml and ~68fmol/ml anandamide in the cells and superfusate together, in average.
Our current data are obtained from two independent experiments, and measurements were done in two laboratories using different machines and conditions (i.e. extraction, solvents, etc). Therefore, I think that our current data indicate the correct range of anandamide that 500 cultured primary sensory neurons could produce following capsaicin or KCl application.
A possible reason for the incorrect measurements, in our previous experiments, could be that instead of anandamide alone, we measured anandamide and other lipid compounds of very similar molecular mass together, because, due to the lack of internal standard and the use of single quad mass spectrometry, we could not differentiate between molecules of very similar molecular mass. Therefore, it appears that the conclusion of the Journal of Neurochemistry paper is based on data with a large artefactual component.
All of the authors agreed to Nagy’s request for withdrawal except Ahluwalia, who didn’t respond, according to the letter. The journal’s response to yesterday’s (August 23) letter was swift; they wrote back this morning to tell the authors they had agreed to retract the paper, which has been cited 56 times, according to Thomson Scientific’s Web of Knowledge.
As Retraction Watch readers may recall, Ahluwalia was also found guilty of faking data as a graduate student at Cambridge and of misconduct at University College London. One of his papers based on work from the latter institution and published in Nature was retracted last fall.