Nat. Neurosci. 15, 64–69 (2012); published online 20 November 2011; corrected after print 15 December 2011

In the version of this article initially published, ref. 36 (given as Kaczowka, S.J. et al. Int. J. Biol. Macromol. 42, 62–67, 2008) was incorrect. The correct reference is Kaczocha, M., Glaser, S.T. & Deutsch, D.G. Identification of intracellular carriers for the endocannabinoid anandamide. Proc. Natl. Acad. Sci. USA 106, 6375–6380 (2009). The error has been corrected in the HTML and PDF versions of the article.