numbers of experimental animals used. He was surprised to find that his own publication, JNC, did not require the sex of animals to be reported.

A recently published survey of 271 randomly selected articles that reported the results of animal studies found less than 60 percent stated clearly the hypothesis, and the number and characteristics of the animals used, including sex (Kilkenny et al., 2009). More than 85 percent did not report any attempt at randomization or blinding to reduce bias in assessing outcomes, and 30 percent did not report statistical methods. This lack of information sharing may well contribute to why animal models are not optimized.

In response to this, guidelines are currently being developed that will ask editors of journals to require authors to address a checklist of 20 items that are the minimum information that should be included in all scientific publications reporting research using animals (e.g., number and specific characteristics of animals used, including species, strain, sex, genetic background; details of housing and husbandry; and experimental, statistical, and analytical methods, including methods to reduce bias).

Murphy noted that although these guidelines will call for the reporting of the sex of animals used, it does not ask authors submitting an article to give the rationale for studying either males or females, or to describe what the potential implications are for not studying the other sex. Including these requirements would be an educational step, Murphy said, and as editors are currently sensitive to these issues, the time could be right to implement such requirements.


Marie-Francoise Chesselet, chair of the Department of Neurobiology at the University of California–Los Angeles and associate editor of Experimental Neurology, is also treasurer of the Society for Neuroscience (SFN) and an ex-officio member of the publications committee for the SFN publication, the Journal of Neuroscience. Money is often a primary reason why many studies do not use both sexes, she said. But a valid scientific explanation and justification should be given for studying only one sex. Chesselet supported Murphy’s suggestion that authors be required to state the potential implications of studying only one sex.

In many papers, Chesselet observed, authors indicate that they balance experimental groups by sex, but do not disclose the exact balance. In some cases that “balance” turns out to be, for example, two males and seven females in one group, and one female and eight males in the other group. This information should be explicitly disclosed, she said.

Proper analysis of data by sex should also be required because, as mentioned in the earlier discussions, even National Institutes of Health–

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