Comment Re:Molecules shmolecules (Score 2) 274
There's a huge bias towards using exclusively male mice in many types of research, and the issue of higher variance in female rodent behavior (due to estrous cycle issues, among others) is well known (see eg: pdf).
There are also related problems more generally with stress and over-training in neuroscience. Experienced investigators are able to produce a much less stressful working environment for animals, so they tend to get different results from neophyte investigators even when following the same protocol. This shows up a lot when a different lab tries to replicate the work of an experienced post-doc and gets null results for the first 6 months then suddenly is able to replicate everything. Thus often is attributed to 'correcting' the protocol (often with extensive communication with the previous lab) when often I think the change is attributable to the investigator in the replicating lab becoming experienced enough to relieve stress (I don't have a great link for this, mostly just an observation from having been around quite a few labs).
Over-training is also a problem, since it often takes thousands (sometimes well into the hundreds of) to train animals in complex cognitive tasks, and it's well known from experiments in humans (and a few in non-human primate and rodent) that neural responses shift profoundly between 'trained' and 'over-trained' states, say between amateur and professional ballerinas watching videos of ballet.
However, these issues are a much bigger problem in pre-clinical research than in basic research. Our understanding of the brain is sufficiently limited that the effects we're used to seeing in basic research questions swamp the potential modulation from gender, stress and training factors (unless you're talking about stress research specifically, but they're pretty careful about controlling for these types of effect). The issue with pre-clinical research is that often the difference between the current treatment and proposed treatment is only a few percent (note: if valid, this can mean thousands of lives saved or hugely improved), and so failing to identify and control for factors such as researcher or mouse gender can overwhelm the supposed primary result.