C57BL/6J and DBA/2J strains present opposite sex differences in flash visual evoked potential latency: a possible confusing factor in gender studies on neurological diseases' transgenic models

The cholinergic neurotransmitter system in the brain is crucial in processing information related to cognitive, behavioral, and motor functions. A cholinergic dysfunction has been correctly described as one of the primary causes of neurodegenerative diseases. Differences in levels of acetylcholine or expression and function of receptors in selected brain areas have been indicated as one of the causes of sexual dimorphism in neurotransmission. However, variability in results among studies based on different mice strains could affect conclusions on this topic. Visual evoked potentials (VEPs) of male and female DBA/2J and C57BL/6J mice, which are two of the most common strains backgrounds in use for developing transgenic mice models of neurological diseases, have been studied. Effects induced by a single low dose of physostigmine have also been performed to evaluate the cholinergic system involvement. VEPs responses to luminous stimuli in C57BL/6J mice have shown a consistently lower latency than in DBA/2J, confirming the previous observation of strain differences in cholinergic function. Interestingly, strains present an opposite-sex difference in VEP latency not apparently related to sensitivity to physostigmine. These findings point at paying extreme attention to the choice of the genetic background of the animal model, especially in those basic and pre-clinical experiments that involve visual functioning.