Passive avoidance behaviour deficit in the mdx mouse.

Thirty per cent of boys with Duchenne muscular dystrophy (DMD) suffer from various degrees of mental retardation. Since dystrophin, the protein absent in muscles of boys with DMD, is produced also in the brain, it was postulated that the deficiency of brain dystrophin might account for the mental retardation found in DMD boys. The mdx mouse, a mouse model of DMD, fails to produce dystrophin in muscle and brain. This prompted us to study the cognitive function of these animals. Learning and memory processes were studied in 10 mdx females and 9 genetically matched controls using the passive avoidance test. Statistically significant differences in the retention of the passive avoidance response was detected between mdx and control mice, indicating an impairment in passive avoidance learning in mdx mice. Our data reinforce the view that brain dystrophin deficiency is correlated with cognitive dysfunction and indicate that mdx mice might be a model for the mental retardation found in DMD boys.