EE was actually found to exacerbate symptoms in female transgenic SOD1(G93A) ALS mice, in a sexually
dimorphic manner . It is possible that in these ALS mice the increased synaptic drive induced by EE could have accelerated specific excitotoxic mechanisms in motor neurones, a possibility which remains to be tested. Furthermore, the limitations of such transgenic animal models which involve overexpression of a specific familial human gene mutation , with respect to ‘genetic construct validity’, means that the direct relevance of such EE effects to the majority of ALS cases (which are sporadic and genetically heterogeneous) requires further investigation. The present article will review the effects of EE on brain disorders, with a focus on animal models of neurodegenerative diseases. I will address specific molecular, cellular and behavioural effects of EE in these models, MG-132 potential mechanisms selleck and implications for future therapeutic interventions for neuroprotection and brain repair. Huntington’s disease (HD) is a fatal, autosomal dominant neurodegenerative disorder which presents as a triad of cognitive, psychiatric and motor symptoms. HD is caused by a tandem repeat (CAG trinucleotide)
expansion encoding an extended tract of glutamines in the huntingtin protein. Understanding the pathogenesis of HD has been greatly accelerated by the development
of transgenic and knock-in animal models, the first of which were the R6 transgenic mouse lines . These and other genetically targeted animal models have demonstrated that the cognitive, psychiatric and motor symptoms are associated with specific effects of the HD mutation in selective neural circuitries and tissues [31,32]. Furthermore, knock-in and transgenic animal models of HD have provided new insights Y-27632 2HCl into mechanisms of pathogenesis, including molecular deficits, synaptic dysfunction and progressive abnormalities in neurones and other cell types [33–35]. The effects of EE were first investigated in the R6/1 HD transgenic mouse model . HD and wild-type mice were randomized post-weaning into either EE and standard housed (SH) conditions. EE was shown to dramatically delay onset of motor deficits in R6/1 HD mice and ameliorate neurodegenerative loss of peristriatal cerebral volume . Subsequently, it has been demonstrated that EE can also ameliorate cognitive deficits  and depressive-like abnormalities  in R6/1 HD mice. Furthermore, evidence has been provided, in R6/2 transgenic mice, that EE initiated around the time of motor onset can also slow progression of the movement disorder . These studies in HD mice have been followed up in clinical cohorts with epidemiological studies.