Rescue of Long-Term Spatial Memory by 7,8-Dihydroxyflavone in Mice with Reduced Oligodendrogenesis.

Oligodendrogenesis is the process by which new oligodendrocytes are produced in the CNS. Oligodendrocytes form myelin, which has a vital role in neural signal transmission and integration. Here we tested mice with reduced adult oligodendrogenesis in the Morris water maze, a test of spatial learning. These mice were found to have impaired long-term (28 d) spatial memory. However, when 7,8-dihydroxyflavone (7,8-DHF) was administered immediately after each training session, their long-term spatial memory impairment was rescued. An increase in the number of newly formed oligodendrocytes in the corpus callosum was also observed. 7,8-DHF has previously been shown to improve spatial memory in animal models of Alzheimer's disease, post-traumatic stress disorder, Wolfram syndrome and Down syndrome, as well as in normal aging. Understanding the underlying mechanisms of the effect of this drug on spatial memory is therefore helpful in assessing it for clinical relevance and development.

DUSP15 expression is reduced in the hippocampus of Myrf knock-out mice but attention and object recognition memory remain intact.

The atypical protein tyrosine phosphatase enzyme, dual-specificity phosphate 15 (DUSP15) is thought to be activated by myelin regulatory factor (MyRF) and to have a role in oligodendrocyte differentiation. Here, we assess whether Dusp15 is reduced in the hippocampus of mice with conditional knock-out of Myrf in oligodendrocyte precursor cells. Using quantitative polymerase chain reaction (qPCR) we found that Dusp15 expression was indeed lower in these mice. Alterations in myelin have been associated with Alzheimer's disease (AD), autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD). Symptoms of these disorders can include impairments of object recognition and attention. We, therefore tested the mice in the object recognition task (ORT) and 5-choice serial reaction time task (5CSRTT). However, we did not find behavioural impairments indicating that attentional abilities and object recognition are not impacted by reduced oligodendrogenesis and hippocampal Dusp15 expression. Gaining insight into the role of newly formed oligodendrocytes and Dusp15 expression is helpful for the development of well targeted treatments for myelin dysregulation.

7,8-dihydroxyflavone enhances long-term spatial memory and alters brain volume in wildtype mice.

Introduction: 7,8-dihydroxyflavone (7,8-DHF) is a low molecular weight compound that can cross the blood brain barrier and has been implicated in numerous functions and behaviours. It is thought to have neuroprotective capability and has been shown to alleviate symptoms in a wide range of diseases. Methods: 7,8-DHF was administered systemically to wildtype mice during Morris water maze training. Long-term spatial memory was assessed 28 days later. Ex-vivo T2-weighted (T2w) imaging was undertaken on a subset of these mice to assess brain-wide changes in volume. Results: We found that systemic 7,8-DHF administration during the training period enhanced spatial memory 28 days later. Volumetric changes were observed in numerous brain regions associated with a broad range of functions including cognition, sensory, and motor processing. Discussion: Our findings give the first whole brain overview of long-term anatomical changes following 7,8-DHF administration providing valuable information for assessing and understanding the widespread effects this drug has been shown to have in behaviour and disease.