Progressive electrophysiological changes in a mouse prion model of terminal neurodegenerative disease

Abstract

AbstractBackgroundIntracerebral injection of prion brain homogenate into mice recapitulates several features of Alzheimer’s disease, including memory deficits, progressive neuronal loss and terminal disease. Pharmacological interventions can preserve species‐specific behaviour and extend survival, but whether treatment can modulate cognition‐related brain activity is unclear. The purpose of this study is to define electrophysiological changes in the murine prion model, and inform future studies of the effects of interventions on neural activity.MethodMice inoculated with either Rocky Mountain Laboratories prion (n = 5) or control brain homogenate (n = 3) underwent surgery to implant seven skull screw recording electrodes (Figure 1). From 4 weeks post‐inoculation, weekly recordings were made by attaching a wireless transmitter to the implant. Prion mice were humanely killed 9‐12 weeks post‐inoculation once they exhibited clinical signs of disease. Brains were retained for histological analysis.Decibel power spectra were generated from recordings using a 2.5 s sliding window with 50% overlap. Theta peak frequency and area under the curve measures were extracted (Figure 2). Effects of prion and week post‐inoculation on these features were determined using mixed effects analyses.ResultPrion mice exhibited a progressive reduction in peak theta frequency, which differed from control mice at 8‐ and 9‐weeks post‐inoculation. The mean ± 95% confidence interval for control mice at 8 weeks post‐inoculation was 8.9±0.4 Hz, compared to 7.0±0.7 Hz for prion mice (Figure 2). The extent of slowing at 9 weeks post‐inoculation correlated with survival outcomes: clinical signs occurred 10‐25 days earlier in mice with a peak theta frequency <6.5 Hz. Delta power showed a week by inoculation interaction, declining in control mice up to 6 weeks post‐inoculation and increasing in the latter weeks of prion infection.ConclusionWe have shown that slowing of electrical activity, a common feature of progressive neurodegenerative diseases, occurs in the murine prion model and correlates with survival. This further validates using the prion model to investigate interventions aimed at treating Alzheimer’s disease and related dementias. Elevated delta power is associated with neurodegenerative disease and muscarinic receptor antagonism, further demonstrating the suitability of the prion model to test pro‐muscarinic interventions in neurodegenerative disease.