Gender-Specific Hippocampal Dysrhythmia and Aberrant Hippocampal and Cortical Excitability in the APPswePS1dE9 Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is a multifactorial disorder leading to progressive memory loss and eventually death. In this study an APPswePS1dE9 AD mouse model has been analyzed using implantable video-EEG radiotelemetry to perform long-term EEG recordings from the primary motor cortex M1 and the hippocampal CA1 region in both genders. Besides motor activity, EEG recordings were analyzed for electroencephalographic seizure activity and frequency characteristics using a Fast Fourier Transformation (FFT) based approach. Automatic seizure detection revealed severe electroencephalographic seizure activity in both M1 and CA1 deflection in APPswePS1dE9 mice with gender-specific characteristics. Frequency analysis of both surface and deep EEG recordings elicited complex age, gender, and activity dependent alterations in the theta and gamma range. Females displayed an antithetic decrease in theta (θ) and increase in gamma (γ) power at 18-19 weeks of age whereas related changes in males occurred earlier at 14 weeks of age. In females, theta (θ) and gamma (γ) power alterations predominated in the inactive state suggesting a reduction in atropine-sensitive type II theta in APPswePS1dE9 animals. Gender-specific central dysrhythmia and network alterations in APPswePS1dE9 point to a functional role in behavioral and cognitive deficits and might serve as early biomarkers for AD in the future

Motor Cortex Theta and Gamma Architecture in Young Adult APPswePS1dE9 Alzheimer Mice.

Alzheimer's disease (AD) is a multifactorial disorder leading to progressive memory loss and eventually death. In this study, an APPswePS1dE9 AD mouse model has been analyzed for motor cortex theta, beta and gamma frequency alterations using computerized 3D stereotaxic electrode positioning and implantable video-EEG radiotelemetry to perform long-term M1 recordings from both genders considering age, circadian rhythm and activity status of experimental animals. We previously demonstrated that APPswePS1dE9 mice exibit complex alterations in hippocampal frequency power and another recent investigation reported a global increase of alpha, beta and gamma power in APPswePS1dE9 in females of 16-17 weeks of age. In this cortical study in APPswePS1dE9 mice we did not observe any changes in theta, beta and particularly gamma power in both genders at the age of 14, 15, 18 and 19 weeks. Importantly, no activity dependence of theta, beta and gamma activity could be detected. These findings clearly point to the fact that EEG activity, particularly gamma power exhibits developmental changes and spatial distinctiveness in the APPswePS1dE9 mouse model of Alzheimer's disease

Functional implications of Ca(v)2.3 R-type voltage-gated calcium channels in the murine auditory system - novel vistas from brainstem-evoked response audiometry

Voltage-gated Ca2+ channels (VGCCs) are considered to play a key role in auditory perception and information processing within the murine inner ear and brainstem. In the past, Ca(v)1.3 L-type VGCCs gathered most attention as their ablation causes congenital deafness. However, isolated patch-clamp investigation and localization studies repetitively suggested that Ca(v)2.3 R-type VGCCs are also expressed in the cochlea and further components of the ascending auditory tract, pointing to a potential functional role of Ca(v)2.3 in hearing physiology. Thus, we performed auditory profiling of Ca(v)2.3(+/+) controls, heterozygous Ca(v)2.3(+/-) mice and Ca(v)2.3 null mutants (Ca(v)2.3(-/-)) using brainstem-evoked response audiometry. Interestingly, click-evoked auditory brainstem responses (ABRs) revealed increased hearing thresholds in Ca(v)2.3(+/-) mice from both genders, whereas no alterations were observed in Ca(v)2.3(-/-) mice. Similar observations were made for tone burst-related ABRs in both genders. However, Ca(v)2.3 ablation seemed to prevent mutant mice from total hearing loss particularly in the higher frequency range (36-42 kHz). Amplitude growth function analysis revealed, i.a., significant reduction in ABR wave W-I and W-III amplitude in mutant animals. In addition, alterations in W-I-W-IV interwave interval were observed in female Ca(v)2.3(+/-) mice whereas absolute latencies remained unchanged. In summary, our results demonstrate that Ca(v)2.3 VGCCs are mandatory for physiological auditory information processing in the ascending auditory tract

Beta frequency analysis of cortical M1 EEG recordings in controls and APPswePS1dE9 mice.

<p>The mean relative beta EEG power [%] was calculated FFT based for males and females considering potential circadian rhythmicity (dark phase (<b>A</b>), light phase (<b>B</b>)). Frequency analysis was performed for all four ages (14, 15, 18, 19 wks). Black, controls; gray, APPswePS1dE9. Note that only animals displaying highest quality EEGs (no EMG/ECG contamination) were finally included into the analysis. For sample size see original data.</p

Theta frequency analysis of cortical M1 EEG recordings in controls and APPswePS1dE9 mice.

<p>The mean relative EEG theta power [%] was calculated FFT based for males and females considering potential circadian rhythmicity (dark phase (<b>A</b>), light phase (<b>B</b>)). Frequency analysis was performed for all four ages (14, 15, 18, 19 wks). Black, controls; gray, APPswePS1dE9. Note that only animals displaying highest quality EEGs (no EMG/ECG contamination) were finally included into the analysis. For sample size see original data.</p