Relevant pharmaco-EEG in vivo data (Baclofen, Fenfluramine)

Currently, preclinical neuroscience research calls for more translationally relevant biomarkers that help better predict clinical outcomes. Electrophysiological events recorded via electroencephalography (EEG) recordings, highly utilised in the clinic, arise as translationally relevant biomarkers, not only for clinical but also preclinical research. At present, EEG abnormalities are frequently observed in subjects with rare neurodevelopmental disorders (such as autism, Fragile X Syndrome, Dravet Syndrome and Ret Syndrome).  

One such EEG biomarker frequently measured in the clinic is event-related potentials (ERPs). ERPs are subtle changes in brain’s electrical activity generated in response to specific stimuli (sensory, cognitive or motor), providing you with a tool to evaluate cognitive processing with a high temporal resolution. Although a commonly utilised biomarker in the clinic (for a review of the use of ERP-EEG in vivo recording in the clinical rare genetic disease populations see Armstrong et al., 2021), ERP-EEG recording is currently not frequently performed in mouse models.  

At InnoSer, we have developed a protocol to test this paradigm using auditory ERP (AERP)-EEG in vivo recording (Figure 1). AERP-EEG in vivo recording is relevant for various rare diseases such as Fragile X Syndrome, infantile-epileptic syndromes, offering you with translational biomarker for your rare disease research. Similarly, AERP-EEG in vivo recording may also be relevant to longitudinally monitor your investigational drug’s effects and pharmacodynamic efficacy in wild type mice (Figures 2-3).  

FIGURE 1. InnoSer’s experimental setup for EEG in vivo recording of auditory event-related potentials (AERP). This experiment is conducted in a sound attenuating chamber (1). Mouse is implanted with a wireless EEG recording system that also collects body movement (XYZ activity) (2) and placed in a Plexiglas cylinder (3). A speaker is set up with adjustable volume and frequency to generate specific acoustic stimuli (4). A recorder is placed inside the chamber to record the sound (5), together with the infrared light synchronisation pulse generator (6) to help synchronize the acoustic stimuli with the recorded EEG signals. During an ERP recording session, multiple trials are provided with a 100 msec white noise stimulus (~70 dB), with 4-6 sec inter trial interval. Trials with movement artifacts (deducted from XYZ activity) are excluded, generating a clean average AERP trace for the auditory cortex electrode.  

FIGURE 2. In WT mice (C57BL/6 mice), a single dose of the GABA-B agonist Baclofen (5 mg/kg, i.p) increases N1 latency. (A) Grand average waveforms with characteristic AERP-EEG deflections showing the differences between vehicle-treated and Baclofen-treated mice in recorded auditory complex amplitude (mV) during the AERP-EEG protocol. P1= positive peak 1; N1= negative peak 1. (B) Compared to vehicle-treated, Baclofen-treated mice tended to have a significant increase in the amplitude (mV) of the P1 component of AERP (P=0.06; independent samples t-test) indicating a more sensitive response of the auditory cortex to the auditory stimulus. (C) Compared to vehicle-treated mice, Baclofen-treated mice showed significant increase (**P=0.008; Mann-Whitney U test) in N1 latency (msec) of AERP indicating a delayed response of the auditory cortex to the auditory stimulus (EEG abnormality). Baclofen was previously shown to improve such EEG abnormalities in response to auditory stimuli in the Fmr1 KO mouse model (Sinclair et al., 2017). 

FIGURE 3. In WT mice (C57BL/6 mice), a single dose of the anti-seizure medication Fenfluramine (40 mg/kg, i.p.) increases N1 latency. (A) Grand average waveforms with characteristic AERP-EEG deflections showing the differences between vehicle-treated and Fenfluramine-treated mice in recorded auditory complex amplitude (mV) during the AERP-EEG protocol. P1= positive peak 1; N1= negative peak 1. (B) Compared to vehicle-treated, fenfluramine-treated mice show significant increase in the amplitude (mV) of the P1 component of AERP (****P<0.0001; paired Mann-Whitney U test), indicating a more sensitive response of the auditory cortex to the auditory stimulus. (C) Compared to vehicle-treated mice, Fenfluramine-treated mice showed significant increase (****P<0.0001; paired Mann-Whitney U test) in N1 latency (msec) of AERP indicating a delayed response of the auditory cortex to the auditory stimulus (EEG abnormality). Similar results of Fenfluramine were previously shown in humans (Oades et al. 1990). Fenfluramine is currently accepted as an anti-epileptic treatment for the early infantile epileptic encephalopathy Dravet Syndrome.   

By working with InnoSer, your research can benefit from implementing EEG-related readouts in the context of various research set-ups. For example, we have previously applied longitudinal EEG to record epileptic-like activity in the Stxbp1 +/- mice relevant for rare infantile epileptic encephalopathy research, which you can view by clicking here.  

Drug development can be an iterative and long process, whereby InnoSer can be your dedicated partner, offering fast turnaround times with back-to-back experiments to help you optimise your lead compounds. Curious to learn more about InnoSer’s capabilities within the drug development space?  View our Discovery and Development CRO Services.