Habenula neurostimulation improves neuropsychiatric symptoms in a Fragile X-ASD transgenic model

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Abstract Submission 

Flavia Venetucci Gouveia¹, Kristina Zhang¹, Rafi Matin¹, Carolina Gorodetsky¹, George Ibrahim¹

¹Hospital for Sick Children, Toronto, Ontario

Flavia Venetucci Gouveia, PhD  
Hospital for Sick Children
Toronto, Ontario

Kristina Zhang  
Hospital for Sick Children
Toronto, Ontario

Rafi Matin  
Hospital for Sick Children
Toronto, Ontario

Carolina Gorodetsky, MD  
Hospital for Sick Children
Toronto, Ontario

George Ibrahim, MD, PhD  
Hospital for Sick Children
Toronto, Ontario

Fragile X syndrome (FX) is the most frequent genetic cause of intellectual disabilities and autism spectrum disorder (ASD) and is caused by mutations in the Fmr1 gene, resulting in changes in the neurocircuitry regulating emotions, cognition, somatosensation and neurotransmitter release 1. The habenula (Hb) is particularly interesting as it is a key component of the neurocircuitry responsible for modulating the reward value of social interactions, the circadian cycle, and the sensory integration necessary for flexible behavioural adjustments 2,3. The Hb is a candidate for deep brain stimulation (DBS) in humans 4, a therapy that modulates dysfunctional neural circuitry by delivering intracranial electrical stimulation 5. Translational studies are necessary to understand DBS's effects and mechanisms of action and facilitate the development of clinical treatments. The Fmr1 knockout (Fmr1-KO) mice are a well-established model of FXS showing comparable behavioural deficits and brain structural and functional differences, as seen in patients with this syndrome 6. This study aimed to investigate DBS of the Hb (Hb-DBS) as a potential neurostimulation therapy for improving the behavioural deficits observed in the Fmr1-KO mouse model of FX-ASD.

Adult male and female Fmr1-KO mice (RRID: IMSR_JAX:004624) were randomly assigned to receive Hb-DBS treatment or control. Background strain wild-type (WT) mice (RRID: IMSR_JAX:004828) were used as behavioural control to determine if the Hb-DBS treatment would reduce the behavioural differences between transgenic and healthy animals, thus reflecting a positive effect of treatment on the neuropsychiatric symptoms observed at baseline. All procedures were performed after approval from the Animal Care Committee in accordance with the Canadian Council on Animal Care (AUP #25-0355H). Animals were group-housed in the Digital Ventilated Cages system (DVC®, Tecniplast) with free access to food, water and environmental enrichments. Following the acclimatization period, Fmr1-KO mice were randomly selected to receive surgery for the implantation of electrodes targeting the Hb (AP: -2mm, ML: 0.3mm, DV: -2.5mm)7 or control surgery. Animals were allowed to recover from surgery for one week. Thereafter, mice in the Hb-DBS group were connected to an external pulse generator and received daily stimulation sessions (3h/session, six sessions total. Stimulation parameters: 0.3V, 100Hz, 60us). Control animals were not connected to the external pulse generator but were kept under the same conditions and for as long as the other group. The circadian cycle pattern, sociability, anxiety-like behaviour, and somatomotor behaviours were evaluated in all mice. Linear mixed effect models were used for statistical analysis (R studio), and the significance level was set as p<0.05.

Baseline differences between genotypes were found in all behavioural measures (Figure 1), with Fmr1-KO showing an inconsistent pattern of the circadian cycle (β=6.90; SE=2.24; df=24; p<0.01), with periods of resting during the active time (i.e., dark time) and periods of activity during the resting time (i.e., light time), increased anxiety-like behaviour (β=71.49; SE=20.44; df=24; p<0.01), reduced sociability (β=128.84; SE=17.284; df=24; p>0.001) and impaired thermic sensitivity (β=6.90; SE=2.24; df=24; p<0.01). Treatment with Hb-DBS was effective in reducing anxiety-like behaviour (β=71.49; SE=25.30; df=46; p<0.01), increasing sociability (β=136.58; SE=21.87; df=24; p>0.001) and improving thermic sensitivity (β=1.12; SE=0.32; df=46; p<0.01), however it did not affect the circadian cycle (β=0.87; SE=0.38; df=15; p>0.05).

Treatment with Hb-DBS improved the neuropsychiatric symptoms observed in the Fmr1-KO mouse model of FX-ASD, with treated animals showing reduced anxiety-like behaviour, increased sociability and enhanced sensory perception. Further studies are necessary to investigate the neurobiological mechanisms associated with behavioural changes.

Deep Brain Stimulation ¹

Neurodevelopmental/ Early Life (eg. ADHD, autism)

Psychiatric (eg. Depression, Anxiety, Schizophrenia) ²

Emotion and Motivation Other

ANIMAL STUDIES

Anxiety

Autism

Emotions

Limbic Systems

Neurological

Psychiatric

Psychiatric Disorders

Other - Fragile X Syndrome