Frontal and occipital brain glutathione levels are unchanged in autistic adults.

BACKGROUND: The neurobiological underpinnings of Autism Spectrum Disorder (ASD) are diverse and likely multifactorial. One possible mechanism is increased oxidative stress leading to altered neurodevelopment and brain function. However, this hypothesis has mostly been tested in post-mortem studies. So far, available in vivo studies in autistic individuals have reported no differences in glutathione (GSH) levels in frontal, occipital, and subcortical regions. However, these studies were limited by the technically challenging quantification of GSH, the main brain antioxidant molecule. This study aimed to overcome previous studies' limitations by using a GSH-tailored spectroscopy sequence and optimised quantification methodology to provide clarity on GSH levels in autistic adults. METHODS: We used spectral editing proton-magnetic resonance spectroscopy (1H-MRS) combined with linear combination model fitting to quantify GSH in the dorsomedial prefrontal cortex (DMPFC) and medial occipital cortex (mOCC) of autistic and non-autistic adults (male and female). We compared GSH levels between groups. We also examined correlations between GSH and current autism symptoms, measured using the Autism Quotient (AQ). RESULTS: Data were available from 31 adult autistic participants (24 males, 7 females) and 40 non-autistic participants (21 males, 16 females); the largest sample to date. The GSH levels did not differ between groups in either region. No correlations with AQ were observed. CONCLUSION: GSH levels as measured using 1H-MRS are unaltered in the DMPFC and mOCC regions of autistic adults, suggesting that oxidative stress in these cortical regions is not a marked neurobiological signature of ASD.

Exploratory evidence for differences in GABAergic regulation of auditory processing in autism spectrum disorder.

Altered reactivity and responses to auditory input are core to the diagnosis of autism spectrum disorder (ASD). Preclinical models implicate ϒ-aminobutyric acid (GABA) in this process. However, the link between GABA and auditory processing in humans (with or without ASD) is largely correlational. As part of a study of potential biosignatures of GABA function in ASD to inform future clinical trials, we evaluated the role of GABA in auditory repetition suppression in 66 adults (n = 28 with ASD). Neurophysiological responses (temporal and frequency domains) to repetitive standard tones and novel deviants presented in an oddball paradigm were compared after double-blind, randomized administration of placebo, 15 or 30 mg of arbaclofen (STX209), a GABA type B (GABAB) receptor agonist. We first established that temporal mismatch negativity was comparable between participants with ASD and those with typical development (TD). Next, we showed that temporal and spectral responses to repetitive standards were suppressed relative to responses to deviants in the two groups, but suppression was significantly weaker in individuals with ASD at baseline. Arbaclofen reversed weaker suppression of spectral responses in ASD but disrupted suppression in TD. A post hoc analysis showed that arbaclofen-elicited shift in suppression was correlated with autistic symptomatology measured using the Autism Quotient across the entire group, though not in the smaller sample of the ASD and TD group when examined separately. Thus, our results confirm: GABAergic dysfunction contributes to the neurophysiology of auditory sensory processing alterations in ASD, and can be modulated by targeting GABAB activity. These GABA-dependent sensory differences may be upstream of more complex autistic phenotypes.

A Case of Delusional Parasitosis With Folie à Deux Treated With Low-Dose Quetiapine.

A patient with a three-month history of persistent delusions of infestation presented to the emergency department with suicidal ideation secondary to complaints of worsening pruritus. Routine investigations failed to disclose any underlying organic cause for her pruritic sensations. The patient ascribed these to a parasitic infestation acquired following a brief stay at her maternal aunt's residence. Following a thorough psychiatric assessment and collateral history obtained from her aunt, it became clear that both the patient and her aunt held similar delusions of infestation. Her aunt was found to be the main inducer. The patient was admitted, successfully treated with low-dose quetiapine, and eventually deemed fit for discharge. Delusional parasitosis and folie à deux are both rare conditions that may sometimes co-occur.

GABAB receptor modulation of visual sensory processing in adults with and without autism spectrum disorder.

Sensory atypicalities in autism spectrum disorder (ASD) are thought to arise at least partly from differences in γ-aminobutyric acid (GABA) receptor function. However, the evidence to date has been indirect, arising from correlational studies in patients and preclinical models. Here, we evaluated the role of GABA receptor directly, in 44 adults (n = 19 ASD). Baseline concentration of occipital lobe GABA+ (GABA plus coedited macromolecules) was measured using proton magnetic resonance spectroscopy (1H-MRS). Steady-state visual evoked potential (SSVEP) elicited by a passive visual surround suppression paradigm was compared after double-blind randomized oral administration of placebo or 15 to 30 mg of arbaclofen (STX209), a GABA type B (GABAB) receptor agonist. In the placebo condition, the neurotypical SSVEP response was affected by both the foreground stimuli contrast and background interference (suppression). In ASD, however, all stimuli conditions had equal salience and background suppression of the foreground response was weaker. In the placebo condition, although there was no difference in GABA+ between groups, GABA+ concentration positively correlated with response to maximum foreground contrast during maximum background interference in neurotypicals, but not ASD. In neurotypicals, sensitivity to visual stimuli was disrupted by 30 mg of arbaclofen, whereas in ASD, it was made more "typical" and visual processing differences were abolished. Hence, differences in GABAergic function are fundamental to autistic (visual) sensory neurobiology and are modulated by GABAB activity.