An investigation of regional cerebral blood flow and tissue structure changes after acute administration of antipsychotics in healthy male volunteers

Effects of diazepam on hippocampal blood flow in people at clinical high risk for psychosis

Elevated hippocampal perfusion has been observed in people at clinical high risk for psychosis (CHR-P). Preclinical evidence suggests that hippocampal hyperactivity is central to the pathophysiology of psychosis, and that peripubertal treatment with diazepam can prevent the development of psychosis-relevant phenotypes. The present experimental medicine study examined whether diazepam can normalize hippocampal perfusion in CHR-P individuals. Using a randomized, double-blind, placebo-controlled, crossover design, 24 CHR-P individuals were assessed with magnetic resonance imaging (MRI) on two occasions, once following a single oral dose of diazepam (5 mg) and once following placebo. Regional cerebral blood flow (rCBF) was measured using 3D pseudo-continuous arterial spin labeling and sampled in native space using participant-specific hippocampus and subfield masks (CA1, subiculum, CA4/dentate gyrus). Twenty-two healthy controls (HC) were scanned using the same MRI acquisition sequence, but without administration of diazepam or placebo. Mixed-design ANCOVAs and linear mixed-effects models were used to examine the effects of group (CHR-P placebo/diazepam vs. HC) and condition (CHR-P diazepam vs. placebo) on rCBF in the hippocampus as a whole and by subfield. Under the placebo condition, CHR-P individuals (mean [±SD] age: 24.1 [±4.8] years, 15 F) showed significantly elevated rCBF compared to HC (mean [±SD] age: 26.5 [±5.1] years, 11 F) in the hippocampus (F(1,41) = 24.7, pFDR < 0.001) and across its subfields (all pFDR < 0.001). Following diazepam, rCBF in the hippocampus (and subfields, all pFDR < 0.001) was significantly reduced (t(69) = -5.1, pFDR < 0.001) and normalized to HC levels (F(1,41) = 0.4, pFDR = 0.204). In conclusion, diazepam normalized hippocampal hyperperfusion in CHR-P individuals, consistent with evidence implicating medial temporal GABAergic dysfunction in increased vulnerability for psychosis.

The Trajectory of Prefrontal GABA Levels in Initially Antipsychotic-Naïve Patients With Psychosis During 2 Years of Treatment and Associations With Striatal Cerebral Blood Flow and Outcome

BACKGROUND

GABAergic (gamma-aminobutyric acidergic) function in the prefrontal cortex seems dysfunctional in patients with first-episode psychosis, but the impact of longer-term treatment and relationship to clinical outcomes and striatal activity are unknown.

METHODS

A longitudinal study of 39 antipsychotic-naïve and benzodiazepine-free patients with psychosis (22.4 ± 5.4 years, 64% women) and 54 matched healthy control participants (HCs) (22.2 ± 4.3 years, 61% women) who were followed up after 6 weeks (28 patients, 51 HCs), 6 months (17 patients, 47 HCs), and 2 years (21 patients, 43 HCs) was completed. GABA levels in the dorsal anterior cingulate cortex and striatal resting cerebral blood flow were assessed on a 3T magnetic resonance scanner at all visits.

RESULTS

GABA levels in the dorsal anterior cingulate cortex were significantly lower in patients at baseline and after 6 weeks but not after 6 months or 2 years. Analyses of groups separately revealed decreased GABA levels after 2 years in HCs but stable levels in patients. Treatment increased striatal resting cerebral blood flow after 6 weeks and 6 months but not after 2 years. GABA levels were negatively associated with striatal resting cerebral blood flow in both groups at all visits. Last, lower baseline GABA levels in patients were related to less functional improvement after 2 years.

CONCLUSIONS

The findings suggest a different trajectory of GABA levels and striatal perfusion in first-episode patients over 2 years of antipsychotic treatment compared with HCs and indicate a downregulatory role of prefrontal GABAergic function on the striatum. Moreover, abnormally low prefrontal GABA level at illness onset may be a marker for a more severe prognosis.

Increased hippocampal blood flow in people at clinical high risk for psychosis and effects of cannabidiol

BACKGROUND

Hippocampal hyperperfusion has been observed in people at Clinical High Risk for Psychosis (CHR), is associated with adverse longitudinal outcomes and represents a potential treatment target for novel pharmacotherapies. Whether cannabidiol (CBD) has ameliorative effects on hippocampal blood flow (rCBF) in CHR patients remains unknown.

METHODS

Using a double-blind, parallel-group design, 33 CHR patients were randomized to a single oral 600 mg dose of CBD or placebo; 19 healthy controls did not receive any drug. Hippocampal rCBF was measured using Arterial Spin Labeling. We examined differences relating to CHR status (controls v. placebo), effects of CBD in CHR (placebo v. CBD) and linear between-group relationships, such that placebo > CBD > controls or controls > CBD > placebo, using a combination of hypothesis-driven and exploratory wholebrain analyses.

RESULTS

Placebo-treated patients had significantly higher hippocampal rCBF bilaterally (all pFWE<0.01) compared to healthy controls. There were no suprathreshold effects in the CBD v. placebo contrast. However, we found a significant linear relationship in the right hippocampus (pFWE = 0.035) such that rCBF was highest in the placebo group, lowest in controls and intermediate in the CBD group. Exploratory wholebrain results replicated previous findings of hyperperfusion in the hippocampus, striatum and midbrain in CHR patients, and provided novel evidence of increased rCBF in inferior-temporal and lateral-occipital regions in patients under CBD compared to placebo.

CONCLUSIONS

These findings suggest that hippocampal blood flow is elevated in the CHR state and may be partially normalized by a single dose of CBD. CBD therefore merits further investigation as a potential novel treatment for this population.

Reduced cortical cerebral blood flow in antipsychotic-free first-episode psychosis and relationship to treatment response

BACKGROUND

Altered cerebral blood flow (CBF) has been found in people at risk for psychosis, with first-episode psychosis (FEP) and with chronic schizophrenia (SCZ). Studies using arterial spin labelling (ASL) have shown reduction of cortical CBF and increased subcortical CBF in SCZ. Previous studies have investigated CBF using ASL in FEP, reporting increased CBF in striatum and reduced CBF in frontal cortex. However, as these people were taking antipsychotics, it is unclear whether these changes are related to the disorder or antipsychotic treatment and how they relate to treatment response.

METHODS

We examined CBF in FEP free from antipsychotic medication (N = 21), compared to healthy controls (N = 22). Both absolute and relative-to-global CBF were assessed. We also investigated the association between baseline CBF and treatment response in a partially nested follow-up study (N = 14).

RESULTS

There was significantly lower absolute CBF in frontal cortex (Cohen's d = 0.84, p = 0.009) and no differences in striatum or hippocampus. Whole brain voxel-wise analysis revealed widespread cortical reductions in absolute CBF in large cortical clusters that encompassed occipital, parietal and frontal cortices (Threshold-Free Cluster Enhancement (TFCE)-corrected <0.05). No differences were found in relative-to-global CBF in the selected region of interests and in voxel-wise analysis. Relative-to-global frontal CBF was correlated with percentage change in total Positive and Negative Syndrome Scale after antipsychotic treatment (r = 0.67, p = 0.008).

CONCLUSIONS

These results show lower cortical absolute perfusion in FEP prior to starting antipsychotic treatment and suggest relative-to-global frontal CBF as assessed with magnetic resonance imaging could potentially serve as a biomarker for antipsychotic response.

Comparison of Cerebral Blood Flow in Regions Relevant to Cognition After Enzalutamide, Darolutamide, and Placebo in Healthy Volunteers: A Randomized Crossover Trial

BACKGROUND

Off-target central nervous system (CNS) effects are associated with androgen receptor (AR)-targeting treatments for prostate cancer. Darolutamide is a structurally distinct AR inhibitor with low blood-brain barrier penetration.

OBJECTIVE

We compared cerebral blood flow (CBF) in grey matter and specific regions related to cognition after darolutamide, enzalutamide, or placebo administration, using arterial spin-label magnetic resonance imaging (ASL-MRI).

METHODS

This phase I, randomized, placebo-controlled, three-period crossover study administered single doses of darolutamide, enzalutamide, or placebo to 23 healthy males (aged 18-45 years) at 6-week intervals. ASL-MRI mapped CBF 4 h post-treatment. Treatments were compared using paired t-tests.

RESULTS

Drug concentrations during scans confirmed similar unbound exposure of darolutamide and enzalutamide, with complete washout between treatments. A significant localized 5.2% (p = 0.01) and 5.9% (p < 0.001) CBF reduction in the temporo-occipital cortices was observed for enzalutamide versus placebo and versus darolutamide, respectively, with no significant differences for darolutamide versus placebo. Enzalutamide reduced CBF in all prespecified regions, with significant reductions versus placebo (3.9%, p = 0.045) and versus darolutamide (4.4%, p = 0.037) in the left and right dorsolateral prefrontal cortices, respectively. Darolutamide showed minimal changes in CBF versus placebo in cognition-relevant regions.

CONCLUSIONS

Darolutamide did not significantly alter CBF, consistent with its low blood-brain barrier penetration and low risk of CNS-related adverse events. A significant reduction in CBF was observed with enzalutamide. These results may be relevant to cognitive function with early and extended use of second-generation AR inhibitors, and warrant further investigation in patients with prostate cancer.

TRIAL REGISTRATION NUMBER

NCT03704519; date of registration: October 2018.

Cerebral blood flow in striatum is increased by partial dopamine agonism in initially antipsychotic-naïve patients with psychosis

BACKGROUND

Resting cerebral blood flow (rCBF) in striatum and thalamus is increased in medicated patients with psychosis, but whether this is caused by treatment or illness pathology is unclear. Specifically, effects of partial dopamine agonism, sex, and clinical correlates on rCBF are sparsely investigated. We therefore assessed rCBF in antipsychotic-naïve psychosis patients before and after aripiprazole monotherapy and related findings to sex and symptom improvement.

METHODS

We assessed rCBF with the pseudo-Continuous Arterial Spin Labeling (PCASL) sequence in 49 first-episode patients (22.6 ± 5.2 years, 58% females) and 50 healthy controls (HCs) (22.3 ± 4.4 years, 63% females) at baseline and in 29 patients and 49 HCs after six weeks. RCBF in striatum and thalamus was estimated with a region-of-interest (ROI) approach. Psychopathology was assessed with the positive and negative syndrome scale.

RESULTS

Baseline rCBF in striatum and thalamus was not altered in the combined patient group compared with HCs, but female patients had lower striatal rCBF compared with male patients (p = 0.009). Treatment with a partial dopamine agonist increased rCBF significantly in striatum (p = 0.006) in the whole patient group, but not significantly in thalamus. Baseline rCBF in nucleus accumbens was negatively associated with improvement in positive symptoms (p = 0.046), but baseline perfusion in whole striatum and thalamus was not related to treatment outcome.

CONCLUSIONS

The findings suggest that striatal perfusion is increased by partial dopamine agonism and decreased in female patients prior to first treatment. This underlines the importance of treatment effects and sex differences when investigating the neurobiology of psychosis.

Neurovascular alterations in bipolar disorder: A review of perfusion weighted magnetic resonance imaging studies

BACKGROUND

Bipolar Disorder (BD) is a severe chronic psychiatric disorder whose aetiology is still largely unknown. However, increasing literature reported the involvement of neurovascular factors in the pathophysiology of BD, suggesting that a measure of Cerebral Blood Flow (CBF) could be an important biomarker of the illness. Therefore, since, to date, Magnetic Resonance Perfusion Weighted Imaging (PWI) techniques, such as Dynamic Susceptibility Contrast (DSC) and Arterial Spin Labelling (ASL), are the most common approaches that allow non-invasive in-vivo perfusion measurements,this review aims to summarize the results from all PWI studies that evaluated the CBF in BD.

METHODS

A bibliographic search in PubMed up until May 2021 was performed. 16 PWI studies that used DSC or ASL sequences met our inclusion criteria.

RESULTS

Overall, the results supported the presence of hyper-perfusion in the cingulate cortex and fronto-temporal regions, as well as the presence of hypo-perfusion in the cerebellum in BD, compared with both healthy controls and patients with unipolar depression. CBF changes after cognitive and aerobic training, as well as in relation with other physiological, clinical, and neurocognitive variables were also reported.

LIMITATIONS

The heterogeneity across the studies, in terms of experimental designs, sample selection, and methodological approach employed, limited the studies' comparison.

CONCLUSIONS

These findings showed CBF alterations in the cingulate cortex, fronto-temporal regions, and cerebellum in BD, suggesting that CBF may be an important pathophysiological marker of BD that merits further investigation to clarify the extent of neurovascular alterations.

Subcortical volume reduction and cortical thinning 3 months after switching to clozapine in treatment resistant schizophrenia

The neurobiological effects of clozapine are under characterised. We examined the effects clozapine treatment on subcortical volume and cortical thickness and investigated whether macrostructural changes were linked to alterations in glutamate or N-acetylaspartate (NAA). Data were acquired in 24 patients with treatment-resistant schizophrenia before and 12 weeks after switching to clozapine. During clozapine treatment we observed reductions in caudate and putamen volume, lateral ventricle enlargement (P < 0.001), and reductions in thickness of the left inferior temporal cortex, left caudal middle frontal cortex, and the right temporal pole. Reductions in right caudate volume were associated with local reductions in NAA (P = 0.002). None of the morphometric changes were associated with changes in glutamate levels. These results indicate that clozapine treatment is associated with subcortical volume loss and cortical thinning and that at least some of these effects are linked to changes in neuronal or metabolic integrity.

Brain responses to glucose ingestion are greater in children than adults and are associated with overweight and obesity

OBJECTIVE

This study investigated whether brain regions involved in the regulation of food intake respond differently to glucose ingestion in children and adults and the relationship between brain responses and weight status.

METHODS

Data included 87 children (ages 7-11 years) and 94 adults (ages 18-35 years) from two cohorts. Healthy weight, overweight, and obesity were defined by Centers for Disease Control and Prevention criteria. Brain responses to glucose were determined by measuring cerebral blood flow using arterial spin labeling magnetic resonance imaging in brain regions involved in the regulation of eating behavior.

RESULTS

Children showed significantly larger increases in brain responses to glucose than adults in the dorsal striatum (p < 0.01), insula (p < 0.01), hippocampus (p < 0.01), and dorsal-lateral prefrontal cortex (p < 0.01). Responses to glucose in the dorsal striatum (odds ratio [OR] = 1.52, 95% CI 1.05-2.20; p = 0.03), hippocampus (OR = 1.51, 95% CI: 1.02-2.22; p = 0.04), insula (OR = 1.64, 95% CI: 1.11-2.42; p = 0.01), and orbitofrontal cortex (OR = 1.63 95% CI: 1.12-2.39; p = 0.01) were positively associated with overweight or obesity, independent of age group.

CONCLUSIONS

Children have greater brain responses to glucose ingestion than adults in regions involved in eating behavior, and these responses are associated with weight status.

Enhancing dopamine tone modulates global and local cortical perfusion as a function of COMT val158met genotype

The cognitive effects of pharmacologically enhancing cortical dopamine (DA) tone are variable across healthy human adults. It has been postulated that individual differences in drug responses are linked to baseline cortical DA activity according to an inverted-U-shaped function. To better understand the effect of divergent starting points along this curve on DA drug responses, researchers have leveraged a common polymorphism (rs4680) in the gene encoding the enzyme catechol-O-methyltransferase (COMT) that gives rise to greater (Met allele) or lesser (Val allele) extracellular levels of cortical DA. Here we examined the extent to which changes in resting cortical perfusion following the administration of two mechanistically-distinct dopaminergic drugs vary by COMT genotype, and thereby track predictions of the inverted-U model. Using arterial spin labeling (ASL) and a double-blind, within-subject design, perfusion was measured in 75 healthy, genotyped participants once each after administration of tolcapone (a COMT inhibitor), bromocriptine (a DA D2/3 agonist), and placebo. COMT genotype and drug interacted such that COMT Val homozygotes exhibited increased prefusion in response to both drugs, whereas Met homozygotes did not. Additionally, tolcapone-related perfusion changes in the right inferior frontal gyrus correlated with altered performance on a task of executive function. No comparable effects were found for a genetic polymorphism (rs1800497) affecting striatal DA system function. Together, these results indicate that both the directionality and magnitude of drug-induced perfusion change provide meaningful information about individual differences in response to enhanced cortical DA tone.

The effect of risperidone on reward-related brain activity is robust to drug-induced vascular changes

Dopamine (DA) mediated brain activity is intimately linked to reward‐driven cerebral responses, while aberrant reward processing has been implicated in several psychiatric disorders. fMRI has been a valuable tool in understanding the mechanism by which DA modulators alter reward‐driven responses and how they may exert their therapeutic effect. However, the potential effects of a pharmacological compound on aspects of neurovascular coupling may cloud the interpretability of the BOLD contrast. Here, we assess the effects of risperidone on reward driven BOLD signals produced by reward anticipation and outcome, while attempting to control for potential drug effects on regional cerebral blood flow (CBF) and cerebrovascular reactivity (CVR). Healthy male volunteers (n = 21) each received a single oral dose of either 0.5 mg, 2 mg of risperidone or placebo in a double‐blind, placebo‐controlled, randomised, three‐period cross‐over study design. Participants underwent fMRI scanning while performing the widely used Monetary Incentive Delay (MID) task to assess drug impact on reward function. Measures of CBF (Arterial Spin Labelling) and breath‐hold challenge induced BOLD signal changes (as a proxy for CVR) were also acquired and included as covariates. Risperidone produced divergent, dose‐dependent effects on separate phases of reward processing, even after controlling for potential nonneuronal influences on the BOLD signal. These data suggest the D2 antagonist risperidone has a wide‐ranging influence on DA‐mediated reward function independent of nonneuronal factors. We also illustrate that assessment of potential vascular confounds on the BOLD signal may be advantageous when investigating CNS drug action and advocate for the inclusion of these additional measures into future study designs.

JuSpace: A tool for spatial correlation analyses of magnetic resonance imaging data with nuclear imaging derived neurotransmitter maps

Recent studies have shown that drug‐induced spatial alteration patterns in resting state functional activity as measured using magnetic resonance imaging (rsfMRI) are associated with the distribution of specific receptor systems targeted by respective compounds. Based on this approach, we introduce a toolbox (JuSpace) allowing for cross‐modal correlation of MRI‐based measures with nuclear imaging derived estimates covering various neurotransmitter systems including dopaminergic, serotonergic, noradrenergic, and GABAergic (gamma‐aminobutric acid) neurotransmission. We apply JuSpace to two datasets covering Parkinson's disease patients (PD) and risperidone‐induced changes in rsfMRI and cerebral blood flow (CBF). Consistently with the predominant neurodegeneration of dopaminergic and serotonergic system in PD, we find significant spatial associations between rsfMRI activity alterations in PD and dopaminergic (D2) and serotonergic systems (5‐HT1b). Risperidone induced CBF alterations were correlated with its main targets in serotonergic and dopaminergic systems. JuSpace provides a biologically meaningful framework for linking neuroimaging to underlying neurotransmitter information.

Effects of Antipsychotic Medication on Brain Structure in Patients With Major Depressive Disorder and Psychotic Features: Neuroimaging Findings in the Context of a Randomized Placebo-Controlled Clinical Trial

IMPORTANCE

Prescriptions for antipsychotic medications continue to increase across many brain disorders, including off-label use in children and elderly individuals. Concerning animal and uncontrolled human data suggest antipsychotics are associated with change in brain structure, but to our knowledge, there are no controlled human studies that have yet addressed this question.

OBJECTIVE

To assess the effects of antipsychotics on brain structure in humans.

DESIGN, SETTING, AND PARTICIPANTS

Prespecified secondary analysis of a double-blind, randomized, placebo-controlled trial over a 36-week period at 5 academic centers. All participants, aged 18 to 85 years, were recruited from the multicenter Study of the Pharmacotherapy of Psychotic Depression II (STOP-PD II). All participants had major depressive disorder with psychotic features (psychotic depression) and were prescribed olanzapine and sertraline for a period of 12 to 20 weeks, which included 8 weeks of remission of psychosis and remission/near remission of depression. Participants were then were randomized to continue receiving this regimen or to be switched to placebo and sertraline for a subsequent 36-week period. Data were analyzed between October 2018 and February 2019.

INTERVENTIONS

Those who consented to the imaging study completed a magnetic resonance imaging (MRI) scan at the time of randomization and a second MRI scan at the end of the 36-week period or at time of relapse.

MAIN OUTCOMES AND MEASURES

The primary outcome measure was cortical thickness in gray matter and the secondary outcome measure was microstructural integrity of white matter.

RESULTS

Eighty-eight participants (age range, 18-85 years) completed a baseline scan; 75 completed a follow-up scan, of which 72 (32 men and 40 women) were useable for final analyses. There was a significant treatment-group by time interaction in cortical thickness (left, t = 3.3; P = .001; right, t = 3.6; P < .001) but not surface area. No significant interaction was found for fractional anisotropy, but one for mean diffusivity of the white matter skeleton was present (t = -2.6, P = .01). When the analysis was restricted to those who sustained remission, exposure to olanzapine compared with placebo was associated with significant decreases in cortical thickness in the left hemisphere (β [SE], 0.04 [0.009]; t34.4 = 4.7; P <.001), and the right hemisphere (β [SE], 0.03 [0.009]; t35.1 = 3.6; P <.001). Post hoc analyses showed that those who relapsed receiving placebo experienced decreases in cortical thickness compared with those who sustained remission.

CONCLUSIONS AND RELEVANCE

In this secondary analysis of a randomized clinical trial, antipsychotic medication was shown to change brain structure. This information is important for prescribing in psychiatric conditions where alternatives are present. However, adverse effects of relapse on brain structure support antipsychotic treatment during active illness.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01427608.

Region-specific effects of acute haloperidol in the human midbrain, striatum and cortex

D2 autoreceptors provide an important regulatory mechanism of dopaminergic neurotransmission. However, D2 receptors are also expressed as heteroreceptors at postsynaptic membranes. The expression and the functional characteristics of both, D2 auto- and heteroreceptors, differ between brain regions. Therefore, one would expect that also the net response to a D2 antagonist, i.e. whether and to what degree overall neural activity increases or decreases, varies across brain areas. In the current study we systematically tested this hypothesis by parametrically increasing haloperidol levels (placebo, 2 and 3 mg) in healthy volunteers and measuring brain activity in the three major dopaminergic pathways. In particular, activity was assessed using fMRI while participants performed a working memory and a reinforcement learning task. Consistent with the hypothesis, across brain regions activity parametrically in- and decreased. Moreover, even within the same area there were function-specific concurrent de- and increases of activity, likely caused by input from upstream dopaminergic regions. In the ventral striatum, for instance, activity during reinforcement learning decreased for outcome processing while prediction error related activity increased. In conclusion, the current study highlights the intricacy of D2 neurotransmission which makes it difficult to predict the function-specific net response of a given area to pharmacological manipulations.

Striatal Volume Increase After Six Weeks of Selective Dopamine D2/3 Receptor Blockade in First-Episode, Antipsychotic-Naïve Schizophrenia Patients

Patients with chronic schizophrenia often display enlarged striatal volumes, and antipsychotic drugs may contribute via the dopamine D_2/3 receptor (D_2/3R) blockade. Separating the effects of disease from medication is challenging due to the lack of a proper placebo-group. To address this, we conducted a longitudinal study of antipsychotic-naïve, first-episode schizophrenia patients to test the hypothesis that selective blockade of D_2/3R would induce a dose-dependent striatal volume increase. Twenty-one patients underwent structural magnetic resonance imaging (sMRI), single-photon emission computed tomography (SPECT), and symptom severity ratings before and after six weeks of amisulpride treatment. Twenty-three matched healthy controls underwent sMRI and baseline SPECT. Data were analyzed using repeated measures and multiple regression analyses. Correlations between symptom severity decrease, volume changes, dose and receptor occupancy were explored. Striatal volumes did not differ between patients and controls at baseline or follow-up, but a significant group-by-time interaction was found (p = 0.01). This interaction was explained by a significant striatal volume increase of 2.1% in patients (Cohens d = 0.45). Striatal increase was predicted by amisulpride dose, but not by either D_2/3R occupancy or baseline symptom severity. A significant reduction in symptom severity was observed at a mean dose of 233.3 (SD = 109.9) mg, corresponding to D_2/3R occupancy of 44.65%. Reduction in positive symptoms correlated significantly with striatal volume increase, driven by reductions in hallucinations. Our data demonstrate a clear link between antipsychotic treatment and striatal volume increase in antipsychotic-naïve schizophrenia patients. Moreover, the treatment-induced striatal volume increase appears clinically relevant by correlating to reductions in core symptoms of schizophrenia.

Normalizing the Abnormal: Do Antipsychotic Drugs Push the Cortex Into an Unsustainable Metabolic Envelope?

The use of antipsychotic medication to manage psychosis, principally in those with a diagnosis of schizophrenia or bipolar disorder, is well established. Antipsychotics are effective in normalizing positive symptoms of psychosis in the short term (delusions, hallucinations and disordered thought). Their long-term use is, however, associated with side effects, including several types of movement (extrapyramidal syndrome, dyskinesia, akathisia), metabolic and cardiac disorders. Furthermore, higher lifetime antipsychotic dose-years may be associated with poorer cognitive performance and blunted affect, although the mechanisms driving the latter associations are not well understood. In this article, we propose a novel model of the long-term effects of antipsychotic administration focusing on the changes in brain metabolic homeostasis induced by the medication. We propose here that the brain metabolic normalization, that occurs in parallel to the normalization of psychotic symptoms following antipsychotic treatment, may not ultimately be sustainable by the cerebral tissue of some patients; these patients may be characterized by already reduced oxidative metabolic capacity and this may push the brain into an unsustainable metabolic envelope resulting in tissue remodeling. To support this perspective, we will review the existing data on the brain metabolic trajectories of patients with a diagnosis of schizophrenia as indexed using available neuroimaging tools before and after use of medication. We will also consider data from pre-clinical studies to provide mechanistic support for our model.

Antipsychotic treatment and basal ganglia volumes: Exploring the role of receptor occupancy, dosage and remission status

Antipsychotic treatment may affect brain morphology, and enlargement of the basal ganglia (BG) is a replicated finding. Here we investigated associations between antipsychotic treatment and BG volumes in patients with psychotic and bipolar disorders. We hypothesized that current treatment and, among those medicated, higher dosage, estimated D2R occupancy and being in remission would predict larger BG volumes. Structural covariance analysis was performed to examine if correlations between BG volumes and cortical thickness differed by treatment status. 224 patients treated with antipsychotics; 26 previously treated, 29 never treated and 301 healthy controls (HC) were included from the TOP study cohort (NORMENT, Norway). T1-weighted MR images were processed using FreeSurfer. D2R occupancy was estimated based on serum concentration measurements for patients receiving stable monotherapy. Statistical analyses were adjusted for age, gender and estimated intracranial volume (ICV). We found larger right (p < 0.003) and left putamen (p < 0.02) and right globus pallidus (GP) (p < 0.03) in currently medicated patients compared to HC. Bilateral regional cortical thinning was also observed in currently and previously medicated patients compared to HC. In medicated patients, higher chlorpromazine equivalent dose (CPZ) was associated with larger left GP (p < 0.04). There was no association with estimated D2R occupancy (n = 47) or remission status. Lower positive correlation between left putamen volume and cortical thickness of the left lateral occipital cortex was found in medicated patients compared to HC. We replicated the BG enlargement in medicated patients, but found no association with estimated D2R occupancy. Further studies are needed to clarify the underlying mechanisms.

Characterisation of nasal devices for delivery of insulin to the brain and evaluation in humans using functional magnetic resonance imaging

This study aimed to characterise three nasal drug delivery devices to evaluate their propensity to deliver human insulin solutions to the nasal cavity for redistribution to the central nervous system. Brain delivery was evaluated using functional magnetic resonance imaging to measure regional cerebral blood flow. Intranasal insulin administration has been hypothesised to exploit nose-to-brain pathways and deliver drug directly to the brain tissue whilst limiting systemic exposure. Three nasal pump-actuator configurations were compared for delivery of 400 IU/mL insulin solution by measuring droplet size distribution, plume geometry, spray pattern and in vitro deposition in a nasal cast. The device with optimal spray properties for nose to brain delivery (spray angle between 30° and 45°; droplet size between 20 and 50 μm) also favoured high posterior-superior deposition in the nasal cast and was utilised in a pharmacological magnetic resonance imaging study. Functional magnetic resonance imaging in healthy male volunteers showed statistically significant decreases in regional cerebral blood flow within areas dense in insulin receptors (bilateral amygdala) in response to intranasally administered insulin (160 IU) compared to saline (control). These changes correspond to the expected effects of insulin in the brain and were achieved using a simple nasal spray device and solution formulation. We recommend that a thorough characterisation of nasal delivery devices and qualitative/quantitative assessment of the administered dose is reported in all studies of nose to brain delivery so that responses can be evaluated with respect to posology and comparison between studies is facilitated.

Grey Matter Volume Differences Associated with Extremely Low Levels of Cannabis Use in Adolescence

Rates of cannabis use among adolescents are high, and are increasing concurrent with changes in the legal status of marijuana and societal attitudes regarding its use. Recreational cannabis use is understudied, especially in the adolescent period when neural maturation may make users particularly vulnerable to the effects of Δ-9-tetrahydrocannabinol (THC) on brain structure. In the current study, we used voxel-based morphometry to compare gray matter volume (GMV) in forty-six 14-year-old human adolescents (males and females) with just one or two instances of cannabis use and carefully matched THC-naive controls. We identified extensive regions in the bilateral medial temporal lobes as well as the bilateral posterior cingulate, lingual gyri, and cerebellum that showed greater GMV in the cannabis users. Analysis of longitudinal data confirmed that GMV differences were unlikely to precede cannabis use. GMV in the temporal regions was associated with contemporaneous performance on the Perceptual Reasoning Index and with future generalized anxiety symptoms in the cannabis users. The distribution of GMV effects mapped onto biomarkers of the endogenous cannabinoid system providing insight into possible mechanisms for these effects.SIGNIFICANCE STATEMENT Almost 35% of American 10th graders have reported using cannabis and existing research suggests that initiation of cannabis use in adolescence is associated with long-term neurocognitive effects. We understand very little about the earliest effects of cannabis use, however, because most research is conducted in adults with a heavy pattern of lifetime use. This study presents evidence suggesting structural brain and cognitive effects of just one or two instances of cannabis use in adolescence. Converging evidence suggests a role for the endocannabinoid system in these effects. This research is particularly timely as the legal status of cannabis is changing in many jurisdictions and the perceived risk by youth associated with smoking cannabis has declined in recent years.

Effect of Cannabidiol on Medial Temporal, Midbrain, and Striatal Dysfunction in People at Clinical High Risk of Psychosis: A Randomized Clinical Trial

Importance

Cannabidiol (CBD) has antipsychotic effects in humans, but how these are mediated in the brain remains unclear.

Objective

To investigate the neurocognitive mechanisms that underlie the therapeutic effects of CBD in psychosis.

Design, Setting, and Participants

In this parallel-group, double-blind, placebo-controlled randomized clinical trial conducted at the South London and Maudsley NHS Foundation Trust in London, United Kingdom, 33 antipsychotic medication-naive participants at clinical high risk (CHR) of psychosis and 19 healthy control participants were studied. Data were collected from July 2013 to October 2016 and analyzed from November 2016 to October 2017.

Interventions

A total of 16 participants at CHR of psychosis received a single oral dose of 600 mg of CBD, and 17 participants at CHR received a placebo. Control participants were not given any drug. All participants were then studied using functional magnetic resonance imaging (fMRI) while performing a verbal learning task.

Main Outcomes and Measures

Brain activation during verbal encoding and recall, indexed using the blood oxygen level-dependent hemodynamic response fMRI signal.

Results

Of the 16 participants in the CBD group, 6 (38%) were female, and the mean (SD) age was 22.43 (4.95) years; of 17 in the placebo group, 10 (59%) were female, and the mean (SD) age was 25.35 (5.24) years; and of 19 in the control group, 8 (42%) were female, and the mean (SD) age was 23.89 (4.14) years. Brain activation (indexed using the median sum of squares ratio of the blood oxygen level-dependent hemodynamic response effects model component to the residual sum of squares) was analyzed in 15 participants in the CBD group, 16 in the placebo group, and 19 in the control group. Participants receiving placebo had reduced activation relative to controls in the right caudate during encoding (placebo: median, -0.027; interquartile range [IQR], -0.041 to -0.016; control: median, 0.020; IQR, -0.022 to 0.056; P < .001) and in the parahippocampal gyrus and midbrain during recall (placebo: median, 0.002; IQR, -0.016 to 0.010; control: median, 0.035; IQR, 0.015 to 0.039; P < .001). Within these 3 regions, activation in the CBD group was greater than in the placebo group but lower than in the control group (parahippocampal gyrus/midbrain: CBD: median, -0.013; IQR, -0.027 to 0.002; placebo: median, -0.007; IQR, -0.019 to 0.008; control: median, 0.034; IQR, 0.005 to 0.059); the level of activation in the CBD group was thus intermediate to that in the other 2 groups. There were no significant group differences in task performance.

Conclusions and Relevance

Cannabidiol may partially normalize alterations in parahippocampal, striatal, and midbrain function associated with the CHR state. As these regions are critical to the pathophysiology of psychosis, the influence of CBD at these sites could underlie its therapeutic effects on psychotic symptoms.

Trial Registration

isrctn.org Identifier: ISRCTN46322781.

A proof-of-principle study of the effect of combined haloperidol and levodopa administration on working memory-related brain activation in humans

OBJECTIVE

Cognitive deficits including impaired working memory are a hallmark feature of schizophrenia. Dopamine D1 receptor modulated changes in prefrontal cortex function play a potentially important role in the pathology underlying such deficits. However, pharmacological interventions that selectively engage the D1 receptor are severely restricted for research in humans. The present study is a proof-of-principle for enhancing cognitive performance and associated brain activation via indirect D1 stimulation, operationalised by combining the nonselective dopamine agonist L-dopa with the D2-antagonist haloperidol.

METHODS

Fourteen healthy volunteers received placebo or combined carbidopa (25 mg)/L-dopa (100 mg) plus haloperidol (2 mg) orally on two separate occasions according to a within-subjects crossover design. Drug-induced differences in brain activity were assessed during an N-back working memory task in a 3T magnetic resonance imaging environment.

RESULTS

Drug treatment was associated with greater functional connectivity between the dorsolateral prefrontal cortex and areas within the salience network during all N-back trials. Drug treatment was also associated with reduced activation, most prominently in the occipital/temporal brain areas during 2-back performance.

CONCLUSIONS

This preliminary study provides initial evidence for combined L-dopa/haloperidol modulation in cognition-related brain areas and networks, which is relevant for the treatment of cognitive impairments in mental illness.