Cognitive enhancement in schizophrenia by buspirone: Role of serotonin(1A) receptor agonism

Exploring Serotonin-1A receptor function in the effects of buspirone on cognition by molecular receptor expression and EEG analytical studies

Buspirone, a commonly prescribed medication for generalized anxiety disorder (GAD), is gaining attention for its narrow window of side effects such as lack of physical dependence, non-sedative properties as compared to other anxiolytic drugs. Its dose-specific therapeutic effects beyond anxiety highlights its clinical significance. Pharmacologically, buspirone activates serotonin-1A pre-synaptic autoreceptors and post-synaptic heteroreceptors which modulate serotonergic neurotransmission induced behavioral changes such as anxiolytic and nootropic effects. This study explored change in neural activity associated serotonin-1A receptors, induced by repeated administration of buspirone at specific doses (0.1 mg/kg and 3 mg/kg). Buspirone induced behavioral changes were assessed by Morris Water Maze (MWM) for cognitive functions, Elevated Plus Maze (EPM) for anxiety, RT-PCR (Reverse transcriptase-polymerase chain reaction) for 5-HT1A receptor expression levels, and EEG (electroencephalography) analysis of neuronal electrical activity in the frontal cortex. Our findings revealed that a low dose of buspirone (0.1 mg/kg) significantly enhanced spatial learning and memory compared to high dose (3 mg/kg). Low-dose treatment elevated mRNA expression levels of serotonin-1A receptors in hippocampus and decreased in midbrain raphe nuclei, with the opposite patterns observed in the high dose. In addition, EEG spectral analysis have revealed dose specific cross coupling frequency of theta-gamma and delta-beta brain waves. At low dose (0.1 mg/kg) positive correlation of theta-gamma coupling effect and negative correlation of delta beta as decoupling effect were observed. Conversely, at high dose (3 mg/kg), results showed opposite pattern with weak correlation of theta gamma coupling effect and positive correlation of delta-beta as coupling effect. These results suggest that buspirone enhances learning and memory with differential activation of pre and postsynaptic serotonin-1A receptors, altering its expression levels which influence neural activity associated with theta-gamma and delta-beta coupling effects. It provides valuable molecular insights on clinical significance of buspirone in mitigating neuropathological disorders such as behavioral disorders and neurocognitive decline associated with disrupted regulation of serotonin-1A neurotransmission at specific doses. Our findings provide molecular insights of dose dependent therapeutic potential of buspirone against neuropathological symptoms of behavioral disorders, neurocognitive decline associated with dysregulated serotonin-1A neurotransmission.

Augmentation therapy with serotonin1A receptor partial agonists on neurocognitive function in schizophrenia: A systematic review and meta-analysis

Background

In a previous meta-analysis, the use of serotonin1A(5-HT1A) receptor partial agonists of the azapirone class as an add-on therapy was associated with beneficial effects on positive symptoms and attention/processing speed in schizophrenia patients. This meta-analysis builds on that study by examining the effects of adjunctive treatment with 5-HT1A partial agonists in improving other domains of neurocognitive function in schizophrenia patients.

Methods

A literature search was performed from 1987 to May 2023 to identify randomized controlled trials. The standardized mean difference (SMD) with 95 % confidence intervals (CI) was calculated when there were two or more studies. Four studies, involving 313 patients, met the inclusion criteria and were used in the analysis.

Results

5-HT1A partial agonists (buspirone or tandospirone) did not have a significant effect on verbal learning (SMD = 0.08, 95 % CI = -0.31 to 0.47) or working memory (SMD = 0.15, 95 % CI = -0.09 to 0.39). Regarding executive functions (Wisconsin Card Sorting Test), positive but non-significant results were seen with the category number (SMD = 0.26, 95 % CI = -0.81 to 1.32), while non-significant effects were noted for percent preservation errors (SMD = -0.10, 95 % CI = -0.53 to 0.33).

Conclusions

The absence of any significant benefits in the cognitive domains studied here may have been due to the variance in the concomitant medication (typical vs atypical antipsychotic drugs), the level of cognition at baseline, or other factors. Further studies with various types of 5-HT1A agonists are warranted to examine the potential cognitive efficacy of stimulating these receptors.

Episodic Memory and Schizophrenia: From Characterization of Relational Memory Impairments to Neuroimaging Biomarkers

Episodic memory research in schizophrenia has a long history already which has clearly established significant impairments and strong associations with brain measures and functional outcome. The purpose of this chapter is not to make an exhaustive review of the recent literature but to highlight some relatively recent developments in the cognitive neuroscience field of episodic memory and schizophrenia. Hence, we present a contemporary view focusing specifically of relational memory which represents a form of episodic memory that refers to associations or binding among items or elements presented together. We describe the major tasks used and illustrate how their combination with brain imaging has: (1) favored the use of experimental memory tasks to isolate specific processes with specific neural correlates, (2) led to a distributed view of the neural correlates of memory impairments in schizophrenia where multiple regions are contributing, and (3) made possible the identification of fMRI biomarkers specific to episodic memory. We then briefly propose what we see as the next steps for memory research in schizophrenia so that the impact of this work can be maximized.

Randomised controlled cognition trials in remitted patients with mood disorders published between 2015 and 2021: A systematic review by the International Society for Bipolar Disorders Targeting Cognition Task Force

BACKGROUND

Cognitive impairments are an emerging treatment target in mood disorders, but currently there are no evidence-based pro-cognitive treatments indicated for patients in remission. With this systematic review of randomised controlled trials (RCTs), the International Society for Bipolar Disorders (ISBD) Targeting Cognition Task force provides an update of the most promising treatments and methodological recommendations.

METHODS

The review included RCTs of candidate pro-cognitive interventions in fully or partially remitted patients with major depressive disorder or bipolar disorder. We followed the procedures of the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) 2020 statement. Searches were conducted on PubMed/MEDLINE, PsycInfo, EMBASE and Cochrane Library from January 2015, when two prior systematic reviews were conducted, until February 2021. Two independent authors reviewed the studies with the Revised Cochrane Collaboration's Risk of Bias tool for Randomised trials.

RESULTS

We identified 16 RCTs (N = 859) investigating cognitive remediation (CR; k = 6; N = 311), direct current or repetitive magnetic stimulation (k = 3; N = 127), or pharmacological interventions (k = 7; N = 421). CR showed most consistent cognitive benefits, with two trials showing improvements on primary outcomes. Neuromodulatory interventions revealed no clear efficacy. Among pharmacological interventions, modafinil and lurasidone showed early positive results. Sources of bias included small samples, lack of pre-screening for objective cognitive impairment, no primary outcome and no information on allocation sequence masking.

CONCLUSIONS

Evidence for pro-cognitive treatments in mood disorders is emerging. Recommendations are to increase sample sizes, pre-screen for impairment in targeted domain(s), select one primary outcome, aid transfer to real-world functioning, investigate multimodal interventions and include neuroimaging.