5-HT1A parital agonism and 5-HT7 antagonism restore episodic memory in subchronic phencyclidine-treated mice: role of brain glutamate, dopamine, acetylcholine and GABA

Implications of Physical Exercise on Episodic Memory and Anxiety: The Role of the Serotonergic System

There is a growing interest in investigating the effects of physical exercise on cognitive performance, particularly episodic memory. Similarly, an increasing number of studies in recent decades have studied the effects of physical activity on mood and anxiety disorders. Moreover, the COVID-19 pandemic has raised awareness of the importance of regular physical activity for both mental and physical health. Nevertheless, the exact mechanisms underlying these effects are not fully understood. Interestingly, recent findings suggest that the serotonergic system may play a key role in mediating the effects of physical exercise on episodic memory and anxiety. In this review, we discuss the impact of physical exercise on both episodic memory and anxiety in human and animal models. In addition, we explore the accumulating evidence that supports a role for the serotonergic system in the effects of physical exercise on episodic memory and anxiety.

Early effects of lurasidone treatment in a chronic mild stress model in male rats

RATIONALE

Stress represents a major contributor to the development of mental illness. Accordingly, exposure of adult rats to chronic stress represents a valuable tool to investigate the ability of a pharmacological intervention to counteract the adverse effects produced by stress exposure.

OBJECTIVES

The aim of this study was to perform a time course analysis of the treatment with the antipsychotic drug lurasidone in normalizing the anhedonic phenotype in the chronic mild stress (CMS) model in order to identify early mechanisms that may contribute to its therapeutic activity.

METHODS

Male Wistar rats were exposed to CMS or left undisturbed for 7 weeks. After two weeks of stress, both controls and CMS rats were randomly divided into two subgroups that received vehicle or lurasidone for five weeks. Weekly measures of sucrose intake were recorded to evaluate anhedonic behavior, and animals were sacrificed at different weeks of treatment for molecular analyses.

RESULTS

We found that CMS-induced anhedonia was progressively improved by lurasidone treatment. Interestingly, after two weeks of lurasidone treatment, 50% of the animals showed a full recovery of the phenotype, which was associated with increased activation of the prefrontal and recruitment of parvalbumin-positive cells that may lead to a restoration of excitatory/inhibitory balance.

CONCLUSION

These results suggest that the capacity of lurasidone to normalize anhedonia at an early stage of treatment may depend on its ability to modulate the function of the prefrontal cortex.

Potential Anti-Amnesic Activity of a Novel Multimodal Derivative of Salicylamide, JJGW08, in Mice

Memory impairments constitute a significant problem worldwide, and the COVID-19 pandemic dramatically increased the prevalence of cognitive deficits. Patients with cognitive deficits, specifically memory disturbances, have underlying comorbid conditions such as schizophrenia, anxiety, or depression. Moreover, the available treatment options have unsatisfactory effectiveness. Therefore, there is a need to search for novel procognitive and anti-amnesic drugs with additional pharmacological activity. One of the important therapeutic targets involved in the modulation of learning and memory processes are serotonin receptors, including 5-HT1A, 5-HT6, and 5-HT7, which also play a role in the pathophysiology of depression. Therefore, this study aimed to assess the anti-amnesic and antidepressant-like potential of JJGW08, a novel arylpiperazine alkyl derivative of salicylamide with strong antagonistic properties at 5-HT1A and D2 receptors and weak at 5-HT2A and 5-HT7 receptors in rodents. First, we investigated the compound’s affinity for 5-HT6 receptors using the radioligand assays. Next, we assessed the influence of the compound on long-term emotional and recognition memory. Further, we evaluated whether the compound could protect against MK-801-induced cognitive impairments. Finally, we determined the potential antidepressant-like activity of the tested compound. We found that JJGW08 possessed no affinity for 5-HT6 receptors. Furthermore, JJGW08 protected mice against MK-801-induced recognition and emotional memory deficits but showed no antidepressant-like effects in rodents. Therefore, our preliminary study may suggest that blocking serotonin receptors, especially 5-HT1A and 5-HT7, might be beneficial in treating cognitive impairments, but it requires further investigation.

MicroRNA schizophrenia: Etiology, biomarkers and therapeutic targets

The three sets of symptoms associated with schizophrenia-positive, negative, and cognitive-are burdensome and have serious effects on public health, which affects up to 1% of the population. It is now commonly believed that in addition to the traditional dopaminergic mesolimbic pathway, the etiology of schizophrenia also includes neuronal networks, such as glutamate, GABA, serotonin, BDNF, oxidative stress, inflammation and the immune system. Small noncoding RNA molecules called microRNAs (miRNAs) have come to light as possible participants in the pathophysiology of schizophrenia in recent years by having an impact on these systems. These small RNAs regulate the stability and translation of hundreds of target transcripts, which has an impact on the entire gene network. There may be improved approaches to treat and diagnose schizophrenia if it is understood how these changes in miRNAs alter the critical related signaling pathways that drive the development and progression of the illness.

Novel Multimodal Salicylamide Derivative with Antidepressant-like, Anxiolytic-like, Antipsychotic-like, and Anti-Amnesic Activity in Mice

Depression, anxiety, and schizophrenia may coexist in psychiatric patients. Moreover, these disorders are very often associated with cognitive impairments. However, pharmacotherapy of these conditions remains challenging due to limited drug effectiveness or numerous side effects. Therefore, there is an urgent need to develop novel multimodal compounds that can be used to treat depression, anxiety, and schizophrenia, as well as memory deficits. Thus, this study aimed to evaluate the potential antidepressant-like, anxiolytic-like, antipsychotic-like effects, and anti-amnesic properties, of the novel arylpiperazine derivative of salicylamide, JJGW07, with an affinity towards serotonin 5-HT1A, 5-HT2A, and 5-HT7 and dopamine D2 receptors. Firstly, we investigated the compound's affinity for 5-HT6 receptors and its functional activity by using in vitro assays. JJGW07 did not bind to 5-HT6 receptors and showed antagonistic properties for 5-HT1A, 5-HT2A, 5-HT7, and D2 receptors. Based on the receptor profile, we performed behavioral studies in mice to evaluate the antidepressant-like, anxiolytic-like, and antipsychotic-like activity of the tested compound using forced swim and tail suspension tests; four-plate, marble-burying, and elevated plus maze tests; and MK-801- and amphetamine-induced hyperlocomotion tests, respectively. JJGW07 revealed antidepressant-like properties in the tail suspension test, anxiolytic-like effects in the four-plate and marble-burying tests, and antipsychotic-like activity in the MK-801-induced hyperlocomotion test. Importantly, the tested compound did not induce catalepsy and motor impairments or influence locomotor activity in rodents. Finally, to assess the potential procognitive and anti-amnesic properties of JJGW07, we used passive avoidance and object recognition tests in mice. JJGW07 demonstrated positive effects on long-term emotional memory and also ameliorated MK-801-induced emotional memory impairments in mice, but showed no procognitive properties in the case of recognition memory. Our results encourage the search for new compounds among salicylamide derivatives, which could be model structures with multitarget mechanisms of action that could be used in psychiatric disorder therapy.

Cognitive Effects of Lurasidone and Cariprazine: A Mini Systematic Review

Cognitive deficits are associated with schizophrenia and show a progressive worsening, often being unresponsive to treatment. New antipsychotic molecules acting as antagonist at the serotoninergic 5-hydroxytryptamine receptor 7 (e.g. lurasidone) or partial agonists at dopamine D3 receptor (e.g. cariprazine) could have an impact on cognition in this patient group. The aim of the systematic review is to explore the efficacy of lurasidone and cariprazine in improving cognition in both animal models and human studies. The following terms: (lurasidone AND cognit*) OR (cariprazine AND cognit*) were searched in Web of Science from inception to December 2021. We included all studies that assessed changes in cognitive function after treatment with cariprazine or lurasidone. Of 201 selected articles, 36 were included. Twenty-four articles used animal models (rats, mice and marmosets), five evaluating the effects of cariprazine and 19 the effects of lurasidone. Twelve articles were clinical studies (cariprazine n = 2; lurasidone n = 10). In both animal and human studies lurasidone showed a greater efficacy on cognitive performance compared to placebo, quetiapine, ziprasidone or treatmentas- usual. Cariprazine was superior to other antipsychotics in improving cognitive functions in both animal and human studies. The cognitive effect of lurasidone could be explained by its potent antagonism at the 5-HT7 receptors combined with partial agonism at 5-HT1A receptors. The pro-cognitive effect of cariprazine is probably explained by its very high affinity for D3 receptors. Head-to-head studies comparing lurasidone and cariprazine are needed to establish the "first-choice" treatment for cognitive dysfunction associated with schizophrenia.

Serotonin 5-HT7 receptor overexpression in the raphe nuclei area produces antidepressive effect and affects brain serotonin system in male mice

Heterodimerization between 5-HT₇ and 5-HT_1A receptors seems to play an important role in the mechanism of depression and antidepressant drug action. It was suggested that the shift of the ratio between 5-HT_1A /5-HT₇ hetero- and 5-HT_1A /5-HT_1A homodimers in presynaptic neurons toward 5-HT_1A /5-HT_1A homodimers is one of the reasons of depression. Consequently, the artificial elevation of 5-HT₇ receptor number in presynaptic terminals might restore physiological homo-/heterodimer ratio resulting in antidepressive effect. Here we showed that adeno-associated virus (AAV)-based 5-HT₇ receptor overexpression in the midbrain raphe nuclei area produced antidepressive effect in male mice of both C57Bl/6J and genetically predisposed to depressive-like behavior ASC (antidepressant sensitive cataleptics) strains. These changes were accompanied by the elevation of 5-HT₇ receptor mRNA level in the frontal cortex of C57Bl/6J and its reduction in the hippocampus of ASC mice. The presence of engineered 5-HT₇ receptor in the midbrain of both mouse strains was further demonstrated. Importantly that 5-HT₇ receptor overexpression resulted in the reduction of 5-HT_1A receptor level in the membrane protein fraction from the midbrain samples of C57Bl/6J, but not ASC, mice. 5-HT₇ receptor overexpression caused an increase of 5-HIAA/5-HT ratio in the midbrain and the frontal cortex of C57Bl/6J and in all investigated brain structures of ASC mice. Thus, 5-HT₇ receptor overexpression in the raphe nuclei area affects brain 5-HT system and causes antidepressive effect both in C57Bl/6J and in "depressive" ASC male mice. Obtained results indicate the involvement of 5-HT₇ receptor in the mechanisms underlying depressive behavior.

Cognition and serotonin in Parkinson's disease

Cognitive impairment affects up to 80% of patients with Parkinson's disease (PD) and is associated with poor quality of life. PD cognitive dysfunction includes poor working memory, impairments in executive function and difficulty in set-shifting. The pathophysiology underlying cognitive impairment in PD is still poorly understood, but there is evidence to support involvements of the cholinergic, dopaminergic, and noradrenergic systems. Only rivastigmine, an acetyl- and butyrylcholinesterase inhibitor, is efficacious for the treatment of PD dementia, which limits management of cognitive impairment in PD. Whereas the role of the serotonergic system in PD cognition is less understood, through its interactions with other neurotransmitters systems, namely, the cholinergic system, it may be implicated in cognitive processes. In this chapter, we provide an overview of the pharmacological, clinical and pathological evidence that implicates the serotonergic system in mediating cognition in PD.

Biased agonism in drug discovery: Is there a future for biased 5-HT1A receptor agonists in the treatment of neuropsychiatric diseases?

Serotonin (5-HT) is one of the fundamental neurotransmitters that contribute to the information essential for an organism's normal, physiological function. Serotonin acts centrally and systemically. The 5-HT_1A receptor is the most widespread serotonin receptor, and participates in many brain-related disorders, including anxiety, depression, and cognitive impairments. The 5-HT_1A receptor can activate several different biochemical pathways and signals through both G protein-dependent and G protein-independent pathways. Preclinical experiments indicate that distinct signaling pathways in specific brain regions may be crucial for antidepressant-like, anxiolytic-like, and procognitive responses. Therefore, the development of new ligands that selectively target a particular signaling pathway(s) could open new possibilities for more effective and safer pharmacotherapy. This review discusses the current state of preclinical studies focusing on the concept of functional selectivity (biased agonism) regarding the 5-HT_1A receptor and its role in antidepressant-like, anxiolytic-like, and procognitive regulation. Such work highlights not only the differential effects of targeted autoreceptors, vs. heteroreceptors, but also the importance of targeting specific downstream intracellular signaling processes, thereby enhancing favorable over unfavorable signaling activation.

Towards Novel Treatments for Schizophrenia: Molecular and Behavioural Signatures of the Psychotropic Agent SEP-363856

Schizophrenia is a complex psychopathology whose treatment is still challenging. Given the limitations of existing antipsychotics, there is urgent need for novel drugs with fewer side effects. SEP-363856 (SEP-856) is a novel psychotropic agent currently under phase III clinical investigation for schizophrenia treatment. In this study, we investigated the ability of an acute oral SEP-856 administration to modulate the functional activity of specific brain regions at basal levels and under glutamatergic or dopaminergic-perturbed conditions in adult rats. We found that immediate-early genes (IEGs) expression was strongly upregulated in the prefrontal cortex and, to a less extent, in the ventral hippocampus, suggesting an activation of these regions. Furthermore, SEP-856 was effective in preventing the hyperactivity induced by an acute injection of phencyclidine (PCP), but not of d-amphetamine (AMPH). The compound effectively normalized the PCP-induced increase in IEGs expression in the PFC at all doses tested, whereas only the highest dose determined the major modulations on AMPH-induced changes. Lastly, SEP-856 acute administration corrected the cognitive deficits produced by subchronic PCP administration. Taken together, our data provide further insights on SEP-856, suggesting that modulation of the PFC may represent an important mechanism for the functional and behavioural activity of this novel compound.

Longitudinal tracing of neurochemical metabolic disorders in working memory neural circuit and optogenetics modulation in rats with vascular cognitive impairment

Chronic cerebral ischemia leads to vascular cognitive impairment (VCI) that exacerbates along with ischemia time and eventually develops into dementia. Recent advances in molecular neuroimaging contribute to understand its pathological characteristics. We previously traced the anisotropic diffusion of water molecules suggests that chronic cerebral ischemia leads to irreversible progressive damage to white matter integrity. However, the abnormalities of gray matter activity following chronic cerebral ischemia remains not entirely understood. In this study, in vivo hydrogen proton magnetic resonance spectroscopy (¹H-MRS) was applied to longitudinally track the neurochemical metabolic disorder of gray matter associated with working memory, and optogenetics modulation of neurochemical metabolism was performed for targeted treatment of VCI. The results showed that the concentration of N-acetylaspartate (NAA) in the right hippocampus, left hippocampus, right medial prefrontal cortex (mPFC) and mediodorsal thalamus was decreased as early as 7 days after chronic cerebral ischemia, subsequently gamma-aminobutyric acid (GABA) declined whereas myo-inositol (mI) and glutamate (Glu) increased at 14 days, as well as choline (Cho) lost at 28 days, concurrently the change of Glu and GABA in the mPFC and hippocampus was ischemia time-dependent manner within 1 month. Behaviorally, working memory and object recognition memory were impaired at 14 days, 28 days that significantly correlated with neurochemical metabolic disorders. Interestingly, using optogenetics modulation of PV neurons in the mPFC, the metabolic abnormalities of NAA and GABA in working memory neural circuit could be repaired after chronic cerebral ischemia, together with behavior improvements. These findings suggested that as early as 1∼4 weeks after chronic cerebral ischemia, the metabolism of NAA, Glu, mI and Cho was synchronously impaired in neural circuit of hippocampus-mediodorsal thalamus-mPFC, and the loss of GABA delayed in the hippocampus, and optogenetics modulation of parvalbumin (PV) neurons in the mPFC can improve the neurochemical metabolism of working memory neural circuit and enhance working memory.

Effect of a 5-HT7 Receptor Antagonist on Reversal Learning in the Rat Attentional Set-Shifting Test

5-HT7 receptor antagonism has been shown to ameliorate ketamine-induced schizophrenia-like deficits in extradimensional set-shifting using the attentional set-shifting task (ASST). However, this rodent paradigm distinguishes between several types of cognitive rigidity associated with neuropsychiatric conditions. The goal of this study was to test 5-HT7 receptor involvement in the reversal learning component of the ASST because this ability depends primarily on the orbito-frontal cortex, which shows strong 5-HT7 receptor expression. We found that impaired performance on the ASST induced by NMDA receptor blockade (MK-801, 0.2 mg/kg) in 14 rats was reversed by coadministration of the 5-HT7 receptor antagonist SB-269970. The strongest effect was found on the reversal phases of ASST, whereas injection of SB-269970 alone had no effect. These results indicate that 5-HT7 receptor mechanisms may have a specific contribution to the complex cognitive deficits, increasing perseverative responding, in psychiatric diseases, including schizophrenia, depression, and anorexia nervosa, which express different forms of cognitive inflexibility.

Lurasidone Improves Psychopathology and Cognition in Treatment-Resistant Schizophrenia

PURPOSE/BACKGROUND

In addition to clozapine, other atypical antipsychotic drugs pharmacologically similar to clozapine, for example, olanzapine, risperidone, and melperone, are also effective in a similar proportion of treatment-resistant schizophrenia (TRS) patients, ~40%. The major goal of this study was to compare 2 doses of lurasidone, another atypical antipsychotic drug, and time to improvement in psychopathology and cognition during a 6-month trial in TRS patients.

METHODS/PROCEDURES

The diagnosis of TRS was based on clinical history and lack of improvement in psychopathology during a 6-week open trial of lurasidone 80 mg/d (phase 1). This was followed by a randomized, double-blind, 24-week trial of lurasidone, comparing 80- and 240-mg/d doses (phase 2).

FINDINGS/RESULTS

Significant non-dose-related improvement in the Positive and Negative Syndrome Scale-Total and subscales and in 2 of 7 cognitive domains, speed of processing and executive function, were noted. Twenty-eight (41.8%) of 67 patients in the combined sample improved ≥20% in the Positive and Negative Syndrome Scale-Total. Of the 28 responders, 19 (67.9%) first reached ≥20% improvement between weeks 6 and 24 during phase 2, including some who had previously failed to respond to clozapine.

IMPLICATIONS/CONCLUSIONS

Improvement with lurasidone is comparable with those previously reported for clozapine, melperone, olanzapine, and risperidone in TRS patients. In addition, this study demonstrated that 80 mg/d lurasidone, an effective and tolerable dose for non-TRS patients, was also effective in TRS patients but required longer duration of treatment. Direct comparison of lurasidone with clozapine in TRS patients is indicated.

A functional HTR1A polymorphism, rs6295, predicts short-term response to lurasidone: confirmation with meta-analysis of other antipsychotic drugs

Stimulation of the serotonin (5-HT)1A receptor (HTR1A) has been shown to contribute to the mechanism of action of some atypical antipsychotic drugs (APDs), including clozapine and lurasidone. A meta-analysis of rs6295, a functional polymorphism located at the promoter region of HTR1A, showed association with clinical response in schizophrenic patients treated with atypical APD. We have now tested whether other SNPs related to rs6295 predict response to lurasidone. We first evaluated whether rs358532 and rs6449693, tag SNPs for rs6295, predicted response to lurasidone, using data from two clinical trials of acutely psychotic schizophrenia patients with European (EUR, n = 171) or African (AFR, n = 131) ancestry; we then determined if those findings could be replicated in a third trial of lurasidone of similar design. Weekly changes (up to 6 weeks) in the Positive and Negative Syndrome Scale (PANSS) Total score and its five subscales were used to assess response. In EUR, a significant association, or trends for association, were observed for PANSS Total (p = 0.035), positive (p = 0.039), negative (p = 0.004), and disorganization (p = 0.0087) subscales, at week 1-6. There was a trend for replication with PANNS Total (p = 0.036) in the third trial. No significant association was observed in AFR or the placebo group. Meta-analysis of five studies, including the three with lurasidone, showed that rs6295 was associated with improvement in positive (p = 0.023) and negative (p ≤ 0.0001) symptoms in EUR patients with schizophrenia. This is the first study to show a significant association between functional HTR1A polymorphisms and treatment response to lurasidone. The meta-analysis provides additional evidence that rs6295 could be a race-dependent biomarker for predicting treatment response to APDs in schizophrenic patients with European Ancestry.

Lurasidone Sub-Chronically Activates Serotonergic Transmission via Desensitization of 5-HT1A and 5-HT7 Receptors in Dorsal Raphe Nucleus

Lurasidone is an atypical mood-stabilizing antipsychotic agent with unique receptor-binding profile, including 5-HT7 receptor (5-HT7R) antagonism. Effects of 5-HT7R antagonism on transmitter systems of schizophrenia and mood disorders, however, have not been well clarified. Thus, this study examined the mechanisms underlying the clinical effects of lurasidone by measuring mesocortical serotonergic transmission. Following systemic and local administrations of lurasidone, MK801 and 5-HT receptor modulators, we determined releases of 5-HT in dorsal raphe nucleus (DRN), mediodorsal thalamic nucleus (MDTN) and medial prefrontal cortex (mPFC) and γ-aminobutyric acid (GABA) in DRN using multiprobe microdialysis with ultra-high-performance liquid chromatography (UHPLC). Serotonergic and GABAergic neurons in the DRN are predominantly regulated by inhibitory 5-HT1A receptor (5-HT1AR) and excitatory 5-HT7R, respectively. Lurasidone acutely generates GABAergic disinhibition by 5-HT7R antagonism, but concomitant its 5-HT1AR agonism prevents serotonergic hyperactivation induced by 5-HT7R inhibition. During treatments with 5-HT1AR antagonist in DRN, lurasidone dose-dependently increased 5-HT release in the DRN, MDTN and mPFC. Contrary, lurasidone chronically enhanced serotonergic transmission and GABAergic disinhibition in the DRN by desensitizing both 5-HT1AR and 5-HT7R. These effects of lurasidone acutely prevented MK801-evoked 5-HT release by GABAergic disinhibition via N-methyl-D-aspartate (NMDA)/glutamate receptor (NMDA-R)-mediated inhibition of 5-HT1AR function, but enhanced MK801-induced 5-HT release by desensitizing 5-HT1AR and 5-HT7R. These results indicate that acutely lurasidone fails to affect 5-HT release, but chronically enhances serotonergic transmission by desensitizing both 5-HT1AR and 5-HT7R. These unique properties of lurasidone ameliorate the dysfunctions of NMDA-R and augment antidepressive effects.

Lurasidone inhibits NMDA receptor antagonist-induced functional abnormality of thalamocortical glutamatergic transmission via 5-HT7 receptor blockade

BACKGROUND AND PURPOSE

Lurasidone is an atypical mood-stabilizing antipsychotic with a unique receptor-binding profile, including 5-HT₇ receptor antagonism; however, the detailed effects of 5-HT₇ receptor antagonism on various transmitter systems relevant to schizophrenia, particularly the thalamo-insular glutamatergic system and the underlying mechanisms, are yet to be clarified.

EXPERIMENTAL APPROACH

We examined the mechanisms underlying the clinical effects of lurasidone by measuring the release of l-glutamate, GABA, dopamine, and noradrenaline in the reticular thalamic nucleus (RTN), mediodorsal thalamic nucleus (MDTN) and insula of freely moving rats in response to systemic injection or local infusion of lurasidone or MK-801 using multiprobe microdialysis with ultra-HPLC.

KEY RESULTS

Systemic MK-801 (0.5 mg·kg^-1 ) administration increased insular release of l-glutamate, dopamine, and noradrenaline but decreased GABA release. Systemic lurasidone (1 mg·kg^-1 ) administration also increased insular release of l-glutamate, dopamine, and noradrenaline but without affecting GABA. Local lurasidone administration into the insula (3 μM) did not affect MK-801-induced insular release of l-glutamate or catecholamine, whereas local lurasidone administration into the MDTN (1 μM) inhibited MK-801-induced insular release of l-glutamate and catecholamine, similar to the 5-HT₇ receptor antagonist SB269970.

CONCLUSIONS AND IMPLICATIONS

The present results indicate that MK-801-induced insular l-glutamate release is generated by activation of thalamo-insular glutamatergic transmission via MDTN GABAergic disinhibition resulting from NMDA receptor inhibition in the MDTN and RTN. Lurasidone inhibited this MK-801-evoked insular l-glutamate release through inhibition of excitatory 5-HT₇ receptor in the MDTN. These effects on thalamo-insular glutamatergic transmission may contribute to the antipsychotic and mood-stabilizing actions of lurasidone.