Schizophrenia and tobacco smoking comorbidity: nAChR agonists in the treatment of schizophrenia-associated cognitive deficits

Role of medial prefrontal cortex voltage-dependent potassium 4.3 channels in nicotine-induced enhancement of object recognition memory in male mice

Nicotine has been shown to enhance object recognition memory in the novel object recognition (NOR) test by activating excitatory neurons in the medial prefrontal cortex (mPFC). However, the exact neuronal mechanisms underlying the nicotine-induced activation of mPFC neurons and the resultant memory enhancement remain poorly understood. To address this issue, we performed brain-slice electrophysiology and the NOR test in male C57BL/6J mice. Whole-cell patch-clamp recordings from layer V pyramidal neurons in the mPFC revealed that nicotine augments the summation of evoked excitatory postsynaptic potentials (eEPSPs) and that this effect was suppressed by N-[3,5-Bis(trifluoromethyl)phenyl]-N'-[2,4-dibromo-6-(2H-tetrazol-5-yl)phenyl]urea (NS5806), a voltage-dependent potassium (Kv) 4.3 channel activator. In line with these findings, intra-mPFC infusion of NS5806 suppressed systemically administered nicotine-induced memory enhancement in the NOR test. Additionally, miRNA-mediated knockdown of Kv4.3 channels in mPFC pyramidal neurons enhanced object recognition memory. Furthermore, inhibition of A-type Kv channels by intra-mPFC infusion of 4-aminopyridine was found to enhance object recognition memory, while this effect was abrogated by prior intra-mPFC NS5806 infusion. These results suggest that nicotine augments the summation of eEPSPs via the inhibition of Kv4.3 channels in mPFC layer V pyramidal neurons, resulting in the enhancement of object recognition memory.

Cross-ancestry genetic investigation of schizophrenia, cannabis use disorder, and tobacco smoking

Individuals with schizophrenia frequently experience co-occurring substance use, including tobacco smoking and heavy cannabis use, and substance use disorders. There is interest in understanding the extent to which these relationships are causal, and to what extent shared genetic factors play a role. We explored the relationships between schizophrenia (Scz; European ancestry N = 161,405; African ancestry N = 15,846), cannabis use disorder (CanUD; European ancestry N = 886,025; African ancestry N = 120,208), and ever-regular tobacco smoking (Smk; European ancestry N = 805,431; African ancestry N = 24,278) using the largest available genome-wide studies of these phenotypes in individuals of African and European ancestries. All three phenotypes were positively genetically correlated (rgs = 0.17-0.62). Genetic instrumental variable analyses suggested the presence of shared heritable factors, but evidence for bidirectional causal relationships was also found between all three phenotypes even after correcting for these shared genetic factors. We identified 327 pleiotropic loci with 439 lead SNPs in the European ancestry data, 150 of which were novel (i.e., not genome-wide significant in the original studies). Of these pleiotropic loci, 202 had lead variants which showed convergent effects (i.e., same direction of effect) on Scz, CanUD, and Smk. Genetic variants convergent across all three phenotypes showed strong genetic correlations with risk-taking, executive function, and several mental health conditions. Our results suggest that both shared genetic factors and causal mechanisms may play a role in the relationship between CanUD, Smk, and Scz, but longitudinal, prospective studies are needed to confirm a causal relationship.

Demographic, biochemical, clinical, and cognitive symptom differences between smokers and non-smokers in Chinese older male patients with chronic schizophrenia

BACKGROUND

Several studies have suggested that smoking may impair cognitive function and worsen psychiatric symptoms in people with schizophrenia, but the results have not been consistent. There have been few studies to date that have examined the effects of smoking in older men with chronic schizophrenia.

METHODS

The participants in our study consisted of 167 order Chinese males with chronic schizophrenia and 359 normal control subjects. We split them into smoking and non-smoking groups based on whether or not they smoked. Second, we compared their differences in terms of general demographic characteristics (such as age, education, body mass index, age of illness onset, and course of disease), disease information (such as hypertension, diabetes, and hyperlipidemia), lifestyle factors (such as physical exercise and lunch break), blood biochemical indicators (such as albumin, triglyceride, total cholesterol, high-density lipoprotein, low-density lipoprotein and fasting blood glucose), and medication usage (such as clozapine, olanzapine, risperidone, and chlorpromazine). Lastly, a neuropsychological test battery was used to assess their psychiatric and cognitive symptoms, for example, the Montreal Cognitive Assessment (MoCA) was used to assess their overall cognitive functioning. Their depressive symptoms were assessed by the geriatric depression scale (GDS). Activities of daily living (ADL) were used to assess their ability to lead a daily life, while the positive and negative syndrome scales (PANSS) were used to assess their psychiatric symptoms.

RESULTS

Smokers who develop schizophrenia at older ages had a higher body mass index than non-smokers. We also found that plasma albumin, triglycerides, low-density lipoprotein, and fasting blood glucose concentrations were significantly higher in smokers. In contrast, smokers with schizophrenia also had lower PANSS total scores, negative symptom scores, and general psychopathology scores. A forward stepwise binary logistics regression analysis demonstrated a significant association between negative symptom scores and smoking status (B = 0.112, p < 0.001, OR = 1.119, 95% confidence interval: 1.059-1.181). Correlation analysis was carried out and it was found that the amount of cigarette consumption per day had a negative correlation with plasma albumin level(r = - 0.290, p = 0.004). However, no such association was found in normal controls.

CONCLUSIONS

Elderly Chinese men with schizophrenia have a higher percentage of smokers, and although smoking can reduce their plasma albumin levels, it does contribute to the prevention of negative symptoms.

Cross-ancestry genetic investigation of schizophrenia, cannabis use disorder, and tobacco smoking

Individuals with schizophrenia frequently experience co-occurring substance use, including tobacco smoking and heavy cannabis use, and substance use disorders. There is interest in understanding the extent to which these relationships are causal, and to what extent shared genetic factors play a role. We explored the relationships between schizophrenia (Scz), cannabis use disorder (CanUD), and ever-regular tobacco smoking (Smk) using the largest available genome-wide studies of these phenotypes in individuals of African and European ancestries. All three phenotypes were positively genetically correlated (rgs = 0.17 - 0.62). Causal inference analyses suggested the presence of horizontal pleiotropy, but evidence for bidirectional causal relationships was also found between all three phenotypes even after correcting for horizontal pleiotropy. We identified 439 pleiotropic loci in the European ancestry data, 150 of which were novel (i.e., not genome-wide significant in the original studies). Of these pleiotropic loci, 202 had lead variants which showed convergent effects (i.e., same direction of effect) on Scz, CanUD, and Smk. Genetic variants convergent across all three phenotypes showed strong genetic correlations with risk-taking, executive function, and several mental health conditions. Our results suggest that both horizontal pleiotropy and causal mechanisms may play a role in the relationship between CanUD, Smk, and Scz, but longitudinal, prospective studies are needed to confirm a causal relationship.

Varenicline enhances recognition memory via α7 nicotinic acetylcholine receptors in the medial prefrontal cortex in male mice

Previous studies postulated that chronic administration of varenicline, a partial and full agonist at α4β2 and α7 nicotinic acetylcholine receptors (nAChRs), respectively, enhances recognition memory. However, whether its acute administration is effective, on which brain region(s) it acts, and in what signaling it is involved, remain unknown. To address these issues, we conducted a novel object recognition test using male C57BL/6J mice, focusing on the medial prefrontal cortex (mPFC), a brain region associated with nicotine-induced enhancement of recognition memory. Systemic administration of varenicline before the training dose-dependently enhanced recognition memory. Intra-mPFC varenicline infusion also enhanced recognition memory, and this enhancement was blocked by intra-mPFC co-infusion of a selective α7, but not α4β2, nAChR antagonist. Consistent with this, intra-mPFC infusion of a selective α7 nAChR agonist augmented object recognition memory. Furthermore, intra-mPFC co-infusion of U-73122, a phospholipase C (PLC) inhibitor, or 2-aminoethoxydiphenylborane (2-APB), an inositol trisphosphate (IP3) receptor inhibitor, suppressed the varenicline-induced memory enhancement, suggesting that α7 nAChRs may also act as Gq-coupled metabotropic receptors. Additionally, whole-cell recordings from mPFC layer V pyramidal neurons in vitro revealed that varenicline significantly increased the summation of evoked excitatory postsynaptic potentials, and this effect was suppressed by U-73122 or 2-APB. These findings suggest that varenicline might acutely enhance recognition memory via mPFC α7 nAChR stimulation, followed by mPFC neuronal excitation, which is mediated by the activation of PLC and IP3 receptor signaling. Our study provides evidence supporting the potential repositioning of varenicline as a treatment for cognitive impairment.

Abnormal interhemispheric functional cooperation in schizophrenia follows the neurotransmitter profiles

BACKGROUND

Interhemispheric cooperation is one of the most prominent functional architectures of the human brain. In patients with schizophrenia, interhemispheric cooperation deficits have been reported using increasingly powerful neurobehavioural and neuroimaging measures. However, these methods rely in part on the assumption of anatomic symmetry between hemispheres. In the present study, we explored interhemispheric cooperation deficits in schizophrenia using a newly developed index, connectivity between functionally homotopic voxels (CFH), which is unbiased by hemispheric asymmetry.

METHODS

Patients with schizophrenia and age- and sexmatched healthy controls underwent multimodal MRI, and whole-brain CFH maps were constructed for comparison between groups. We examined the correlations of differing CFH values between the schizophrenia and control groups using various neurotransmitter receptor and transporter densities.

RESULTS

We included 86 patients with schizophrenia and 86 matched controls in our analysis. Patients with schizophrenia showed significantly lower CFH values in the frontal lobes, left postcentral gyrus and right inferior temporal gyrus, and significantly greater CFH values in the right caudate nucleus than healthy controls. Moreover, the differing CFH values in patients with schizophrenia were significantly correlated with positive symptom score and illness duration. Functional connectivity within frontal lobes was significantly reduced at the voxel cluster level compared with healthy controls. Finally, the abnormal CFH map of patients with schizophrenia was spatially associated with the densities of the dopamine D1 and D2 receptors, fluorodopa, dopamine transporter, serotonin transporter and acetylcholine transporter.

CONCLUSION

Regional abnormalities in interhemispheric cooperation may contribute to the clinical symptoms of schizophrenia. These CFH abnormalities may be associated with dysfunction in neurotransmitter systems strongly implicated in schizophrenia.

Nicotine's effect on cognition, a friend or foe?

Tobacco smoking is a preventable cause of morbidity and mortality throughout the world. Smoking comes in form of absorption of many compounds, among which nicotine is the main psychoactive component of tobacco and its positive and negative reinforcement effects are proposed to be the key mechanism for the initiation and maintenance of smoking. Growing evidence suggests that the cognitive enhancement effects of nicotine may also contribute to the difficulty of quitting smoking, especially in individuals with psychiatric disorders. In this review, we first introduce the beneficial effect of nicotine on cognition including attention, short-term memory and long-term memory. We next summarize the beneficial effect of nicotine on cognition under pathological conditions, including Alzheimer's disease, Parkinson's disease, Schizophrenia, Stress-induced Anxiety, Depression, and drug-induced memory impairment. The possible mechanism underlying nicotine's effect is also explored. Finally, nicotine's detrimental effect on cognition is discussed, including in the prenatal and adolescent periods, and high-dose nicotine- and withdrawal-induced memory impairment is emphasized. Therefore, nicotine serves as both a friend and foe. Nicotine-derived compounds could be a promising strategy to alleviate neurological disease-associated cognitive deficit, however, due to nicotine's detrimental effect, continued educational programs and public awareness campaigns are needed to reduce tobacco use among pregnant women and smoking should be quitted even if it is e-cigarette, especially for the adolescents.

Smoking status ameliorates cholinergic impairments in cortical inhibition in patients with schizophrenia

Rationale Modulation of cortical excitability, in particular inhibition, is impaired in patients with schizophrenia. Chronic nicotine consumption, which is prevalent in this group, has been shown to alter cortical excitability in healthy individuals and to increase inhibitory activity. Thus, beneficial effects of smoking on impaired cortical excitability in patients with schizophrenia have been proposed, though direct experimental evidence is still lacking.

OBJECTIVES

We aimed to explore the effect of chronic smoking on cortical excitability by comparing smoking and non-smoking patients with schizophrenia.

METHOD

Twenty-six smoking and 19 non-smoking patients diagnosed with schizophrenia were included. Transcranial magnetic stimulation (TMS) applied to the primary motor cortex served as experimental paradigm for measuring corticospinal and intracortical excitability as follows: Resting motor threshold (RMT) and the input/output curve (I/O curve) were obtained to assess corticospinal excitability. Intracortical excitability was explored using paired-pulse TMS techniques (intracortical facilitation (ICF), short-latency intracortical inhibition (SICI) and short-latency afferent inhibition (SAI)).

RESULTS

A significantly stronger inhibition in the cholinergically driven SAI protocol was observed in smokers compared to non-smokers. All other measures did not show significant differences between groups.

CONCLUSION

Our results suggest an increased inhibition within cholinergic circuits due to chronic nicotine consumption in schizophrenia. This increase may compensate impaired cholinergic neurotransmission and could explain the high rate of smokers in schizophrenia.

Nicotine pretreatment alleviates MK-801-induced behavioral and cognitive deficits in mice by regulating Pdlim5/CRTC1 in the PFC

Increasing evidence shows that smoking-obtained nicotine is indicated to improve cognition and mitigate certain symptoms of schizophrenia. In this study, we investigated whether chronic nicotine treatment alleviated MK-801-induced schizophrenia-like symptoms and cognitive impairment in mice. Mice were injected with MK-801 (0.2 mg/kg, i.p.), and the behavioral deficits were assessed using prepulse inhibition (PPI) and T-maze tests. We showed that MK-801 caused cognitive impairment accompanied by increased expression of PDZ and LIM domain 5 (Pdlim5), an adaptor protein that is critically associated with schizophrenia, in the prefrontal cortex (PFC). Pretreatment with nicotine (0.2 mg · kg-1 · d-1, s.c., for 2 weeks) significantly ameliorated MK-801-induced schizophrenia-like symptoms and cognitive impairment by reversing the increased Pdlim5 expression levels in the PFC. In addition, pretreatment with nicotine prevented the MK-801-induced decrease in CREB-regulated transcription coactivator 1 (CRTC1), a coactivator of CREB that plays an important role in cognition. Furthermore, MK-801 neither induced schizophrenia-like behaviors nor decreased CRTC1 levels in the PFC of Pdlim5-/- mice. Overexpression of Pdlim5 in the PFC through intra-PFC infusion of an adreno-associated virus AAV-Pdlim5 induced significant schizophrenia-like symptoms and cognitive impairment. In conclusion, chronic nicotine treatment alleviates schizophrenia-induced memory deficits in mice by regulating Pdlim5 and CRTC1 expression in the PFC.

An α7 nAChR approach for the baseline-dependent modulation of deviance detection in schizophrenia: A pilot study assessing the combined effect of CDP-choline and galantamine

BACKGROUND

Cognitive operations including pre-attentive sensory processing are markedly impaired in patients with schizophrenia (SCZ) but evidence significant interindividual heterogeneity, which moderates treatment response with nicotinic acetylcholine receptor (nAChR) agonists. Previous studies in healthy volunteers have shown baseline-dependency effects of the α7 nAChR agonist cytidine 5'-diphosphocholine (CDP-choline) administered alone and in combination with a nicotinic allosteric modulator (galantamine) on auditory deviance detection measured with the mismatch negativity (MMN) event-related potential (ERP).

AIM

The objective of this pilot study was to assess the acute effect of this combined α7 nAChR-targeted treatment (CDP-choline/galantamine) on speech MMN in patients with SCZ (N = 24) stratified by baseline MMN responses into low, medium, and high baseline auditory deviance detection subgroups.

METHODS

Patients with a stable diagnosis of SCZ attended two randomized, double-blind, placebo-controlled and counter-balanced testing sessions where they received a placebo or a CDP-choline (500 mg) and galantamine (16 mg) treatment. MMN ERPs were recorded during the presentation of a fast multi-feature speech MMN paradigm including five speech deviants. Clinical measures were acquired before and after treatment administration.

RESULTS

While no main treatment effect was observed, CDP-choline/galantamine significantly increased MMN amplitudes to frequency, duration, and vowel speech deviants in low group individuals. Individuals with higher positive and negative symptom scale negative, general, and total scores expressed the greatest MMN amplitude improvement following CDP-choline/galantamine.

CONCLUSIONS

These baseline-dependent nicotinic effects on early auditory information processing warrant different dosage and repeated administration assessments in patients with low baseline deviance detection levels.

Smoking and attention in schizophrenia spectrum disorders: What are we neglecting?

Introduction

Individuals with schizophrenia spectrum disorders (SSDs) record elevated rates of smoking, which is often attributed to their effort to self-medicate cognitive and attentional symptoms of their illness. Empirical evidence for this hypothesis is conflicting, however. In this study, we aimed to test predictions derived from the cognitive self-medication hypothesis. We predicted that cigarette smoking status and extent would predict the attentional performance of participants with SSDs. Simultaneously, we wished to address methodological gaps in previous research. We measured distinct attentional components and made adjustments for the effects of other, attention-modulation variables.

Methods

Sixty-one smokers (82.0% males, 26.73 ± 6.05 years) and 61 non-smokers (50.8% males, 27.10 ± 7.90 years) with recent-onset SSDs completed an X-type Continuous Performance Test, which was used to derive impulsivity and inattention component scores. Relationships between the two component scores and cigarette smoking status and extent were assessed using hierarchical regression. Effects of estimated premorbid intellectual functioning and antipsychotic medication dosage were held constant.

Results

Smokers had significantly higher inattention component scores than non-smokers when covariates were controlled (p = 0.026). Impulsivity remained unaffected by smoking status (p = 0.971). Cigarette smoking extent, i.e., the number of cigarettes smoked per day, was not associated with either inattention (p = 0.414) or impulsivity (p = 0.079).

Conclusion

Models of smoking-related attentional changes can benefit from the inclusion of sample-specific component scores and attention-modulating covariates. Under these conditions, smokers with SSDs can show a partial attentional benefit. However, the limited scope of this benefit suggests that the cognitive self-medication hypothesis requires further testing or reconsidering.

Smoking Addiction in Patients with Schizophrenia Spectrum Disorders and Its Perception and Intervention in Healthcare Personnel Assigned to Psycho-Rehabilitation Programs: A Qualitative Research

Patients with schizophrenia spectrum disorders have a higher prevalence and frequency of smoking rates when compared to the rest of the population; to this, it must be added that they develop a greater dependence and have some worse health consequences than the general population. This is qualitative research on the perception of smoking in healthcare professionals assigned to psycho-rehabilitation programs for patients with schizophrenia spectrum disorders. The point of view of health personnel (Psychologists, Psychiatrists, Pedagogists, and Nurses) about cigarette smoking in these patients was analyzed, focusing on their implications in disturbance and comparing them with e-cigarettes too. The methodology used to collect the data was a semi-structured interview with five questions. The research path was carried out in two assisted therapeutic communities that are clinics for the rehabilitation of serious mental illness in the period between November and July 2022. The results showed that the opinion of health professionals on smoking is very negative. Research has also shown that nearly all patients are smokers; however, their high grade of addiction is caused by periods of high stress due to various factors that lead patients to consume a greater number of cigarettes. Almost all respondents have a positive opinion of the e-cigarette, which was defined as an excellent substitute for traditional cigarettes.

The impact of smoking status on cognition and brain morphology in schizophrenia spectrum disorders

BACKGROUND

Cigarette smoking is associated with worse cognition and decreased cortical volume and thickness in healthy cohorts. Chronic cigarette smoking is prevalent in schizophrenia spectrum disorders (SSD), but the effects of smoking status on the brain and cognition in SSD are not clear. This study aimed to understand whether cognitive performance and brain morphology differed between smoking and non-smoking individuals with SSD compared to healthy controls.

METHODS

Data were obtained from the Australian Schizophrenia Research Bank. Cognitive functioning was measured in 299 controls and 455 SSD patients. Cortical volume, thickness and surface area data were analysed from T1-weighted structural scans obtained in a subset of the sample (n = 82 controls, n = 201 SSD). Associations between smoking status (cigarette smoker/non-smoker), cognition and brain morphology were tested using analyses of covariance, including diagnosis as a moderator.

RESULTS

No smoking by diagnosis interactions were evident, and no significant differences were revealed between smokers and non-smokers across any of the variables measured, with the exception of a significantly thinner left posterior cingulate in smokers compared to non-smokers. Several main effects of smoking in the cognitive, volume and thickness analyses were initially significant but did not survive false discovery rate (FDR) correction.

CONCLUSIONS

Despite the general absence of significant FDR-corrected findings, trend-level effects suggest the possibility that subtle smoking-related effects exist but were not uncovered due to low statistical power. An investigation of this topic is encouraged to confirm and expand on our findings.

Impact of Nicotine on Cognition in Patients With Schizophrenia: A Narrative Review

Nicotine is the psychoactive component given tobacco has several main components and acts as an agonist for nicotinic acetylcholine receptors (nAChRs) in the nervous system. Although the ligand-gated cation channels known as nAChRs are found throughout the nervous system and body, this review focuses on neuronal nAChRs. Individuals with psychiatric diseases such as schizophrenia, comorbid substance use disorders, attention-deficit hyperactivity disorder, major depression, and bipolar disorder have increased rates of smoking. These psychiatric disorders are associated with various cognitive deficits, including working memory, deficits in attention, and response inhibition functions. The cognitive-enhancing effects of nicotine may be particularly relevant predictors of smoking initiation and continuation in this comorbid population. Individuals with schizophrenia make up a significant proportion of smokers. Literature suggests that patients smoke to alleviate cognitive deficiencies due to the stimulating effects of nicotine. This narrative review examines the role of nicotine on cognition in schizophrenia.

Chimeric Structures in Mental Illnesses-"Magic" Molecules Specified for Complex Disorders

Mental health problems cover a wide spectrum of diseases, including mild to moderate anxiety, depression, alcohol/drug use disorders, as well as bipolar disorder and schizophrenia. Pharmacological treatment seems to be one of the most effective opportunities to recover function efficiently and satisfactorily. However, such disorders are complex as several target points are involved. This results in a necessity to combine different types of drugs to obtain the necessary therapeutic goals. There is a need to develop safer and more effective drugs. Considering that mental illnesses share multifactorial processes, the paradigm of one treatment with multiple modes of action rather than single-target strategies would be more effective for successful therapies. Therefore, hybrid molecules that combine two pharmacophores in one entity show promise, as they possess the desired therapeutic index with a small off-target risk. This review aims to provide information on chimeric structures designed for mental disorder therapy (i.e., schizophrenia and depression), and new types of drug candidates currently being tested. In addition, a discussion on some benefits and limitations of multifunctional, bivalent drug candidates is also given.

The role of the SLC6A3 3' UTR VNTR in nicotine effects on cognitive, affective, and motor function

RATIONALE

Nicotine has been widely studied for its pro-dopaminergic effects. However, at the behavioural level, past investigations have yielded heterogeneous results concerning effects on cognitive, affective, and motor outcomes, possibly linked to individual differences at the level of genetics. A candidate polymorphism is the 40-base-pair variable number of tandem repeats polymorphism (rs28363170) in the SLC6A3 gene coding for the dopamine transporter (DAT). The polymorphism has been associated with striatal DAT availability (9R-carriers > 10R-homozygotes), and 9R-carriers have been shown to react more strongly to dopamine agonistic pharmacological challenges than 10R-homozygotes.

OBJECTIVES

In this preregistered study, we hypothesized that 9R-carriers would be more responsive to nicotine due to genotype-related differences in DAT availability and resulting dopamine activity.

METHODS

N=194 non-smokers were grouped according to their genotype (9R-carriers, 10R-homozygotes) and received either 2-mg nicotine or placebo gum in a between-subject design. Spontaneous blink rate (SBR) was obtained as an indirect measure of striatal dopamine activity and smooth pursuit, stop signal, simple choice and affective processing tasks were carried out in randomized order.

RESULTS

Reaction times were decreased under nicotine compared to placebo in the simple choice and stop signal tasks, but nicotine and genotype had no effects on any of the other task outcomes. Conditional process analyses testing the mediating effect of SBR on performance and how this is affected by genotype yielded no significant results.

CONCLUSIONS

Overall, we could not confirm our main hypothesis. Individual differences in nicotine response could not be explained by rs28363170 genotype.

The effects of galangin in prepulse inhibition test and experimental schizophrenia models

OBJECTIVE

Acetylcholinesterase inhibitors are the focus of interest in the management of schizophrenia. We aimed to investigate the effects of acute galangin administration, a flavonoid compound with acetylcholinesterase inhibiting activity, on schizophrenia-associated cognitive deficits in rats and schizophrenia models in mice.

METHODS

Apomorphine-induced prepulse inhibition (PPI) disruption for cognitive functions, nicotinic, muscarinic, and serotonergic mechanism involvement, and brain acetylcholine levels were investigated in Wistar rats. Apomorphine-induced climbing, MK-801-induced hyperlocomotion, and catalepsy tests were used as schizophrenia models in Swiss albino mice. The effects of galangin were compared with acetylcholinesterase inhibitor donepezil, and typical and atypical antipsychotics haloperidol and olanzapine, respectively.

RESULTS

Galangin (50,100 mg/kg) enhanced apomorphine-induced PPI disruption similar to donepezil, haloperidol, and olanzapine (p < 0.05). This effect was not altered in the combination of galangin with the nicotinic receptor antagonist mecamylamine (1 mg/kg), the muscarinic receptor antagonist scopolamine (0.05 mg/kg), or the serotonin-1A receptor antagonist WAY-100635 (1 mg/kg) (p > 0.05). Galangin (50,100 mg/kg) alone increased brain acetylcholine concentrations (p < 0.05), but not in apomorphine-injected rats (p > 0.05). Galangin (50 mg/kg) decreased apomorphine-induced climbing and MK-801-induced hyperlocomotion similar to haloperidol and olanzapine (p < 0.05), but did not induce catalepsy, unlike them.

CONCLUSION

We suggest that galangin may help enhance schizophrenia-associated cognitive deficits, and nicotinic, muscarinic cholinergic, and serotonin-1A receptors are not involved in this effect. Galangin also exerted an antipsychotic-like effect without inducing catalepsy and may be considered as an advantageous antipsychotic agent.

Sex Differences in Obesity and Cognitive Function in Chinese Elderly Patients With Chronic Schizophrenia

BACKGROUND

It is well known that schizophrenia is associated with sex differences. However, no study has explored the sex differences in obesity and cognitive function in elderly Chinese patients with schizophrenia.

OBJECTIVE

This study aimed to compare sex differences in obesity and cognitive function in elderly Chinese individuals with schizophrenia.

METHODS

A total of 304 elderly patients with schizophrenia and 130 sex- and age-matched healthy controls from the community were recruited. Demographic, clinical, and lipid parameters were collected for all subjects. The Montreal Cognitive Assessment (MoCA) was used to assess the global cognitive functions of the participants, while the Positive and Negative Syndrome Scale (PANSS) was used to assess psychopathological symptoms in patients with schizophrenia.

RESULTS

Of the patients with schizophrenia, the prevalence of obesity in men and women was 11.7% (19/163) and 21.3% (30/141), respectively. The score (14.51 ± 6.504) of MOCA in elderly male patients with schizophrenia was significantly higher than that (11.40 ± 6.822) in female patients. There was a positive correlation between the MOCA scores and body mass index (BMI) (r=0.206, p=0.018) in male elderly patients with schizophrenia. Conversely, the MOCA scores of female elderly patients with schizophrenia did not correlate with BMI (p>0.05). However, we found no sex differences in obesity and cognition among control older adults.

CONCLUSIONS

Our findings suggest that there are significant sex differences in obesity and cognitive function in elderly Chinese patients with schizophrenia.

Association Study of Polymorphisms in Neuronal Nicotinic Acetylcholine Receptor Subunit Genes With Schizophrenia in the Han Chinese Population

OBJECTIVE

To investigate the relation between nicotinic acetylcholine receptor subunit (nAChR) genes and schizophrenia, and the relation between tag single nucleotide polymorphism (rs1317286, rs1044396, rs6494212, rs16969968, and rs684513) and schizophrenia in Han Chinese people.

METHODS

The protein-protein interaction (PPI) network among nAChR protein and 350 proteins encoded by schizophrenia-related susceptibility genes was constructed through the String database to explore whether nAChR genes were associated with schizophrenia in these known databases. Then, five single nucleotide polymorphisms (SNPs) of CHRNA3 (rs1317286), CHRNA4 (rs1044396), CHRNA7 (rs6494212), and CHRNA5 (rs16969968, rs684513) were analyzed in a sample of 1,035 schizophrenic patients and 816 healthy controls. The interaction between the markers was analyzed using multifactor dimensionality reduction (MDR) software. Power analysis was performed using the Quanto program.

RESULTS

There are no significant differences in genotype or allele distribution were identified between the patients and controls (p>0.05). The haplotypes constructed by four markers rs1317286, rs6494212, rs16969968, and rs684513 were not associated with schizophrenia either. However, a significant association between models made of rs1317286, rs1044396, rs6494212, and rs684513 and schizophrenia was revealed in interaction analysis (p<0.05).

CONCLUSION

The nAChR protein may have effects on the development of schizophrenia through the interaction with proteins encoded by schizophrenia-related susceptibility genes, but no relation was found between selected polymorphisms and schizophrenia in the collected Han Chinese people. However, interaction analysis suggested four-SNP model has an important effect on schizophrenia.

Cholinergic receptor nicotinic beta 3 subunit polymorphisms and smoking in male Chinese patients with schizophrenia

OBJECTIVE

The aim of this study was to examine if cholinergic receptor nicotinic beta 3 subunit (CHRNB3) was a common genetic basis for both nicotine dependence and schizophrenia.

METHODS

Two CHRNB3 promoter single nucleotide polymorphisms (SNPs) were genotyped in 773 patients with schizophrenia and 302 healthy volunteers. Associations between smoking, schizophrenia, smoking+schizophrenia and CHRNB3 were analyzed. The mRNA expression of CHRNB3 in human brains was examined, and the expression correlations between CHRNB3 and dopaminergic and GABAergic receptor genes were evaluated.

RESULTS

The association between CHRNB3 and smoking was significant in the total sample, less significant in the smoking with schizophrenia, and suggestive in the smoking without schizophrenia. CHRNB3 had significant mRNA expression that was correlated with dopaminergic or GABAergic receptor expression in human brains. The two CHRNB3 SNPs had significant cis-acting regulatory effects on CHRNB3 mRNA expression.

CONCLUSIONS

Risk for smoking behavior was associated with CHRNB3. CHRNB3 mRNA is abundant in human brain and could play important role in the pathogenesis of smoking behavior.

Anticholinergic Burden and Cognitive Performance in Patients With Schizophrenia: A Systematic Literature Review

Objective: Cognitive impairment in schizophrenia forms the key cause of the disease's disability, leading to serious functional, and socioeconomic implications. Dopaminergic-cholinergic balance is considered essential to cognitive performance in schizophrenia and patients are often treated with many drugs with anticholinergic properties. This study aims to examine the cognitive impact of anticholinergic burden in patients with schizophrenia. Methods: A systematic literature review was performed on English-language studies published on PubMed, Embase, and Web of Science, from inception to June 2021, to identify research studies that examined the effect of anticholinergic load on cognition in clinically stable patients with schizophrenia. No restrictions on study design, age of participants, or geographical distribution were applied. Two researchers performed independently the screening and shortlisting of the eligible articles. A narrative synthesis of the main characteristics and findings of studies included was reported. Results: In total, 17 articles of varying methodological design met the inclusion criteria. Three of them found statistically significant improvement in cognition after anticholinergic tapering without adverse effects. Thirteen studies found a statistically significant association between high anticholinergic burden and cognitive impairment (neurocognitive composite scores and individual cognitive domains such as learning and memory, executive function, processing speed), apart from a study, related to the specific characteristics of clozapine. Conclusions: Medication with increased anticholinergic load has been found in most of the studies to negatively affect neurocognitive performance of patients with schizophrenia. However, the clinical and methodological heterogeneity of studies included limit our interpretation and conclusions.

CDP-choline and galantamine, a personalized α7 nicotinic acetylcholine receptor targeted treatment for the modulation of speech MMN indexed deviance detection in healthy volunteers: a pilot study

RATIONALE

The combination of CDP-choline, an α7 nicotinic acetylcholine receptor (α7 nAChR) agonist, with galantamine, a positive allosteric modulator of nAChRs, is believed to counter the fast desensitization rate of the α7 nAChRs and may be of interest for schizophrenia (SCZ) patients. Beyond the positive and negative clinical symptoms, deficits in early auditory prediction-error processes are also observed in SCZ. Regularity violations activate these mechanisms that are indexed by electroencephalography-derived mismatch negativity (MMN) event-related potentials (ERPs) in response to auditory deviance.

OBJECTIVES/METHODS

This pilot study in thirty-three healthy humans assessed the effects of an optimized α7 nAChR strategy combining CDP-choline (500 mg) with galantamine (16 mg) on speech-elicited MMN amplitude and latency measures. The randomized, double-blinded, placebo-controlled, and counterbalanced design with a baseline stratification method allowed for assessment of individual response differences.

RESULTS

Increases in MMN generation mediated by the acute CDP-choline/galantamine treatment in individuals with low baseline MMN amplitude for frequency, intensity, duration, and vowel deviants were revealed.

CONCLUSIONS

These results, observed primarily at temporal recording sites overlying the auditory cortex, implicate α7 nAChRs in the enhancement of speech deviance detection and warrant further examination with respect to dysfunctional auditory deviance processing in individuals with SCZ.

Association of cigarette smoking with cognitive impairment in male patients with chronic schizophrenia

BACKGROUND

Previous studies have shown that patients with schizophrenia have higher smoking rates and worse cognitive function than healthy controls. However, there is no consistent conclusion about the relationship between smoking and cognitive impairment.

OBJECTIVES

The main purpose of this study was to explore the effects of smoking on cognitive function by using MATRICS Cognitive Consensus Battery (MCCB) in Chinese male patients with schizophrenia.

METHODS

There were 164 patients with chronic schizophrenia and 82 healthy controls. All subjects were interviewed about smoking status. The cognitive function was assessed by MCCB and Stroop tests. The Positive and Negative Syndrome Scale (PANSS) was used to assess the clinical symptoms of the patients.

RESULTS

Compared with healthy controls, patients had lower MCCB scores in all of its domain scores (all p < 0.05). In the patients, the scores of spatial span test (42.3 ± 11.6), digital sequence test (42.9 ± 10.6), and Hopkins Verbal Learning Test (42.2 ± 10.1) were lower in smokers than those in nonsmokers (all p < 0.05, effect size: 0.28-0.45). Logistic regression analysis showed that the smoking status of the patients was correlated with digital sequence score (p < 0.05, OR = 1.072, 95%CI: 1.013-1.134). Multivariate regression analysis showed that the spatial span total score (β = - 0.26, t = - 2.74, p < 0.001) was associated with the duration of smoking in patients with schizophrenia.

CONCLUSIONS

Our findings show that smoking patients with chronic schizophrenia exhibit more severe cognitive impairment than nonsmoking patients, especially in working memory and executive function.

Approved and emerging smoking cessation treatments for people with schizophrenia spectrum disorders: A narrative review

This review focuses on smoking cessation treatments for people with schizophrenia spectrum disorders. It concludes with comments on the significance of the research and why it constitutes an original contribution. We searched PubMed (National Library of Medicine), and PsycINFO (Ovid) (2006-2020) for studies on schizophrenic disorder (schizophrenia or psychotic or psychosis or severe mental illness) and smoking cessation treatment (smoking cessation treatment or varenicline or tobacco cessation or reduction or bupropion or NRT or behavioral treatment or e-cigarette). Studies found evidence suggesting that pharmacotherapy combined with behavioural therapy for smoking cessation is effective amongst smokers with schizophrenia spectrum disorders, although more long-term research is required. This review summarised and critically reviewed also studies on vaping as a smoking cessation strategy for smokers with schizophrenia spectrum disorders and evidence suggests that they may effective as smoking cessation tool and may be less harmful alternatives to combustible cigarette smoking. Consequently, e-cigarettes could be considered as an applicable instrument for Tobacco Harm Reduction (THR) and smoking cessation. Overall, there are very few studies of e-cigarettes for smoking cessation in patients with schizophrenia and these studies are very small. They have promising results, but more research is needed.

Effects of Smoking Status on Remission and Metabolic and Cognitive Outcomes in Schizophrenia Patients Treated with Clozapine

BACKGROUND

Even though clozapine is the recommended last-resort antipsychotic, many patients fail to respond and show treatment-refractory psychotic symptoms. Smoking has been suggested as a possible risk factor for poor clozapine response, hampering remission and negatively impacting somatic outcomes.

METHODS

Our aim was to test whether smoking status is associated with remission rates and other symptomatic and somatic outcomes. We therefore assessed remission rates according to The Remission in Schizophrenia Working Group (RSWG) criteria, and metabolic and cognitive outcomes among patients with schizophrenia-spectrum disorders treated with clozapine for at least 6 months. For analyses, we grouped our cohort into 3 groups according to clozapine treatment duration (6 months, 2 years, 5 years).

RESULTS

One hundred five patients were included in our analyses and grouped according to their clozapine treatment duration. In the 6-months analyses, patients who smoked were significantly more likely to be younger of age (p=0.002) despite on average shorter duration of clozapine treatment (p=0.041) and significantly more likely to be treated with mood-stabilizing co-medication (p=0.030) compared to nonsmokers. Remission rates (p=0.490), as well as a set of metabolic and cognitive variables did not differ between the 2 groups. A related pattern could be observed for the 2- and 5-years analyses.

CONCLUSIONS

Smoking behavior among clozapine-treated schizophrenia patients might delineate a cohort with an earlier onset of the disease. Nevertheless, most findings comparing disease-specific and clinical outcomes among smokers and nonsmokers were negative. Further research is needed to identify strategies to overcome insufficient remission rates in this patient group.

The effects of acute nicotine administration on cognitive and early sensory processes in schizophrenia: a systematic review

Nicotine use, which is mostly done through smoking tobacco, is among the most burdensome comorbidities of schizophrenia. However, the ways in which nicotine affects the cognitive and early sensory alterations found in this illness are still debated. After conducting a systematic literature search, 29 studies were selected. These studies involve individuals with schizophrenia who underwent cognitive and/or early sensory function assessments after acute nicotine administration and include 560 schizophrenia subjects and 346 non-schizophrenia controls. The findings highlight that a single dose of nicotine can improve a range of cognitive functions in schizophrenia subjects, such as attention, working memory, and executive functions, with attention being the most responsive domain. In addition, nicotine can modulate early detection of changes in the sensory environment at both the auditory and visual levels. Nevertheless, effects vary strongly depending on the type of neuropsychological assessment and nicotine intake conditions used in each study. The current findings suggest the need to consider a potential decrease of cognitive and early sensory performance when patients with schizophrenia quit smoking.

Tobacco smoking, related harm and motivation to quit smoking in people with schizophrenia spectrum disorders

This narrative review focuses on the topic of tobacco smoking amongst people with schizophrenia spectrum disorders. We searched PubMed, PsycInfo and Scopus databases for schizophrenia spectrum disorders and smoking and included articles about the epidemiology of tobacco smoking in people with schizophrenia spectrum disorders, examining the relationship between smoking and mental health. This narrative review describes that a higher prevalence, frequency and impact of both high nicotine dependence and its harmful effects in patients with schizophrenia spectrum disorders compared with those in the general population. Despite several existent theories, the reasons for high smoking rates, the high dependence on nicotine and severity of nicotine withdrawal symptoms are not fully understood. The main aim of this paper is to inform mental health personnel and particularly clinical and health psychologists about the impact and role of tobacco smoking for smokers with schizophrenia spectrum disorders.

Reduced striatal dopamine synthesis capacity in patients with schizophrenia during remission of positive symptoms

While there is consistent evidence for increased presynaptic dopamine synthesis capacity in the striatum of patients with schizophrenia during psychosis, it is unclear whether this also holds for patients during psychotic remission. This study investigates whether striatal dopamine synthesis capacity is altered in patients with schizophrenia during symptomatic remission of positive symptoms, and whether potential alterations relate to symptoms other than positive, such as cognitive difficulties. Twenty-three patients with schizophrenia in symptomatic remission of positive symptoms according to Andreasen, and 24 healthy controls underwent 18F-DOPA-PET and behavioural-cognitive assessment. Imaging data were analysed with voxel-wise Patlak modelling with cerebellum as reference region, resulting in the influx constant kicer reflecting dopamine synthesis capacity. For the whole striatum and its subdivisions (i.e. limbic, associative, and sensorimotor), averaged regional kicer values were calculated, compared across groups, and correlated with behavioural-cognitive scores, including a mediation analysis. Patients had negative symptoms (Positive and Negative Syndrome Scale-negative 14.13 ± 5.91) and cognitive difficulties, i.e. they performed worse than controls in Trail-Making-Test-B (TMT-B; P = 0.01). Furthermore, kicer was reduced in patients for whole striatum (P = 0.004) and associative (P = 0.002) and sensorimotor subdivisions (P = 0.007). In patients, whole striatum kicer was negatively correlated with TMT-B (rho = -0.42, P = 0.04; i.e. the lower striatal kicer, the worse the cognitive performance). Mediation analysis showed that striatal kicer mediated the group difference in TMT-B. Results demonstrate that patients with schizophrenia in symptomatic remission of positive symptoms have decreased striatal dopamine synthesis capacity, which mediates the disorder's impact on cognitive difficulties. Data suggest that striatal dopamine dysfunction contributes to cognitive difficulties in schizophrenia.

Cognitive impairment from early to middle adulthood in patients with affective and nonaffective psychotic disorders

BACKGROUND

Cognitive impairment is a core feature of psychotic disorders, but the profile of impairment across adulthood, particularly in African-American populations, remains unclear.

METHODS

Using cross-sectional data from a case-control study of African-American adults with affective (n = 59) and nonaffective (n = 68) psychotic disorders, we examined cognitive functioning between early and middle adulthood (ages 20-60) on measures of general cognitive ability, language, abstract reasoning, processing speed, executive function, verbal memory, and working memory.

RESULTS

Both affective and nonaffective psychosis patients showed substantial and widespread cognitive impairments. However, comparison of cognitive functioning between controls and psychosis groups throughout early (ages 20-40) and middle (ages 40-60) adulthood also revealed age-associated group differences. During early adulthood, the nonaffective psychosis group showed increasing impairments with age on measures of general cognitive ability and executive function, while the affective psychosis group showed increasing impairment on a measure of language ability. Impairments on other cognitive measures remained mostly stable, although decreasing impairments on measures of processing speed, memory and working memory were also observed.

CONCLUSIONS

These findings suggest similarities, but also differences in the profile of cognitive dysfunction in adults with affective and nonaffective psychotic disorders. Both affective and nonaffective patients showed substantial and relatively stable impairments across adulthood. The nonaffective group also showed increasing impairments with age in general and executive functions, and the affective group showed an increasing impairment in verbal functions, possibly suggesting different underlying etiopathogenic mechanisms.

Delay discounting and reward sensitivity in a 2 × 2 study of bipolar disorder and alcohol dependence

BACKGROUND AND AIMS

Separate studies have shown increased delay discounting in people with bipolar disorder (BD) and people with alcohol dependence (AD) relative to people without mental health problems. Delay discounting was compared in people with no mental health problems, AD, BD and AD plus BD. Associations of delay discounting with self-reported impulsivity and reward sensitivity were also assessed.

DESIGN

The study was a two-by-two factorial comparative observational design.

SETTING

Data were collected at baseline diagnostic visits as part of a neuroimaging study at a medical university in South Carolina, USA.

PARTICIPANTS

Twenty-two BD + AD, 33 BD, 28 AD and 27 people without mental health problems participated.

MEASUREMENTS

Diagnostic and clinician-rated symptom measures, self-report questionnaires and a computerized delay discounting task were administered. Two-by-two general linear univariate models were tested to examine between-group differences on discounting rates, and bivariate correlations and hierarchical regression analyses were performed to examine associations between discounting rates and self-reported reward sensitivity and impulsivity.

FINDINGS

There was a significant main effect of AD (P = 0.006, η2  = 0.068). The main effect of BD and the BD × AD interaction terms were non-significant (P ≥ 0.293, η2  ≤ 0.010). Reward sensitivity and impulsivity were not significantly associated with discounting rates after adjustment for the other (P ≥ 0.089).

CONCLUSIONS

People with alcohol dependence appear to have higher delay discounting, while previously found associations between bipolar disorder and delay discounting may be secondary to alcohol use disorder.

Genome-wide association study implicates CHRNA2 in cannabis use disorder

Cannabis is the most frequently used illicit psychoactive substance worldwide; around one in ten users become dependent. The risk for cannabis use disorder (CUD) has a strong genetic component, with twin heritability estimates ranging from 51 to 70%. Here we performed a genome-wide association study of CUD in 2,387 cases and 48,985 controls, followed by replication in 5,501 cases and 301,041 controls. We report a genome-wide significant risk locus for CUD (P = 9.31 × 10^-12) that replicates in an independent population (P_replication = 3.27 × 10^-3, P_{meta-analysis} = 9.09 × 10^-12). The index variant (rs56372821) is a strong expression quantitative trait locus for cholinergic receptor nicotinic α2 subunit (CHRNA2); analyses of the genetically regulated gene expression identified a significant association of CHRNA2 expression with CUD in brain tissue. At the polygenic level, analyses revealed a significant decrease in the risk of CUD with increased load of variants associated with cognitive performance. The results provide biological insights and inform on the genetic architecture of CUD.

Relationship of common variants in CHRNA5 with early-onset schizophrenia and executive function

Altered cholinergic neural transmission is hypothesized to increase susceptibility to cognitive deficits in psychotic disorders such as schizophrenia (SCZ). The nicotinic acetylcholine receptor α5 subunit gene (CHRNA5) is reported to be associated with cognitive function in nicotine-dependent populations and SCZ in non-smoking SCZ patients. Nevertheless, it is still not clear whether the CHRNA5 gene contributes to susceptibility to the cognitive deficits of SCZ without smoking. To further clarify the role of CHRNA5, we designed a two-stage, case-control study to examine the association between CHRNA5 and SCZ and its clinical features adjusted for smoking status in early-onset SCZ patients. A total of 15 tag single nucleotide polymorphisms (SNPs) on CHRNA5 were genotyped in the discovery stage, which included 485 early-onset SCZ patients and 1018 controls, and then, we replicated this association in a confirmatory population of 674 patients and 1886 controls. The rs16969968 SNP was identified as significantly associated with SCZ in both datasets. In addition, the severity of psychotic symptoms and cognitive deficits was assessed using the Positive and Negative Syndrome Scale (PANSS) and the Wisconsin Card Sorting Test (WCST). The rs16969968 SNP was associated with psychotic symptoms in patients and with cognitive function in patients and controls. Our results show that rs16969968 on CHRNA5 is tightly linked to genetic susceptibility, psychotic symptoms and cognitive deficits in SCZ in an early-onset Chinese population, suggesting that CHRNA5 may play an important role in the etiology of SCZ.

Procognitive effects of varenicline in the animal model of schizophrenia depend on α4β2- and α 7-nicotinic acetylcholine receptors

BACKGROUND

Varenicline, a partial agonist of the α4β2 nicotinic acetylcholine receptor (α4β2-nAChR), is currently used to facilitate smoking cessation. Preclinical and clinical studies have suggested that this compound may also be effective in treating cognitive impairments in schizophrenia. However, it is unclear which nicotinic acetylcholine receptor subtypes may be involved because varenicline is not only a partial agonist for α4β2-nAChRs but also a full agonist for α7 nicotinic acetylcholine receptors (α7-nAChRs).

AIM

We investigated the effects of varenicline, compared to the α4β2-nAChR partial agonist TC-2403 and the α7-nAChR full agonist PNU-282987, in a ketamine-based model of schizophrenia-like cognitive deficits on the attentional set-shifting task in rats. The second goal was to elucidate whether the procognitive efficacy of varenicline was due to the compound's action on α4β2-nAChRs or α7-nAChRs.

METHODS

Ketamine was administered to rats for 10 consecutive days and the test was performed 14 days following the last injection. The tested compounds were administered 30 min prior to the attentional set-shifting task.

RESULTS

Varenicline, TC-2403 and PNU-282987 ameliorated ketamine-evoked set-shifting deficits. While the α4β2-nAChR antagonist dihydro-β-erythroidine and the α7-nAChR antagonist methyllycaconitine completely prevented the procognitive actions of TC-2403 and PNU-282987, respectively, varenicline's effect was only partially blocked by any given antagonist. Moreover, the combined treatment with TC-2403 and PNU-282987 more effectively facilitated rats' set-shifting ability than activation of either type of nicotinic acetylcholine receptor alone.

CONCLUSION

The present findings demonstrated that varenicline's actions on both α7-nAChRs and α4β2-nAChRs may be necessary to produce its full procognitive effect in the present experimental setting.

Nicotine improves probabilistic reward learning in wildtype but not alpha7 nAChR null mutants, yet alpha7 nAChR agonists do not improve probabilistic learning

Cognitive impairments, e.g., reward learning, are present in various psychiatric disorders and warrant treatment. Improving reward-related learning could synergistically enhance psychosocial treatments and cognition generally. A critical first step is to understand the mechanisms underlying reward learning. The dopamine system has been implicated in such learning, but less known is how indirect activation of this system may affect reward learning. We determined the role of alpha7 nicotinic acetylcholine receptors (nAChR) on a probabilistic reversal learning task (PRLT) in mice that includes reward and punishment. Male alpha7 knockout (KO), heterozygous (HT), and wildtype (WT) littermate mice (n = 84) were treated with vehicle, 0.03, or 0.3 mg/kg nicotine. Two cohorts of C57BL/6NJ male mice were treated with various alpha7 nAChR ligands, including the full agonists PNU282877 and AR-R-17779, the positive allosteric modulator CCMI, the partial agonist SSR180711, and the antagonist methyllycaconitine. All mice were then tested in the PRLT. Nicotine (0.3 mg/kg) significantly improved initial reward learning in alpha7 WT and HT mice but did not improve learning in KO mice, suggesting an involvement of the alpha7 nAChR in the pro-learning effects of nicotine. Neither alpha7 nAChR treatments (PNU282987, AR-R-17779, CCMI, SSR180711, nor methyllycaconitine) affected mouse PRLT performance however. Nicotine improved reward learning via a mechanism that may include alpha7 nAChRs. This improvement unlikely relied solely on alpha7 nAChRs however, since no alpha7 nAChR ligand improved reward learning in normal mice. Future assessments of the effects of other nAChR subtypes on reward learning are needed.

The effects of cannabidiol (CBD) on cognition and symptoms in outpatients with chronic schizophrenia a randomized placebo controlled trial

RATIONALE

Preliminary evidence suggests that cannabidiol (CBD) may be effective in the treatment of neurodegenerative disorders; however, CBD has never been evaluated for the treatment of cognitive impairments associated with schizophrenia (CIAS).

OBJECTIVE

This study compared the cognitive, symptomatic, and side effects of CBD versus placebo in a clinical trial.

METHODS

This study was a 6-week, randomized, placebo-controlled, parallel group, fixed-dose study of oral CBD (600 mg/day) or placebo augmentation in 36 stable antipsychotic-treated patients diagnosed with chronic schizophrenia. All subjects completed the MATRICS Consensus Cognitive Battery (MCCB) at baseline and at end of 6 weeks of treatment. Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS) at baseline and biweekly.

RESULTS

There was no main effect of time or drug on MCCB Composite score, but a significant drug × time effect was observed (p = 0.02). Post hoc analyses revealed that only placebo-treated subjects improved over time (p = 0.03). There was a significant decrease in PANSS Total scores over time (p < 0. 0001) but there was no significant drug × time interaction (p = 0.18). Side effects were similar between CBD and placebo, with the one exception being sedation, which was more prevalent in the CBD group.

CONCLUSIONS

At the dose studied, CBD augmentation was not associated with an improvement in MCCB or PANSS scores in stable antipsychotic-treated outpatients with schizophrenia. Overall, CBD was well tolerated with no worsening of mood, suicidality, or movement side effects.

TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT00588731.

α7 Nicotinic receptor-modulating agents reverse the hyperdopaminergic tone in the MAM model of schizophrenia

Recent evidence has emerged supporting a role for the cholinergic system in schizophrenia, including the potential of α7 modulators as a treatment strategy. However, preclinical studies to date have relied on studies in normal systems rather than on a validated developmental model of schizophrenia. Furthermore, there have been only few studies on whether orthosteric and allosteric modulators have differential impacts in such models. Thus, we investigated the effects of α7 agonists and positive allosteric modulators (PAMs) on dopamine (DA) neuron activity in the ventral tegmental area (VTA) in the methylazoxymethanol acetate (MAM) developmental disruption model of schizophrenia. Four different drugs were evaluated: PNU282987 (full agonist), SSR180711 (partial agonist) NS1738 (PAM type I) and PNU120596 (PAM type II). PNU120596 increased the number of spontaneously active VTA DA neurons in normal rats. In contrast, PNU282987 and SSR180711 reduced the hyperdopaminergic tone in MAM rats. This appeared to be due to effects on DA afferent regulation, in that PNU282987 or SSR180711 infusion into the ventral hippocampus of MAM rats replicated the decrease in the number of spontaneously active VTA DA neurons. In contrast, infusion of the same drugs into the basolateral amygdala increased the number of spontaneously active VTA DA neurons in normal rats without impacting MAM rats. These data suggest that α7 receptors may represent a promising target in the development of new pharmacological therapies for schizophrenia.

Influence of Venus and Mars in the cognitive sky of schizophrenia. Results from the first-step national FACE-SZ cohort

OBJECTIVES

Sex differences can yield important clues regarding illness pathophysiology and its treatment. Schizophrenia (SZ) has a lower incidence rate, and a better prognosis, in women versus men. The present study investigated the cognitive profiles of both sexes in a large multi-centre sample of community-dwelling SZ patients.

METHOD

544 community-dwelling stable SZ subjects (141 women and 403 men; mean age 34.5±12.1 and 31.6±8.7years, respectively) were tested with a comprehensive battery of neuropsychological tests.

RESULTS

Although community-dwelling SZ men had more risk factors for impaired cognition (including first-generation antipsychotics administration and comorbid addictive disorders), women had lower scores on a wide range of cognitive functions, including current and premorbid intellectual functioning, working memory, semantic memory, non-verbal abstract thinking and aspects of visual exploration. However, women scored higher in tests of processing speed and verbal learning, as well as having a lower verbal learning bias. No sex difference were evident for visuospatial learning abilities, cued verbal recall, sustained attention and tests of executive functions, including cognitive flexibility, verbal abstract thinking, verbal fluency and planning abilities.

CONCLUSION

Sex differences are evident in the cognitive profiles of SZ patients. The impact on daily functioning and prognosis, as well as longitudinal trajectory, should be further investigated in the FACE-SZ follow-up study. Sex differences in cognition have implications for precision-medicine determined therapeutic strategies.

LIMITS

Given the restricted age range of the sample, future research will have to determine cognitive profiles across gender in late onset SZ.

Nicotine self-administration reverses cognitive deficits in a rat model for schizophrenia

High comorbidity between schizophrenia and tobacco addiction has been well established. Explanatory theories include nicotine as a cognitive enhancer ameliorating symptoms of schizophrenia and underlying shared substrates increasing susceptibility to addiction in these individuals. To test these non-mutually exclusive theories, the maternal immune activation (MIA) model was utilized. To this end, pregnant Sprague Dawley rats were subcutaneously injected with a bacterial endotoxin, lipopolysaccharide (0.5 mg/kg), on gestation days 10 and 11. Selective attention and working memory in adult male offspring were subsequently assessed using the latent inhibition and delayed non-matching to sample paradigms both before and after nicotine or saline self-administration. MIA led to deficits in both latent inhibition and delayed non-matching to sample in male offspring. Further, these animals showed a small but significantly increased responding for nicotine during self-administration acquisition, although there was no difference in dose-response effect or in progressive ratio testing. However, nicotine, but not saline self-administration, significantly ameliorated the cognitive deficits induced by MIA. While the male offspring of mothers prenatally exposed to lipopolysaccharide was only slightly more sensitive to the reinforcing effects of nicotine, after self-administration, the MIA-induced cognitive deficits significantly improved. These data lend support for the self-medication hypothesis of schizophrenia.

Analyzing the genes related to nicotine addiction or schizophrenia via a pathway and network based approach

The prevalence of tobacco use in people with schizophrenia is much higher than in general population, which indicates a close relationship between nicotine addiction and schizophrenia. However, the molecular mechanism underlying the high comorbidity of tobacco smoking and schizophrenia remains largely unclear. In this study, we conducted a pathway and network analysis on the genes potentially associated with nicotine addiction or schizophrenia to reveal the functional feature of these genes and their interactions. Of the 276 genes associated with nicotine addiction and 331 genes associated with schizophrenia, 52 genes were shared. From these genes, 12 significantly enriched pathways associated with both diseases were identified. These pathways included those related to synapse function and signaling transduction, and drug addiction. Further, we constructed a nicotine addiction-specific and schizophrenia-specific sub-network, identifying 11 novel candidate genes potentially associated with the two diseases. Finally, we built a schematic molecular network for nicotine addiction and schizophrenia based on the results of pathway and network analysis, providing a systematic view to understand the relationship between these two disorders. Our results illustrated that the biological processes underlying the comorbidity of nicotine addiction and schizophrenia was complex, and was likely induced by the dysfunction of multiple molecules and pathways.

Assessment of the Association Between Cigarette Smoking and Cognitive Performance in Patients With Schizophrenia-Spectrum Disorders: A Case-Control Study

The prevalence of cigarette smoking is significantly higher in patients with schizophrenia compared to the general population. Schizophrenia is also characterized by cognitive impairments that can be detected in the premorbid phase of illness. However, studies addressing the association between cigarette smoking and cognition in patients with psychosis have provided mixed findings. Therefore, the aim of this study was to assess the relationship between tobacco smoking and cognitive performance in patients with schizophrenia. In this case-control study, we recruited 67 inpatients with schizophrenia (34 cigarette smokers) and 62 healthy controls (30 cigarette smokers) at two clinical sites (Wroclaw and Szczecin, Poland). Cognitive performance was examined using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Smoking dependence was determined using the Fagerström Test for Nicotine Dependence (FTND) and the pack-year index. Results show that, after adjustment for potential confounders, smokers with schizophrenia presented significantly lower scores on delayed memory tests compared to non-smokers with schizophrenia (F = 11.07, p = 0.002). In healthy controls, after adjustment for age, sex, and education level, smokers had significantly lower scores in immediate memory (47.1 ± 6.4 vs. 52.0 ± 4.0, F = 11.64, p = 0.001), visuospatial/constructional functions (34.8 ± 3.8 vs. 37.7 ± 1.8, F = 12.86, p = 0.001) and global cognition (177.0 ± 15.7 vs. 191.2 ± 14.0, F = 12.63, p = 0.001) compared to non-smokers. There were no significant correlations between FTND scores or pack-year index and cognitive performance neither in patient nor control group. Our results show that cigarette smoking is related to worse delayed memory performance in schizophrenia patients as well as deficits of immediate memory, visuospatial/constructional functions, and global cognition in controls. Longitudinal studies are required to establish causal interference between smoking and cognition in patients with schizophrenia.

Amino acid and peptide prodrugs of diphenylpropanones positive allosteric modulators of α7 nicotinic receptors with analgesic activity

α7 Nicotinic acetylcholine receptors (nAChRs) are ion channels implicated in a number of CNS pathological processes, including pain and psychiatric, cognitive and inflammatory diseases. Comparing with orthosteric agonism, positive allosteric modulation of these channels constitutes an interesting approach to achieve selectivity versus other nicotinic receptors. We have recently described new chalcones and 1,3-diphenylpropanones as positive allosteric modulators (PAMs) of α7 nAChRs, which proved to have good analgesic activities but poor pharmacokinetic properties. Here we report the preparation of amino acid and peptide derivatives as prodrugs of these modulators with the aim of improving their in vivo biological activity. While the valine derivative showed very short half life in aqueous solutions to be considered a prodrug, Val-Val and Val-Pro-Val are suitable precursors of the parent 1,3-diphenylpropanones, via chemical and enzymatic transformation, respectively. Compounds 19 (Val-Val) and 21 (Val-Pro-Val), prodrugs of the 2',5',4-trihydroxy-1,3-diphenylpropan-1-one 3, showed significant antinociceptive activity in in vivo assays. The best compound, 21, displayed a better profile in the analgesia test than its parent compound 3, exhibiting about the same potency but long-lasting effects.

Attenuation of ketamine-induced impairment in verbal learning and memory in healthy volunteers by the AMPA receptor potentiator PF-04958242

There is a need to develop treatments for cognitive impairment associated with schizophrenia (CIAS). The significant role played by N-methyl-d-aspartate receptors (NMDARs) in both the pathophysiology of schizophrenia and in neuronal plasticity suggests that facilitation of NMDAR function might ameliorate CIAS. One strategy to correct NMDAR hypofunction is to stimulate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) as AMPAR and NMDAR functioning are coupled and interdependent. In rats and nonhuman primates (NHP), AMPAR potentiators reduce spatial working memory deficits caused by the nonselective NMDAR antagonist ketamine. The current study assessed whether the AMPAR potentiator PF-04958242 would attenuate ketamine-induced deficits in verbal learning and memory in humans. Healthy male subjects (n=29) participated in two randomized treatment periods of daily placebo or PF-04958242 for 5 days separated by a washout period. On day 5 of each treatment period, subjects underwent a ketamine infusion for 75 min during which the effects of PF-04958242/placebo were assessed on ketamine-induced: (1) impairments in verbal learning and recall measured by the Hopkins Verbal Learning Test; (2) impairments in working memory on a CogState battery; and (3) psychotomimetic effects measured by the Positive and Negative Syndrome Scale and Clinician-Administered Dissociative Symptoms Scale. PF-04958242 significantly reduced ketamine-induced impairments in immediate recall and the 2-Back and spatial working memory tasks (CogState Battery), without significantly attenuating ketamine-induced psychotomimetic effects. There were no pharmacokinetic interactions between PF-04958242 and ketamine. Furthermore, PF-04958242 was well tolerated. 'High-impact' AMPAR potentiators like PF-04958242 may have a role in the treatment of the cognitive symptoms, but not the positive or negative symptoms, associated with schizophrenia. The excellent concordance between the preclinical (rat, NHP) and human studies with PF-04958242, and in silico modeling of AMPAR-NMDAR interactions in the hippocampus, highlights the translational value of this study.

Targeting neuronal dysfunction in schizophrenia with nicotine: Evidence from neurophysiology to neuroimaging

Patients with schizophrenia self-administer nicotine at rates higher than is self-administered for any other psychiatric illness. Although the reasons are unclear, one hypothesis suggests that nicotine is a form of 'self-medication' in order to restore normal levels of nicotinic signaling and target abnormalities in neuronal function associated with cognitive processes. This brief review discusses evidence from neurophysiological and neuroimaging studies in schizophrenia patients that nicotinic agonists may effectively target dysfunctional neuronal circuits in the illness. Evidence suggests that nicotine significantly modulates a number of these circuits, although relatively few studies have used modern neuroimaging techniques (e.g. functional magnetic resonance imaging (fMRI)) to examine the effects of nicotinic drugs on disease-related neurobiology. The neuronal effects of nicotine and other nicotinic agonists in schizophrenia remain a priority for psychiatry research.

Not All Differences between Patients with Schizophrenia and Healthy Subjects Are Pathological: Performance on the Conners' Continuous Performance Test

OBJECTIVE

This study analyzed attentional performance in patients with schizophrenia during a continuous performance task requiring a high response rate.

METHOD

The Conners' Continuous Performance Test-II (CPT-II) was administered to 64 patients with schizophrenia and 64 healthy comparison subjects. A cross-sectional design was used in order to allow analysis of the means between patients and healthy subjects. Differences in performance were assessed for significance using ANCOVA. Percentiles were also analyzed in order to determine whether a participant showed normal or pathological performance. Pearson's correlation was used to detect possible relationships between attentional performance and psychopathology.

RESULTS

Of the 12 CPT-II measures, response style and slowing of reaction time (RT) between targets increased to similar extents between patients and healthy comparison subjects. Patients performed significantly less well than non-patient group on all other measures. Nevertheless, patient's performance on four of these measures remained within the normal range, and patient's performance on the remaining measures qualified as pathological only in the case of variability in hit RT. No significant correlations between attention performance and symptoms were found.

CONCLUSIONS

These results suggest that although patients may show lower attentional functioning than non-patients on tasks requiring a high response rate, their attentional performance remains within the normal range on most dimensions.

Nicotine ameliorates schizophrenia-like cognitive deficits induced by maternal LPS exposure: a study in rats

Maternal exposure to infectious agents is a predisposing factor for schizophrenia with associated cognitive deficits in offspring. A high incidence of smoking in these individuals in adulthood might be, at least in part, due to the cognitive-enhancing effects of nicotine. Here, we have used prenatal exposure to maternal lipopolysaccharide (LPS, bacterial endotoxin) at different time points as a model for cognitive deficits in schizophrenia to determine whether nicotine reverses any associated impairments. Pregnant rats were treated subcutaneously with LPS (0.5 mg/kg) at one of three neurodevelopmental time periods [gestation days (GD) 10-11, 15-16, 18-19]. Cognitive assessment in male offspring commenced in early adulthood [postnatal day (PND) 60] and included: prepulse inhibition (PPI), latent inhibition (LI) and delayed non-matching to sample (DNMTS). Following PND 100, daily nicotine injections (0.6 mg/kg, subcutaneously) were administered, and animals were re-tested in the same tasks (PND 110). Only maternal LPS exposure early during fetal neurodevelopment (GD 10-11) resulted in deficits in all tests compared to animals that had been prenatally exposed to saline at the same gestational time point. Repeated nicotine treatment led to global (PPI) and selective (LI) improvements in performance. Early but not later prenatal LPS exposure induced consistent deficits in cognitive tests with relevance for schizophrenia. Nicotine reversed the LPS-induced deficits in selective attention (LI) and induced a global enhancement of sensorimotor gating (PPI).

1,3-diphenylpropan-1-ones as allosteric modulators of α7 nACh receptors with analgesic and antioxidant properties

Nicotine acethylcholine receptors (nAChRs) play critical roles in cognitive processes, neuroprotection and inflammation.

RESULTS

According to their substituents, 1,3-diphenylpropan-1-one derivatives act as α7 nAChRs negative allosteric modulators (NAM, OMe) or Type I positive allosteric modulators (PAMs, OH). Compounds 7 and 31 were the most effective (989 and 666% enhancement of ACh-induced currents) and potent (EC50: 12.9 and 6.85 μM) PAMs. They exhibited strong radical scavenging values. Compound 31, selective over other neuronal nAChR subtypes and with acceptable pharmacokinetic profile, showed antinociceptive effects in a model of inflammatory pain.

CONCLUSION

Compound 31 is a novel, potent and selective α7 nAChR PAM, displaying antioxidant and analgesic activities. The 1,3-diphenylpropan-1-one scaffold could be the base toward more advanced type I PAMs for the treatment of nAChR-mediated diseases.

nAChR dysfunction as a common substrate for schizophrenia and comorbid nicotine addiction: Current trends and perspectives

INTRODUCTION

The prevalence of tobacco use in the population with schizophrenia is enormously high. Moreover, nicotine dependence is found to be associated with symptom severity and poor outcome in patients with schizophrenia. The neurobiological mechanisms that explain schizophrenia-nicotine dependence comorbidity are not known. This study systematically reviews the evidence highlighting the contribution of nicotinic acetylcholine receptors (nAChRs) to nicotine abuse in schizophrenia.

METHODS

Electronic data bases (Medline, Google Scholar, and Web of Science) were searched using the selected key words that match the aims set forth for this review. A total of 276 articles were used for the qualitative synthesis of this review.

RESULTS

Substantial evidence from preclinical and clinical studies indicated that dysregulation of α7 and β2-subunit containing nAChRs account for the cognitive and affective symptoms of schizophrenia and nicotine use may represent a strategy to remediate these symptoms. Additionally, recent meta-analyses proposed that early tobacco use may itself increase the risk of developing schizophrenia. Genetic studies demonstrating that nAChR dysfunction that may act as a shared vulnerability factor for comorbid tobacco dependence and schizophrenia were found to support this view. The development of nAChR modulators was considered an effective therapeutic strategy to ameliorate psychiatric symptoms and to promote smoking cessation in schizophrenia patients.

CONCLUSIONS

The relationship between schizophrenia and smoking is complex. While the debate for the self-medication versus addiction vulnerability hypothesis continues, it is widely accepted that a dysfunction in the central nAChRs represent a common substrate for various symptoms of schizophrenia and comorbid nicotine dependence.