Different effects of Bifeprunox, Aripiprazole, and Haloperidol on body weight gain, food and water intake, and locomotor activity in rats

Dopamine D2-like receptors on conditioned and unconditioned fear: A systematic review of rodent pharmacological studies

Growing evidence supports dopamine's role in aversive states, yet systematic reviews focusing on dopamine receptors in defensive behaviors are lacking. This study presents a systematic review of the literature examining the influence of drugs acting on dopamine D2-like receptors on unconditioned and conditioned fear in rodents. The review reveals a predominant use of adult male rats in the studies, with limited inclusion of female rodents. Commonly employed tests include the elevated plus maze and auditory-cued fear conditioning. The findings indicate that systemic administration of D2-like drugs has a notable impact on both innate and learned aversive states. Generally, antagonists tend to increase unconditioned fear, while agonists decrease it. Moreover, both agonists and antagonists typically reduce conditioned fear. These effects are attributed to the involvement of distinct neural circuits in these states. The observed increase in unconditioned fear induced by D2-like antagonists aligns with dopamine's role in suppressing midbrain-mediated responses. Conversely, the reduction in conditioned fear is likely a result of blocking dopamine activity in the mesolimbic pathway. The study highlights the need for future research to delve into sex differences, explore alternative testing paradigms, and identify specific neural substrates. Such investigations have the potential to advance our understanding of the neurobiology of aversive states and enhance the therapeutic application of dopaminergic agents.

Role of Anonychium africanum (Plantae, Fabaceae) in Metal Oxido-Inflammatory Response: Protection Evidence in Gonad of Male Albino Rat

Male fertility is strongly affected by the overexpression of free radicals induced by heavy metals. The aim of this study was to evaluate the potential antioxidant, anti-inflammatory, and gonado-protective effects of natural compounds. Biochemical and morphological assays were performed on male albino rats divided into five groups: a control group (water only), a group orally exposed to a metal mixture of Pb-Cd-Hg-As alone and three groups co-administered the metal mixture and an aqueous extract of the Nigerian medicinal plant, Anonychium africanum (Prosopis africana, PA), at three different concentrations (500, 1000, and 1500 mg/kg) for 60 days. The metal mixture induced a significant rise in testicular weight, metal bioaccumulation, oxidative stress, and pro-inflammatory and apoptotic markers, while the semen analysis indicated a lower viability and a decrease in normal sperm count, and plasma reproductive hormones showed a significant variation. Parallel phytochemical investigations showed that PA has bioactive compounds like phlobatannins, flavonoids, polyphenols, tannins, saponins, steroids, and alkaloids, which are protective against oxidative injury in neural tissues. Indeed, the presence of PA co-administered with the metal mixture mitigated the toxic metals' impact, which was determined by observing the oxido-inflammatory response via nuclear factor erythroid 2-related factor 2, thus boosting male reproductive health.

Haloperidol and aripiprazole impact on the BDNF and glucocorticoid receptor levels in the rat hippocampus and prefrontal cortex: effect of the chronic mild stress

Objective. Changes in the brain derived neurotrophic factor (BDNF) and glucocorticoid receptor (GR) expression in the prefrontal cortex (PFC) and hippocampus (HIP) are associated with psychiatric diseases and stress response. Chronic mild stress (CMS) may alter BDNF as well as GR levels in both the PFC and the HIP. The aim of the present study was to find out whether chronic treatment with a typical antipsychotic haloperidol (HAL) and an atypical antipsychotic aripiprazole (ARI) may modify the CMS effect on the BDNF and GR expression in the above-mentioned structures. Methods. The rats were exposed to CMS for 3 weeks and from the 7^th day of CMS injected with vehicle (VEH), HAL (1 mg/kg) or ARI (10 mg/kg) for 4 weeks. BDNF and GR mRNA levels were established in the PFC and the HIP by Real Time PCR, whereas, PFC and HIP samples were obtained by punching them from 500 µm thick frozen sections. C-Fos immunoreactivity was analyzed in the PFC and the HIP on 30 µm thick paraformaldehyde fixed sections. Weight gain and corticosterone (CORT) levels were also measured. Results. The CMS and HAL suppressed the BDNF and GR mRNA levels in the PFC. In the HIP, CMS elevated BDNF mRNA levels that were suppressed by HAL and ARI treatments. The CMS decreased the c-Fos immunoreactivity in the PFC in both HAL- and ARI-treated animals. In the HIP, HAL increased the c-Fos immunoreactivity that was again diminished in animals exposed to CMS. Stressed animals gained markedly less weight until the 7^th day of CMS, however, later their weight gain did not differ from the unstressed ones or was even higher in CMS+HAL group. Un-stressed HAL and ARI animals gained less weight than the VEH ones. Neither CMS nor HAL/ARI affected the plasma CORT levels. Conclusion. The present data indicate that HAL and ARI in the doses 1 mg/kg or 10 mg/kg, respectively, does not modify the effect of the CMS preconditioning on the BDNF and GR mRNA levels in the PFC or the HIP. However, HAL seems to modify the CMS effect on the HIP activation.

Effect on Body Weight and Adipose Tissue by Cariprazine: A Head-to-Head Comparison Study to Olanzapine and Aripiprazole in Rats

Cariprazine (Car) is a recently approved second generation antipsychotic (SGA) with unique pharmacodynamic profile, being a partial agonist at both dopamine D2/3 receptor subtypes, with almost 10 times greater affinity towards D3. SGAs are known to increase body weight, alter serum lipids, and stimulate adipogenesis but so far, limited information about the adverse effects is available with this drug. In order to study this new SGA with such a unique mechanism of action, we compared Car to substances that are considered references and are well characterized: olanzapine (Ola) and aripiprazole (Ari). We studied the effects on body weight and also assessed the adipogenesis in rats. The drugs were self-administered in two different doses to female, adult, Wistar rats for six weeks. Weekly body weight change, vacuole size of adipocytes, Sterol Regulatory Element Binding Protein-1 (SREBP-1) and Uncoupling Protein-1 (UCP-1) expression were measured from the visceral adipose tissue (AT). The adipocyte’s vacuole size, and UCP-1 expression were increased while body weight gain was diminished by Car. by increasing UCP-1 might stimulate the thermogenesis, that could potentially explain the weight gain lowering effect through enhanced lipolysis.

Role of dopamine D1-like and D2-like receptors in the activation of ingestive behaviour in thirsty rats licking for water

RATIONALE

Analysis of lick pattern for sucrose and NaCl and of the forced swimming response after dopamine antagonist administration led us to suggest that dopamine on D₁-like receptors is involved in behavioural activation, and the level of activation is "reboosted" on the basis of an evaluation process involving D₂-like receptors. Although some studies investigated licking microstructure for water after dopamine antagonists, the within-session time course of their effect was never investigated.

OBJECTIVES

The aims of this study were to further investigate the role of dopamine receptors in the mechanisms governing water ingestion, focussing on the within-session time course of the microstructure parameters, and to test the proposed hypothesis.

MATERIALS AND METHODS

The effects of the dopamine D₁-like receptor antagonist SCH 23390 (0.01-0.04 mg/kg) and of the dopamine D₂-like receptor antagonist raclopride (0.025-0.25 mg/kg) on licking microstructure for water were examined in 20-h water-deprived rats in 30-min sessions.

RESULTS

As previously observed with sucrose and NaCl, SCH 23390 reduced licking by reducing burst number, suggesting reduced behavioural activation. Moreover, it resulted in an increased burst size. Raclopride reduced the size of licking bursts, while their number was either increased or decreased depending on the dose.

CONCLUSION

The results support the suggestion that D₁ receptors are involved in behavioural activation and D₂ receptors are involved in a related evaluation process. Within the framework of the proposed hypothesis, the increased burst size after D₁-like receptor blockade might be interpreted as a pro-hedonic effect consequent to the increased cost of the activation of the licking response.

Aripiprazole-induced adverse metabolic alterations in polyI:C neurodevelopmental model of schizophrenia in rats

Schizophrenia appears to be linked to higher incidence of metabolic syndrome even in the absence of antipsychotic treatment. Atypical antipsychotics substantially differ in their propensity to induce metabolic alterations. Aripiprazole is considered to represent an antipsychotic drug with low risk of metabolic syndrome development. The aim of this study was to evaluate metabolic phenotype of neurodevelopmental polyI:C rat model and assess metabolic effects of chronic aripiprazole treatment with regard to complex neuroendocrine regulations of energy homeostasis. Polyinosinic:polycytidylic acid (polyI:C) was administered subcutaneously at a dose of 8 mg/kg in 10 ml on gestational day 15 to female Wistar rats. For this study 20 polyI:C and 20 control adult male offspring were used, randomly divided into 2 groups per 10 animals for chronic aripiprazole treatment and vehicle. Aripiprazole (5 mg/kg, dissolved tablets, ABILIFY^®) was administered once daily via oral gavage for a month. Altered lipid profile in polyI:C model was observed and a trend towards different dynamics of weight gain in polyI:C rats was noted in the absence of significant antipsychotic treatment effect. PolyI:C model was not associated with changes in other parameters i.e. adipokines, gastrointestinal hormones and cytokines levels. Aripiprazole did not influence body weight but it induced alterations in neurohumoral regulations. Leptin and GLP-1 serum levels were significantly reduced, while ghrelin level was elevated. Furthermore aripiprazole decreased serum levels of pro-inflammatory cytokines. Our data indicate dysregulation of adipokines and gastrointestinal hormones present after chronic treatment with aripiprazole which is considered metabolically neutral in the polyI:C model of schizophrenia.

Effects of short- and long-term aripiprazole treatment on Group I mGluRs in the nucleus accumbens: Comparison with haloperidol

The D2 receptor partial agonist, aripiprazole, has shown increased therapeutic efficacy for schizophrenia, autism and Tourette's syndrome compared to traditional antipsychotics such as the D2 receptor antagonist, haloperidol. Recent evidence suggests this superior profile may be associated with downstream effects on glutamatergic synapses. Group 1 metabotropic glutamate receptors (mGluRs) and their endogenous modulators, Norbin and Homer1, are regulated by D2 receptor activity, particularly within the nucleus accumbens (NAc), a target region of aripiprazole and haloperidol. This study sought to evaluate the effects of aripiprazole on Group 1 mGluRs, Norbin and Homer1 in the NAc, in comparison to haloperidol. Sprague-Dawley rats were orally administered daily doses of aripiprazole (2.25mg/kg), haloperidol (0.3mg/kg) or vehicle for 1 or 10-weeks. Immunoblot analyses revealed Group 1 mGluR protein levels were not altered following 1-week and 10-week aripiprazole or haloperidol treatment, compared to vehicle treated rodents. However, 1-week aripiprazole and haloperidol treatment significantly elevated Homer1a and Norbin protein expression, respectively. After 10 weeks of treatment, aripiprazole, but not haloperidol, significantly increased Norbin expression. These findings indicate the antipsychotics, aripiprazole and haloperidol, exert differential temporal effects on Norbin and Homer1 expression that may have consequences on synaptic glutamatergic transmission underlying their therapeutic profile.

Antipsychotic Drugs: From Receptor-binding Profiles to Metabolic Side Effects

BACKGROUND

Antipsychotic-induced metabolic side effects are major concerns in psychopharmacology and clinical psychiatry. Their pathogenetic mechanisms are still not elucidated.

METHODS

Herein, we review the impact of neurotransmitters on metabolic regulation, providing insights into antipsychotic-induced metabolic side effects.

RESULTS

Antipsychotic drugs seem to interfere with feeding behaviors and energy balance, processes that control metabolic regulation. Reward and energy balance centers in central nervous system constitute the central level of metabolic regulation. The peripheral level consists of skeletal muscles, the liver, the pancreas, the adipose tissue and neuroendocrine connections. Neurotransmitter receptors have crucial roles in metabolic regulation and they are also targets of antipsychotic drugs. Interaction of antipsychotics with neurotransmitters could have both protective and harmful effects on metabolism.

CONCLUSION

Emerging evidence suggests that antipsychotics have different liabilities to induce obesity, diabetes and dyslipidemia. However this diversity cannot be explained merely by drugs'pharmacodynamic profiles, highlighting the need for further research.

Aripiprazole, A Drug that Displays Partial Agonism and Functional Selectivity

BACKGROUND

The treatment of schizophrenia is challenging due to the wide range of symptoms (positive, negative, cognitive) associated with the disease. Typical antipsychotics that antagonize D2 receptors are effective in treating positive symptoms, but extrapyramidal side-effects (EPS) are a common occurrence. Atypical antipsychotics targeting 5-HT2A and D2 receptors are more effective at treating cognitive and negative symptoms compared to typical antipsychotics, but these drugs also result in side-effects such as metabolic syndromes.

OBJECTIVE

To identify evidence in the literature that elucidates the pharmacological profile of aripiprazole.s.

METHODS

We searched PubMed for peer reviewed articles on aripiprazole and its clinical efficacy, side-effects, pharmacology, and effects in animal models of schizophrenia symptoms.

RESULTS

Aripiprazole is a newer atypical antipsychotic that displays a unique pharmacological profile, including partial D2 agonism and functionally selective properties. Aripiprazole is effective at treating the positive symptoms of schizophrenia and has the potential to treat negative and cognitive symptoms at least as well as other atypical antipsychotics. The drug has a favorable side-effect profile and has a low propensity to result in EPS or metabolic syndromes. Animal models of schizophrenia have been used to determine the efficacy of aripiprazole in symptom management. In these instances, aripiprazole resulted in the reversal of deficits in extinction, pre-pulse inhibition, and social withdrawal. Because aripiprazole requires a greater than 90% occupancy rate at D2 receptors to be clinically active and does not produce EPS, this suggests a functionally selective effect on intracellular signaling pathways.

CONCLUSION

A combination of factors such as dopamine system stabilization via partial agonism, functional selectivity at D2 receptors, and serotonin-dopamine system interaction may contribute to the ability of aripiprazole to successfully manage schizophrenia symptoms. This review examines these mechanisms of action to further clarify the pharmacological actions of aripiprazole.

Chronic administration of aripiprazole activates GSK3β-dependent signalling pathways, and up-regulates GABAA receptor expression and CREB1 activity in rats

Aripiprazole is a D2-like receptor (D2R) partial agonist with a favourable clinical profile. Previous investigations indicated that acute and short-term administration of aripiprazole had effects on PKA activity, GSK3β-dependent pathways, GABAA receptors, NMDA receptor and CREB1 in the brain. Since antipsychotics are used chronically in clinics, the present study investigated the long-term effects of chronic oral aripiprazole treatment on these cellular signalling pathways, in comparison with haloperidol (a D2R antagonist) and bifeprunox (a potent D2R partial agonist). We found that the Akt-GSK3β pathway was activated by aripiprazole and bifeprunox in the prefrontal cortex; NMDA NR2A levels were reduced by aripiprazole and haloperidol. In the nucleus accumbens, all three drugs increased Akt-GSK3β signalling; in addition, both aripiprazole and haloperidol, but not bifeprunox, increased the expression of Dvl-3, β-catenin and GABAA receptors, NMDA receptor subunits, as well as CREB1 phosphorylation levels. The results suggest that chronic oral administration of aripiprazole affects schizophrenia-related cellular signalling pathways and markers (including Akt-GSK3β signalling, Dvl-GSK3β-β-catenin signalling, GABAA receptor, NMDA receptor and CREB1) in a brain-region-dependent manner; the selective effects of aripiprazole on these signalling pathways might be associated with its unique clinical effects.

Atypical antipsychotics and effects on feeding: from mice to men

RATIONALE

So-called atypical antipsychotics (AAPs) are associated with varying levels of weight gain and associated metabolic disturbances, which in patients with serious mental illness (SMI) have been linked to non-compliance and poor functional outcomes. Mechanisms underlying AAP-induced metabolic abnormalities are only partially understood. Antipsychotic-induced weight gain may occur as a result of increases in food intake and/or changes in feeding.

OBJECTIVE

In this review, we examine the available human and preclinical literature addressing AAP-related changes in feeding behavior, to determine whether changes in appetite and perturbations in regulation of food intake could be contributing factors to antipsychotic-induced weight gain.

RESULTS

In general, human studies point to disruption by AAPs of feeding behaviors and food consumption. In rodents, increases in cumulative food intake are mainly observed in females; however, changes in feeding microstructure or motivational aspects of food intake appear to occur independent of sex.

CONCLUSIONS

The findings from this review indicate that the varying levels of AAP-related weight gain reflect changes in both appetite and feeding behaviors, which differ by type of AAP. However, inconsistencies exist among the studies (both human and rodent) that may reflect considerable differences in study design and methodology. Future studies examining underlying mechanisms of antipsychotic-induced weight gain are recommended in order to develop strategies addressing the serious metabolic side effect of AAPs.

Aripiprazole Increases the PKA Signalling and Expression of the GABAA Receptor and CREB1 in the Nucleus Accumbens of Rats

The GABAA receptor is implicated in the pathophysiology of schizophrenia and regulated by PKA signalling. Current antipsychotics bind with D2-like receptors, but not the GABAA receptor. The cAMP-responsive element-binding protein 1 (CREB1) is also associated with PKA signalling and may be related to the positive symptoms of schizophrenia. This study investigated the effects of antipsychotics in modulating D2-mediated PKA signalling and its downstream GABAA receptors and CREB1. Rats were treated orally with aripiprazole (0.75 mg/kg, ter in die (t.i.d.)), bifeprunox (0.8 mg/kg, t.i.d.), haloperidol (0.1 mg/kg, t.i.d.) or vehicle for 1 week. The levels of PKA-Cα and p-PKA in the prefrontal cortex (PFC), nucleus accumbens (NAc) and caudate putamen (CPu) were detected by Western blots. The mRNA levels of Gabrb1, Gabrb2, Gabrb3 and Creb1, and their protein expression were measured by qRT-PCR and Western blots, respectively. Aripiprazole elevated the levels of p-PKA and the ratio of p-PKA/PKA in the NAc, but not the PFC and CPu. Correlated with this elevated PKA signalling, aripiprazole elevated the mRNA and protein expression of the GABAA (β-1) receptor and CREB1 in the NAc. While haloperidol elevated the levels of p-PKA and the ratio of p-PKA/PKA in both NAc and CPu, it only tended to increase the expression of the GABAA (β-1) receptor and CREB1 in the NAc, but not the CPu. Bifeprunox had no effects on PKA signalling in these brain regions. These results suggest that aripiprazole has selective effects on upregulating the GABAA (β-1) receptor and CREB1 in the NAc, probably via activating PKA signalling.

Aripiprazole and Haloperidol Activate GSK3β-Dependent Signalling Pathway Differentially in Various Brain Regions of Rats

Aripiprazole, a dopamine D₂ receptor (D₂R) partial agonist, possesses a unique clinical profile. Glycogen synthase kinase 3β (GSK3β)-dependent signalling pathways have been implicated in the pathophysiology of schizophrenia and antipsychotic drug actions. The present study examined whether aripiprazole differentially affects the GSK3β-dependent signalling pathways in the prefrontal cortex (PFC), nucleus accumbens (NAc), and caudate putamen (CPu), in comparison with haloperidol (a D₂R antagonist) and bifeprunox (a D₂R partial agonist). Rats were orally administrated aripiprazole (0.75 mg/kg), bifeprunox (0.8 mg/kg), haloperidol (0.1 mg/kg) or vehicle three times per day for one week. The levels of protein kinase B (Akt), p-Akt, GSK3β, p-GSK3β, dishevelled (Dvl)-3, and β-catenin were measured by Western Blots. Aripiprazole increased GSK3β phosphorylation in the PFC and NAc, respectively, while haloperidol elevated it in the NAc only. However, Akt activity was not changed by any of these drugs. Additionally, both aripiprazole and haloperidol, but not bifeprunox, increased the expression of Dvl-3 and β-catenin in the NAc. The present study suggests that activation of GSK3β phosphorylation in the PFC and NAc may be involved in the clinical profile of aripiprazole; additionally, aripiprazole can increase GSK3β phosphorylation via the Dvl-GSK3β-β-catenin signalling pathway in the NAc, probably due to its relatively low intrinsic activity at D₂Rs.

Brexpiprazole: so far so good

This article describes the role of a newly approved antipsychotic agent brexpiprazole in the treatment of schizophrenia and major depressive disorder. This drug has high affinity for 5-HT1A, 5-HT2A, D2 and α1B,2C receptors. It displays partial agonism at 5-HT1A and D2 receptors and potent antagonism at 5-HT2A and α1B,2C adrenergic receptors. It also has some affinity (antagonism) for D3, 5-HT2B, 5-HT7 and α1A,1D receptors, and moderate affinity for H1 and low affinity for M1 receptors. These all lead to a favorable antipsychotic profile in terms of improvement of cognitive performance and sleep patterns, as well as effects on affective states and potential to treat core symptoms in schizophrenia and major depressive disorder, including cognitive deficits with a low risk of adverse effects (extrapyramidal symptoms, metabolic complications, weight gain, akathisia potential) that are commonly encountered with other typical and second-generation antipsychotic drugs. In our review, we have made an attempt to decipher the pharmacological profile of brexpiprazole from two major trials (VECTOR and BEACON). We have also tried to give a concise but detailed overview of brexpiprazole by head to head comparison of the pharmacological profile of brexpiprazole and its earlier congeners aripiprazole and prototype antipsychotic drug chlorpromazine by accessing individual summaries of product characteristics from the US Food and Drug Administration database, 2015. Relevant preclinical and clinical studies associated with this drug have been discussed with emphasis on efficacy and safety concerns. From the studies done so far, it can be concluded that brexpiprazole can be an effective monotherapy for schizophrenia and as an adjunct to other antidepressant medications in major depressive disorder.

Toxicity assessment due to sub-chronic exposure to individual and mixtures of four toxic heavy metals

Humans are exposed to a cocktail of heavy metal toxicants in the environment. Though heavy metals are deleterious, there is a paucity of information on toxicity of low dose mixtures. In this study, lead (Pb) (0.01mg/L), mercury (Hg) (0.001mg/L), cadmium (Cd) (0.005mg/L) and arsenic (As) (0.01mg/L) were administered individually and as mixtures to 10 groups of 40 three-week old mice (20 males and 20 females), for 120 days. The study established that low dose exposures induced toxicity to the brain, liver, and kidney of mice. Metal mixtures showed higher toxicities compared to individual metals, as exposure to low dose Pb+Hg+Cd reduced brain weight and induced structural lesions, such as neuronal degeneration in 30-days. Pb+Hg+Cd and Pb+Hg+As+Cd exposure induced hepatocellular injury to mice evidenced by decreased antioxidant activities with marginal increases in MDA. These were accentuated by increases in ALT, AST and ALP. Interactions in metal mixtures were basically synergistic in nature and exposure to Pb+Hg+As+Cd induced renal tubular necrosis in kidneys of mice. This study underlines the importance of elucidating the toxicity of low dose metal mixtures so as to protect public health.

Update on the Mechanism of Action of Aripiprazole: Translational Insights into Antipsychotic Strategies Beyond Dopamine Receptor Antagonism

Dopamine partial agonism and functional selectivity have been innovative strategies in the pharmacological treatment of schizophrenia and mood disorders and have shifted the concept of dopamine modulation beyond the established approach of dopamine D2 receptor (D2R) antagonism. Despite the fact that aripiprazole was introduced in therapy more than 12 years ago, many questions are still unresolved regarding the complexity of the effects of this agent on signal transduction and intracellular pathways, in part linked to its pleiotropic receptor profile. The complexity of the mechanism of action has progressively shifted the conceptualization of this agent from partial agonism to functional selectivity. From the induction of early genes to modulation of scaffolding proteins and activation of transcription factors, aripiprazole has been shown to affect multiple cellular pathways and several cortical and subcortical neurotransmitter circuitries. Growing evidence shows that, beyond the consequences of D2R occupancy, aripiprazole has a unique neurobiology among available antipsychotics. The effect of chronic administration of aripiprazole on D2R affinity state and number has been especially highlighted, with relevant translational implications for long-term treatment of psychosis. The hypothesized effects of aripiprazole on cell-protective mechanisms and neurite growth, as well as the differential effects on intracellular pathways [i.e. extracellular signal-regulated kinase (ERK)] compared with full D2R antagonists, suggest further exploration of these targets by novel and future biased ligand compounds. This review aims to recapitulate the main neurobiological effects of aripiprazole and discuss the potential implications for upcoming improvements in schizophrenia therapy based on dopamine modulation beyond D2R antagonism.