Antipsychotic-like effects of a novel phosphodiesterase 10A inhibitor MT-3014 in rats

Group I mGluRs positive allosteric modulators improved schizophrenia-related behavioral and molecular deficits in the Poly I:C rat model

RATIONALE

Maternal polyinosinic-polycytidylic acid (Poly I:C) exposure leads to an increase in various proinflammatory cytokines and causes schizophrenia-like symptoms in offspring. In recent years, group I metabotropic glutamate receptors (mGluRs) have emerged as a potential target in the pathophysiology of schizophrenia.

OBJECTIVES

The aim of our study was to investigate the behavioral and molecular changes by using the mGlu1 receptor positive allosteric modulator (PAM) agent RO 67-7476, and the negative allosteric modulator (NAM) agent JNJ 16259685 and the mGlu5 receptor PAM agent VU-29, and NAM agent fenobam in the Poly I:C-induced schizophrenia model in rats.

METHODS

Female Wistar albino rats were treated with Poly I:C on day 14 of gestation after mating. On the postnatal day (PND) 35, 56 and 84, behavioral tests were performed in the male offspring. On the PND84, brain tissue was collected and the level of proinflammatory cytokines was determined by ELISA method.

RESULTS

Poly I:C caused impairments in all behavioral tests and increased the levels of proinflammatory cytokines. While PAM agents caused significant improvements in prepulse inhibition (PPI), novel object recognition (NOR), spontaneous alternation and reference memory tests, they brought the levels of proinflammatory cytokines closer to the control group. NAM agents were ineffective on behavioral tests. It was observed that PAM agents significantly improved Poly I:C-induced disruption in behavioral and molecular analyses.

CONCLUSIONS

These results suggest that PAM agents, particularly the mGlu5 receptor VU-29, are also promising and could be a potential target in schizophrenia.

Vortioxetine improved negative and cognitive symptoms of schizophrenia in subchronic MK-801 model in rats

Schizophrenia is a devastating psychiatric disorder with complex symptoms and neurobiology. Serotonergic dysregulation is known to contribute to the pathogenesis of schizophrenia although dopaminergic and glutamatergic systems are thought to have central roles in neurobiology. No significant success can be achieved in the treatment of negative and cognitive symptoms while positive symptoms can be significantly reduced with current pharmacotherapy. Vortioxetine is a new multimodal antidepressant with 5-HT1A agonism, 5-HT1B partial agonism, 5-HT3, 5-HT7, and 5-HT1D antagonism, and serotonin reuptake inhibition. A limited number of studies suggest its therapeutic effect on the negative and cognitive symptoms of schizophrenia. Therefore, we investigated the potential beneficial effects of vortioxetine on behavioral and molecular deficits in the MK-801 model of schizophrenia in rats. Female Wistar albino rats (10-12 weeks) were grouped as saline, MK-801 (0.2 mg/kg), MK-801 + vortioxetine (2.5 mg/kg), MK-801 + vortioxetine (5 mg/kg), MK-801 + vortioxetine (10 mg/kg), MK-801 + risperidone (0.3 mg/kg), MK-801 + haloperidol (1 mg/kg) (n = 8 in each group). MK-801 has been daily administered (i.p.) for 14 days. Vortioxetine and antipsychotic treatments were injected for 21 days after a washout period of MK-801 and locomotor activity (LA), social interaction (SI), novel object recognition (NOR), Y-maze and prepulse inhibition (PPI) tests were performed at the 16-20th days of treatments, respectively. ELISA test was conducted to evaluate molecular analyses. MK-801 decreased PPI (%), social behaviors, and discrimination index in NOR and alternation (%) in the Y-maze test. In NOR and Y-maze tests, especially vortioxetine 5 and 10 mg/kg increased discrimination index and alternation (%) compared to MK-801. In addition, vortioxetine administration increased social behaviors. Moreover, MK-801 decreased GAD67 and parvalbumin levels while vortioxetine increased these protein levels compared to MK-801. Herein, we first suggested a potential therapeutic effect of vortioxetine, a new multimodal antidepressant, on negative and cognitive symptoms and neurobiological deficits including GAD67 and parvalbumin low expression in the MK-801 model in rats. It would be beneficial to confirm our results in different rodent models and to shed light on the possible mechanisms underlying these effects.

Phosphodiesterase inhibitors in psychiatric disorders

RATIONALE

Challenges in drug development for psychiatric disorders have left much room for the introduction of novel treatments with better therapeutic efficacies and indices. As a result, intense research has focused on identifying new targets for developing such pharmacotherapies. One of these targets may be the phosphodiesterase (PDE) class of enzymes, which play important roles in intracellular signaling. Due to their critical roles in cellular pathways, these enzymes affect diverse neurobiological functions from learning and memory formation to neuroinflammation.

OBJECTIVES

In this paper, we reviewed studies on the use of PDE inhibitors (PDEIs) in preclinical models and clinical trials of psychiatric disorders including depression, anxiety, schizophrenia, post-traumatic stress disorder (PTSD), bipolar disorder (BP), sexual dysfunction, and feeding disorders.

RESULTS

PDEIs are able to improve symptoms of psychiatric disorders in preclinical models through activating the cAMP-PKA-CREB and cGMP-PKG pathways, attenuating neuroinflammation and oxidative stress, and stimulating neural plasticity. The most promising therapeutic candidates to emerge from these preclinical studies are PDE2 and PDE4 inhibitors for depression and anxiety and PDE1 and PDE10 inhibitors for schizophrenia. Furthermore, PDE3 and 4 inhibitors have shown promising results in clinical trials in patients with depression and schizophrenia.

CONCLUSIONS

Larger and better designed clinical studies of PDEIs in schizophrenia, depression, and anxiety are warranted to facilitate their translation into the clinic. Regarding the other conditions discussed in this review (most notably PTSD and BP), better characterization of the effects of PDEIs in preclinical models is required before clinical studies.

Cognitive Deficit in Schizophrenia: From Etiology to Novel Treatments

Schizophrenia is a major mental illness characterized by positive and negative symptoms, and by cognitive deficit. Although cognitive impairment is disabling for patients, it has been largely neglected in the treatment of schizophrenia. There are several reasons for this lack of treatments for cognitive deficit, but the complexity of its etiology-in which neuroanatomic, biochemical and genetic factors concur-has contributed to the lack of effective treatments. In the last few years, there have been several attempts to develop novel drugs for the treatment of cognitive impairment in schizophrenia. Despite these efforts, little progress has been made. The latest findings point to the importance of developing personalized treatments for schizophrenia which enhance neuroplasticity, and of combining pharmacological treatments with non-pharmacological measures.

Papaverine ameliorates prenatal alcohol-induced experimental attention deficit hyperactivity disorder by regulating neuronal function, inflammation, and oxidative stress

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder with complex aetiology and phenotypes. Phosphodiesterase10A (PDE10A) has been shown to provide benefits in various brain conditions. We investigated the role of papaverine, a selective PDE10A inhibitor on core phenotypes in prenatal alcohol exposure (PAE) model of ADHD. In order to identify probable mechanisms involved, the effects on several protein markers of neuronal function such as, neuronal survival-BDNF, neuronal transcription factor-pCREB, brain inflammation (IL-6, IL-10, and TNF-α), and brain oxidative stress (TBARS and GSH) were studied in frontal cortex, cerebellum, and striatum. PAE resulting hyper-locomotion, inattention, and anxiety were studied by the use of open-field, y-maze, and elevated plus maze, respectively. Administration of papaverine (15/30 mg kg-1 ) to PAE group of animals resulted in amelioration of hyperactivity, inattention, and anxiety. Also, papaverine resulted in significant increase of the levels in BDNF, pCREB, IL-10, and GSH along with significant decrease of TNF-α, IL-6, and TBARS in different brain areas of PAE group. Papaverine, a selective PDE10A inhibitor rectified behavioural phenotypes associated with ADHD, possibly by altering the protein markers associated with neuronal survival, neuronal transcription factor, brain inflammation, and brain oxidative stress. Implicating PDE10A as a possible target for furthering our understanding of ADHD phenotypes.