Brexpiprazole piperazin-1-yl]butoxy}quinolin-2(1H)-one) is a novel drug candidate in clinical development for psychiatric disorders with high affinity for serotonin, dopamine, and noradrenaline receptors. In particular, it bound with high affinity (K i , 1 nM) to human serotonin 1A (h5-HT 1A )-, h5-HT 2A -, long form of human D 2 (hD 2L )-, ha 1B -, and ha 2C -adrenergic receptors. It displayed partial agonism at h5-HT 1A and hD 2 receptors in cloned receptor systems and potent antagonism of h5-HT 2A receptors and ha 1B/2C -adrenoceptors. Brexpiprazole also had affinity (K i , 5 nM) for hD 3 -, h5-HT 2B -, h5-HT 7 -, ha 1A -, and ha 1D -adrenergic receptors, moderate affinity for hH 1 (K i 5 19 nM), and low affinity for hM 1 receptors (K i . 1000 nM). Brexpiprazole potently bound to rat 5-HT 2A and D 2 receptors in vivo, and ex vivo binding studies further confirmed high 5-HT 1A receptor binding potency. Brexpiprazole inhibited DOI (2,5-dimethoxy-4-iodoamphetamine)-induced head twitches in rats, suggestive of 5-HT 2A antagonism. Furthermore, in vivo D 2 partial agonist activity of brexpiprazole was confirmed by its inhibitory effect on reserpine-induced DOPA accumulation in rats. In rat microdialysis studies, brexpiprazole slightly reduced extracellular dopamine in nucleus accumbens but not in prefrontal cortex, whereas moderate increases of the dopamine metabolites, homovanillic acid and DOPAC (3,4-dihydroxy-phenyl-acetic acid), in these areas also suggested in vivo D 2 partial agonist activity. In particular, based on a lower intrinsic activity at D 2 receptors and higher binding affinities for 5-HT 1A/2A receptors than aripiprazole, brexpiprazole would have a favorable antipsychotic potential without D 2 receptor agonistand antagonist-related adverse effects. In conclusion, brexpiprazole is a serotonin-dopamine activity modulator with a unique pharmacology, which may offer novel treatment options across a broad spectrum of central nervous system disorders.

BACKGROUND AND PURPOSEPhytocannabinoids in Cannabis sativa have diverse pharmacological targets extending beyond cannabinoid receptors and several exert notable anticonvulsant effects. For the first time, we investigated the anticonvulsant profile of the phytocannabinoid cannabidivarin (CBDV) in vitro and in in vivo seizure models. EXPERIMENTAL APPROACHThe effect of CBDV (1-100 mM) on epileptiform local field potentials (LFPs) induced in rat hippocampal brain slices by 4-aminopyridine (4-AP) application or Mg 2+ -free conditions was assessed by in vitro multi-electrode array recordings. Additionally, the anticonvulsant profile of CBDV (50-200 mg·kg -1 ) in vivo was investigated in four rodent seizure models: maximal electroshock (mES) and audiogenic seizures in mice, and pentylenetetrazole (PTZ) and pilocarpine-induced seizures in rats. The effects of CBDV in combination with commonly used antiepileptic drugs on rat seizures were investigated. Finally, the motor side effect profile of CBDV was investigated using static beam and grip strength assays. KEY RESULTS CBDV significantly attenuated status epilepticus-like epileptiform LFPs induced by 4-AP and Mg 2+-free conditions. CBDV had significant anticonvulsant effects on the mES (Ն100 mg·kg ) alone had no effect against pilocarpine-induced seizures, but significantly attenuated these seizures when administered with valproate or phenobarbital at this dose. CBDV had no effect on motor function. CONCLUSIONS AND IMPLICATIONSThese results indicate that CBDV is an effective anticonvulsant in a broad range of seizure models. Also it did not significantly affect normal motor function and, therefore, merits further investigation as a novel anti-epileptic in chronic epilepsy models. LINKED ARTICLESThis article is part of a themed section on Cannabinoids. To view the other articles in this section visit http://dx

Epidermal growth factor (EGF) and its structurally related proteins are implicated in the developmental regulation of various brain neurons, including midbrain dopaminergic neurons. There are EGF and EGF receptor abnormalities in both brain tissues and blood from schizophrenic patients. We administered EGF to neonatal rats to transiently perturb endogenous EGF receptor signaling and evaluated the neurobehavioral consequences. EGF-treatment-induced transient impairment in tyrosine hydroxylase expression. The animals grew normally, exhibited normal weight increase, glial growth, and gross brain structures, and later lost the tyrosine hydroxylase abnormality. During and after development, however, the rats began to display various behavioral abnormalities. Abnormal sensorimotor gating was apparent, as measured by deficits in prepulse inhibition of acoustic startle. Motor activity and social interaction scores of the EGF-treated animals were also impaired in adult rats, though not in earlier developmental stages. In parallel, there was a significant abnormality in dopamine metabolism in the brain stem of the adult animals. Gross learning ability appeared to be normal as measured by active avoidance. These behavioral alterations, which are often present in schizophrenic models, were ameliorated by subchronic treatment with clozapine. Although the molecular and/or physiologic background(s) of these behavioral abnormalities await further investigation, the results of the present experiment indicate that abnormal EGF receptor stimulation given during limited neonatal stages can result in severe and persistent cognitive/behavioral dysfunctions, which appear only in adulthood.

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Epidermal growth factor (EGF) comprises a structurally related family of proteins containing heparin-binding EGF-like growth factor (HB-EGF) and transforming growth factor alpha (TGF␣) that regulates the development of dopaminergic neurons as well as monoamine metabolism. We assessed the contribution of EGF to schizophrenia by measuring EGF family protein levels in postmortem brains and in fresh serum of schizophrenic patients and control subjects. EGF protein levels were decreased in the prefrontal cortex and striatum of schizophrenic patients, whereas the levels of HB-EGF and TGF␣ were not significantly different in any of the regions examined. Conversely, EGF receptor expression was elevated in the prefrontal cortex. Serum EGF levels were markedly reduced in schizophrenic patients, even in young, drug-free patients. Chronic treatment of animals with the antipsychotic drug haloperidol had no influence on EGF levels in the brain or serum. These findings suggest that there is abnormal EGF production in various central and peripheral tissues of patients with both acute and chronic schizophrenia. EGF might thus provide a molecular substrate for the pathologic manifestation of the illness, although additional studies are required to determine a potential link between impaired EGF signaling and the pathology/etiology of schizophrenia.

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Although evidence for mitochondrial dysfunction in the pathogenesis of bipolar disorder (BD) has been reported, the precise biological basis remains unknown, hampering the search for novel biomarkers. In this study, we performed metabolomics of cerebrospinal fluid (CSF) from male BD patients (n=54) and age-matched male healthy controls (n=40). Subsequently, post-mortem brain analyses, genetic analyses, metabolomics of CSF samples from rats treated with lithium or valproic acid were also performed. After multivariate logistic regression, isocitric acid (isocitrate) levels were significantly higher in the CSF from BD patients than healthy controls. Furthermore, gene expression of two subtypes (IDH3A and IDH3B) of isocitrate dehydrogenase (IDH) in the dorsolateral prefrontal cortex from BD patients was significantly lower than that of controls, although the expression of other genes including, aconitase (ACO1, ACO2), IDH1, IDH2 and IDH3G, were not altered. Moreover, protein expression of IDH3A in the cerebellum from BD patients was higher than that of controls. Genetic analyses showed that IDH genes (IDH1, IDH2, IDH3A, IDH3B) and ACO genes (ACO1, ACO2) were not associated with BD. Chronic (4 weeks) treatment with lithium or valproic acid in rats did not alter CSF levels of isocitrate, and mRNA levels of Idh3a, Idh3b, Aco1 and Aco2 genes in the rat brain. These findings suggest that abnormality in the metabolism of isocitrate by IDH3A in the mitochondria plays a key role in the pathogenesis of BD, supporting the mitochondrial dysfunction hypothesis of BD. Therefore, IDH3 in the citric acid cycle could potentially be a novel therapeutic target for BD.

Glutamate, a major excitatory neurotransmitter, plays important roles in synaptic plasticity, such as long-term potentiation (LTP) and new synapse formation. Growing evidence suggests that glutamate signaling is involved in the neurobiology of psychiatric disorders, including schizophrenia, major depressive disorder (MDD) and bipolar disorder (BP). Postmortem brain studies demonstrated altered spine density in brains from patients with these psychiatric disorders, indicating that remodeled neuronal circuits may contribute to the pathobiology of these psychiatric diseases. Drugs targeting the glutamate system have typically attracted attention as they show efficacy in animal studies and potential therapeutic effects in the clinical setting. In particular, the Nmethyl- D-aspartate (NMDA) receptor antagonist, ketamine exerts a rapid and robust antidepressant effect in treatment-resistant patients with MDD and BP, whereas conventional antidepressants require several weeks for therapeutic onset. Animal studies showed that ketamine induced rapid synaptogenesis, suggestive of synaptic plasticity via NMDA receptor signaling being an essential event in the treatment of depression. Therefore, drugs modulating glutamate signaling could also be potential therapeutic drugs for psychiatric disorders. First, we summarize the role of glutamate signaling on dendritic spine formation, maintenance and remodeling. Then, we discuss the abnormalities identified in dendritic spine and glutamate signaling from postmortem brain studies and animal models of psychiatric disorders. Finally, we review the potential benefits of drugs acting on the NMDA receptor in clinical and animal models of psychiatric disorders.