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Prenatal environmental insults increase the risk of neurodevelopmental psychiatric conditions in the offspring. Structural modifications of dendritic spines are central to brain development and plasticity. Using maternal immune activation (MIA) as a rodent model of prenatal environmental insult, previous results have reported dendritic structural deficits in the frontal cortex. However, very little is known about the molecular mechanism underlying MIA-induced synaptic structural alterations in the offspring. Using prenatal (E12.5) injection with polyinosinic-polycytidylic acid potassium salt as a mouse MIA model, we show here that upregulation of the serotonin 5-HT2A receptor (5-HT2AR) is at least in part responsible for some of the effects of prenatal insults on frontal cortex dendritic spine structure and sensorimotor gating processes. Mechanistically, we report that this upregulation of frontal cortex 5-HT2AR expression is associated with MIA-induced reduction of nuclear translocation of the glucocorticoid receptor (GR) and, consequently, a decrease in the enrichment of GR at the 5-HT2AR promoter. The translational significance of these preclinical findings is supported by data in postmortem human brain samples suggesting dysregulation of GR translocation in frontal cortex of schizophrenia subjects. We also found that repeated corticosterone administration augmented frontal cortex 5-HT2AR expression and reduced GR binding to the 5-HT2AR promoter. However, virally (adeno-associated virus) mediated augmentation of GR function reduced frontal cortex 5-HT2AR expression and improved sensorimotor gating processes via 5-HT2AR. Together, these data support a negative regulatory relationship between GR signaling and 5-HT2AR expression in the mouse frontal cortex that may carry implications for the pathophysiology underlying 5-HT2AR dysregulation in neurodevelopmental psychiatric disorders. National Institutes of Health R01MH084894 (to J. G.-M.), R01MH111940 (to J. G.-M.), NIH-N01DA-17-8932 (to P. M. B.), NIH-N01DA-19-8949 (to P. M. B.), and F30MH116550 (to J. M. S.), and Basque Government IT1211-19 (to J. J. M.) participated in the funding of this study. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Schizophrenia is a devastating mental disorder resulting in marked morbidity and mortality despite the optimal use of all currently available interventions. For this reason, the release of lumateperone (CaptylaR), also known as ITI-007, an orally administered, atypical antipsychotic provided a welcome novel tool for clinicians to utilize precision medicine to tailor an optimal treatment plan to the specific needs of each person with schizophrenia. To generate a foundation for clinicians to assess the risks and benefits of lumateperone in relation to other interventions for schizophrenia, we conducted a search of items for ‘ITI-007’ and ‘lumateperone’ on PubMed, ScienceDirect, Web of Science, Google Scholar, and www.clinicaltrials.gov . We present a critical evaluation of the limited information about lumateperone for schizophrenia, its use approved by the US Food and Drug Administration. Lumateperone merits consideration for patients with treatment-resistant schizophrenia and for patients with schizophrenia who are vulnerable to developing metabolic dysfunction and movement disorders. On the other hand, lumateperone should not be used for (a) women who are pregnant or breastfeeding, children, adolescents, and elderly patients with dementia-related psychosis, (b) patients who are at risk for cerebrovascular diseases, (c) patients who use inducers and moderate or strong inhibitors of the cytochrome P450-3A4 (CYP3A4) isozyme, and (d) patients who use alcohol and other sedating agents. Clinical trials from multiple centers without financial conflicts of interest to market lumateperone are needed to directly compare and contrast lumateperone and other antipsychotic agents to generate trustworthy evidence to be assessed objectively by clinicians treating patients with schizophrenia. Future investigations will provide the foundations to identify the evidence for comprehensive evaluations of the role of lumateperone in the treatment of people with schizophrenia and other conditions.

Background Recent studies have shown a relationship between the composition of the maternal diet and acquiring a risk of mental illnesses through changes in the offspring’s brain. This study assessed the role of a modified maternal diet on the levels of serotonin (5-HT)2C and 5-HT2A receptors in the offspring brain. Methods Wistar rat dams during gestation and lactation were maintained either on a standard (SD) or special diets: high-fat (HFD), high-carbohydrate (rich in sucrose, HCD) or mixed (MD). Offspring were weaned to SD after lactation, and at postnatal days (PNDs) 28 and 63 changes in the 5-HT2C and 5-HT2A receptor levels were evaluated in their prefrontal cortex (PFCx), nucleus accumbens (NAc), dorsal striatum (DSTR) and hippocampus (HIP). Results Maternal HFD reduced the expression of 5-HT2C receptors in male rats at PND 28 in the PFCx, NAc, and DSTR but increased it at PND 63 in male animals in the NAc and DSTR. HCD induced a decrease in the expression of 5-HT2C receptors in male offspring at PND 28 but increased it in female rats at PND 63 in the PFCx. MD reduced 5-HT2C receptor expression in males at PND 28 in the PFCx and increased it in male and female offspring at PND 28 in the HIP. Moreover, maternal HFD reduced 5-HT2A receptor levels within the PFCx in adolescent male offspring. Conclusion Our findings indicate that a modified maternal diet induces age- and sex-specific adaptive changes mainly in 5-HT2C receptors, which may contribute to disturbances in the offspring brain. Graphic abstract

Major depressive disorder (MDD) and generalized anxiety disorder (GAD) are severe and difficult-to-treat psychiatric illnesses with high rates of comorbidity. Although both disorders are treated with serotonergic based psychotropic agents, little is known on the influence of the serotonergic neurotransmitter system on the occurrence of comorbid GAD when clinically depressed. To investigate this poorly understood clinical question, we examined the involvement of frontolimbic post-synaptic 5-HT2A receptors in 20 medication-resistant depressed (MRD) patients with half of them diagnosed with comorbid GAD with 123I-5-I-R91150 SPECT. To explore whether 5-HT2A receptor-binding indices (BI) associated with comorbid GAD could be related to distinct psychopathological symptoms, all were assessed with the symptom Checklist-90-Revised (SCL-90-R). MRD patients with comorbid GAD displayed significantly higher 5-HT2A receptor BI in the hippocampal–amygdala complex, compared to MRD patients without GAD. Correlation analyses revealed that the 5-HT2A receptor BI in these areas were significantly related to the SCL-90-R subscale hostility (HOS), especially for those MRD patients with comorbid GAD. Comorbid MRD-GAD may be characterized with increased hippocampal–amygdala 5-HT2A receptor BI which could represent enhanced levels in hostility in such kinds of patients. Adapted psychotherapeutic interventions may be warranted.

Here we review the literature assessing the roles of the brain dopaminergic and serotonergic systems in the modulation of pain as revealed by in vivo human studies using positron emission tomography. In healthy subjects, dopamine D-2/D-3 receptor availability particularly in the striatum and serotonin 5-HT1A and 5-HT2A receptor availabilities in the cortex predict the subject's response to tonic experimental pain. High availability of dopamine D-2/D-3 or serotonin 5-HT2A receptors is associated with high pain intensity, whereas high availability of 5-HT1A receptors associates with low pain intensity. Chronic neuropathic pain is associated with high striatal dopamine D-2/D-3 receptor availability, for which low endogenous dopamine tone is a plausible explanation, although a compensatory increase in striatal dopamine D-2/D-3 receptor density may also contribute. In contrast, chronic musculoskeletal pain is associated with low baseline availability of striatal dopamine D-2/D-3 receptors. In healthy subjects, brain serotonin 5-HT1A as well as dopamine D-2/D-3 receptor availabilities associate with the subject's response criterion rather than the capacity to discriminate painful thermal stimuli suggesting that these neurotransmitter systems act mainly on non-sensory rather than sensory factors of thermally induced pain experience. Additionally, 5-HT1A receptor availability predicts the subject's discriminative ability but not response criterion for non-painful tactile test stimuli, while no such correlation is observed with dopamine D-2/D-3 receptors. These findings suggest that dopamine acting on striatal dopamine D-2/D-3 receptors and serotonin acting on cortical 5-HT1A and 5-HT2A receptors contribute to top-down pain regulation in humans.

G protein-coupled receptors (GPCRs) were assumed to exist and function in the plasma membrane as monomeric proteins that became activated by binding of one agonist ligand to one receptor molecule (Bourne et al., 1990). However, although previous findings based on rather indirect measures such as radioligand binding had suggested a direct interaction of two receptors with each other (Limbird et al., 1975; Ferre et al., 1991), it was the application of a protein-protein interaction assay by bioluminescence resonance energy transfer (BRET) that revealed the phenomenon of molecular proximity between beta2-adrenergic receptors in living cells (Angers et al., 2000). Since then, this topic has been a major subject of research and numerous in silico and in vitro studies have suggested expression of family A GPCRs as homodimers and higher-order homomers in heterologous expression systems. However, the demonstration that reconstitution of a single beta2-adrenergic receptor molecule into lipoprotein particles leads to efficient activation of G proteins raised concerns about the functional significance of family A GPCR homomers (Whorton et al., 2007), and this is currently a controversial topic (for an extensive review on GPCR homodimers/homomers, see Milligan, 2013; see also Bouvier and Hebert, 2014; Lambert and Javitch, 2014). Another fundamental yet relatively independent question is that related to expression of different GPCR subtypes as heteromers. It is well accepted that the family C GABAB receptor needs two protomers (GABAB-R1 and GABAB-R2) to reach the plasma membrane as a functional dimeric receptor (Jones et al., 1998; Kaupmann et al., 1998; White et al., 1998). On the other hand, although multiple lines of evidence indicate that family A GPCR heteromers may exist, particularly in tissue cultures (Gonzalez-Maeso, 2011; Ferre et al., 2014), only relatively recent studies started to test this formulation in whole animal models.

The effects of 3-week treatment with a typical antipsychotic drug chlorpromazine and three atypical antipsychotic drugs (risperidone, olanzapine and perospirone) on the binding to dopamine D2 and serotonin 5-HT2A receptors were examined in the rat striatum and frontal cortex, respectively. Subchronic treatment with chlorpromazine (10 mg/kg) and perospirone (1 mg/kg) significantly increased D2 receptors, while no increase was observed with lower dose of chlorpromazine (5 mg/kg), perospirone (0.1 mg/kg), risperidone (0.25, 0.5 mg/kg) or olanzapine (1, 2 mg/kg). On the other hand, 3-week administration of chlorpromazine (5, 10 mg/kg) and olanzapine (1, 2 mg/kg) significantly decreased 5-HT2A receptors, but risperidone (0.25, 0.5 mg/kg) or perospirone (0.1, 1 mg/kg) had no effect. The measurement of in vivo drug occupation for D2 and 5-HT2A receptors using N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) suggested that high occupation of 5-HT2A receptors with lower D2 receptor occupancy might be involved in the absence of up-regulation of D2 receptors after subchronic treatment with some atypical antipsychotic drugs.

Rationale Schizophrenia remains among the most prevalent neuropsychiatric disorders, and current treatment options are accompanied by unwanted side effects. New treatments that better address core features of the disease with minimal side effects are needed. Objectives As a new therapeutic approach, 1-(4-fluoro-phenyl)-4-((6bR, 10aS)-3-methyl-2,3,6b,9,10,10a-hexahydro-1H,7H-pyrido[3′,4′:4,5]pyrrolo[1,2,3-de]quinoxalin-8-yl)-butan-1-one (ITI-007) is currently in human clinical trials for the treatment of schizophrenia. Here, we characterize the preclinical functional activity of ITI-007. Results ITI-007 is a potent 5-HT2A receptor ligand (Ki = 0.5 nM) with strong affinity for dopamine (DA) D2 receptors (Ki = 32 nM) and the serotonin transporter (SERT) (Ki = 62 nM) but negligible binding to receptors (e.g., H1 histaminergic, 5-HT2C, and muscarinic) associated with cognitive and metabolic side effects of antipsychotic drugs. In vivo it is a 5-HT2A antagonist, blocking (±)-2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI)-induced headtwitch in mice with an inhibitory dose 50 (ID50) = 0.09 mg/kg, per oral (p.o.), and has dual properties at D2 receptors, acting as a postsynaptic D2 receptor antagonist to block D-amphetamine hydrochloride (D-AMPH) hyperlocomotion (ID50 = 0.95 mg/kg, p.o.), yet acting as a partial agonist at presynaptic striatal D2 receptors in assays measuring striatal DA neurotransmission. Further, in microdialysis studies, this compound significantly and preferentially enhances mesocortical DA release. At doses relevant for antipsychotic activity in rodents, ITI-007 has no demonstrable cataleptogenic activity. ITI-007 indirectly modulates glutamatergic neurotransmission by increasing phosphorylation of GluN2B-type N-methyl-d-aspartate (NMDA) receptors and preferentially increases phosphorylation of glycogen synthase kinase 3β (GSK-3β) in mesolimbic/mesocortical dopamine systems. Conclusion The combination of in vitro and in vivo activities of this compound support its development for the treatment of schizophrenia and other psychiatric and neurologic disorders.