Prefrontal allopregnanolone synergizes with D1 receptor activation to disrupt sensorimotor gating in male Sprague-Dawley rats.

RATIONALE: The prepulse inhibition (PPI) of the startle reflex is the best-established index of sensorimotor gating. We documented that the neurosteroid allopregnanolone (AP) is necessary to reduce PPI in response to D1 dopamine receptor agonists. Since Sprague-Dawley (SD) rats are poorly sensitive to the PPI-disrupting effects of these drugs, we hypothesized that AP might increase this susceptibility. OBJECTIVES: We tested whether AP is sufficient to increase the vulnerability of SD rats to PPI deficits in response to the D1 receptor full agonist SKF82958. METHODS: SD rats were tested for PPI after treatment with SKF82958 (0.05-0.3 mg/kg, SC) in combination with either intraperitoneal (1-10 mg/kg) or intracerebral (0.5 µg/µl/side) AP administration into the medial prefrontal cortex (mPFC) or nucleus accumbens shell. To rule out potential confounds, we measured whether SKF82958 affected the endogenous mPFC levels of AP. RESULTS: SD rats exhibited marked PPI deficits in response to the combination of systemic and intra-mPFC AP with SKF82958 but not with the D2 receptor agonist quinpirole (0.3-0.6 mg/kg, SC). SKF82958 did not elevate mPFC levels of AP but enhanced the content of its precursor progesterone. The PPI deficits caused by SKF82958 in combination with AP were opposed by the AP antagonist isoallopregnanolone (10 mg/kg, IP) and the glutamate NMDA receptor positive modulator CIQ (5 mg/kg, IP). CONCLUSION: These results suggest that AP enables the detrimental effects of D1 receptor activation on sensorimotor gating. AP antagonism or glutamatergic modulation counters these effects and may have therapeutic potential for neuropsychiatric disorders characterized by gating deficits.

Acquisition and expression of fat conditioned flavor preferences following dopamine D1, opioid and NMDA receptor antagonism in C57BL/6 mice.

Objectives: Inbred mouse strains differ in the pharmacology mediating sugar and fat intake and conditioned flavor preferences (CFP). C57BL/6, BALB/c and SWR inbred mice are differentially sensitive to dopamine (DA) D1, opioid and muscarinic receptor antagonism of sucrose, saccharin or fat intake, and to DA, opioid, muscarinic and N-methyl-D-aspartate (NMDA) receptor antagonism of acquisition of sucrose-CFP. DA D1, opioid and NMDA receptor antagonists differentially alter fat (Intralipid)-CFP in BALB/c and SWR mice. The present study examined whether naltrexone, SCH23390 or MK-801 altered acquisition and expression of Intralipid-CFP in C57BL/6 mice.Methods: In acquisition, groups of male food-restricted C57BL/6 mice received vehicle, naltrexone (1, 5 mg/kg), SCH23390 (50, 200 nmol/kg) or MK-801 (100, 200 µg/kg) before 10 training sessions in which mice alternately consumed two novel-flavored 5% (CS+) and 0.5% (CS-) Intralipid solutions. Six two-bottle CS choice tests followed with both flavors mixed in 0.5% Intralipid without injections. In expression, C57BL/6 mice underwent the 10 training sessions without injections followed by two-bottle CS choice tests 30 min following vehicle, naltrexone (1, 5 mg/kg), SCH23390 (200, 800 nmol/kg) or MK-801 (100, 200 µg/kg).Results: Fat-CFP acquisition in C57BL/6 mice was significantly though marginally reduced following naltrexone, SCH23390 and MK-801. Fat-CFP expression was similarly reduced by naltrexone, SCH23390 and MK-801 in C57BL/6 mice. Discussion: C57BL/6 mice were more sensitive to DA D1, opioid and NMDA antagonists in the expression of fat-CFP relative to sugar-CFP, but were less sensitive to DA D1 and NMDA antagonists in the acquisition of fat-CFP relative to sugar-CFP.

PHA-680626 Is an Effective Inhibitor of the Interaction between Aurora-A and N-Myc.

Neuroblastoma is a severe childhood disease, accounting for ~10% of all infant cancers. The amplification of the MYCN gene, coding for the N-Myc transcription factor, is an essential marker correlated with tumor progression and poor prognosis. In neuroblastoma cells, the mitotic kinase Aurora-A (AURKA), also frequently overexpressed in cancer, prevents N-Myc degradation by directly binding to a highly conserved N-Myc region. As a result, elevated levels of N-Myc are observed. During recent years, it has been demonstrated that some ATP competitive inhibitors of AURKA also cause essential conformational changes in the structure of the activation loop of the kinase that prevents N-Myc binding, thus impairing the formation of the AURKA/N-Myc complex. In this study, starting from a screening of crystal structures of AURKA in complexes with known inhibitors, we identified additional compounds affecting the conformation of the kinase activation loop. We assessed the ability of such compounds to disrupt the interaction between AURKA and N-Myc in vitro, using Surface Plasmon Resonance competition assays, and in tumor cell lines overexpressing MYCN, by performing Proximity Ligation Assays. Finally, their effects on N-Myc cellular levels and cell viability were investigated. Our results identify PHA-680626 as an amphosteric inhibitor both in vitro and in MYCN overexpressing cell lines, thus expanding the repertoire of known conformational disrupting inhibitors of the AURKA/N-Myc complex and confirming that altering the conformation of the activation loop of AURKA with a small molecule is an effective strategy to destabilize the AURKA/N-Myc interaction in neuroblastoma cancer cells.

Repurposing cancer drugs identifies kenpaullone which ameliorates pathologic pain in preclinical models via normalization of inhibitory neurotransmission.

Inhibitory GABA-ergic neurotransmission is fundamental for the adult vertebrate central nervous system and requires low chloride concentration in neurons, maintained by KCC2, a neuroprotective ion transporter that extrudes intracellular neuronal chloride. To identify Kcc2 gene expression­enhancing compounds, we screened 1057 cell growth-regulating compounds in cultured primary cortical neurons. We identified kenpaullone (KP), which enhanced Kcc2/KCC2 expression and function in cultured rodent and human neurons by inhibiting GSK3ß. KP effectively reduced pathologic pain-like behavior in mouse models of nerve injury and bone cancer. In a nerve-injury pain model, KP restored Kcc2 expression and GABA-evoked chloride reversal potential in the spinal cord dorsal horn. Delta-catenin, a phosphorylation-target of GSK3ß in neurons, activated the Kcc2 promoter via KAISO transcription factor. Transient spinal over-expression of delta-catenin mimicked KP analgesia. Our findings of a newly repurposed compound and a novel, genetically-encoded mechanism that each enhance Kcc2 gene expression enable us to re-normalize disrupted inhibitory neurotransmission through genetic re-programming.

Molecular Docking and Virtual Screening Based Prediction of Drugs for COVID-19.

AIMS: To predict potential drugs for COVID-19 by using molecular docking for virtual screening of drugs approved for other clinical applications. BACKGROUND: SARS-CoV-2 is the betacoronavirus responsible for the COVID-19 pandemic. It was listed as a potential global health threat by the WHO due to high mortality, high basic reproduction number, and lack of clinically approved drugs and vaccines. The genome of the virus responsible for COVID-19 has been sequenced. In addition, the three-dimensional structure of the main protease has been determined experimentally. OBJECTIVE: To identify potential drugs that can be repurposed for treatment of COVID-19 by using molecular docking based virtual screening of all approved drugs. METHODS: A list of drugs approved for clinical use was obtained from the SuperDRUG2 database. The structure of the target in the apo form, as well as structures of several target-ligand complexes, were obtained from RCSB PDB. The structure of SARS-CoV-2 Mpro determined from X-ray diffraction data was used as the target. Data regarding drugs in clinical trials for COVID-19 was obtained from clinicaltrials.org. Input for molecular docking based virtual screening was prepared by using Obabel and customized python, bash, and awk scripts. Molecular docking calculations were carried out with Vina and SMINA, and the docked conformations were analyzed and visualized with PLIP, Pymol, and Rasmol. RESULTS: Among the drugs that are being tested in clinical trials for COVID-19, Danoprevir and Darunavir were predicted to have the highest binding affinity for the Main protease (Mpro) target of SARS-CoV-2. Saquinavir and Beclabuvir were identified as the best novel candidates for COVID-19 therapy by using Virtual Screening of drugs approved for other clinical indications. CONCLUSION: Protease inhibitors approved for treatment of other viral diseases have the potential to be repurposed for treatment of COVID-19.

Involvement of Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 3 in Oxytocin Neuronal Activity in Lactating Rats With Pup Deprivation.

Oxytocin, a hypothalamic neuropeptide essential for breastfeeding, is mainly produced in oxytocin neurons in the supraoptic nucleus (SON) and paraventricular nucleus. However, mechanisms underlying oxytocin secretion, specifically the involvement of hyperpolarization-activated cyclic nucleotide-gated channel 3 (HCN3) in oxytocin neuronal activity, remain unclear. Using a rat model of intermittent and continuous pup deprivation (PD) at the middle stage of lactation, we analyzed the contribution of HCN3 in oxytocin receptor (OTR)-associated signaling cascade to oxytocin neuronal activity in the SON. PD caused maternal depression, anxiety, milk shortage, involution of the mammary glands, and delays in uterine recovery, particularly in continuous PD. PD increased hypothalamic but not plasma oxytocin levels in enzyme-linked immunosorbent assay. In the SON, PD increased c-Fos expression but reduced expressions of cyclooxygenase-2 and HCN3 in Western blots and/or immunohistochemistry. Moreover, PD significantly increased the molecular association of OTR with HCN3 in coimmunoprecipitation. In brain slices, inhibition of HCN3 activity with DK-AH269 blocked prostaglandin E2-evoked increase in the firing activity and burst discharge in oxytocin neurons in patch-clamp recordings. In addition, oxytocin-evoked increase in the molecular association between OTR and HCN3 in brain slices of the SON was blocked by pretreatment with indomethacin, an inhibitor of cyclooxygenase-2. These results indicate that normal activity of oxytocin neurons is under the regulation of an oxytocin receptor-cyclooxygenase-2-HCN3 pathway and that PD disrupts maternal behavior through increasing intranuclear oxytocin secretion in the SON but likely reducing bolus oxytocin release into the blood through inhibition of HCN3 activity.

Antidepressant-Like Effect of ß-Lactolin, a Glycine-Threonine-Tryptophan-Tyrosine Peptide.

The number of patients with mental illnesses, including depression, is rapidly increasing, and daily lifestyle is closely associated with the development of symptoms. Consequently, corrective measures, such as diet-based treatment for diseases, are receiving great attention. We previously showed that ß-lactolin, a ß-lactopeptide of glycine-threonine-tryptophan-tyrosine peptide, inhibits monoamine oxidase and improves memory impairment in mice, but the effects on depression have not been investigated. Here we showed that ß-lactolin improved depression-like behavior via dopamine-D1-like receptor. Orally administered ß-lactolin reduced immobility time in tail suspension test (TST). Pretreatment with SCH23390, dopamine D1-like receptor antagonist, attenuated the reduction in TST by ß-lactolin. These effects were observed by the treatment with whey digest rich in ß-lactolin. In addition, ß-lactolin increased the levels of dopamine in the frontal cortex associated with the depression-like behavior. The present study suggests that supplements or nutraceutical compounds in whey digests (such as ß-lactolin) show antidepressant-like effect.

Pregabalin increases food intake through dopaminergic systems in the hypothalamus.

Pregabalin is useful for treating neuropathic pain, but known to increase body weight as a side effect. To investigate the mechanism of this increase in body weight, we focused on dopamine in the lateral hypothalamus (LH) and examined the effects of pregabalin on dopamine levels in the LH and food intake. The dopamine levels in the LH was gradually decreased during fasting. When the animals were fed, dopamine levels in the LH was significantly increased, indicating that dopamine levels in the LH reflects energy state. The systemic injection of pregabalin tended to decrease dopamine levels in the LH after feeding. The dopamine levels in the LH was also significantly increased by glucose injection, which was inhibited by pregabalin. These results suggest that pregabalin inhibits dopaminergic function in the LH, which might increase food intake. To make these points clear, we examined the effects of pregabalin on food intake and blood glucose levels. Pregabalin significantly increased food intake, whereas pregabalin did not affect blood glucose levels. These results indicate that pregabalin stimulates feeding behavior, but not glucose metabolism. Moreover, the non-selective dopamine receptor antagonist cis-(Z)-flupenthixol injected into the LH significantly increased food intake, though neither the dopamine D1 receptor antagonist SCH 23390 nor the D2 receptor antagonist l-sulpiride injected into the LH affected food intake. These results indicate that the inhibition of dopaminergic function in the LH increases food intake. In conclusion, the present results suggest that pregabalin increases food intake through the inhibition of dopaminergic functions in the LH.

AURKA Suppresses Leukemic THP-1 Cell Differentiation through Inhibition of the KDM6B Pathway.

Aberrations in histone modifications are being studied in mixed-lineage leukemia (MLL)-AF9-driven acute myeloid leukemia (AML). In this study, we focused on the regulation of the differentiation of the MLL-AF9 type AML cell line THP-1. We observed that, upon phorbol 12-myristate 13-acetate (PMA) treatment, THP-1 cells differentiated into monocytes by down-regulating Aurora kinase A (AURKA), resulting in a reduction in H3S10 phosphorylation. We revealed that the AURKA inhibitor alisertib accelerates the expression of the H3K27 demethylase KDM6B, thereby dissociating AURKA and YY1 from the KDM6B promoter region. Using Flow cytometry, we found that alisertib induces THP-1 differentiation into monocytes. Furthermore, we found that treatment with the KDM6B inhibitor GSK-J4 perturbed the PMA-mediated differentiation of THP-1 cells. Thus, we discovered the mechanism of AURKA-KDM6B signaling that controls the differentiation of THP-1 cells, which has implications for biotherapy for leukemia.

Repeated shock stress facilitates basolateral amygdala synaptic plasticity through decreased cAMP-specific phosphodiesterase type IV (PDE4) expression.

Previous studies have shown that exposure to stressful events can enhance fear memory and anxiety-like behavior as well as increase synaptic plasticity in the rat basolateral amygdala (BLA). We have evidence that repeated unpredictable shock stress (USS) elicits a long-lasting increase in anxiety-like behavior in rats, but the cellular mechanisms mediating this response remain unclear. Evidence from recent morphological studies suggests that alterations in the dendritic arbor or spine density of BLA principal neurons may underlie stress-induced anxiety behavior. Recently, we have shown that the induction of long-term potentiation (LTP) in BLA principal neurons is dependent on activation of postsynaptic D1 dopamine receptors and the subsequent activation of the cyclic adenosine 5'-monophosphate (cAMP)-protein kinase A (PKA) signaling cascade. Here, we have used in vitro whole-cell patch-clamp recording from BLA principal neurons to investigate the long-term consequences of USS on their morphological properties and synaptic plasticity. We provided evidence that the enhanced anxiety-like behavior in response to USS was not associated with any significant change in the morphological properties of BLA principal neurons, but was associated with a changed frequency dependence of synaptic plasticity, lowered LTP induction threshold, and reduced expression of phosphodiesterase type 4 enzymes (PDE4s). Furthermore, pharmacological inhibition of PDE4 activity with rolipram mimics the effects of chronic stress on LTP induction threshold and baseline startle. Our results provide the first evidence that stress both enhances anxiety-like behavior and facilitates synaptic plasticity in the amygdala through a common mechanism of PDE4-mediated disinhibition of cAMP-PKA signaling.

Effect of tolvaptan on renal handling of water and sodium, GFR and central hemodynamics in autosomal dominant polycystic kidney disease during inhibition of the nitric oxide system: a randomized, placebo-controlled, double blind, crossover study.

BACKGROUND: Tolvaptan slows progression of autosomal dominant polycystic kidney disease (ADPKD) by antagonizing the vasopressin-cAMP axis. Nitric oxide (NO) stimulates natriuresis and diuresis, but its role is unknown during tolvaptan treatment in ADPKD. METHODS: Eighteen patients with ADPKD received tolvaptan 60 mg or placebo in a randomized, placebo-controlled, double blind, crossover study. L-NMMA (L-NG-monomethyl-arginine) was given as a bolus followed by continuous infusion during 60 min. We measured: GFR, urine output (UO), free water clearance (CH2O), fractional excretion of sodium (FENa), urinary excretion of aquaporin-2 channels (u-AQP2) and epithelial sodium channels (u-ENaCγ), plasma concentrations of vasopressin (p-AVP), renin (PRC), angiotensinII (p-AngII), aldosterone (p-Aldo), and central blood pressure (cBP). RESULTS: During tolvaptan with NO-inhibition, a more pronounced decrease was measured in UO, CH2O (61% vs 43%) and FENa (46% vs 41%) after placebo than after tolvaptan; GFR and u-AQP2 decreased to the same extent; p-AVP increased three fold, whereas u-ENaCγ, PRC, p-AngII, and p-Aldo remained unchanged. After NO-inhibition, GFR increased after placebo and remained unchanged after tolvaptan (5% vs -6%). Central diastolic BP (CDBP) increased to a higher level after placebo than tolvaptan. Body weight fell during tolvaptan treatment. CONCLUSIONS: During NO inhibition, tolvaptan antagonized both the antidiuretic and the antinatriuretic effect of L-NMMA, partly via an AVP-dependent mechanism. U-AQP2 was not changed by tolvaptan, presumeably due to a counteracting effect of elevated p-AVP. The reduced GFR during tolvaptan most likely is caused by the reduction in extracellular fluid volume and blood pressure. TRIAL REGISTRATION: Clinical Trial no: NCT02527863 . Registered 18 February 2015.

Distinct Roles of Dopamine Receptors in the Lateral Thalamus in a Rat Model of Decisional Impulsivity.

The thalamus and central dopamine signaling have been shown to play important roles in high-level cognitive processes including impulsivity. However, little is known about the role of dopamine receptors in the thalamus in decisional impulsivity. In the present study, rats were tested using a delay discounting task and divided into three groups: high impulsivity (HI), medium impulsivity (MI), and low impulsivity (LI). Subsequent in vivo voxel-based magnetic resonance imaging revealed that the HI rats displayed a markedly reduced density of gray matter in the lateral thalamus compared with the LI rats. In the MI rats, the dopamine D1 receptor antagonist SCH23390 or the D2 receptor antagonist eticlopride was microinjected into the lateral thalamus. SCH23390 significantly decreased their choice of a large, delayed reward and increased their omission of lever presses. In contrast, eticlopride increased the choice of a large, delayed reward but had no effect on the omissions. Together, our results indicate that the lateral thalamus is involved in decisional impulsivity, and dopamine D1 and D2 receptors in the lateral thalamus have distinct effects on decisional impulsive behaviors in rats. These results provide a new insight into the dopamine signaling in the lateral thalamus in decisional impulsivity.

Acupuncture Attenuated Vascular Dementia-Induced Hippocampal Long-Term Potentiation Impairments via Activation of D1/D5 Receptors.

BACKGROUND AND PURPOSE: Emerging evidence suggests that acupuncture could improve cognitive impairment in vascular dementia by enhancing synaptic plasticity in the hippocampus. The purpose of this study is to investigate whether dopamine, a key mediator of synaptic plasticity, is involved in this cognitive improvement. METHODS: Vascular dementia model was established by bilateral common carotid arteries occlusion in male Wistar rats. Three days after the operation, animals received acupuncture treatment for 2 weeks, once daily. The D1/D5 receptors antagonist SCH23390 was administered intraperitoneally 15 minutes before each acupuncture treatment. Morris water maze was examined after acupuncture. Long-term potentiation was studied by an electrophysiological technique. Dopamine and metabolites levels were detected by microdialysis and high-performance liquid chromatography from brain tissue. The expression of D1R and D5R was analyzed by immunofluorescence. RESULTS: Acupuncture remarkably reversed cognitive deficits in 2-vessel occlusion model (2VO) rats, and the acupuncture points Zusanli (ST36) and Baihui (GV20) were confirmed to be the most effective combination. Electrophysiological recording data showed that 2VO-induced impairments of long-term potentiation were prevented by acupuncture. In addition, acupuncture promoted the release of dopamine and its major metabolites in the hippocampus of 2VO rats. The immunofluorescence experiment showed that the decrease of D1R and D5R in hippocampal dentate gyrus region of 2VO rats was reversed by acupuncture. Furthermore, we found that the effects of acupuncture against 2VO-induced impairments in cognition and synaptic plasticity were abolished by SCH23390. CONCLUSIONS: Improvement in cognition and hippocampal synaptic plasticity induced by acupuncture was achieved via activation of D1/D5 receptors in 2VO rats.

5-HT2C Agonists Modulate Schizophrenia-Like Behaviors in Mice.

All FDA-approved antipsychotic drugs (APDs) target primarily dopamine D2 or serotonin (5-HT2A) receptors, or both; however, these medications are not universally effective, they may produce undesirable side effects, and provide only partial amelioration of negative and cognitive symptoms. The heterogeneity of pharmacological responses in schizophrenic patients suggests that additional drug targets may be effective in improving aspects of this syndrome. Recent evidence suggests that 5-HT2C receptors may be a promising target for schizophrenia since their activation reduces mesolimbic nigrostriatal dopamine release (which conveys antipsychotic action), they are expressed almost exclusively in CNS, and have weight-loss-promoting capabilities. A difficulty in developing 5-HT2C agonists is that most ligands also possess 5-HT2B and/or 5-HT2A activities. We have developed selective 5-HT2C ligands and herein describe their preclinical effectiveness for treating schizophrenia-like behaviors. JJ-3-45, JJ-3-42, and JJ-5-34 reduced amphetamine-stimulated hyperlocomotion, restored amphetamine-disrupted prepulse inhibition, improved social behavior, and novel object recognition memory in NMDA receptor hypofunctioning NR1-knockdown mice, and were essentially devoid of catalepsy. However, they decreased motivation in a breakpoint assay and did not promote reversal learning in MK-801-treated mice. Somewhat similar effects were observed with lorcaserin, a 5-HT2C agonist with potent 5-HT2B and 5-HT2A agonist activities, which is approved for treating obesity. Microdialysis studies revealed that both JJ-3-42 and lorcaserin reduced dopamine efflux in the infralimbic cortex, while only JJ-3-42 decreased it in striatum. Collectively, these results provide additional evidence that 5-HT2C receptors are suitable drug targets with fewer side effects, greater therapeutic selectivity, and enhanced efficacy for treating schizophrenia and related disorders than current APDs.

Nucleus accumbens dopamine receptors mediate hypothalamus-induced antinociception in the rat formalin test.

BACKGROUND: Lateral hypothalamus (LH) involves in modulation of tonic pain. Regarding the direct and indirect neural connections between the LH and nucleus accumbens (NAc), we aimed to examine the pain modulatory role of NAc dopamine receptors in modulation of LH-induced analgesia in the formalin test. METHODS: Vehicle-control groups received saline or DMSO into the NAc and saline into the LH. Carbachol-control groups received carbachol (250 nmol/L) into the LH, 5 min after saline or DMSO injection into the NAc. In treatment groups, intra-NAc administration of SCH-23390 or sulpiride (D1-and D2-like dopamine receptor antagonists, respectively) was performed 5 min before carbachol injection. Formalin test was done in all rats 5 min after the second injection. RESULTS: The blockade of NAc dopamine receptors reduced carbachol-induced antinociception during both phases of formalin test and reduction in LH-induced analgesia during the late phase was more than that during the early phase. Furthermore, contribution of D2-like dopamine receptors to mediation of anti-hyperalgesic effect of carbachol was greater than that of D1-like dopamine receptors during the late phase. CONCLUSIONS: The findings suggest that LH-VTA-NAc circuit is contributed to the modulation of formalin-induced pain. These findings demonstrate that transmission at D1- and D2-like dopamine receptors mediates the LH-induced analgesia. SIGNIFICANCE: Blockade of accumbal dopamine receptors attenuated analgesia induced by carbachol injection into the lateral hypothalamus during both phases of formalin test. Effect of blockade of D1- and D2-like dopamine receptors on reduction in antinociception was more during the late phase. Contribution of D2-like dopamine receptors to mediation of antinociception during the late phase was greater than the early phase.

Dorsal striatum D1-expressing neurons are involved with sensorimotor gating on prepulse inhibition test.

Prepulse inhibition (PPI) is a behavioral test in which the startle reflex response to a high-intensity stimulus (pulse) is inhibited by the prior presentation of a weak stimulus (prepulse). The classic neural circuitry that mediates startle response is localized in the brainstem; however, recent studies point to the contribution of structures involved in higher cognitive functions in regulating the sensorimotor gating, particularly forebrain regions innervated by dopaminergic nuclei. The aim of the present study was to verify the role of dorsal striatum (DS) and dopaminergic transmitting mediated by D1 and D2 receptors on PPI test in rats. DS inactivation induced by muscimol injection did not affect PPI (%PPI and startle response), although it impaired the locomotor activity and caused catalepsy. Infusion of D1-like antagonist SCH23390 impaired %PPI but did not disturb the startle response and locomotor activity evaluated immediately after PPI test. D2 antagonist microinjection (sulpiride) did not affect %PPI and startle response, but impaired motor activity. These results point to an important role of DS, probably mediated by direct basal ganglia pathway, on modulation of sensorimotor gating, in accordance with clinical studies showing PPI deficits in schizophrenia, Tourette syndrome, and compulsive disorders - pathologies related to basal ganglia dysfunctions.

Dopamine is Required for Activity-Dependent Amplification of Arc mRNA in Developing Postnatal Frontal Cortex.

The activity-regulated gene Arc/Arg3.1 encodes a postsynaptic protein crucially involved in glutamatergic synaptic plasticity. Genetic mutations in Arc pathway and altered Arc expression in human frontal cortex have been associated with schizophrenia. Although Arc expression has been reported to vary with age, what mechanisms regulate Arc mRNA levels in frontal cortex during postnatal development remains unclear. Using quantitative mRNA analysis of mouse frontal cortical tissues, we mapped the developmental profiles of Arc expression and found that its mRNA levels are sharply amplified near the end of the second postnatal week, when mouse pups open their eyes for the first time after birth. Surprisingly, electrical stimulation of the frontal cortex before eye-opening is not sufficient to drive the amplification of Arc mRNA. Instead, this amplification needs both electrical stimulation and dopamine D1-type receptor (D1R) activation. Furthermore, visual stimuli-driven amplification of Arc mRNA is also dependent on D1R activation and dopamine neurons located in the ventral midbrain. These results indicate that dopamine is required to drive activity-dependent amplification of Arc mRNA in the developing postnatal frontal cortex and suggest that joint electrical and dopaminergic activation is essential to establish the normal expression pattern of a schizophrenia-associated gene during frontal cortical development.

Dual Impact of Tolvaptan on Intracellular and Extracellular Water in Chronic Kidney Disease Patients with Fluid Retention.

Objective Tolvaptan, an oral selective V2-receptor antagonist, is a water diuretic that ameliorates fluid retention with a lower risk of a worsening renal function than conventional loop diuretics. Although loop diuretics predominantly decrease extracellular water (ECW) compared with intracellular water (ICW), the effect of tolvaptan on fluid distribution remains unclear. We therefore examined how tolvaptan changes ICW and ECW in accordance with the renal function. Methods Six advanced chronic kidney disease patients (stage 4 or 5) with fluid retention were enrolled in this study. Tolvaptan (7.5 mg/day) added to conventional diuretic treatment was administered to remove fluid retention. The fluid volume was measured using a bioimpedance analysis device before (day 0) and after (day 5 or 6) tolvaptan treatment. Results Body weight decreased by 2.6%±1.3% (64.4±6.5 vs. 62.8±6.3 kg, p=0.06), and urine volume increased by 54.8%±23.9% (1,215±169 vs. 1,709±137 mL/day, p=0.03) between before and after tolvaptan treatment. Tolvaptan significantly decreased ICW (6.5%±1.5%, p=0.01) and ECW (7.5%±1.4%, p=0.02), which had similar reduction rates (p=0.32). The estimated glomerular filtration rate remained unchanged during the treatment (14.6±2.8 vs. 14.9±2.7 mL/min/1.732 m, p=0.35). Conclusion Tolvaptan ameliorates body fluid retention, and induces an equivalent reduction rate of ICW and ECW without a worsening renal function. Tolvaptan is a novel water diuretic that has a different effect on fluid distribution compared with conventional loop diuretics.

Region-specific activation of the AMPK system by cocaine: The role of D1 and D2 receptors.

The 5' adenosine monophosphate-activated protein kinase (AMPK) functions as an intracellular energy sensor that regulates and maintains energy balance. The psychostimulant drug cocaine has profound effects on behavior that are accentuated with repeated use, which is a process termed sensitization. Thus, the present study examined whether the sensitizing effects of cocaine could be observed in the AMPK system and aimed to determine whether these effects were mediated by dopamine (DA) D1 or D2 receptors. In the first set of experiments, rats were injected daily for 5days with either cocaine (15mg/kg, intraperitoneal [IP]) or saline. On the day 6, each group was divided into two subgroups and given either cocaine or saline. In the second set of experiments, rats were pretreated with SCH23390 (0.5mg/kg, IP), haloperidol (1mg/kg, IP), or both agents in combination, followed by cocaine or saline treatment. In the drug-naïve state, acute treatment with cocaine produced an increase in locomotor activity and increased AMPK phosphorylation in the frontal cortex but decreased it in the dorsal striatum. In the drug-sensitized state (following repeated treatment), the behavioral responsiveness to cocaine was augmented and accompanied by alterations in AMPK activity. The phosphorylation levels of the upstream kinases Ser-431-LKB1 and Thr-196-CaMK4 were congruent with the changes in AMPK activity. Thr-184/187-TAK1 was phosphorylated after chronic cocaine treatment in the dorsal striatum but not in the frontal cortex. The opposite effects induced by cocaine in the AMPK system in the dorsal striatum and frontal cortex may be explained by the differential activations of DA D1 and D2 receptors in these brain regions.