Hypothesis: Amelioration of obesity-induced cognitive dysfunction via a lorcaserin-betahistine combination treatment.

The prolonged exposure to obesogenic diets disrupts the mesocortical dopaminergic input to the prefrontal cortex (PFC). This leads to suboptimal dopamine levels in this brain region, which affects cognition and control of food intake. Treatments that restore mesocortical dopaminergic neurotransmission may improve obesity-associated cognitive dysfunction and modulate food intake to induce weight loss. Given the complexity and multifactorial nature of obesity, combination treatments would likely achieve sizeable and sustained body weight loss and improve obesity-linked outcomes, such as cognitive dysfunction. Given this background, we hypothesize that concomitant activation of serotonin 5-HT2C and histamine H1 receptors, coupled with antagonism of histamine H3 receptors, synergistically modulates mesocortical dopamine neurotransmission and ameliorates obesity-induced cognitive dysfunction. We propose to test the hypothesis in a diet-induced obesity (DIO) rat model by treating animals with the 5-HT2C agonist lorcaserin and the H1 agonist and H3 antagonist betahistine. Consistent with our hypothesis, both lorcaserin and betahistine have been shown to reduce body weight in humans with obesity and animals. Both drugs have been demonstrated to improve cognitive functions by influencing dopaminergic signaling in the PFC. The proposed combination treatment addresses the paucity of studies on obesity treatments that improve cognitive function. This research may also help identify a potential targetable mechanism connecting obesity and neurocognitive outcomes.

Extension of Tissue Plasminogen Activator Treatment Window by Granulocyte-Colony Stimulating Factor in a Thromboembolic Rat Model of Stroke.

When given beyond 4.5 h of stroke onset, tissue plasminogen activator (tPA) induces deleterious side effects in the ischemic brain, notably, hemorrhagic transformation (HT). We examined the efficacy of granulocyte-colony stimulating factor (G-CSF) in reducing delayed tPA-induced HT, cerebral infarction, and neurological deficits in a thromboembolic (TE) stroke model, and whether the effects of G-CSF were sustained for longer periods of recovery. After stroke induction, rats were given intravenous saline (control), tPA (10 mg/kg), or G-CSF (300 µg/kg) + tPA 6 h after stroke. We found that G-CSF reduced delayed tPA-associated HT by 47%, decreased infarct volumes by 33%, and improved motor and neurological deficits by 15% and 25%, respectively. It also prevented delayed tPA treatment-induced mortality by 46%. Immunohistochemistry showed 1.5- and 1.8-fold enrichment of the endothelial progenitor cell (EPC) markers CD34+ and VEGFR2 in the ischemic cortex and striatum, respectively, and 1.7- and 2.8-fold increases in the expression of the vasculogenesis marker von Willebrand factor (vWF) in the ischemic cortex and striatum, respectively, in G-CSF-treated rats compared with tPA-treated animals. Flow cytometry revealed increased mobilization of CD34+ cells in the peripheral blood of rats given G-CSF. These results corroborate the efficacy of G-CSF in enhancing the therapeutic time window of tPA for stroke treatment via EPC mobilization and enhancement of vasculogenesis.

Methylphenidate significantly alters the functional coupling between the prefrontal cortex and dopamine neurons in the ventral tegmental area.

Amphetamine-like psychostimulants, including methylphenidate, have been shown to produce two opposing effects on dopamine (DA) neurons: a DA receptor-mediated feedback inhibition and a non-DA receptor-mediated excitation. To test whether the latter effect is mediated through the prefrontal cortex (PFC), we made dual-site recordings from the PFC and ventral tegmental area (VTA). Consistent with previous reports, methylphenidate inhibited VTA DA neurons. The D2 receptor antagonist raclopride completely reversed the inhibition and further increased the activity, particularly bursting, to above pre-drug baseline. This increase in DA cell activity was blocked by the α1 receptor antagonist prazosin, suggesting an effect mediated through α1 receptors. Recordings in the PFC showed that methylphenidate increased PFC UP state duration and shifted the functional coupling between the PFC and DA neurons from negative to positive. The former effect was partially reversed by not only prazosin, but also raclopride, whereas the latter was reversed only by raclopride. These results suggest that methylphenidate increases PFC cell activity through both α1 and D2 receptors. Its effect on PFC-DA cell functional coupling, however, is mediated through D2 receptors. The finding that the latter effect was unaffected by prazosin further suggests that it does not play a significant role in the α1-mediated excitatory effect of methylphenidate on DA neurons. However, the shift in PFC-DA cell functional coupling from negative to positive may significantly alter the relative timing between DA and glutamate release from DA and PFC terminals and thus the synaptic plasticity that depends on DA-glutamate interaction.

Adjunctive Therapy Approaches for Ischemic Stroke: Innovations to Expand Time Window of Treatment.

Tissue plasminogen activator (tPA) thrombolysis remains the gold standard treatment for ischemic stroke. A time-constrained therapeutic window, with the drug to be given within 4.5 h after stroke onset, and lethal side effects associated with delayed treatment, most notably hemorrhagic transformation (HT), limit the clinical use of tPA. Co-administering tPA with other agents, including drug or non-drug interventions, has been proposed as a practical strategy to address the limitations of tPA. Here, we discuss the pharmacological and non-drug approaches that were examined to mitigate the complications-especially HT-associated with delayed tPA treatment. The pharmacological treatments include those that preserve the blood-brain barrier (e.g., atovarstatin, batimastat, candesartan, cilostazol, fasudil, minocycline, etc.), enhance vascularization and protect the cerebrovasculature (e.g., coumarin derivate IMM-H004 and granulocyte-colony stimulating factor (G-CSF)), and exert their effects through other modes of action (e.g., oxygen transporters, ascorbic acid, etc.). The non-drug approaches include stem cell treatments and gas therapy with multi-pronged biological effects. Co-administering tPA with the abovementioned therapies showed promise in attenuating delayed tPA-induced side effects and stroke-induced neurological and behavioral deficits. Thus, adjunctive treatment approach is an innovative therapeutic modality that can address the limitations of tPA treatment and potentially expand the time window for ischemic stroke therapy.

Granulocyte colony-stimulating factor attenuates delayed tPA-induced hemorrhagic transformation in ischemic stroke rats by enhancing angiogenesis and vasculogenesis.

Treatment with tissue plasminogen activator (tPA) beyond the therapeutic time window (>4.5 hours post stroke) may produce hemorrhagic transformation (HT). Strategies that could extend the narrow time window of tPA will benefit a significant number of stroke patients. Male Sprague-Dawley rats underwent middle cerebral artery occlusion (MCAo) and given vehicle, tPA (10 mg/kg), or tPA and granulocyte colony-stimulating factor (G-CSF, 300 µg/kg), at 6 hours after MCAo. Twenty-four hours post treatment, G-CSF+tPA-treated stroke rats displayed 25% improvement in neurological functions and 38.9% reduction of hemorrhage, with Western blots showing 1.9- and 1.2-fold increments in Ang-2 expression in the ischemic cortex and striatum, respectively, and 3-fold increase in phosphorylated endothelial nitric oxide synthase expression in the ipsilateral cortex relative to tPA-treated rats. Immunohistochemistry also showed 2- and 2.8-fold increase in von-Willebrand expression, 3.2- and 2.2-fold increased CD34+ expression, and 4- and 13-fold upregulation of VEGFR-2 expression in the ischemic cortex and striatum, respectively, in G-CSF+tPA-treated stroke rats relative to tPA-treated subjects. Altogether, these findings indicate that G-CSF attenuated delayed tPA-induced HT likely via the enhancement of angiogenesis and vasculogenesis. The use of G-CSF to protect the vasculature may improve the clinical outcome of tPA even outside the currently indicated therapeutic window for ischemic stroke.

5,7-Dihydroxy-6-methoxy-4'-phenoxyflavone, a derivative of oroxylin A improves attention-deficit/hyperactivity disorder (ADHD)-like behaviors in spontaneously hypertensive rats.

Oroxylin A, a major flavonoid in Scutellaria baicalensis, has been shown to alleviate attention-deficit/hyperactivity disorder (ADHD)-like behaviors in the spontaneously hypertensive rat (SHR) model of ADHD. As part of our continuing effort to discover effective ADHD drug candidates, we synthesized a number of oroxylin A derivatives and characterized their biological activities. Among all oroxylin A analogs, compound 7-7 (5,7-dihydroxy-6-methoxy-4'-phenoxyflavone) showed the most remarkable inhibition of dopamine reuptake alike methylphenidate, a dopamine transporter (DAT) blocker and typical drug for ADHD, and oroxylin A. It did not influence norepinephrine reuptake unlike atomoxetine, a selective norepinephrine inhibitor. Moreover, compound 7-7 reduced hyperactivity, sustained inattention and impulsivity in the SHR as measured by the open field, Y-maze and electro-foot shock aversive water drinking tests, respectively. Most drugs that enhance brain dopamine levels (e.g. DAT blockers like cocaine and methylphenidate) produce behavioral effects like those of stimulants causing them to be abused. However, the repeated treatment of compound 7-7 failed to elicit locomotor sensitization in rats, and neither produced conditioned place preference response nor maintained self-administration behavior. Altogether, the present study suggests the promising therapeutic value of compound 7-7 as an ADHD drug. Furthermore, compound 7-7 may be considered as an alternative therapy to psychostimulant ADHD treatments (e.g. amphetamine and methylphenidate) for which use has been deemed controversial due to their abuse liability.

Prunella vulgaris attenuates prepulse inhibition deficit and attention disruption induced by MK-801 in mice.

Prunella vulgaris var. lilacina is widely distributed in Korea, Japan, China, and Europe, and it has been traditionally used to treat inflammation or hypertension. In the present study, we investigated the effects of the ethanolic extract of the spikes of Prunella vulgaris var. lilacina (EEPV) on dizocilpine (MK-801)-induced schizophrenia-like phenotype behaviors such as the disruption of prepulse inhibition and attention deficits in mice. We also determined the effect of EEPV on MK-801-induced alterations in phosphorylated extracellular signal-regulated kinase, phosphorylated protein kinase B, phospho-glycogen synthase kinase 3-ß, and phosphorylated cAMP response element-binding protein levels in the cortex and hippocampus of mice. MK-801-induced prepulse inhibition deficits were ameliorated by the administration of EEPV, as shown in the acoustic startle response test. Furthermore, EEPV attenuated the MK-801-induced attention deficits in the water finding test. We also found that EEPV attenuated the increased phosphorylated extracellular signal-regulated kinase, phosphorylated protein kinase B, or phospho-glycogen synthase kinase 3-ß levels induced by MK-801 in the cortex but not in the hippocampus. These results suggest that EEPV could be useful for treating schizophrenia because EEPV ameliorates prepulse inhibition disruption and attention deficits induced by MK-801.

Conditioned place preference studies with atomoxetine in an animal model of ADHD: effects of previous atomoxetine treatment.

To investigate the putative rewarding effects of atomoxetine, a non-stimulant medication for Attention-deficit/hyperactivity disorder (ADHD), we conducted conditioned place preference (CPP) tests in an animal model of ADHD, the spontaneously hypertensive rat (SHR). The effects of drug pre-exposure were also evaluated, thus, parallel experiments were done in rats which have undergone 14 days of atomoxetine treatment. The responses of SHR were compared with the rat strain representing the "normal" heterogeneous population, the Wistar rats. Neither rat strain showed significant CPP to atomoxetine. However, previous atomoxetine treatment produced place preference responses in rats, more profoundly in Wistar rats conditioned with the low and moderate atomoxetine doses. In conclusion, acute exposure to atomoxetine does not have any rewarding effect, however, drug pretreatment produces responses characteristic of reward or psychological dependence, more specifically in the "normal" vs. the ADHD animal model. The present findings call for more studies with atomoxetine, especially those that investigate the effects of long-term or chronic drug treatment.

Methylphenidate self-administration and conditioned place preference in an animal model of attention-deficit hyperactivity disorder: the spontaneously hypertensive rat.

The abuse potential of methylphenidate, the most commonly used drug for attention-deficit hyperactivity disorder (ADHD), has been shown in many studies. However, it is not yet known whether methylphenidate has reinforcing or rewarding effects in any animal model of ADHD. In this study, we investigated whether methylphenidate facilitates self-administration and induces conditioned place preference in the spontaneously hypertensive rat (SHR), the most validated animal model of ADHD. We also explored whether the behavioral responses of SHR differ from those of Wistar rats, the strain representing the 'normal' heterogeneous population. ADHD is highly prevalent among adolescents, such that behavioral assays should be conducted in adolescent SHR. In line with this, we carried out conditioned place preference tests in adolescent SHR and Wistar rats and observed strain and age-related differences in behavioral responses to the motivational effects of methylphenidate. Self-administration tests confirmed the reinforcing effect of methylphenidate in SHR, and showed that, in FR2 and FR3 schedules, SHR responded more to methylphenidate infusions than the Wistar rats. In conditioned place preference tests, both strains responded similarly to the rewarding effects of methylphenidate. However, it was found that adolescence also alters the euphorigenic effects of methylphenidate, most especially in SHR. The implications of these findings are discussed.