Breast cancer is one of the most challenging diseases to treat in humans worldwide. There are several alternatives in treating this life-threatening disease; however, chemoresistance is probably the biggest obstacle to the treatment of breast cancer. It may be essential to develop a therapeutic candidate material with less reversible effects and high treatment efficiency to solve this problem. The present study applied an ionizing radiation approach employing nomifensine (NF) to transform its chemical characteristics and investigated its potential to kill human breast cancer cells (MCF-7). Irradiated (IR-) NF was analyzed using high-performance liquid chromatography. The findings showed that NF inhibited the proliferation of breast cancer cells and increased the rate of apoptosis. In addition, IR-NF induced the accumulation of cytosolic reactive oxygen species and enhanced mitochondrial aggregation. Additionally, mitogen-activated protein kinases (extracellular signal-regulated kinase 1/2, p38 and c-Jun NH 2-terminal kinase) were involved in damage signaling induced by IR-NF and IR-NF suppressed β-catenin nuclear translocation. It is suggested that irradiation can be an effective method to maximize the efficacy of existing drugs and that IR-NF has the potential to be a drug candidate for treating patients with breast cancer.

Volatile anesthetics accelerate dopamine turnover in the brain, especially when used in conjunction with psychotropic agents such as methamphetamine and nomifensine. The effect of intravenous propofol anesthesia on the extracellular dopamine concentrations is unclear. The aim of this study was to compare the effect of two anesthetics on the extracellular concentrations of dopamine and metabolites using an in vivo microdialysis model. Male Sprague Dawley rats were implanted with a microdialysis probe into the right striatum. The probe was perfused with modified Ringer's solution, and the dialysate was directly injected into a high-performance liquid chromatography system every 20 min. The rats were intraperitoneally administered saline, methamphetamine at 2 mg/kg, or nomifensine at 10 mg/kg. After treatment, the rats were anesthetized with intravenous propofol (20 mg/kg followed by 25 or 50 mg/kg/h) or inhalational sevoflurane (2.5%) for 1 h. Propofol showed no effect on the extracellular concentration of dopamine during anesthesia; however, propofol decreased the dopamine concentration after anesthesia in the high-dose group. Sevoflurane anesthesia increased the concentration of metabolites. Systemic administration of methamphetamine and nomifensine increased the extracellular concentration of dopamine. Sevoflurane anesthesia significantly enhanced the increase in the dopamine concentration induced by both methamphetamine and nomifensine, whereas propofol anesthesia showed no effect on the methamphetamine- and nomifensine-induced dopamine increase during anesthesia. The enhancing effect of psychotropic agent-induced acceleration of dopamine turnover was smaller for propofol anesthesia than for sevoflurane anesthesia.

Emotional distracters impair cognitive function. Emotional processing is dysregulated in affective disorders such as depression, phobias, schizophrenia, and post-traumatic stress disorder (PTSD). Among the processes impaired by emotional distracters, and whose dysregulation is documented in affective disorders, is the ability to time in the seconds-to-minutes range, i.e., interval timing. Presentation of task-irrelevant distracters during a timing task results in a delay in responding suggesting a failure to maintain subjective time in working memory, possibly due to attentional and working memory resources being diverted away from timing, as proposed by the Relative Time-Sharing (RTS) model. We investigated the role of the prelimbic cortex in the detrimental effect of anxiety-inducing task-irrelevant distracters on the cognitive ability to keep track of time, using local infusions of norepinephrine and dopamine reuptake inhibitor (NDRI) nomifensine in a modified peak-interval procedure with neutral and anxiety-inducing distracters. Given that some anti-depressants have beneficial effects on attention and working memory, e.g., decreasing emotional response to negative events, we hypothesized that nomifensine would improve maintenance of information in working memory in trials with distracters, resulting in a decrease of the disruptive effect of emotional events on the timekeeping abilities. Our results revealed a dissociation of the effects of nomifensine infusion in prelimbic cortex between interval timing and resource allocation, and between neutral and anxiety-inducing distraction. Nomifensine was effective only during trials with distracters, but not during trials without distracters. Nomifensine reduced the detrimental effect of the distracters only when the distracters were anxiety-inducing, but not when they were neutral. Results are discussed in relation to the brain circuits involved in RTS of resources, and the pharmacological management of affective disorders.

The rat dorsal striatum exhibits domain-dependent kinetics of dopamine release and clearance. The present report describes the domain-dependent actions of nomifensine (20 mg/kg i.p.), a competitive dopamine uptake inhibitor, on evoked dopamine responses recorded by voltammetry during electrical stimulation of the medial forebrain bundle. In slow domains, nomifensine increases the initial rate of evoked overflow, increases response overshoot, does not affect the slope of the linear segment of the dopamine clearance profile, and slows the non-linear segment of the clearance profile. In fast domains, nomifensine does not affect the initial rate of overflow, increases the end-of-stimulus overshoot, and decreases the slope of the linear segment of the dopamine clearance profile. Collectively, these findings do not concur with existing models of evoked dopamine release that describe the effect of nomifensine as an increase in the effective KM of dopamine uptake. These findings suggest that dopamine clearance after evoked release is affected by both dopamine uptake and a restricted extracellular diffusion process.

Accumulating evidence suggests that the nucleus accumbens, which is involved in mechanisms of reward and addiction, plays a role in the pathogenesis of depression and in the action of antidepressants. In the current study, intraperitoneal injection of nomifensine, a dopamine reuptake inhibitor, decreased depression-like behaviors in the Wistar Kyoto rat model of depression in the sucrose-preference and forced swim tests. Nomifensine also reduced membrane excitability in medium spiny neurons in the core of the nucleus accumbens in the childhood Wistar Kyoto rats as evaluated by electrophysiological recording. In addition, the expression of dopamine D2-like receptor mRNA was downregulated in the nucleus accumbens, striatum and hippocampus of nomifensine-treated childhood Wistar Kyoto rats. These experimental findings indicate that impaired inhibition of medium spiny neurons, mediated by dopamine D2-like receptors, may be involved in the formation of depression-like behavior in childhood Wistar Kyoto rats, and that nomifensine can alleviate depressive behaviors by reducing medium spiny neuron membrane excitability.

Clinical studies have shown the therapeutic efficacy of an increase in dopamine (DA) transmission in treatment of major depressive disorder (MDD). In the present study, we investigated whether blockade of DA transporters in addition to serotonin (5-HT) and norepinephrine (NE) produced additional adaptations of monoaminergic systems. In vivo electrophysiological recordings were carried out in male anesthetized rats. Vehicle, the 5-HT reuptake inhibitor escitalopram, the NE/DA reuptake blocker nomifensine and their combination (triple reuptake inhibition; TRI) were delivered for 2 or 14 days. Firing activity of NE, 5-HT and DA neurons was assessed. Tonic activation of 5-HT1A receptors and α1- and α2-adrenoceptors was determined in the hippocampus and extracellular DA levels in the nucleus accumbens (NAc). Unlike escitalopram, nomifensine and TRI administration increased the tonic activation of α2-adrenoceptors in the hippocampus despite decreasing NE neuronal firing activity after 2 and 14 days of administration. The firing activity of 5-HT neurons was increased after prolonged nomifensine and TRI regimens, while addition of nomifensine to escitalopram prevented the early 2-day suppression of firing by 5-HT reuptake inhibition. The tonic activation of 5-HT1A receptors was enhanced only with escitalopram. Whereas escitalopram and nomifensine decreased firing activity of DA neurons after a 2-day administration, their combination normalized it to baseline level after 14 days; this was accompanied by a robust increase in extracellular DA levels in the NAc. In summary, these results indicate that TRI increases NE and DA but not 5-HT transmission, suggesting a differential efficacy profile in MDD patients.

In vivo electrochemical detection was employed to examine iron-induced oxidative injury on dopamine dynamics in the nigrostriatal system of urethane-anesthetized rats. Seven days after an intranigral infusion of iron, oxidative stress was confirmed by an elevated lipid peroxidation in lesioned substantia nigra (SN). Local application of potassium (K+) evoked dopamine releases from the dopamine-containing nerve terminals in the striatum. Both amplitude and rate of clearance (Tc) of evoked dopamine releases were lower in striatum with lesioned SN; however, the time course parameters of dopamine release in the lesioned group were not different from those of the intact group, indicating a reduction in dopamine clearance. Indeed, iron-induced oxidative stress attenuated the effect of nomifensine, a high-affinity dopamine uptake blocker, on dopamine clearance. In striatum with intact SN, the amplitude and time course parameters of signals by exogenous dopamine were increased and Tc was decreased by nomifensine. In contrast, nomifensine did not significantly alter the dopamine signals of the lesioned group. Taken together, in addition to the increased lipid peroxidation in SN, our in vivo electrochemical data demonstrates that iron-induced oxidative injury attenuates K+-evoked dopamine release and dopamine uptake in the ipsilateral striatum. The diminished nomifensine effect implies a lack of high-affinity dopamine uptake sites.

Although evidence exists of the presence of a serotonin (5-HT) reuptake system in lymphocytes, no information is available on the pharmacological characterization of this structure. Our study aimed to investigate this matter, therefore, by means of the binding of [3H]-paroxetine ([3H]PAR), a selective 5-HT reuptake inhibitor (SSRI), which is considered the ligand of choice for binding studies. Lymphocytes were obtained from a pool of 20 healthy subjects who volunteered for the study. The results showed the presence of a specific and saturable [3H]PAR binding to lymphocyte membranes, with a Hill number close to unity indicative of the presence of one site only. The most potent drugs inhibiting [3H]PAR binding were SSRIs (paroxetine, fluoxetine, citalopram) followed by clomipramine, imipramine, and 5-HT, whereas haloperidol, mazindol, and nomifensine had a negligible effect. These findings suggest that [3H]-PAR in human resting lymphocytes specifically labels the 5-HT transporter.

Six experiments examined the effects of selective median (MRN)- and dorsal (DRN)-raphé nucleus lesions on the performance of the five-choice serial reaction time task. In this test rats are required to localize brief visual stimuli presented randomly in one of five locations in approximately 30 min sessions of 100 trials. Both accuracy and latency to respond are measured, as well as the incidence of premature and perseverative responding. Selective 5-HT lesions were induced by intra-raphé infusions of 5,7-dihydroxytryptamine following pretreatment with both a noradrenergic and a dopaminergic re-uptake inhibitor. Analysis of tissue monoamine content demonstrated that the MRN lesion profoundly depleted hippocampal 5-HT (by about 90%) without affecting noradrenaline and dopamine, whereas the DRN lesion primarily depleted (by about 80%) nucleus accumbens and caudate-putamen 5-HT. Rats with 5-HT lesions of the MRN performed the task with a similar degree of accuracy to that exhibited by sham-operated controls. Although the MRN lesion did not affect the latency to respond correctly to the visual targets the lesioned animals collected the food reward significantly faster than the controls. A transient increase in the number of premature responses also resulted from this lesion. In contrast the DRN lesion produced a transient but significant increase in the accuracy of performance, and increased both the speed and the probability of responding. The similarity of the effects following global forebrain 5-HT depletion and the selective DRN lesion suggests that the 5-HT projections of the DRN rather than the MRN may play an important role in impulsive behaviour following 5-HT depletion.

Degeneration of nigrostriatal dopaminergic neurons in Parkinson's disease begins from the axonal terminals in the striatum and, then, in retrograde fashion, progresses to the cell bodies in the substantia nigra. Investigation of the dynamics of axonal terminal degeneration may help in the identification of new targets for neuroprotective treatment and be used as a tool for testing potential drugs. We have shown that the degeneration rate of dopaminergic axonal terminals changes over time, and that the striatal dopamine concentration is the most sensitive parameter to the action of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). This model was validated using neuroprotectors with well-known mechanisms of action: the dopamine transporter inhibitor nomifensine and SEMAX peptide that stimulates the secretion of endogenous neurotrophic factors or acts as an antioxidant. Nomifensine was shown to almost completely protect dopaminergic fibers from the toxic effect of MPTP and maintain the striatal dopamine concentration at the control level. However, SEMAX, slightly but reliably, increased striatal dopamine when administered before MPTP treatment, which indicates that it is more effective as an inductor of endogenous neurotrophic factor secretion rather than as an antioxidant.

Growing research indicates oxytocin may be involved in relieving anxiety and attenuating the rewarding effects of psychostimulants. This study investigated the effects of subchronic oxytocin treatments on mesolimbic dopamine transmission in areas associated with anxiety and addiction, the amygdala and the nucleus accumbens (NAc), respectively. Using in vivo fixed potential amperometry, stimulation-evoked dopamine release was recorded in anesthetized mice pretreated with subchronic oxytocin (four i.p. injections of 1 mg/kg oxytocin or saline with 48 h between injections). During dopamine recordings, mice received an i.p. drug challenge of either oxytocin (1 mg/kg), the dopamine reuptake blocker nomifensine (10 mg/kg), or saline. Overall, subchronic oxytocin pretreatment did alter properties of dopamine release in these limbic structures. In the amygdala, dopamine release was decreased following the oxytocin challenge but only in oxytocin pretreated mice. In the NAc, baseline dopamine release was attenuated in oxytocin pretreated mice relative to saline pretreated mice. Furthermore, oxytocin pretreated mice displayed a reduced dopaminergic response to the drug challenge of nomifensine relative to control mice. Together these results suggest that oxytocin may be useful at treating aspects of anxiety and drug abuse. Elucidating the neural effects of oxytocin is critical given the multitude of potential therapeutic uses for this drug.

Emotionally charged distracters delay timing behavior. Increasing catecholamine levels within the prelimbic cortex has beneficial effects on timing by decreasing the delay after aversive distracters. We examined whether increasing catecholamine levels within the prelimbic cortex also protects against the deleterious timing delays caused by novel distracters or by familiar appetitive distracters. Rats were trained in a peak-interval procedure and tested in trials with either a novel (unreinforced) distracter, a familiar appetitive (food-reinforced) distracter, or no distracter after being locally infused within the prelimbic cortex with catecholamine reuptake blocker nomifensine. Prelimbic infusion of nomifensine did not alter timing accuracy and precision. However, it increased the delay caused by novel distracters in an inverted-U dose-dependent manner, while being ineffective for appetitive distracters. Together with previous data, these results suggest that catecholaminergic modulation of prelimbic top-down attentional control of interval timing varies with distracter's valence: prelimbic catecholamines increase attentional control when presented with familiar aversive distracters, have no effect on familiar neutral or familiar appetitive distracters, and decrease it when presented with novel distracters. These findings detail complex interactions between catecholaminergic modulation of attention to timing and nontemporal properties of stimuli, which should be considered when developing therapeutic methods for attentional or affective disorders.

The main clinically used antidepressant drugs are selective monoamine reuptake inhibitors, including selective serotonin reuptake inhibitors (citalopram, sertraline), selective dopamine reuptake inhibitor (nomifensine) and selective noradrenaline reuptake inhibitor (reboxetine), but they have various side effects. Because cannabinoid CB(1) receptor antagonists (SR141716A, AM251) enhance monoamine release, they might be beneficial in the therapy of affective disorders. We hypothesized that the use of monoamine reuptake inhibitors in combination with cannabinoid CB(1) receptor antagonists would allow a lower dose of monoamine reuptake inhibitors to be used in the therapy of depression, thereby reducing or eliminating the side effects. To test this hypothesis, we examined the combination of SR141716A or AM251 with citalopram, sertraline, nomifensine or reboxetine at subthreshold doses to see whether these combinations would show an additive effect in the forced swimming test and the tail suspension test with mice. Subthreshold doses of cannabinoid CB(1) receptor antagonist and selective serotonin reuptake inhibitors, which separately had no effect on the immobility of mice in the tests, showed a clear effect when the drugs were administered at 40 and 30 min, respectively, before the tests, without any change of motor activity. Therefore, the use of subthreshold doses of these agents in combination might be useful to enhance mainly serotonergic neurotransmission, and to reduce or eliminate the side effects of citalopram and sertraline.

The ability of estrogen to modulate mesolimbic dopamine (DA) was examined using in vivo voltammetry. Estrogen priming (5 micrograms, 48 h) of ovariectomized (ovx) female rats resulted in a slight decrease in K(+)-stimulated DA release measured in the nucleus accumbens: this decrease was accompanied by a significant increase in both DA reuptake and DA clearance times. Following estrogen priming nomifensine, a potent inhibitor of the DA uptake carrier, was still able to potentiate K(+)-stimulated DA release and alter the time course of DA availability, but the response was attenuated compared with ovx controls. Direct infusion of 17 beta-estradiol hemisuccinate (17 beta-E, 20-50 pg) into the nucleus accumbens resulted in a biphasic potentiation of K(+)-stimulated release. An initial increase in release was observed 2 min after 17 beta-E infusion; this increase, although reduced by 15 min, was still significantly higher than control values. A subsequent potentiation was observed 60 min after the initial 17 beta-E infusion; this response remained for at least an additional 60 min. Nomifensine did not significantly alter K(+)-stimulated DA release following 17 beta-E infusion, but was still able to potentiate the total time DA was available extracellularly. These data suggest that the mesolimbic A10 DA neurons that terminate in the nucleus accumbens can be modulated in vivo by estrogen and that this modulation may be mediated by both genomic (long term) and nongenomic (short term) mechanisms.

Galantamine, an acetylcholine esterase (AChE) inhibitor used to treat dementia symptoms, also acts as an allosteric potentiating ligand (APL) at nicotinic acetylcholine receptors (nAChRs). This study was designed to evaluate the allosteric effect of galantamine on nAChR regulation of nigrostrial dopaminergic neuronal function in the hemiparkinsonian rat model established by unilateral nigral 6-hydroxydopamine (6-OHDA) injection. Methamphetamine, a dopamine releaser, induced ipsilateral rotation, whereas dopamine agonists apomorphine (a non-selective dopamine receptor agonist), SKF38393 (a selective dopamine D1 receptor agonist), and quinpirole (a selective dopamine D2 receptor agonist) induced contralateral rotation. When 6-OHDA-injected rats were co-treated with nomifensine, a dopamine transporter inhibitor, a more pronounced and a remarkable effect of nicotine and galantamine was observed. Under these conditions, the combination of nomifensine with nicotine or galantamine induced the ipsilateral rotation similar to the methamphetamine-induced rotational behavior, indicating that nicotine and galantamine also induce dopamine release from striatal terminals. Both nicotine- and galantamine-induced rotations were significantly blocked by flupenthixol (an antagonist of both D1 and D2 dopamine receptors) and mecamylamine (an antagonist of nAChRs), suggesting that galantamine modulation of nAChRs on striatal dopaminergic terminals regulates dopamine receptor-mediated movement. Immunohistochemical staining showed that α4 nAChRs were highly expressed on striatal dopaminergic terminals, while no α7 nAChRs were detected. Pretreatment with the α4 nAChR antagonist dihydroxy-β-erythroidine significantly inhibited nicotine- and galantamine-induced rotational behaviors, whereas pretreatment with the α7 nAChR antagonist methyllycaconitine was ineffective. Moreover, the α4 nAChR agonist ABT-418 induced ipsilateral rotation, while the α7 nAChR agonist PNU282987 had no significant effect on rotational behavior. These results suggest that galantamine can enhance striatal dopamine release through allosteric modulation of α4 nAChRs on nigrostriatal dopaminergic terminals.

STriatal-Enriched protein tyrosine Phosphatase (STEP) is a neural-specific protein that opposes the development of synaptic strengthening and whose levels are altered in several neurodegenerative and psychiatric disorders. Since STEP is expressed in brain regions implicated in social behavior, namely the striatum, the CA2 region of the hippocampus, cortex and amygdala, here we investigated whether social memory and social patterns were altered in STEP knockout (KO) mice. Our data robustly demonstrated that STEP KO mice presented specific social memory impairment as indicated by the three-chamber sociability test, the social discrimination test, the 11-trial habituation/dishabituation social recognition test, and the novel object recognition test (NORT). This affectation was not related to deficiencies in the detection of social olfactory cues, altered sociability or anxiety levels. However, STEP KO mice showed lower exploratory activity, reduced interaction time with an intruder, less dominant behavior and higher immobility time in the tail suspension test than controls, suggesting alterations in motivation. Moreover, the extracellular levels of dopamine (DA), but not serotonin (5-HT), were increased in the dorsal striatum of STEP KO mice. Overall, our results indicate that STEP deficiency disrupts social memory and other social behaviors as well as DA homeostasis in the dorsal striatum.

Recent studies have revealed the important role of NUDT5 in estrogen signaling and breast cancer, but research on the corresponding targeted therapy has just started. Drug repositioning strategy can effectively reduce the time and economic resources spent on drug discovery. To find novel inhibitors of NUDT5, we investigated the previously identified connectivity map-based drug association models and found eighteen FDA approved drugs as candidates. The molecular docking and molecular dynamic simulation were performed and revealed that fourteen organic drugs have the potential to bind the NUDT5 target. Eight representative drugs were selected to perform the cell line viability inhibition analysis, and the results showed that seven of them were able to suppress MCF7 breast cancer cells. Two drugs, nomifensine and isoconazole, showed lower IC50 than the known antiestrogens raloxifene and tamoxifen, and they deserve further pharmacodynamic investigations to test their feasibility for use as NUDT5 inhibitors.

Increasing evidence suggests that long-term consumption of high-caloric diets increases the risk of developing cognitive dysfunctions. In the present study, we assessed the catecholaminergic activity in the hippocampus as a modulatory mechanism that is altered in rats exposed to six months of a high-sucrose diet (HSD). Male Wistar rats fed with this diet developed a metabolic disorder and showed impaired spatial memory in both water maze and object location memory (OLM) tasks. Intrahippocampal free-movement microdialysis showed a diminished dopaminergic and noradrenergic response to object exploration during OLM acquisition compared to rats fed with normal diet. In addition, electrophysiological results revealed an impaired long-term potentiation (LTP) of the perforant to dentate gyrus pathway in rats exposed to a HSD. Local administration of nomifensine, a catecholaminergic reuptake inhibitor, prior to OLM acquisition or LTP induction, improved long-term memory and electrophysiological responses, respectively. These results suggest that chronic exposure to HSD induces a hippocampal deterioration which impacts on cognitive and neural plasticity events negatively; these impairments can be ameliorated by increasing or restituting the affected catecholaminergic activity.

N-oleoyl-dopamine (OLDA) is an amide of dopamine and oleic acid, synthesized in catecholaminergic neurons. The present study investigates OLDA targets in midbrain dopaminergic (DA) neurons. Substantia Nigra compacta (SNc) DA neurons recorded in brain slices were excited by OLDA in wild type mice. In transient receptor potential vanilloid 1 (TRPV1) knockout (KO) mice, however, SNc DA neurons displayed sustained inhibition of firing. In the presence of the dopamine type 2 receptor (D2R) antagonist sulpiride or the dopamine transporter blocker nomifensine no such inhibition was observed. Under sulpiride OLDA slightly excited SNc DA neurons, an action abolished upon combined application of the cannabinoid1 and 2 receptor antagonists AM251 and AM630. In ventral tegmental area (VTA) DA neurons from TRPV1 KO mice a transient inhibition of firing by OLDA was observed. Thus OLDA modulates the firing of nigrostriatal DA neurons through interactions with TRPV1, cannabinoid receptors and dopamine uptake. These findings suggest further development of OLDA-like tandem molecules for the treatment of movement disorders including Parkinson's disease.

Major depression is a serious mood disorder affecting millions of adults and children worldwide. While the etiopathology of depression remains obscure, antidepressant medications increase synaptic levels of monoamine neurotransmitters in brain regions associated with the disease. Monoamine transmitters activate multiple signaling cascades some of which have been investigated as potential mediators of depression or antidepressant drug action. However, the diacylglycerol arm of phosphoinositide signaling cascades has not been systematically investigated, even though downstream targets of this cascade have been implicated in depression. With the ultimate goal of uncovering the primary postsynaptic actions that may initiate cellular antidepressive signaling, we have examined the antidepressant-induced production of CDP-diacylglycerol which is both a product of diacylglycerol phosphorylation and a precursor for the synthesis of physiologically critical glycerophospholipids such as the phosphatidylinositides. For this, drug effects on [3H]cytidine-labeled CDP-diacylglycerol and [3H]inositol-labeled phosphatidylinositides were measured in response to the tricyclics desipramine and imipramine, the selective serotonin reuptake inhibitors fluoxetine and paroxetine, the atypical antidepressants maprotiline and nomifensine, and several monoamine oxidase inhibitors.