Effects of aripiprazole on MK-801-induced prepulse inhibition deficits and mitogen-activated protein kinase signal transduction pathway

Based on NMDA hypofunction hypothesis for negative symptoms and cognitive deficits in schizophrenia, MK-801-induced animal models of schizophrenia may help us understand the different effects between typical and atypical antipsychotics. On the other hand, the mitogen-activated protein kinase (MAPK) signaling pathways may participate in antipsychotic actions. The aim of this study was to investigate the effects of aripiprazole on MK-801-induced prepulse inhibition (PPI) disruption and MAPK phosphorylation in mice. To clarify the effects of aripiprazole on MK-801-induced PPI disruption, we measured PPI of 51 ddY male mice after aripiprazole was administered 15 min prior to the injection of MK-801, and measured activation of cytosol and nuclear MAPK phosphorylation by western blotting. Aripiprazole (4.0 mg/kg) significantly reversed the MK-801 (0.15 mg/kg)-induced PPI deficits. Pretreatment of aripiprazole (40 mg/kg) had a tendency to suppress MK-801 (1.0 mg/kg)-induced pMEK/MEK (Ser218/222) activation. In addition, aripiprazole treatment showed a significant decrease of pERK/ERK. Our data suggested that aripiprazole may reverse MK-801-induced PPI deficits through regulation of MAPK phosphorylation in the same way as the atypical antipsychotic drug, clozapine.     

Lamotrigine blocks the initiation and expression of repeated high-dose methamphetamine-induced prepulse inhibition deficit in rats

Our group developed a new psychostimulant animal model reflecting some clinical aspects of schizophrenia better than the conventional model does. In this model, long-lasting prepulse inhibition (PPI) deficit at the basement state is induced via repeated administration of methamphetamine (METH, 2.5 mg/kg) without challenge injection of this psychostimulant. This study elucidates the effects of lamotrigine (LTG, 30 mg/kg) on the initiation and expression of a steady-state PPI deficit induced by the repeated METH administration. We assessed the effect of coadministration of LTG and METH on the initiation of PPI deficit. The LTG was injected 120 min after each METH injection for 5 times on every alternate day and for an additional 5 times every day, amounting to a total of 10 times. After 11–13 days of the withdrawal period, we measured PPI using the SR-LAB system. Using other animals after 20 min of LTG injection, we subsequently examined the effect of a single injection of LTG on the expression of PPI deficit caused by the repeated METH administration. The LTG blocked the initiation of PPI deficit induced by the repeated METH administration at 68 dB of prepulse intensity, but had no effect on the startle amplitude. The LTG prevented the initiation and expression of neuroplastic PPI deficit detected at the baseline state without any METH challenge injection, which was induced by the repeated administration of this psychostimulant. Results suggest that LTG is useful for blocking progressive deterioration of neurocognitive function and recovering the neurocognitive deficit in schizophrenia.     

In vivo 5-HT(6) receptor occupancy by antipsychotic drugs in the rat brain

The 5-HT₆ receptor subtype is predominantly expressed in the central nervous system, and preclinical evidence suggests that it plays a critical role in the regulation of molecular pathways underlying cognitive function. Patients with schizophrenia show cognitive impairment as a fundamental symptom, and it is proposed that the procognitive properties of some antipsychotics such as olanzapine and clozapine would be, in part, due to the central blockade of 5-HT₆ receptors. In this study, we characterized the brain 5-HT₆ receptor occupancy of olanzapine, clozapine and chlorpromazine in relation to their pharmacokinetic profiles using in vivo [³H]GSK215083 binding assay in rat brain. Oral administration of olanzapine (3 mg/kg), clozapine (30 mg/kg) and chlorpromazine (30 mg/kg) produced significant 5-HT₆ receptor occupancy in the brain, inhibiting radioligand binding by 88, 97 and 81%, respectively. The blood concentrations required to achieve significant occupancy were clinically achievable (9.6, 26.9 and 98.6 nM for olanzapine, clozapine and chlorpromazine, respectively). This data provides preclinical evidence to support the hypothesis that brain 5-HT₆ antagonism contributes to the procognitive properties of antipsychotic drugs such as olanzapine and clozapine.     

The suppression of endogenous adrenalin in the prolongation of ketamine anesthesia

This study investigated whether or not the anesthetic effect of ketamine in rats is dependent on adrenal gland hormones. The study was performed on two main rat groups, intact and adrenalectomized. Rat were divided into subgroups and given appropriate doses of ketamine, metyrapone or metyrosine. Durations of anesthesia in the groups were then recorded. Endogenous catecholamine levels were measured in samples taken from peripheral blood. This experimental results showed that ketamine did not induce anesthesia in intact rats at doses of 15 or 30 mg/kg, and that at 60 mg/kg anesthesia was established for only 11 min. However, ketamine induced significant anesthesia even at a dose of 30 mg/kg in animals in which production of endogenous catecholamine (adrenalin, noradrenalin dopamine) was inhibited with metyrosine at a level of 45–47%. Ketamine at 60 mg/kg in animals in which endogenous catecholamine was inhibited at a level of 45–47% established anesthesia for 47.6 min. However, ketamine at 30 and 60 mg/kg induced longer anesthesia in adrenalectomized rats with higher noradrenalin and dopamine levels but suppressed adrenalin production. Adrenalin plays an important role in the control of duration of ketamine anesthesia, while noradrenalin, dopamine and corticosterone have no such function. If endogenous adrenalin is suppressed, ketamine can even provide sufficient anesthesia at a 2-fold lower dose. This makes it possible for ketamine to be used in lengthy surgical procedures.     

C-Fos identification of neuroanatomical sites associated with haloperidol and clozapine disruption of maternal behavior in the rat

Rat maternal behavior is a complex social behavior. Most antipsychotic drugs disrupt active maternal responses (e.g., pup retrieval, pup licking and nest building). Our previous work shows that typical antipsychotic haloperidol disrupts maternal behavior by blocking dopamine D₂ receptors, whereas atypical clozapine works by blocking 5-HT_2A/2C receptors. The present study used c-Fos immunohistochemistry technique, together with pharmacological tools and behavioral observations, and delineated the neuroanatomical bases of the disruptive effects of haloperidol and clozapine. Postpartum female rats were treated with haloperidol (0.2 mg/kg sc) or clozapine (10.0 mg/kg sc), with or without pretreatment of quinpirole (a selective dopamine D₂/D₃ agonist, 1.0 mg/kg sc) or 2,5-dimethoxy-4-iodo-amphetamine (DOI, a selective 5-HT_2A/2C agonist, 2.5 mg/kg sc). They were then sacrificed 2 h later after a maternal behavior test was conducted. Brain regions that have been previously implicated in the regulation of rat maternal behavior and/or in the antipsychotic action were examined. Behaviorally, both haloperidol and clozapine disrupted pup retrieval, pup licking and nest building. Pretreatment of quinpirole, but not DOI, reversed the haloperidol-induced disruptions. In contrast, pretreatment of DOI, but not quinpirole, reversed the clozapine-induced deficits. Neuroanatomically, the nucleus accumbens (both the shell and core), dorsolateral striatum and lateral septum showed increased c-Fos expression to the treatment of haloperidol. In contrast, the nucleus accumbens shell showed increased expression of c-Fos to the treatment of clozapine. More importantly, pretreatment of quinpirole and DOI produced opposite response profiles in the brain regions where haloperidol and clozapine had an effect. Based on these findings, we concluded that haloperidol disrupts active maternal behavior primarily by blocking dopamine D₂ receptors in a neural circuitry involving the nucleus accumbens, dorsolateral striatum and lateral septum. In contrast, clozapine appears to disrupt maternal behavior mainly by blocking serotonin 5-HT_2A/2C receptors in the nucleus accumbens shell.     

5-HT1A receptor activation counteracts c-Fos immunoreactivity induced in serotonin neurons of the raphe nuclei after immobilization stress in the male rat

The serotoninergic system and the 5-HT_1A receptors have been involved in the brain response to acute stress. The aim of our study was evaluate the role of the 5-HT_1A receptors in serotoninergic cells of rostral and caudal raphe nuclei under acute immobilization in rats. Double immunocytochemical staining of 5-hydroxy-tryptamine and c-Fos protein and stereology techniques were used to study the specific cell activation in the raphe nuclei neurons in five groups (control group, immobilization group (immobilization lasting 1 h), DPAT group (8-OH-DPAT 0.3 mg/kg, s.c.), DPAT + IMMO group (8-OH-DPAT 0.3 mg/kg, s.c., 30′ prior acute immobilization) and WAY + DPAT + IMMO group (WAY-100635 0.3 mg/kg, s.c. and 8-OH-DPAT 0.3 mg/kg, s.c., 45′ and 30′, respectively, before immobilization). Our results showed an increase in the number of c-Fos immunoreactive nuclei in serotoninergic cells in both dorsal and median raphe nuclei in the immobilized group. The 8-OH-DPAT pretreatment counteracted the excitatory effects of the acute immobilization in these brain regions. In addition, WAY-100635 administration reduced the effect of 8-OH-DPAT injection, suggesting a selective 5-HT_1A receptor role. Raphe pallidus and raphe obscurus did not show any differences among experimental groups. We suggest that somatodendritic 5-HT_1A receptors in rostral raphe nuclei may play a crucial role in both mediating the consequences of uncontrollable stress and the possible beneficial effects of treatment with 5-HT_1A receptor agonists.     

Clozapine and PD149163 elevate prepulse inhibition in Brown Norway rats

Unmedicated schizophrenia patients exhibit deficits in prepulse inhibition (PPI) of the acoustic startle response. Similar deficits can be induced in rodents via a variety of manipulations and these deficits can be reversed by antipsychotics. Brown Norway (BN) rats exhibit natural PPI deficits under certain parametric conditions. We treated BN rats with haloperidol or clozapine to determine if the BN rat is a useful animal model with predictive validity for the effects of antipsychotics. In addition, we also tested PD149163, a neurotensin-1 receptor agonist, which has been shown to exhibit antipsychotic-like effects in several other animal models. BN rats received subcutaneous injections of either saline or one of two doses of haloperidol (0.5 mg/kg, 1.0 mg/kg), clozapine (7.5 mg/kg, 10 mg/kg) or PD149163 (1.0 mg/kg, 2.0 mg/kg). PPI was measured in startle chambers 30 min after injection. Systemic clozapine and PD149163 but not haloperidol facilitated PPI in BN rats (p < .001). This drug response profile suggests that the BN rat may be useful for detecting atypical antipsychotics and antipsychotics with novel mechanisms of action. The results also add to the evidence suggesting that PD149163 may have antipsychotic properties.     

Effects of olanzapine and clozapine on memory acquisition, consolidation and retrieval in mice using the elevated plus maze test

Clozapine and olanzapine are antipsychotic drugs commonly used to treat schizophrenia and psychosis; however, few studies have investigated their effects on cognitive function using animal models. Thus, the effects of olanzapine and clozapine on memory acquisition, consolidation and retrieval were investigated in naive mice using a modified elevated plus maze (mEPM) task. Olanzapine (0.15 and 0.30 mg/kg) and clozapine (0.5 and 1 mg/kg) were injected intraperitoneally (i.p.) into male Balb-c mice before training, immediately after training or before the second day of the trial. Our results showed that both olanzapine and clozapine disrupted the acquisition of spatial memory. In addition, clozapine impaired the consolidation of spatial memory, while olanzapine had no effect. Furthermore, olanzapine and clozapine significantly disrupted memory retrieval in naive mice. Thus, these results at least suggest that olanzapine can be a superior treatment for schizophrenia compared to clozapine.     

Ketamine-related expression of glutamatergic postsynaptic density genes: Possible implications in psychosis

Systemic administration of ketamine, a non-competitive antagonist of the N-methyl-d-aspartate receptor (NMDA-R), produces a condition of NMDA-R hypofunction, which is considered one of the putative molecular mechanisms involved in psychosis. In this study, we evaluated the effect of ketamine on glutamatergic markers of the postsynaptic density (PSD), a pivotal site for dopamine–glutamate interaction. We assessed gene expression of Homer1a, α and βCaMKII, and dopamine transporter (DAT) by two different doses of ketamine. These genes were chosen because of their impact on signal transduction and dopamine–glutamate interplay in postsynaptic density. Moreover, Homer1a is modulated by antipsychotics and represents a candidate gene for schizophrenia. Male Sprague–Dawley rats were injected with saline, 12 mg/kg ketamine or 50 mg/kg ketamine, and sacrificed 90 minutes after injections. In situ hybridization histochemistry was used to quantitate the rate of gene expression in rat forebrain. Homer1a was induced by 50 mg/kg ketamine in ventral striatum and by both 50 and 12 mg/kg ketamine in nucleus accumbens, whereas gene expression was not affected in dorsal striatum. αCaMKII was increased by 12 mg/kg ketamine against saline in almost all subregions assessed. βCaMKII was not affected by ketamine. DAT was increased by both doses of ketamine in the ventro-tegmental area and substantia nigra pars compacta. We suggest that these changes may represent molecular adaptations to the perturbation in glutamatergic transmission induced by ketamine blockade of NMDA receptors and may be implicated in molecular alterations occurring in schizophrenia.     

The effect of intra-arterial papaverine on ECoG activity in the ketamine anesthetized rat

The opium alkaloid papaverine (PPV) causes vasodilatation of the cerebral arteries through direct action on smooth muscle that reduces the constriction of smooth muscle. Intra-arterial papaverine (IAP) has been used widely to increase the regional cerebral blood flow in order to reverse the cerebral vasospasm that occurs during endovascular procedures. IAP-induced seizures have been reported, although PPV has anticonvulsive effects. This study determined the effects of IAP on electrocorticography (ECoG) in the ketamine anesthetized rats. We used 24 Sprague–Dawley male rats weighing 200–250 g. The animals were divided randomly into four groups: three treatment groups (groups 1–3) and a control (group 4). Groups 1, 2, and 3 were given 1, 7, and 14 mg/kg IAP, respectively. The ECoG was compared across groups. Our results indicated that IAP did not cause seizures and that it decreased the frequency of ketamine-induced epileptiform activity in the 14 mg/kg group.     

Determination of amino acid levels in the rat striatum,after administration of ethanol alone and associated with ketamine,a glutamatergic antagonist

The main goal of this study was to determine the amino acids (glutamate, aspartate, glutamine and tyrosine) levels in the rat striatum, after ethanol administration alone and/or associated with ketamine. In protocol 1 (Et + ketamine-1), ethanol was administered to male Wistar rats until the 7th day, and at the next day the group received only ketamine (25 mg/kg, i.p.) up to the 14th day. In protocol 2 (Et + ketamine-2), ethanol was also administered up to the 7th day, and was associated with ketamine from the 8th up to the 14th day. In other groups, animals were treated daily with ethanol (4 g/kg, p.o.), for 7 or 14 days or ketamine daily for 7 days. Controls were administered with distilled water for 7 days. Results showed that, in protocol 1, aspartate (ASP) levels increased after ketamine administration, as compared to the controls. This effect was inhibited in the group Et + ketamine-1. Ethanol (7 days) increased glutamate (GLU) levels, as compared to control, and this effect did not differ significantly from that observed in the ketamine group. When ketamine was administered after the ethanol withdrawal (protocol 1), no alterations in those amino acid concentrations were seen, as compared to the control and ketamine groups. A tendency for increasing GLU levels was observed, after administration of ethanol (14 days) or ketamine alone or associated (protocol 2), when compared to control values. In protocol 2, TYR levels decreased as related to controls and to the 14-day ethanol-treated group. We can assume that ketamine presents only an antagonist effect, in animals pretreated with ethanol, followed by ketamine administered from the 8th day on. This is due to the fact that NMDA receptors are already sensitized, leading to a decrease in these receptors functions and consequently to ASP and GLU releases.     

Social isolation produces anxiety-like behaviors and changes PSD-95 levels in the forebrain

Lesions of the rat entopeduncular nucleus (EPN), the equivalent to the human globus pallidus internus (GPi), have been shown to improve deficient prepulse inhibition (PPI) induced by the dopamine agonist apomorphine. We here tested the effect of EPN lesions on the PPI-disruptive effect of the non-competitive NMDA receptor antagonist dizocilpine in rats. Neurotoxic bilateral lesions of the EPN were induced by ibotenic acid (4 μg in 0.4 μl). Rats were tested for PPI and locomotor activity after systemic injection of dizocilpine (vehicle and 0.15 mg/kg). Bilateral EPN lesions further deteriorated the PPI deficit induced by dizocilpine, while locomotion was not affected. This work indicates that the EPN is an important brain region within the neuronal circuit responsible for NMDA receptor antagonist-induced PPI deficits.     

Effects of antipsychotic drugs on BDNF, GSK-3β, and β-catenin expression in rats subjected to immobilization stress

Brain-derived neurotrophic factor (BDNF), glycogen synthase kinase-3β (GSK-3β), and β-catenin have been reported to be altered in patients with schizophrenia and have been targeted by antipsychotic drugs. Atypical antipsychotics, but not typical antipsychotics, exert neuroprotective effects by regulating these proteins. In this study, we analyzed the effects of the atypical antipsychotic drugs olanzapine and aripiprazole and a typical antipsychotic drug, haloperidol, on the expression of BDNF, phosphorylated GSK-3β, and β-catenin in the hippocampus of rats subjected to immobilization stress. Rats were subjected to immobilization stress 6 h/day for 3 weeks. The effects of olanzapine (2 mg/kg), aripiprazole (1.5 mg/kg), and haloperidol (1.0 mg/kg) were determined on BDNF, serine⁹-phosphorylated GSK-3β, and β-catenin expression by Western blotting. Immobilization stress significantly decreased the expression of BDNF, phosphorylated GSK-3β, and β-catenin in the hippocampus. Chronic administration of olanzapine and aripiprazole significantly attenuated the decreased expression of these proteins in the hippocampus of rats caused by immobilization stress, and significantly increased the levels of these proteins even without the immobilization stress. However, chronic haloperidol had no such effect. These results suggest that olanzapine and aripiprazole may exert beneficial effects by upregulating BDNF, phosphorylated GSK-3β, and β-catenin in patients with schizophrenia.     

Ketamine-induced rotational asymmetry in evaluation of motor disturbances in rats with middle cerebral artery occlusion

Intraperitoneal injection of ketamine in subanesthetic doses to Wistar rats with unilateral occlusion of the middle cerebral artery caused ipsilateral rotation (2-10 rpm), which was recorded in an automatic rotameter. The optimal dose of ketamine was 50 mg/kg. The animals were examined in an automatic rotameter for 40 min. Motor asymmetry persisted for no less than 2 months after surgery. According to the neurological test (Menzies scale) motor asymmetry in animals with focal brain ischemia persisted for no more than 30 days. The degree of ketamine-induced motor asymmetry in intact rats was 0.10±0.03 rpm.     

Effects of ethanol, Δ-tetrahydrocannabinol,or their combination on object recognition memory and object preference in adolescent and adult male rats

Recent advances have been made in our understanding of the deleterious effects of both ethanol and THC on adolescent behavior and brain development. However, very little is known about the combined effects of EtOH + THC during adolescence, a time in which these drugs are often used together. The purpose of this experiment was to: (1) determine whether EtOH and/or THC induced greater working memory impairment in adolescent than adult male rats using the novel object recognition (NOR) task and (2) determine whether the EtOH + THC combination would produce a more potent additive effect in adolescents than adults when compared to these drugs alone. NOR was performed with a 24 h delay under each of the four drug conditions: vehicle; 1.5 g/kg ethanol; 1.0 mg/kg THC; and 1.5 g/kg EtOH + 1.0 mg/kg THC, at 72 h intervals. The results show that there was an age effect on working memory in NOR after the EtOH + THC challenge. Specifically, adolescent animals showed a preference for the familiar object whereas adults showed no preference for the novel or familiar object, the latter being characteristic of a classic working memory deficit. These effects were not dependent on changes in exploration across session, global activity across drug condition, or total object exploration. These novel findings clearly indicate that further understanding of this age–drug interaction is crucial to elucidating the influence that adolescent EtOH + THC use may have on repeated drug use and abuse later in life.     

Lamotrigine blocks repeated high-dose methamphetamine-induced behavioral sensitization to dizocilpine (MK-801), but not methamphetamine in rats

We recently proposed a new psychostimulant animal model of the progressive pathophysiological changes of schizophrenia. Studies using that model produced a treatment strategy for preventing progression. Lamotrigine (LTG) blocks repeated high-dosage methamphetamine (METH)-induced initiation and expression of prepulse inhibition deficit and development of apoptosis in the medial prefrontal cortex (mPFC). Moreover, it inhibits METH-induced increases in extracellular glutamate levels in the mPFC (Nakato et al., 2011, Neurosci. Lett.). Abnormal behavior induced by METH or NMDA receptor antagonists is regarded as an animal model of schizophrenia. This study examined the effects of LTG on the development of behavioral sensitization to METH and cross-sensitization to dizocilpine (MK-801) by repeated administration of high-dose METH (2.5 mg/kg, 10 times s.c.). Rats were injected repeatedly with LTG (30 mg/kg) after 120 min METH administration (2.5 mg/kg). Repeated co-administration of LTG blocked the development of behavioral cross-sensitization to MK-801 (0.15 mg/kg), but it did not prevent behavioral sensitization to METH (0.2 mg/kg). The LTG-induced prevention of increased glutamate by high-dose METH might be related to the former finding. Combined results of our previous studies and this study suggest that LTG is useful to treat schizophrenia, especially at a critical point in its progression.     

Inactivation of the ventromedial prefrontal cortex mimics re-emergence of heroin seeking caused by heroin reconditioning

The purpose of this study was to investigate the role of the ventromedial prefrontal cortex (vmPFC) in the expression of extinguished heroin seeking as measured by conditioned place preference (CPP) in males Sprague–Dawley rats (n = 25). Heroin place conditioning (0.3 mg/kg SC × 4 sessions) was followed by a test of preference 24 h later, extinction (saline × 4 sessions), heroin reconditioning (saline or 1.0 mg/kg × 1 session), and a second test of place preference 24 h later. Fifteen minutes prior to this test, rats received intra-vmPFC infusions (bilateral, 0.5 μl/side) of a mixture of GABA_A (muscimol; 0.03 nmol) and a GABA_B (baclofen; 0.3 nmol) agonists, or vehicle. As expected on the basis of previous studies, reconditioning with heroin resulted in the re-emergence of a CPP. Importantly, inactivation of the vmPFC produced the same effect in animals that did not receive heroin on the session of reconditioning. These results indicate that the vmPFC modulates expression of extinguished heroin seeking and suggest that prefrontal inhibitory mechanisms are involved in relapse to drug seeking.     

Effect of muscle length on the recruitment property of single motor units in humans

Antipsychotic therapy is frequently associated with several side effects such as hyperprolactinemia. The influence of a putative antipsychotic JL 13 on prolactin release was assessed after intraperitoneal injection in gentled male rats in comparison with clozapine and haloperidol. A total of 30 or 150 min after administration, whole blood was collected for preparing serum samples. Prolactin was quantified by radioimmunoassay method. At 30 min, JL 13 like clozapine, increased prolactin concentration only at the higher dose (30 mg/kg) while haloperidol at both tested doses induced a dramatic increase of prolactin concentration. At 150 min after injection, only haloperidol (0.3 mg/kg) significantly increased serum prolactin level. This minimal effect on prolactinemia reinforces the similarity of clozapine and JL 13 regarding the atypical antipsychotic profile.     

Chronic high-dose haloperidol has qualitatively similar effects to risperidone and clozapine on immediate-early gene and tyrosine hydroxylase expression in the rat locus coeruleus but not medial prefrontal cortex

Acute administration of clozapine has been reported to activate the locus coeruleus (LC) and beta-adrenoceptor-dependent Fos immunoreactivity in the medial prefrontal cortex (mPFC) in rodents. Haloperidol is reported to exhibit a similar acute effect on LC firing and beta-adrenoceptor dependent Fos immunoreactivity in the mPFC but only at high doses. We compared the effects of chronic 4-week treatment with risperidone (1mg/kg/day s.c.), clozapine (10mg/kg/day s.c.) or a high dose of haloperidol (4mg/kg/day s.c.) on immediate-early gene protein (c-Fos, Egr-1 and Egr-2) and tyrosine hydroxylase (TH) expression. In the mPFC, haloperidol decreased, whereas clozapine increased, c-Fos immunoreactivity. Only haloperidol increased Egr-1 immunoreactivity. There was no significant effect on Egr-2 immunoreactivity. In the LC, both Egr-1 and Egr-2 expression was down regulated by all three antipsychotics. Clozapine and risperidone increased TH immunoreactivity in both mPFC and LC. Haloperidol caused a smaller increase in TH expression in the LC, but did not alter expression in the mPFC. In conclusion, despite qualitatively similar effects in the LC, chronic treatment with haloperidol had different effects to clozapine and risperidone in the mPFC. This may relate to the reported advantage of clozapine and risperidone over haloperidol against prefrontal cortical-dependent cognitive and negative symptoms.