Cannabidiol and Sodium Nitroprusside: Two Novel Neuromodulatory Pharmacological Interventions to Treat and Prevent Psychosis

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1 Send Orders for Reprints to 970 CNS & Neurological Disorders - Drug Targets, 2015, 14, Cannabidiol and Sodium Nitroprusside: Two Novel Neuromodulatory Pharmacological Interventions to Treat and Prevent Psychosis José Alexandre Crippa *,1, Jaime Eduardo Cecílio Hallak 1, Vanessa Costhek Abílio 2, Acioly Luiz Tavares de Lacerda 3 and Antonio Waldo Zuardi 1 1 Department of Neuroscience and Behavior, University of São Paulo, Ribeirão Preto, São Paulo, Brazil 2 Department of Pharmacology, Universidade Federal de São Paulo, São Paulo, Brazil 3 Department of Psychiatry, Universidade Federal de São Paulo. São Paulo, Brazil Abstract: Since most patients with schizophrenia do not respond properly to treatment, scientific effort has been driven to the development of new compounds acting on pharmacological targets beyond the dopaminergic system. Therefore, the aim is to review basic and clinical research findings from studies evaluating the effects of cannabidiol (CBD), an inhibitor of the reuptake and metabolism of anandamide and several other effects on nervous system, and sodium nitroprusside, a nitric oxide donor, on the prevention and treatment of psychosis. Animal and human research supports that CBD and sodium nitroprusside might be effective in the prevention and treatment of psychosis in general and especially in schizophrenia. The evidence available to date shows that CBD and sodium nitroprusside act in pathways associated with psychotic and that they may be important agents in the management of prodromal psychotic states and psychosis. This underscores the relevance of further research on the effects of these agents and others that mediate the activity of the cannabinoid system and of nitric oxide, as well as comparative studies of their antipsychotic effects and those of other antipsychotic drugs currently used to treat schizophrenia. Keywords: Antipsychotic, cannabidiol, psychosis, schizophrenia, sodium nitroprusside. 1. INTRODUCTION Different sources of evidence suggest that early intervention in psychosis is associated with better outcomes. In addition, data from prevention programs have demonstrated that attenuated psychotic manifestations can be reliable predictors to transition in a significant proportion of subjects in ultra high risk for psychosis (UHR). Research has shown that even UHR subjects who do not develop psychosis usually have impaired social functioning, high distress levels and various comorbid conditions, carrying a poor prognosis for a range of adverse sequela. Keeping this is mind, preventive interventions have been designed to address a number of psychopatological manifestations and functional impairments associated with them [1]. Although still limited, pharmacological trials involving UHR subjects have provided insights on the potential role of some drugs as strategies to prevent psychosis. Antipsychotic drugs were shown to prevent transition to psychosis in UHR subjects, with decreases in transition rates ranging from 37 to 45% [2]. However, major concerns have been raised in respect to preventive interventions based on antipsychotics because of tolerability issues. In fact, significant side effects occur in most individuals exposed to this class of medicat- ions, including metabolic syndrome and extrapyramidal such as akathisia, parkinsonism and tardive dyskinesia. Additionally, since the introduction of the first antipsychotic six decades ago, D2 receptor antagonists were proven to have little efficacy in the treatment of the negative and cognitive of schizophrenia and a significant proportion of patients are refractory to drugs whose main mechanism of action is related to decreases in dopamine activity. Motivated mainly by safety and tolerability concerns, recently published guidelines have discouraged the use of antipsychotic drugs as first line treatment for UHR subjects [2]. Thus, there is an urgent need for pharmacological compounds with novel mechanisms of action to treat UHR and schizophrenia subjects. Considerable efforts have been directed over the past decades to develop novel compounds with pharmacological targets beyond the dopaminergic system; however, evidence on the efficacy of agents acting in pathways other than dopamine is still scarce. In the present manuscript, we present and discuss basic and clinical research findings from studies evaluating the effects of cannabidiol (an inhibitor of the reuptake and metabolism of anandamide and several other effects on nervous system) and sodium nitroprusside (a nitric oxide donor) on the prevention and treatment of psychotic symptomatology. *Address correspondence to this author at the Hospital das Clínicas - Terceiro Andar; Av. Bandeirantes, 3900; RibeirãoPreto -São Paulo, CEP , Brazil. jcrippa@fmrp.usp.br /15 $ Bentham Science Publishers

2 Cannabidiol and Sodium Nitroprusside CNS & Neurological Disorders - Drug Targets, 2015, Vol. 14, No SEARCHING STRATEGY AND SELECTION CRITERIA The articles selected for the review were identified through searches in English, Portuguese, and Spanish in the electronic databases ISI Web of Knowledge, SciELO, PubMed, and PsycINFO, combining the search terms "cannabidiol and psychosis", "cannabidiol and schizophrenia", "sodium nitroprusside and psychosis" and "sodium nitroprusside and schizophrenia". The reference lists of the publications included, review articles, and book chapters were handsearched for additional references. Experimental animal and human studies were included, with no time restraints Cannabidiol Recent evidence suggests that a new drug to alleviate psychotic could be obtained from one of the oldest plants used by humans as a medicine: Cannabis sativa. This may sound paradoxical, as the earliest references to the use of Cannabis - confirmed over time and by recent research - show that high concentrations of its main psychoactive component, 9 -tetrahydrocannabinol ( 9 -THC) in fact induce psychotic [3]. However, we know today that cannabis contains more than 80 cannabinoids, many of which have pharmacological properties. The first evidence that one of such compounds could antagonize the effects of 9 -THC emerged from a study on the interaction between cannabidiol (CBD) and 9 -THC in healthy volunteers [4]. The co-administration of the two cannabinoids induced less anxiety and psychotomimetic than 9 -THC alone. This observation triggered a series of studies, in both animals and humans, which have established a link between CBD and antipsychotic effects (Table 1). In animals, evidence of the antipsychotic effects of CBD was obtained from different models used to assess antipsychotic activity, including apomorphine-induced stereotypy, prolactin levels, amphetamine- and ketamineinduced hyperlocomotion, MK-801 induced pre-pulse inhibition (PPI) disruption, social withdrawal provoked by 9 -THC and MK-801, and MK-801-induced hyperactivity [3]. Recently, we have demonstrated that CBD also attenuates the contextual fear conditioning deficit [12] and PPI disruption displayed by spontaneously hypertensive rats (SHR), suggested by our group as a new animal model to study schizophrenia [29]. There have been, however, some negative results that may be attributable to methodological differences in the models or in CBD administration regimes: MK-801-induced hyperactivity was attenuated by CBD in a modified experimental set-up, but not in the open field test [1]. Also, Long and colleagues found no effects of acute doses of CBD on hyperlocomotion induced by amphetamine, although chronic treatment was effective [9]. In SHR, no beneficial effects of acute CBD were observed on either the hyperlocomotion or social interaction deficits presented by this strain [13]. We speculated whether the chronic administration of CBD could be effective against these behavioral manifestations and, recently, we found that the long-term treatment with CBD in adolescence is able to prevent hyperlocomotion, PPI disruption, and the fear conditioning deficits displayed by adult SHRs (submitted), pointing for the first time to the preventive potential of this compound against schizophrenia. The view that CBD could have antipsychotic effects is further supported by studies in healthy human subjects with artificially induced psychosis. CBD was shown to attenuate psychotic caused by acute administration of 9 - THC, the perceptual impairment of the illusory image (Binocular Depth Inversion test) induced by nabilone, and depersonalization induced by ketamine [3]. Naturalistic studies with marijuana users suggest a protective effect of high CBD concentrations in samples of the plant against psychotic. Researchers measured 9 -THC/CBD ratios in hair samples of cannabis users and observed that subjects who had only 9 -THC in their hair had more positive psychotic than those with a mixture of 9 -THC and CBD [18, 20]. Studying users in episodes of acute intoxication by cannabis samples with high and low concentrations of CBD, those same researchers failed to find any protective effects of CBD against psychotomimetic [20]. However, this lack of protective effects could be attributed to a lower CBD/THC ratio in the cannabis samples smoked by users compared with studies in which such effects were observed. The first case report of a schizophrenia patient treated with CBD involved a female patient with severe side effects from conventional antipsychotics [24]. The patient was treated with CBD for four weeks and had a significant reduction in the Brief Psychiatric Rating Scale (BPRS) scores. In a similar study, three male patients with treatment resistant schizophrenia were treated with CBD for 30 days and only one had a partial improvement [25]. However, of the two patients who did not respond, one responded only to clozapine and the other did not respond even to this drug. An open clinical trial with six outpatients with Parkinson s disease (PD) who had psychotic showed a significant reduction in the scores of the BPRS and the Parkinson Psychosis Questionnaire under CBD treatment added to treatment as usual [26]. To date, two double-blind controlled clinical trials investigated the efficacy and tolerability of CBD in schizophrenia patients. One study compared the effects of CBD and amisulpride, an atypical antipsychotic, in 42 schizophrenia patients treated for four weeks [28]. Both treatments caused significant reductions in psychotic, with no differences between them; however, CBD induced fewer side effects. The other study compared CBD and placebo in first-episode schizophrenia patients treated for 14 days in a cross-over condition [27]. CBD significantly attenuated psychotic after 14 days when compared to baseline, although the differences from placebo failed to reach statistical significance. Despite the existence of negative results, the studies mentioned above suggested an antipsychotic action of CBD. The mechanism through which CBD exerts its antipsychotic effect is not yet clear; however, some experimental results allow the formulation of initial hypotheses.

3 972 CNS & Neurological Disorders - Drug Targets, 2015, Vol. 14, No. 8 Crippa et al. Table 1. Antipsychotic effects of cannabidiol (CBD). Animal Models Mode Subjects Results (Symbol*) Dose with Significant Results References Apomorphine stereotypy Rats Reduction (+) 60 mg/kg Zuardi et al., 1991 [5] Prolactin levels Rats Increase (+) 240 mg/kg Zuardi et al [5] Amphetamine hyperlocomotion Mice Reduction (+) 30, 60 mg/kg Ketamine hyperlocomotion Mice Reduction (+) 30 mg/kg Moreira & Guimarães, 2005 [6] Moreira & Guimarães, 2005 [6] MK PPI disruption Mice Reduction (+) 5 mg/kg Long et al., 2006 [7] 9 -THC- social withdrawal Rats Reduction (+) 20 mg/kg Malone et al., 2009 [8] D-amphetamine hyperlocomotion Mice Negative acute effect Reduction after chronic (21 days) use ( - ) (+) - 50 mg/kg Long et al., 2010 [9] PPI - increase Mice Increase (acute and chronic) (+) 1, 5, 50 mg/kg Long et al., 2010 [9] MK PPI disruption Rats No change ( - ) - MK hyperlocomoion Rats No effect ( - ) - MK social withdrawal Rats Reduction (partially) (+) 3, 10 mg/kg Gururajan et al., 2011 [10] Gururajan et al., 2011 [10] Gururajan et al., 2011 [10] 9 -THC (chronic) - social withdrawal Rats Potentiated ( - ) 3 mg/kg Klein et al., 2011 [11] SHR 1 decreased freezing 2 Rats Reduction (+) 1 mg/kg Levin et al., 2012 [12] response to CFC SHR 1 strain -hyperlocomotion Rats No change ( - ) - Almeida et al., 2013 [13] SHR 1 strain - deficit in social interaction Rats No change ( - ) - Almeida et al., 2013 [13] SHR 1 strain -PPI disruption Rats Reduction (+) 30 mg/kg Levin et al., 2014 [14] Psychotic Models in Humans 9 -THC induced psychotic Healthy humans Reduction (+) 1mg/kg Zuardi et al., 1982 [15] Nabilone-induce impaired perception of BDI 3 Healthy humans Reduction (+) 200 mg Leweke et al., 2000 [16] Auditory evoked mismatch negativity Healthy humans CBD + THC > THC alone (+) 5, 4 mg Juckel et al., 2007 [17] 9 -THC/CBD ratio in hair samples Cannabis users Protective effect on psychotic (+) - Morgan and Curran, 2008 [18] 9 -THC (IV) induced psychotic Healthy humans Reduction (+) 5 mg (IV) Bhattacharyya et al., 2010 [19] Acute cannabis intoxication Cannabis users No difference between low (0.02) and high (0.64) CBD/THC ratio ( - ) - Morgan et al., 2010 [20] Ketamine induced dissociative Healthy humans Reduction (+) 600 mg Hallak et al., 2011 [21] 9 -THC/CBD ratio in hair samples Cannabis users Protective effect on psychotic (+) - Morgan et al., 2012 [22] 9 -THC (IV) induced psychotic Healthy humans Reduction (+) 600 mg Englund et al., 2013 [23]

4 Cannabidiol and Sodium Nitroprusside CNS & Neurological Disorders - Drug Targets, 2015, Vol. 14, No (Table 1) contd.. Clinical Studies Mode Subjects Results (Symbol*) Dose with Significant Results References Case report Case report Open clinical trial Double-blind, cross-over clinical trial compared with placebo Double-blind, randomized clinical trial compared with amisulpride One schizophrenia patients Three treatmentresistant schizophrenia patients Six Parkinson s Disease with psychotic sympt oms Eighteen firstepisode schizophrenia patients Forty-two schizophrenia patients Reduction psychotic (+) One patient had partial improvement (+/-) Reduction psychotic (+) Reduction psychotic (+/-) Significant clinical improvement equivalent to amilsulpride (+) Up to 1500 mg/day (four weeks) Up to 1280 mg/day (30 days) 150 to 400mg/day (four weeks) 800 mg/day (14 days) 800 mg/day (four weeks) Zuardi et al., 1995 [24] Zuardi et al., 2006 [25] Zuardi et al., 2009 [26] Leweke et al., 2011 [27] Leweke et al., 2012 [28] * Positive (+) or Negative (-) antipsychotic effect; 1- SHR = Spontaneously Hypertensive Rats; 2 - CFC = Contextual Fear Conditioning; 3 - BDI = Binocular Depth Inversion. Experimental evidence provides clues concerning brain areas that seem to underlie the antipsychotic action of CBD. In animals, CBD increased neuronal activation as assessed through c-fos expression in the prefrontal cortex and nucleus accumbens, but not in the dorsal striatum, a profile similar to that seen for clozapine and different from that of haloperidol. This atypical antipsychotic profile is consistent with the noncatatonic effect of CBD in rodents. In healthy humans, functional magnetic resonance imaging (fmri) studies showed opposite brain activation patterns following the administration of CBD and 9 -THC in a dose able to induce psychotic [3, 30]. Compared to placebo, the psychotic-like effects of 9 -THC were correlated with decreased activation in the ventral striatum and anterior cingulate gyrus during word recall, in the dorsal striatum during oddball stimuli processing, and in the right temporal cortex during auditory processing. In all these areas, the effects of CBD on brain activation compared to placebo were opposite to those of THC, suggesting that they may be involved in CBD s antipsychotic properties (Fig. 1). The pharmacological mechanisms underlying the antipsychotic action of CBD must be complex as this cannabinoid interferes with neurotransmitter systems in a number of ways [3]. Specifically, the inhibition of the reuptake and metabolism of anandamide may be implicated in the antipsychotic effect of CBD. Anandamide concentrations in the cerebrospinal fluid (CSF) of schizophrenia patients are higher than those of healthy volunteers and patients with affective disorders and dementia, and are negatively correlated with psychotic [33]. This inverse correlation suggests the existence of a feedback mechanism in which the anandamide increase counterbalances the occurrence of psychotic. Two additional observations lend support to this view: (1) patients in prodromal states of psychosis have higher levels of anandamide in the CSF than controls and higher anandamide concentrations are associated with delayed onset of full-blown psychosis [34]; and (2) the clinical improvement of schizophrenia patients under CBD has been associated with increased CSF anandamide levels [28]. The influence of CBD on anandamide regulation in brain areas related to the pathophysiology of schizophrenia could explain its antipsychotic action, as hypothesized recently [3]. Additional mechanisms that could explain the antipsychotic action of CBD include the CBD-induced increase in hippocampal neurogenesis, its interaction with 5HT1A and TRPV1 receptors, and its antioxidant and neuroprotective effects [35-38]. It is also important to highlight that certain second-generation ( atypical ) antipsychotics, such as aripiprazole and ziprasidone also activate 5-HT1A receptors. This mechanism may, at least in part, help to explain the favorable safety extrapyramidal side effects profile of CBD Sodium Nitroprusside A new paradigm for the treatment of schizophrenia seems to arise from the modulation of the nitric oxide (NO) pathway. Our group has recently published the results of a double-blind placebo controlled trial showing that an infusion of sodium nitroprusside (SNP) improved acute psychotic of schizophrenia patients within few hours. After the infusion, SNP leads to an increase in the levels of NO. To our knowledge, this was the first time that the antipsychotic properties of SNP in humans were shown [39]. The rationale for this experiment was based on the glutamatergic hypothesis of schizophrenia. There is robust evidence suggesting that this hypothesis offers a better explanation for the main presented by schizophrenia patients than the dopamine hypothesis alone, since drugs such as ketamine and phencyclidine (PCP), which cause the blockade of N-methyl-D-aspartate (NMDA) glutamate receptors, induce positive, negative, thought disorder, and cognitive that closely resemble those of schizophrenia [40].

5 974 CNS & Neurological Disorders - Drug Targets, 2015, Vol. 14, No. 8 Crippa et al. Fig. (1). Bar graph (mean+ SEM) of fmri activation results on: left caudate during visual oddball salience processing; ventral striatum during word retrieval; right temporal cortex during auditory processing. Opposite effects of THC and CBD relative to placebo were observed in these brain areas, in which there was a significant correlation, during specific tasks, between psychotic and 9-THC attenuation of fmri activation [19, 31, 32]. The NMDA receptor (Fig. 2) is activated by a complex interaction between the neurotransmitter glutamate, the coagonists d-serine and glycine, and the depolarization of postsynaptic membrane potential resulting in calcium influx into the cell. Calcium binds to calmodulin and stimulates the neuronal nitric oxide synthase (nnos) enzyme, which produces NO in the central nervous system (CNS). Then, NO activates soluble guanylate cyclase that increases the production of cyclic GMP (cgmp), which in turn influences the activity of kinase cascades, mrna stability and translation, transcription factors and primary gene products in target cells. In other words, the blockade of NMDA reduces the production of NO [40]. After a preclinical study showing that the infusion of SNP attenuated the psychosis-like behavior and c-fos expression in the brain of rats induced by PCP, our group designed this translational trial to evaluate the effects of the NO donor in acute schizophrenia exacerbation in humans. We found a marked improvement of positive, negative, anxious and depressive in patients with schizophrenia after a single four-hour infusion of SNP compared to placebo [39]. Although the trial involved a small sample and replication is required in larger samples, the results are promising and strongly encourage further investigation. Despite the above, there is no consensus concerning the role of nitric oxide in schizophrenia, and there are several studies showing contradictory results in this area (see Table 2). Some of them support our hypotheses and suggest a deficit in NO-mediated neurotransmission in schizophrenia, whereas others support the opposite, that is, an enhancement of activity in NO-mediated neurotransmission. In an attempt to understand these contradictory findings [41], we made a separate analysis including only those studies that involved schizophrenia patients under antipsychotic treatment and found a significant difference between patients and controls

6 Cannabidiol and Sodium Nitroprusside CNS & Neurological Disorders - Drug Targets, 2015, Vol. 14, No Fig. (2). Regular function of the N-methyl-D-aspartate (NMDA) and psychosis as a result of disrupted (nitric oxide) NO production. (A) The activation of NMDA receptors by glutamate results in calcium influx into the cell, which binds to calmodulin (CaM) and stimulates the neuronal nitric oxide synthase (nnos) enzyme to produce NO. NO activates guanylate cyclase, which increases the levels of the second messenger cyclic GMP which in turn influences the activity of kinase cascades, transcription factors and primary gene products. (B) Phencyclidine (PCP) blocks the calcium influx into NMDA receptorsand affects the conversion of L-arginine into NO and L-citrulline by nnos disrupting regular kinase cascades and causing psychosis. (C) The reestablishment of NO availability by the administration of annodonor reverses PCP-induced psychosis. (effect size g = 0.663, 95%CI = to 0.961, p < 0.001), showing that patients taking antipsychotic medications have higher levels of plasma/serum NO than healthy volunteers [42]. In one interesting example, Lee and colleagues [43] reported decreased serum levels of NO in schizophrenia patients compared to control subjects at baseline, and that a six-week antipsychotic treatment with risperidone increased NO levels, which, in turn, were associated with psychotic improvement. The authors described that, among the patients with clinical improvement ( 30% in PANSS total score), NO levels increased significantly after risperidone treatment, and argued that this better outcome could be due to a normalization of reduced NO levels after treatment [43].

7 976 CNS & Neurological Disorders - Drug Targets, 2015, Vol. 14, No. 8 Crippa et al. Table 2. Pharmacological studies in schizophrenia evaluating nitric oxide (NO) and/or their metabolites. References Study Main Findings Deutsch et al., 1997 [44] Taneli et al., 2004 [45] Atmaca et al., 2007 [46] Lee and Kim, 2008 [43] Goff et al., 2009 [47] Arinola and Idonije, 2009 [48] Nakano et al., 2010 [49] Zhang et al., 2012 [50] Minutolo et al., 2012 [51] Hallak et al., 2013 [39] Adjuvant therapy with Methylene Blue showed a modest improvement in CGI, with no significant improvement in the BPRS or SANS 8S Increased plasma total nitrite levels / no significant difference was found after 6 week antipsychotic treatment 20S /20C Increased plasma total nitrite levels and decreased after 6 week treatment with olanzapine 21S / 21C Decreased plasma total nitrite levels before and after 6 week risperidone treatment / Increased plasma total nitrite levels after treatment in the responders subgroup 55S (31 Drug Naïve) / 55C Sildenafil 50 and 100 mg did not affect cognitive performance and expression in schizophrenia compared to placebo Higher levels of NO in drug free S compared to C and treated S Baseline NO metabolites plasma levels were lower in S compared to C, which were increased after risperidone treatment. No effects of haloperidol (20 mg) or risperidone (6 mg) in elevated NO levels in S Patients presented higher nitrate levels than controls; subjects under olanzapine reported lower nitrate levels than those treated with risperidone or haloperidol. Nitrate levels were correlated with PANSS total score After the infusion of sodium nitroprusside, a rapid (within 4 hours) improvement of was observed. The placebo and experimental groups had significant differences in the BPRS total score and subscale scores, which persisted for 4 weeks after infusion. Total Nitrite- Nitrite + Nitrate / CGI- Clinical Global Impression / BPRS- Brief Psychiatric Rating Scale / SANS- Schedule for the Assessment of Negative Symptoms / S- Schizophrenia Patients / C- Control. Additionally, in support to the view that SNP could be effective in schizophrenia, we found three interesting studies that showed increased cgmp levels in the cerebrospinal fluid of schizophrenia patients after treatment with antipsychotic drugs [52-54]. As seen before, NO induces increases in cgmp concentrations through the activation of soluble guanylate cyclase. In the same direction, there are two studies that investigated the effects of increasing cgmp levels in patients with schizophrenia through the use of sildenafil, an inhibitor of phosphodiesterase type 5 (PDE5), the enzyme responsible for the degradation of cgmp: Akhondzadeh and colleagues [55] reported the use of sildenafil as an effective strategy for the management of negative in schizophrenia, although it failed to counteract cognitive in another study. Recently, Brennand and colleagues [56] reprogrammed fibroblasts from schizophrenia patients into human induced pluripotent stem cells (hipscs) and subsequently differentiated them into neurons. These neurons showed diminished neuronal connectivity in conjunction with decreased neurite numbers, PSD-95 (postsynaptic density protein 95) levels, and glutamate receptor expression. PSD- 95, also known as SAP-90 (synapse-associated protein 90), is a protein that directly links the NR2 subunit of the NMDA receptor to nnos. Since this link is critical for the production of NO in the CNS as is glutamate receptor expression, these findings indicate that some neuronal components necessary to produce adequate levels of NO in the brain are diminished in the neurons of schizophrenia patients, corroborating the hypothesis of impaired NO neurotransmission in schizophrenia. Several pre-clinical studies support the modulatory role of NO signaling in schizophrenia, pointing to potential benefits of both increases and decreases in NO production [41, 42]. On one side, nitric oxide synthase (NOS) inhibitors can improve schizophrenia-related behavioral abnormalities induced by dopamine agonists and NMDA antagonists and an increase in brain NO levels are induced by neonatal ventral hippocampus, lesion, a neurodevelopmental animal model of schizophrenia. Conversely, the antipsychotic property of SNP described by us [39] is supported by data describing its beneficial effects against schizophrenia-related behaviors induced by dopamine agonists and NMDA antagonists. Along the same line, nitric oxide synthase inhibitors have also been shown to potentiate PCP-induced behavioral abnormalities and nnos knockout mice exhibit schizophrenia-like behaviors. Importantly, neonatal NOS inhibition induces schizophrenia-like behaviors in adulthood, indicating the role of NO signaling in the neurodevelopmental pathophysiological processes underlying schizophrenia and suggesting that this might be a potential target for preventive treatments. An important challenge for the clinical use of SNP by infusion is dealing with its side-effects. These include headache, apprehension, dizziness and restlessness associated with excessively rapid decreases in blood pressure; and ataxia, seizures, confusion and drowsiness usually due to cyanide toxicity. Therefore, the search for newer and safer ways of SNP administration is clearly needed. CONCLUSION The effects of CBD and SNP on schizophrenia patients strengthen the hypotheses of the involvement of the endocannabinoid system in schizophrenia and of the activation of the NMDA-NO-cGMP cascade as a form of improving schizophrenia faster than currently used antipsychotics. This sets new treatment paradigms in the field, informed by research based on animal models of the disorder. We believe that the development of drugs that are able to inhibit the reuptake and metabolism of anandamide, such as CBD, or to increase NO levels in the brain, such as SNP, are promising targets to be pursued in the development of the next generation of antipsychotic drugs. Therefore, the investigation of the potential preventive action of these compounds in patients in prodromal states of

8 Cannabidiol and Sodium Nitroprusside CNS & Neurological Disorders - Drug Targets, 2015, Vol. 14, No psychosis and in individuals at ultra high risk, as well as comparative studies of their antipsychotic effects and of those produced by other antipsychotics in schizophrenia patients, are clearly necessary and opportune. CONFLICT OF INTEREST JEH, AWZ and JAC are co-inventors of the patent Fluorinated CBD compounds, compositions and uses thereof. Pub. No.: WO/2014/ International Application No.: PCT/IL2014/ ACKNOWLEDGEMENTS We kindly thank Prof Maia-de-Oliveira for his comments and suggestions in the manuscript. Financial Support J.A. C (1B), A.W.Z (1C). V.C.A (1D). A.L.T.L (2) and J.E.C.H (1D) are recipients of Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brazil) Productivity fellowships. Research was supported in part by a grant from Fundação de Apoio ao Ensino, Pesquisa e Assistência do Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo (FAEPA, Brazil), Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo, Sao Paulo, Brazil (NAPNA) and National Institute for Translational Medicine (INCT-TM; CNPq, Brazil). REFERENCES [1] Miyamoto S, Miyake N, Jarskog LF, Fleischhacker WW, Lieberman JA. Pharmacological treatment of schizophrenia: a critical review of the pharmacology and clinical effects of current and future therapeutic agents. Mol Psychiatry 2012; 17: [2] McGorry PD, Nelson B, Phillips LJ, et al. Randomized controlled trial of interventions for young people at ultra-high risk of psychosis: twelve-month outcome. J Clin Psychiatry 2013; 74: [3] Zuardi AW, Crippa JA, Hallak JE, et al. 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