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Background and Objectives: Peripheral nerve blockade is associated with excellent patient outcomes after surgery; however, neurologic and other complications can be devastating for the patient. This article reports the development and preliminary results of a multicenter audit describing the quality and safety of peripheral nerve blockade.Methods: From January 2006 to May 2008, patients who received peripheral nerve blockade had data relating to efficacy and complications entered into databases. All patients who received nerve blocks performed by all anesthetists during each hospital's contributing period were included. Patients were followed up by phone to detect potential neurologic complications. The timing of follow-up was either at 7 to 10 days or 6 weeks postoperatively, depending on practice location and time period. Late neurologic deficits were defined as a new onset of sensory and/or motor deficit consistent with a nerve/plexus distribution without other identifiable cause, and one of the following: electrophysiologic evidence of nerve damage, new neurologic signs, new onset of neuropathic pain in a nerve distribution area, paresthesia in relevant nerve/plexus distribution area.Results: A total of 6950 patients received 8189 peripheral nerve or plexus blocks. Of the 6950 patients, 6069 patients were successfully followed up. In these 6069 patients, there were a total of 7156 blocks forming the denominator for late neurologic complications. Thirty patients (0.5%) had clinical features requiring referral for neurologic assessment. Three of the 30 patients had a block-related nerve injury, giving an incidence of 0.4 per 1000 blocks (95% confidence interval, 0.08-1.1:1000). The incidence of systemic local anesthetic toxicity was 0.98 per 1000 blocks (95% confidence interval, 0.42-1.9:1000).Conclusions: These results indicate that the incidence of serious complications after peripheral nerve blockade is uncommon and that the origin of neurologic symptoms/signs in the postoperative period is most likely to be unrelated to nerve blockade. [ABSTRACT FROM AUTHOR]

Rationale: Medications are urgently needed to treat symptoms of drug withdrawal and mitigate dysphoria and psychiatric comorbidities that drive opioid abuse and relapse. ITI-333 is a novel molecule in development for treatment of substance use disorders, psychiatric comorbidities, and pain., Objective: Characterize the preclinical profile of ITI-333 using pharmacological, behavioral, and physiological assays., Methods: Cell-based assays were used to measure receptor binding and intrinsic efficacy of ITI-333; animal models were employed to assess effects on opioid reinstatement, precipitated oxycodone withdrawal, and drug abuse liability., Results: In vitro, ITI-333 is a potent 5-HT 2A receptor antagonist (K i  = 8 nM) and a biased, partial agonist at μ-opioid (MOP) receptors (K i  = 11 nM; lacking β-arrestin agonism) with lesser antagonist activity at adrenergic α 1A (K i  = 28 nM) and dopamine D 1 (K i  = 50 nM) receptors. In vivo, ITI-333 blocks 5-HT 2A receptor-mediated head twitch and MOP receptor-mediated effects on motor hyperactivity in mice. ITI-333 alone is a naloxone-sensitive analgesic (mice) which suppresses somatic signs of naloxone-precipitated oxycodone withdrawal (mice) and heroin cue-induced reinstatement responding without apparent tolerance or physical dependence after chronic dosing (rats). ITI-333 did not acutely impair gastrointestinal or pulmonary function (rats) and was not intravenously self-administered by heroin-maintained rats or rhesus monkeys., Conclusions: ITI-333 acts as a potent 5-HT 2A receptor antagonist, as well a biased MOP receptor partial agonist with low intrinsic efficacy. ITI-333 mitigates opioid withdrawal/reinstatement, supporting its potential utility as a treatment for OUD., (© 2024. The Author(s).)

Development of more efficacious medications with improved safety profiles to manage and treat multiple forms of pain is a critical element of healthcare. To this end, we have designed and synthesized a novel class of tetracyclic pyridopyrroloquinoxalinone derivatives with analgesic properties. The receptor binding profiles and analgesic properties of these tetracyclic compounds were studied. Systematic optimizations of this novel scaffold culminated in the discovery of the clinical candidate, (6 bR ,10 aS )-8-[3-(4-fluorophenoxy)propyl]-6 b ,7,8,9,10,10 a -hexahydro-1 H -pyrido[3',4':4,5]pyrrolo[1,2,3- de ]quinoxalin-2(3 H )-one (compound 5 , ITI-333), which exhibited potent binding affinity to serotonin 5-HT 2A ( K i = 8.3 nM) and μ-opioid receptors (MOR, K i = 11 nM) and moderate affinity to adrenergic α 1A ( K i = 28 nM) and dopamine D 1 ( K i = 50 nM) receptors. ITI-333 acts as a 5-HT 2A receptor antagonist, a MOR partial agonist, and an adrenergic α 1A receptor antagonist. ITI-333 exhibited dose-dependent analgesic effects in rodent models of acute pain. Currently, this investigational new drug is in phase I clinical development.

Lumateperone is indicated for the treatment of schizophrenia in adults and for depressive episodes associated with bipolar I or II disorder (bipolar depression) in adults, as monotherapy and as adjunctive therapy with lithium or valproate (Calabrese et al., 2021). It is currently under evaluation for the treatment of major depressive disorder (www.ClinicalTrials.gov). Lumateperone acts by selectively modulating serotonin, dopamine, and glutamate neurotransmission in the brain. However, other mechanisms could be involved in the actions of lumateperone, and because of the connection between the immune system and psychiatric health, we hypothesized that lumateperone might improve symptoms of depression, at least in part, by normalizing pathologic inflammation. Here, we show that in male and female C57BL/6 mice subjected to an acute immune challenge, lumateperone reduced aberrantly elevated levels of key proinflammatory cytokines (e.g., IL-1β, IL-6, and TNF-α) in both brain and serum; lumateperone also reduced proinflammatory cytokines in male mice under acute behavioral stress. Further, we demonstrate that lumateperone altered key genes/pathways involved in maintaining tissue integrity and supporting blood-brain barrier function, such as claudin-5 and intercellular adhesion molecule 1. In addition, in acutely stressed male Sprague Dawley rats, lumateperone conferred anxiolytic- and antianhedonic-like properties while enhancing activity in the mammalian target of rapamycin complex 1 pathway in the PFC. Together, our preclinical findings indicate that lumateperone, in addition to its ability to modulate multiple neurotransmitter systems, could also act by reducing the impact of acute inflammatory challenges. SIGNIFICANCE STATEMENT Lumateperone is indicated in adults to treat schizophrenia and depressive episodes associated with bipolar I or II disorder, as monotherapy and adjunctive therapy with lithium or valproate. Because aberrant immune system activity is associated with increased depressive symptoms, the relationship between lumateperone and immune function was studied. Here, lumateperone reduced the levels of proinflammatory cytokines that were increased following an immune challenge or stress in mice. Additionally, lumateperone altered genes and pathways that maintain blood-brain barrier integrity, restored an index of blood-brain barrier function, reduced anxiety-like behavior in rodents, and enhanced mammalian target of rapamycin complex 1 pathway signaling in the PFC. These results highlight the anti-inflammatory actions of lumateperone and describe how lumateperone may reduce immune pathophysiology, which is associated with depressive symptoms., (Copyright © 2023 Dutheil et al.)

Age-related cardiovascular diseases (CVDs) remain among the leading global causes of death, and vascular smooth muscle cell (VSMC) remodeling plays an essential role in its pathology. Reduced NO-cGMP pathway signaling is a major feature and pathogenic mechanism underlying vasodilator dysfunction. Recently, we identified phosphodiesterase (PDE) 1, an enzyme that hydrolyzes and inactivates the cyclic nucleotides cAMP and cGMP, and thereby provides a potential treatment target for restoring age-related vascular dysfunction due to aging of VSMC. Based on this hypothesis, we here tested the effects of PDE1 inhibition in a model of SMC-specific accelerated aging mice. SMC-KO and their WT littermates received either vehicle or the PDE1 inhibitor lenrispodun for 8 weeks. Vascular function was measured both in vivo (Laser Doppler technique) and ex vivo (organ bath). Moreover, we deployed UV irradiation in cell culture experiments to model accelerated aging in an in vitro situation. SMC-KO mice display a pronounced loss of vasodilator function in the isolated aorta, the cutaneous microvasculature, and mesenteric arteries. Ex vivo , in isolated vascular tissue, we found that PDE1 inhibition with lenrispodun improves vasodilation, while no improvement was observed in isolated aorta taken from mice after chronic treatment in vivo . However, during lenrispodun treatment in vivo , an enhanced microvascular response in association with upregulated cGMP levels was seen. Further, chronic lenrispodun treatment decreased TNF-α and IL-10 plasma levels while the elevated level of IL-6 in SMC-KO mice remained unchanged after treatment. PDE1 and senescence markers, p16 and p21 , were increased in both SMC-KO aorta and cultured human VSMC in which DNA was damaged by ultraviolet irradiation. This increase was lowered by chronic lenrispodun. In contrast, lenrispodun increased the level of PDE1A in both situations. In conclusion, we demonstrated that PDE1 inhibition may be therapeutically useful in reversing aspects of age-related VSMC dysfunction by potentiating NO-cGMP signaling, preserving microvascular function, and decreasing senescence. Yet, after chronic treatment, the effects of PDE1 inhibition might be counteracted by the interplay between differential PDE1A and C expression. These results warrant further pharmacodynamic profiling of PDE enzyme regulation during chronic PDE1 inhibitor treatment., Competing Interests: GS, RD, AL, and LZ were employed by Intracellular-Therapies, Inc. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Golshiri, Ataabadi, Jüttner, Snyder, Davis, Lin, Zhang, de Vries, Garrelds, Leijten, Danser and Roks.)

Persistently unrepaired DNA damage has been identified as a causative factor for vascular ageing. We have previously shown that a defect in the function or expression of the DNA repair endonuclease ERCC1 (excision repair cross complement 1) in mice leads to accelerated, nonatherosclerotic ageing of the vascular system from as early as 8 weeks after birth. Removal of ERCC1 from endothelial alone partly explains this ageing, as shown in endothelial-specific Ercc1 knockout mice. In this study, we determined vascular ageing due to DNA damage in vascular smooth muscle cells, as achieved by smooth muscle-selective genetic removal of ERCC1 DNA repair in mice (SMC-KO: SM22 α Cre+ Ercc1 fl/-). Vascular ageing features in SMC-KO and their wild-type littermates (WT: SM22 α Cre+ Ercc1 fl/+) were examined at the age of 14 weeks and 25 weeks. Both SMC-KO and WT mice were normotensive. Compared to WT, SMC-KO showed a reduced heart rate, fractional shortening, and cardiac output. SMC-KO showed progressive features of nonatherosclerotic vascular ageing as they aged from 14 to 25 weeks. Decreased subcutaneous microvascular dilatation and increased carotid artery stiffness were observed. Vasodilator responses measured in aortic rings in organ baths showed decreased endothelium-dependent and endothelium-independent responses, mostly due to decreased NO-cGMP signaling. NADPH oxidase 2 and phosphodiesterase 1 inhibition improved dilations. SMC-KO mice showed elevated levels of various cytokines that indicate a balance shift in pro- and anti-inflammatory pathways. In conclusion, SMC-KO mice showed a progressive vascular ageing phenotype in resistant and conduit arteries that is associated with cardiac remodeling and contractile dysfunction. The changes induced by DNA damage might be limited to VSMC but eventually affect EC-mediated responses. The fact that NADPH oxidase 2 as wells as phosphodiesterase 1 inhibition restores vasodilation suggests that both decreased NO bioavailability and cGMP degradation play a role in local vascular smooth muscle cell ageing induced by DNA damage., Competing Interests: Sophie Dutheil, Suman Chalgeri, Lei Zhang, Amy Lin, Robert E Davis, and Gretchen L Snyder are employees of Intracellular Therapies Inc. New York, U.S.A., (Copyright © 2021 Ehsan Ataei Ataabadi et al.)

Diminished nitric oxide-cGMP-mediated relaxation plays a crucial role in cardiovascular aging, leading to decreased vasodilation, vascular hypertrophy and stiffening, and ultimately, cardiovascular dysfunction. Aging is the time-related worsening of physiologic function due to complex cellular and molecular interactions, and it is at least partly driven by DNA damage. Genetic deletion of the DNA repair enzyme ERCC1 endonuclease in Ercc1 Δ/- mice provides us an efficient tool to accelerate vascular aging, explore mechanisms, and test potential treatments. Previously, we identified the cGMP-degrading enzyme phosphodiesterase 1 as a potential treatment target in vascular aging. In the present study, we studied the effect of acute and chronic treatment with ITI-214, a selective phosphodiesterase 1 inhibitor on vascular aging features in Ercc1 Δ/- mice. Compared with wild-type mice, Ercc1 Δ/- mice at the age of 14 weeks showed decreased reactive hyperemia, diminished endothelium-dependent and -independent responses of arteries in organ baths, carotid wall hypertrophy, and elevated circulating levels of inflammatory cytokines. Acute ITI-214 treatment in organ baths restored the arterial endothelium-independent vasodilation in Ercc1 Δ/- mice. An 8-week treatment with 100 mg/kg per day ITI-214 improved endothelium-independent relaxation in both aorta and coronary arteries, at least partly restored the diminished reactive hyperemia, lowered the systolic and diastolic blood pressure, normalized the carotid hypertrophy, and ameliorated inflammatory responses exclusively in Ercc1 Δ/- mice. These findings suggest phosphodiesterase 1 inhibition would provide a powerful tool for nitric oxide-cGMP augmentation and have significant therapeutic potential to battle arteriopathy related to aging. SIGNIFICANCE STATEMENT: The findings implicate the key role of phosphodiesterase 1 in vascular function and might be of clinical importance for the prevention of mortalities and morbidities related to vascular complications during aging, as well as for patients with progeria that show a high risk of cardiovascular disease., (Copyright © 2021 by The American Society for Pharmacology and Experimental Therapeutics.)

Schizophrenia is associated with a tremendous individual and societal burden. The disease is characterized by a complex set of symptoms including psychosis, hallucinations, delusions and related positive symptoms combined with social function deficits, cognitive disturbances and, often, devastating mood disorder, such as comorbid depression. Management of the disease often requires lifelong pharmacotherapy. However, many pharmacotherapies do not improve all symptoms (e.g., social withdrawal, depression, cognitive deficits) and can be associated with intolerable side effects such as weight gain and metabolic disturbances, motor dysfunction and endocrine dysregulation. Lumateperone (ITI-007, CAPLYTA™) is a novel antipsychotic agent, discovered and developed by Intra-Cellular Therapies, Inc. (ITCI) and approved for treatment of schizophrenia in adults in December 2019. Lumateperone simultaneously modulates serotonin, dopamine and glutamate neurotransmission, three key neurotransmitters implicated in schizophrenia. It achieves efficacy with a favorable safety profile. The clinical development program included 20 clinical trials with over 1900 individuals exposed to lumateperone. The program demonstrated the efficacy for lumateperone in two positive well controlled trials in patients with schizophrenia. The unique pharmacology of lumateperone supports the observed benefits across a wide range of symptoms, including social function and depression, and supports its favorable safety profile. Here, we review the discovery of lumateperone's unique biological effects and its clinical actions in the treatment of schizophrenia., Competing Interests: Conflict of interest statement The authors are current or former full-time employees of Intra-Cellular Therapies Inc. a clinical-stage pharmaceutical company engaged in the development of therapies for CNS diseases., (© 2021 Elsevier Inc. All rights reserved.)

A novel, potent, and highly specific inhibitor of calcium-calmodulin-dependent phosphodiesterases (PDE) of the PDE1 family, ITI-214, was used to investigate the role of PDE1 in inflammatory responses. ITI-214 dose-dependently suppressed lipopolysaccharide (LPS)-induced gene expression of pro-inflammatory cytokines in an immortalized murine microglial cell line, BV2 cells. RNA profiling (RNA-Seq) was used to analyze the impact of ITI-214 on the BV2 cell transcriptome in the absence and the presence of LPS. ITI-214 was found to regulate classes of genes that are involved in inflammation and cell migration responses to LPS exposure. The gene expression changes seen with ITI-214 treatment were distinct from those elicited by inhibitors of other PDEs with anti-inflammatory activity (e.g., a PDE4 inhibitor), indicating a distinct mechanism of action for PDE1. Functionally, ITI-214 inhibited ADP-induced migration of BV2 cells through a P2Y12-receptor-dependent pathway, possibly due to increases in the extent of cAMP and VASP phosphorylation downstream of receptor activation. Importantly, this effect was recapitulated in P2 rat microglial cells in vitro, indicating that these pathways are active in native microglial cells. These studies are the first to demonstrate that inhibition of PDE1 exerts anti-inflammatory effects through effects on microglia signaling pathways. The ability of PDE1 inhibitors to prevent or dampen excessive inflammatory responses of BV2 cells and microglia provides a basis for exploring their therapeutic utility in the treatment of neurodegenerative diseases associated with increased inflammation and microglia proliferation such as Parkinson's disease and Alzheimer's disease., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Schizophrenia is a pervasive neuropsychiatric disorder affecting over 1% of the world's population. Dopamine system dysfunction is strongly implicated in the etiology of schizophrenia. Data support the long-standing concept of schizophrenia as a disease characterized by hyperactivity within midbrain (striatal D2) dopamine systems. In addition, there is now considerable evidence that glutamate neurotransmission, mediated through NMDA-type receptors, is deficient in patients with schizophrenia and that hypoactivity in cortical dopamine and glutamate pathways is a key feature of this serious mental disorder. While current antipsychotic medications-with a common mechanism involving dopamine D2 receptor antagonism or pre-synaptic partial agonism-adequately address positive symptoms of the disease, such as the acute hallucinations and delusions, they fail to substantially improve negative features, such as social isolation, and can further compromise poor cognitive function associated with schizophrenia. In fact, cognitive impairment is a core feature of schizophrenia. The treatment of cognitive impairment and other residual symptoms associated with schizophrenia, therefore, remains a significant unmet medical need. With current cell-surface receptor-based pharmacology falling short of addressing these core cognitive symptoms, more recent approaches to treatment development have focused on processes within the cell. In this review, we discuss the importance of cyclic nucleotide (cNT) phosphodiestereases (PDEs)-intracellular enzymes that control the activity of key second messenger signaling pathways in the brain-which have been proposed as targets for new schizophrenia therapies. We also discuss the challenge facing those developing drugs to target specific PDE enzymes involved in psychopathology without involving other systems that produce concomitant side effects.

Rationale: Therapeutic agents for memory enhancement in psychiatric disorders, such as schizophrenia, are urgently needed., Objective: The aim of this study is to characterize the preclinical profile of ITI-214, a potent inhibitor of phosphodiesterase 1 (PDE1)., Methods: ITI-214 was assayed for inhibition of PDE1 versus other PDE enzyme families using recombinant human PDE enzymes and for off-target binding to 70 substrates (General SEP II diversity panel; Caliper Life Sciences). Effects of ITI-214 (0.1-10 mg/kg, po) on memory performance were assayed in rats using the novel object recognition (NOR) paradigm, with drug given at specified time points prior to or following exposure to objects in an open field. ITI-214 was evaluated for potential drug-drug interaction with risperidone in rats using conditioned avoidance response (CAR) and pharmacokinetic assessments., Results: ITI-214 inhibited PDE1A (K i = 33 pmol) with >1000-fold selectivity for the nearest other PDE family (PDE4D) and displayed minimal off-target binding interactions in a 70-substrate selectivity profile. By using specific timing of oral ITI-214 administration, it was demonstrated in the NOR that ITI-214 is able to enhance acquisition, consolidation, and retrieval memory processes. All memory effects were in the absence of effects on exploratory behavior. ITI-214 did not disrupt the risperidone pharmacokinetic profile or effects in CAR., Conclusions: ITI-214 improved the memory processes of acquisition, consolidation, and retrieval across a broad dose range (0.1-10 mg/kg, po) without disrupting the antipsychotic-like activity of a clinical antipsychotic medication, specifically risperidone. Clinical development of ITI-214 is currently in progress.

A diverse set of 3-aminopyrazolo[3,4-d]pyrimidinones was designed and synthesized. The structure-activity relationships of these polycyclic compounds as phosphodiesterase 1 (PDE1) inhibitors were studied along with their physicochemical and pharmacokinetic properties. Systematic optimizations of this novel scaffold culminated in the identification of a clinical candidate, (6aR,9aS)-2-(4-(6-fluoropyridin-2-yl)benzyl)-5-methyl-3-(phenylamino)-5,6a,7,8,9,9a-hexahydrocyclopenta[4,5]imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4-(2H)-one phosphate (ITI-214), which exhibited picomolar inhibitory potency for PDE1, demonstrated excellent selectivity against all other PDE families and showed good efficacy in vivo. Currently, this investigational new drug is in Phase I clinical development and being considered for the treatment of several indications including cognitive deficits associated with schizophrenia and Alzheimer's disease, movement disorders, attention deficit and hyperactivity disorders, and other central nervous system (CNS) and non-CNS disorders.

Schizophrenia is a chronic and debilitating neuropsychiatric disorder affecting approximately 1% of the world's population. This disease is associated with considerable morbidity placing a major financial burden on society. Antipsychotics have been the mainstay of the pharmacological treatment of schizophrenia for decades. The traditional typical and atypical antipsychotics demonstrate clinical efficacy in treating positive symptoms, such as hallucinations and delusions, while are largely ineffective and may worsen negative symptoms, such as blunted affect and social withdrawal, as well as cognitive function. The inability to treat these latter symptoms may contribute to social function impairment associated with schizophrenia. The dysfunction of multiple neurotransmitter systems in schizophrenia suggests that drugs selectively targeting one neurotransmission pathway are unlikely to meet all the therapeutic needs of this heterogeneous disorder. Often, however, the unintentional engagement of multiple pharmacological targets or even the excessive engagement of intended pharmacological targets can lead to undesired consequences and poor tolerability. In this article, we will review marketed typical and atypical antipsychotics and new therapeutic agents targeting dopamine receptors and other neurotransmitters for the treatment of schizophrenia. Representative typical and atypical antipsychotic drugs and new investigational drug candidates will be systematically reviewed and compared by reviewing structure-activity relationships, pharmacokinetic properties, drug metabolism and safety, pharmacological properties, preclinical data in animal models, clinical outcomes and associated side effects.

Rationale: Schizophrenia remains among the most prevalent neuropsychiatric disorders, and current treatment options are accompanied by unwanted side effects. New treatments that better address core features of the disease with minimal side effects are needed., Objectives: As a new therapeutic approach, 1-(4-fluoro-phenyl)-4-((6bR, 10aS)-3-methyl-2,3,6b,9,10,10a-hexahydro-1H,7H-pyrido[3',4':4,5]pyrrolo[1,2,3-de]quinoxalin-8-yl)-butan-1-one (ITI-007) is currently in human clinical trials for the treatment of schizophrenia. Here, we characterize the preclinical functional activity of ITI-007., Results: ITI-007 is a potent 5-HT2A receptor ligand (K i  = 0.5 nM) with strong affinity for dopamine (DA) D2 receptors (K i  = 32 nM) and the serotonin transporter (SERT) (K i  = 62 nM) but negligible binding to receptors (e.g., H1 histaminergic, 5-HT2C, and muscarinic) associated with cognitive and metabolic side effects of antipsychotic drugs. In vivo it is a 5-HT2A antagonist, blocking (±)-2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI)-induced headtwitch in mice with an inhibitory dose 50 (ID50) = 0.09 mg/kg, per oral (p.o.), and has dual properties at D2 receptors, acting as a postsynaptic D2 receptor antagonist to block D-amphetamine hydrochloride (D-AMPH) hyperlocomotion (ID50 = 0.95 mg/kg, p.o.), yet acting as a partial agonist at presynaptic striatal D2 receptors in assays measuring striatal DA neurotransmission. Further, in microdialysis studies, this compound significantly and preferentially enhances mesocortical DA release. At doses relevant for antipsychotic activity in rodents, ITI-007 has no demonstrable cataleptogenic activity. ITI-007 indirectly modulates glutamatergic neurotransmission by increasing phosphorylation of GluN2B-type N-methyl-D-aspartate (NMDA) receptors and preferentially increases phosphorylation of glycogen synthase kinase 3β (GSK-3β) in mesolimbic/mesocortical dopamine systems., Conclusion: The combination of in vitro and in vivo activities of this compound support its development for the treatment of schizophrenia and other psychiatric and neurologic disorders.

We report the synthesis and structure-activity relationships of a class of tetracyclic butyrophenones that exhibit potent binding affinities to serotonin 5-HT(2A) and dopamine D2 receptors. This work has led to the discovery of 4-((6bR,10aS)-3-methyl-2,3,6b,9,10,10a-hexahydro-1H,7H-pyrido[3',4':4,5]pyrrolo[1,2,3-de]quinoxalin-8-yl)-1-(4-fluorophenyl)-butan-1-one 4-methylbenzenesulfonate (ITI-007), which is a potent 5-HT(2A) antagonist, postsynaptic D2 antagonist, and inhibitor of serotonin transporter. This multifunctional drug candidate is orally bioavailable and exhibits good antipsychotic efficacy in vivo. Currently, this investigational new drug is under clinical development for the treatment of neuropsychiatric and neurological disorders.

Schizophrenia is a pervasive neuropsychiatric disorder affecting over 1% of the world's population. Dopamine system dysfunction is strongly implicated in the etiology of schizophrenia. Data support the long-standing concept of schizophrenia as a disease characterized by hyperactivity within midbrain (striatal D2) dopamine systems. In addition, there is now considerable evidence that glutamate neurotransmission, mediated through NMDA-type receptors, is deficient in schizophrenic patients and that hypoactivity in cortical dopamine and glutamate pathways is a key feature of the schizophrenic brain. While current antipsychotic medications-typically dopamine D2 antagonists-adequately address positive symptoms of the disease, such as the acute hallucinations and delusions, they fail to substantially improve negative features, such as social isolation, and can further compromise poor cognitive function in schizophrenic patients. In fact, cognitive impairment is a core feature of schizophrenia. The treatment of cognitive impairment and other residual symptoms associated with schizophrenia, therefore, remains a significant unmet medical need. With current cell-surface receptor-based pharmacology falling short of addressing these core symptoms associated with schizophrenia, more recent approaches to treatment development have focused on processes within the cell. In this review, we discuss the importance of a number of intracellular targets, including cyclic nucleotide phosphodiestereases, and non-phosphodiesterase approaches such as ITI-007, which have been proposed to regulate hyperdopaminergic function, hypoglutamatergic function and/or the delicate balance of the two associated with cognitive deficits in schizophrenia. We also discuss the challenge facing those developing drugs to target specific pathways involved in psychopathology without involving other systems that produce concomitant side effects.

Muscarinic receptors, activated by acetylcholine, play critical roles in the functional regulation of medium spiny neurons in the striatum. However, the muscarinic receptor signaling pathways are not fully elucidated due to their complexity. In this study, we investigated the function of muscarinic receptors in the striatum by monitoring DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of M(r) 32 kDa) phosphorylation at Thr34 (the PKA-site) using mouse striatal slices. Treatment of slices with a non-selective muscarinic receptor agonist, oxotremorine (10 μM), rapidly and transiently increased DARPP-32 phosphorylation. The increase in DARPP-32 phosphorylation was completely abolished either by a dopamine D(1) receptor antagonist (SCH23390), tetrodotoxin, genetic deletion of M5 receptors, muscarinic toxins for M1 and M4 receptors, or 6-hydroxydopamine lesioning of dopaminergic neurons, whereas it was enhanced by nicotine. Analysis in D(1)-DARPP-32-Flag/D(2)-DARPP-32-Myc transgenic mice revealed that oxotremorine increases DARPP-32 phosphorylation selectively in D(1)-type/striatonigral, but not in D(2)-type/striatopallidal, neurons. When D(1) and D(2) receptors were blocked by selective antagonists to exclude the effects of released dopamine, oxotremorine increased DARPP-32 Thr34 phosphorylation only in D(2)-type/striatopallidal neurons. This increase required activation of M1 receptors and was dependent upon adenosine A(2A) receptor activity. The results demonstrate that muscarinic receptors, especially M5 receptors, act at presynaptic dopaminergic terminals, regulate the release of dopamine in cooperation with nicotinic receptors, and activate D(1) receptor/DARPP-32 signaling in the striatonigral neurons. Muscarinic M1 receptors expressed in striatopallidal neurons interact with adenosine A(2A) receptors and activate DARPP-32 signaling., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Rationale: Alteration of dopamine neurotransmission in the prefrontal cortex, especially hypofunction of dopamine D1 receptors, contributes to psychotic symptoms and cognitive deficit in schizophrenia. D1 receptors signal through the cAMP/PKA second messenger cascade, which is modulated by phosphodiesterase (PDE) enzymes that hydrolyze and inactivate cyclic nucleotides. Though several PDEs are expressed in cortical neurons, the PDE4 enzyme family (PDE4A-D) has been implicated in the control of cognitive function. The best studied isoform, PDE4B, interacts with a schizophrenia susceptibility factor, disrupted in schizophrenia 1 (DISC1)., Objectives: We explore the control of mouse frontal cortex dopamine D1 receptor signaling and associated behavior by PDE4., Results: Inhibition of PDE4 by rolipram induced activation of cAMP/PKA signaling in cortical slices and in vivo, leading to the phosphorylation of DARPP-32 and other postsynaptic and presynaptic PKA-substrates. Rolipram also enhanced DARPP-32 phosphorylation invoked by D1 receptor activation. Immunohistochemical studies demonstrated PDE4A, PDE4B, and PDE4D expression in DARPP-32-positive neurons in layer VI of frontal cortex, most likely in D1 receptor-positive, glutamatergic corticothalamic pyramidal neurons. Furthermore, the ability of rolipram treatment to improve the performance of mice in a sensorimotor gating test was DARPP-32-dependent., Conclusions: PDE4, which is co-expressed with DARPP-32 in D1 receptor-positive cortical pyramidal neurons in layer VI, modulates the level of D1 receptor signaling and DARPP-32 phosphorylation in the frontal cortex, likely influencing cognitive function. These biochemical and behavioral actions of PDE4 inhibitors may contribute to the hypothesized antipsychotic actions of this class of compounds.

Purpose of Review: Regional anesthesia is evolving rapidly and increasing in popularity as evidenced by the large number of publications on the topic. In this healthcare environment, continual assessment of the safety and efficacy of clinical practice is critical. Neurologic complications of regional anesthesia can result in disability and are feared by patients and clinicians. Ultrasound guidance is unique as a nerve localizing technique in terms of being able to image needle-nerve proximity and potentially prevent direct trauma to nerves. This article reviews the recent literature relevant to neurologic complications of regional anesthesia., Recent Findings: The incidence of intraneural injection during regional anesthesia is higher than previously appreciated. Defining intraneural injection and its significance are the subject of current debate. Clinical studies with small sample sizes suggest that intraneural injection may not necessarily be responsible for nerve injury. Inflammatory mechanisms may contribute to perioperative nerve injury. Ultrasound guidance has not been proven to reduce the incidence of nerve injury due to peripheral nerve blockade (PNB). Increased utilization of PNB is not associated with an increase in perioperative nerve injury., Summary: The pathogenesis of perioperative nerve injury is complex with multiple potential etiologies and mechanisms. The role of intraneural injections as a modifiable risk factor for neurologic complications due to regional anesthesia remains topical. Relevant publications include studies on the morphology of peripheral nerves and risk of perioperative nerve injury in the context of both neuraxial anesthesia and PNB.

Two distinct families of small molecules were discovered as novel alpha7 nicotinic acetylcholine receptor (nAChR) antagonists by pharmacophore-based virtual screening. These novel antagonists exhibited selectivity for the neuronal alpha7 subtype over other nAChRs and good brain penetration. Neuroprotection was demonstrated by representative compounds 7i and 8 in a mouse seizure-like behavior model induced by the nerve agent diisopropylfluorophosphate (DFP). These novel nAChR antagonists have potential use as antidote for organophosphorus nerve agent intoxication., (2010 Elsevier Ltd. All rights reserved.)

Surgical excision is the mainstay of treatment for potentially curable solid tumours. Metastatic disease is the most important cause of cancer-related death in these patients. The likelihood of tumour metastases depends on the balance between the metastatic potential of the tumour and the anti-metastatic host defences, of which cell-mediated immunity, and natural killer cell function in particular, is a critical component. It is increasingly recognized that anaesthetic technique and other perioperative factors have the potential to effect long-term outcome after cancer surgery. Surgery can inhibit important host defences and promote the development of metastases. Anaesthetic technique and drug choice can interact with the cellular immune system and effect long-term outcome. The potential effect of i.v. anaesthetics, volatile agents, local anaesthetic drugs, opiates, and non-steroidal anti-inflammatory drugs are reviewed here. There is particular interest at present in the effect of regional anaesthesia, which appears to be beneficial. Retrospective analyses have shown an outcome benefit for paravertebral analgesia for breast cancer surgery and epidural analgesia for prostatectomy. Blood transfusion, pain, stress, and hypothermia are other potentially important perioperative factors to consider.

Organophosphorus (OP) compounds cause toxic symptoms, including convulsions, coma, and death, as the result of irreversible inhibition of acetylcholinesterase (AChE). The development of effective treatments to block these effects and attenuate long-term cognitive and motor disabilities that result from OP intoxication is hampered by a limited understanding of the CNS pathways responsible for these actions. We employed a candidate method (called CNSProfile) to identify changes in the phosphorylation state of key neuronal phosphoproteins evoked by the OP compound, diisopropyl fluorophosphate (DFP). Focused microwave fixation was used to preserve the phosphorylation state of phosphoproteins in brains of DFP-treated mice; hippocampus and striatum were analyzed by immunoblotting with a panel of phospho-specific antibodies. DFP exposure elicited comparable effects on phosphorylation of brain phosphoproteins in both C57BL/6 and FVB mice. DFP treatment significantly altered phosphorylation at regulatory residues on glutamate receptors, including Serine897 (S897) of the NR1 NMDA receptor. NR1 phosphorylation was bi-directionally regulated after DFP in striatum versus hippocampus. NR1 phosphorylation was reduced in striatum, but elevated in hippocampus, compared with controls. DARPP-32 phosphorylation in striatum was selectively increased at the Cdk5 kinase substrate, Threonine75 (T75). Phencynonate hydrochloride, a muscarinic cholinergic antagonist, prevented seizure-like behaviors and the observed changes in phosphorylation induced by DFP. The data reveal region-specific effects of nerve agent exposure on intracellular signaling pathways that correlate with seizure-like behavior and which are reversed by the muscarinic receptor blockade. This approach identifies specific targets for nerve agents, including substrates for Cdk5 kinase, which may be the basis for new anti-convulsant therapies., (Copyright 2010 Elsevier B.V. All rights reserved.)

Dopamine plays a central role in the regulation of psychomotor functions. The effect of dopamine is largely mediated through the cAMP/PKA signaling cascade and therefore controlled by phosphodiesterases (PDEs). Multiple PDEs with different substrate specificities and subcellular localization are expressed in the striatum, and the functional roles of PDE10A, PDE4, and PDE1B are extensively studied. Biochemical and behavioral profiles of PDE inhibition by selective inhibitors and/or genetic deletion related to dopaminergic neurotransmission are compared among those PDEs. The inhibition of PDE up-regulates cAMP/PKA signaling in three neuronal subtypes, resulting in the stimulation of dopamine synthesis at dopaminergic terminals, the inhibition of dopamine D(2)-receptor signaling in striatopallidal neurons, and the stimulation of dopamine D(1)-receptor signaling in striatonigral neurons. Predominant roles of PDE families or isoforms are implicated in each neuronal subtype: PDE4 at dopaminergic terminals, PDE10A and PDE4 in striatopallidal neurons, and PDE1B in striatonigral neurons. PDE10A and PDE4 inhibition may exhibit D(2) antagonist-like, antipsychotic effects, whereas PDE1B inhibition may exhibit D(1) agonist-like effects in the striatum. Development of PDE isoform-specific inhibitors is essential for better understanding of the function of each PDE isoform and treatment of neuropsychiatric disorders.

Phosphodiesterase (PDE) is a critical regulator of cAMP/protein kinase A (PKA) signaling in cells. Multiple PDEs with different substrate specificities and subcellular localization are expressed in neurons. Dopamine plays a central role in the regulation of motor and cognitive functions. The effect of dopamine is largely mediated through the cAMP/PKA signaling cascade, and therefore controlled by PDE activity. We used in vitro and in vivo biochemical techniques to dissect the roles of PDE4 and PDE10A in dopaminergic neurotransmission in mouse striatum by monitoring the ability of selective PDE inhibitors to regulate phosphorylation of presynaptic [e.g., tyrosine hydroxylase (TH)] and postsynaptic [e.g., dopamine- and cAMP-regulated phosphoprotein of M(r) 32 kDa (DARPP-32)] PKA substrates. The PDE4 inhibitor, rolipram, induced a large increase in TH Ser40 phosphorylation at dopaminergic terminals that was associated with a commensurate increase in dopamine synthesis and turnover in striatum in vivo. Rolipram induced a small increase in DARPP-32 Thr34 phosphorylation preferentially in striatopallidal neurons by activating adenosine A(2A) receptor signaling in striatum. In contrast, the PDE10A inhibitor, papaverine, had no effect on TH phosphorylation or dopamine turnover, but instead robustly increased DARPP-32 Thr34 and GluR1 Ser845 phosphorylation in striatal neurons. Inhibition of PDE10A by papaverine activated cAMP/PKA signaling in both striatonigral and striatopallidal neurons, resulting in potentiation of dopamine D(1) receptor signaling and inhibition of dopamine D(2) receptor signaling. These biochemical results are supported by immunohistochemical data demonstrating differential localization of PDE10A and PDE4 in striatum. These data underscore the importance of individual brain-enriched cyclic-nucleotide PDE isoforms as therapeutic targets for neuropsychiatric and neurodegenerative disorders affecting dopamine neurotransmission.

Isoflurane, propofol and ketamine are representative general anesthetics with distinct molecular mechanisms of action that have neuroprotective properties in models of excitotoxic ischemic damage. We characterized the effects of these agents on neuronal glutamate and dopamine signaling by profiling drug-induced changes in brain intracellular protein phosphorylation in vivo to test the hypothesis that they affect common downstream effectors. Anesthetic-treated and control mice were killed instantly by focused microwave irradiation, frontal cortex and striatum were removed, and the phosphorylation profile of specific neuronal signaling proteins was analyzed by immunoblotting with a panel of phospho-specific antibodies. At anesthetic doses that produced loss of righting reflex, isoflurane, propofol, and ketamine all reduced phosphorylation of the activating residue T183 of ERK2 (but not of ERK1); S897 of the NR1 NMDA receptor subunit; and S831 (but not S845) of the GluR1 AMPA receptor subunit in cerebral cortex. At sub-anesthetic doses, these drugs only reduced phosphorylation of ERK2. Isoflurane and ketamine also reduced phosphorylation of spinophilin at S94, but oppositely regulated phosphorylation of presynaptic (tyrosine hydroxylase) and postsynaptic (DARPP-32) markers of dopaminergic neurotransmission in striatum. These data reveal both shared and agent-specific actions of CNS depressant drugs on critical intracellular protein phosphorylation signaling pathways that integrate multiple second messenger systems. Reduced phosphorylation of ionotropic glutamate receptors by all three anesthetics indicates depression of normal glutamatergic synaptic transmission and reduced potential excitotoxicity. This novel approach indicates a role for phosphorylation-mediated down-regulation of glutamatergic synaptic transmission by general anesthetics and identifies specific in vivo targets for focused evaluation of anesthetic mechanisms.

Adenosine A(2A) receptors are predominantly expressed in the dendrites of enkephalin-positive gamma-aminobutyric acidergic medium spiny neurons in the striatum. Evidence indicates that these receptors modulate striatal dopaminergic neurotransmission and regulate motor control, vigilance, alertness, and arousal. Although the physiological and behavioral correlates of adenosine A(2A) receptor signaling have been extensively studied using a combination of pharmacological and genetic tools, relatively little is known about the signal transduction pathways that mediate the diverse biological functions attributed to this adenosine receptor subtype. Using a candidate approach based on the coupling of these receptors to adenylate cyclase-activating G proteins, a number of membranal, cytosolic, and nuclear phosphoproteins regulated by PKA were evaluated as potential mediators of adenosine A(2A) receptor signaling in the striatum. Specifically, the adenosine A(2A) receptor agonist, CGS 21680, was used to determine whether the phosphorylation state of each of the following PKA targets is responsive to adenosine A(2A) receptor stimulation in this tissue: Ser40 of tyrosine hydroxylase, Ser9 of synapsin, Ser897 of the NR1 subunit of the N-methyl-d-aspartate-type glutamate receptor, Ser845 of the GluR1 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid-type glutamate receptor, Ser94 of spinophilin, Thr34 of the dopamine- and cAMP-regulated phosphoprotein, M(r) 32,000, Ser133 of the cAMP-response element-binding protein, Thr286 of Ca(2+)/calmodulin-dependent protein kinase II, and Thr202/Tyr204 and Thr183/Tyr185 of the p44 and p42 isoforms, respectively, of mitogen-activated protein kinase. Although the substrates studied differed considerably in their responsiveness to selective adenosine A(2A) receptor activation, the phosphorylation state of all postsynaptic PKA targets was up-regulated in a time- and dose-dependent manner by treatment with CGS 21680, whereas presynaptic PKA substrates were unresponsive to this agent, consistent with the postsynaptic localization of adenosine A(2A) receptors. Finally, the phosphorylation state of these proteins was further assessed in vivo by systemic administration of caffeine.

Adenosine is known to modulate the function of neostriatal neurons. Adenosine acting on A(2A) receptors increases the phosphorylation of dopamine- and cAMP-regulated phosphoprotein of M(r) 32 kDa (DARPP-32) at Thr34 (the cAMP-dependent protein kinase [PKA] site) in striatopallidal neurons, and opposes dopamine D2 receptor signaling. In contrast, the role of adenosine A(1) receptors in the regulation of dopamine/DARPP-32 signaling is not clearly understood. Here, we investigated the effect of adenosine A(1) receptors on D(1), D(2) and A(2A) receptor signaling using mouse neostriatal slices. An A(1) receptor agonist, 2-chloro-N(6)-cyclopentyladenosine (100 nM), caused a transient increase, followed by a transient decrease, in DARPP-32 Thr34 phosphorylation. Our data support the following model for the actions of the A(1) receptor agonist. The A(1) receptor-induced early increase in Thr34 phosphorylation was mediated by presynaptic inhibition of dopamine release, and the subsequent removal of tonic inhibition by D(2) receptors of A(2A) receptor/G(olf)/cAMP/PKA signaling. The A(1) receptor-induced late decrease in Thr34 phosphorylation was mediated by a postsynaptic G(i) mechanism, resulting in inhibition of D(1) and A(2A) receptor-coupled G(olf)/cAMP/PKA signaling in direct and indirect pathway neurons, respectively. In conclusion, A(1) receptors play a major modulatory role in dopamine and adenosine receptor signaling.

Protein phosphatase 1 plays a major role in the governance of excitatory synaptic activity, and is subject to control via the neuromodulatory actions of dopamine. Mechanisms involved in regulating protein phosphatase 1 activity include interactions with the structurally related cytoskeletal elements spinophilin and neurabin, synaptic scaffolding proteins that are highly enriched in dendritic spines. The requirement for these proteins in dopamine-related neuromodulation was tested using knockout mice. Dopamine D1-mediated regulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor activity was deficient in both striatal and prefrontal cortical neurons from neurabin knockout mice; in spinophilin knockout mice this deficit was manifest only in striatal neurons. At corticostriatal synapses long-term potentiation was deficient in neurabin knockout mice, but not in spinophilin knockout mice, and was rescued by a D1 receptor agonist. In contrast, long-term depression was deficient in spinophilin knockout mice but not in neurabin knockout mice, and was rescued by D2 receptor activation. Spontaneous excitatory post-synaptic current frequency was increased in neurabin knockout mice, but not in spinophilin knockout mice, and this effect was normalized by D2 receptor agonist application. Both knockout strains displayed increased induction of GluR1 Ser(845) phosphorylation in response to D1 receptor stimulation in slices, and also displayed enhanced locomotor activation in response to cocaine administration. These effects could be dissociated from cocaine reward, which was enhanced only in spinophilin knockout mice, and was accompanied by increased immediate early gene induction. These data establish a requirement for synaptic scaffolding in dopamine-mediated responses, and further indicate that spinophilin and neurabin play distinct roles in dopaminergic signal transduction and psychostimulant response.

Spinophilin is a protein phosphatase-1- and actin-binding protein that modulates excitatory synaptic transmission and dendritic spine morphology. We have recently shown that the interaction of spinophilin with the actin cytoskeleton depends upon phosphorylation by protein kinase A. We have now found that spinophilin is phosphorylated by Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in neurons. Ca(2+)/calmodulin-dependent protein kinase II, located within the post-synaptic density of dendritic spines, is known to play a role in synaptic plasticity and is ideally positioned to regulate spinophilin. Using tryptic phosphopeptide mapping, site-directed mutagenesis and microsequencing analysis, we identified two sites of CaMKII phosphorylation (Ser-100 and Ser-116) within the actin-binding domain of spinophilin. Phosphorylation by CaMKII reduced the affinity of spinophilin for F-actin. In neurons, phosphorylation at Ser-100 by CaMKII was Ca(2+) dependent and was associated with an enrichment of spinophilin in the synaptic plasma membrane fraction. These results indicate that spinophilin is phosphorylated by multiple kinases in vivo and that differential phosphorylation may target spinophilin to specific locations within dendritic spines.

Phosphorylation of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor subunit GluR1 at Ser(845) enhances AMPA channel activity. This study demonstrates that Ser(845) is rapidly dephosphorylated upon AMPA receptor activation in nucleus accumbens slices. AMPA-induced dephosphorylation at Ser(845) was blocked by CNQX, an AMPA receptor antagonist, by nifedipine, an L-type Ca(2+) channel antagonist, or by cyclosporin A, a calcineurin inhibitor. N-methyl-D-aspartate (NMDA) treatment also decreased phosphorylation of Ser(845), an effect that was blocked by MK-801, an NMDA receptor antagonist, but not by nifedipine. Accumbens neurons are enriched for dopamine- and cyclic AMP (cAMP)-regulated phosphoprotein, Mr 32,000 (DARPP-32), a potent inhibitor of protein phosphatase 1 (PP1) when phosphorylated by PKA (at Thr(34)). We tested the hypothesis that the AMPA/KA or NMDA-stimulated dephosphorylation of DARPP-32 via calcineurin, leading to increased PP1 activity and dephosphorylation of GluR1. AMPA or NMDA treatment decreased phospho-Thr(34)-DARPP-32 levels, effects that were blocked by receptor antagonists, or cyclosporin A. However, dephosphorylation of Ser(845) mediated by AMPA or NMDA receptors was unaffected in DARPP-32/inhibitor-1 knockout mice. These data suggest that AMPA- or NMDA-induced dephosphorylation of GluR1 at Ser(845) occurs by a mechanism that is independent of DARPP-32 and PP1, but involves activation of calcineurin. Thus, Ca(2+)-dependent dephosphorylation of GluR1 may serve as a negative feedback mechanism for the regulation of AMPA receptor activity in neurons.

Spinophilin is a protein phosphatase 1 (PP1)- and actin-binding protein that modulates excitatory synaptic transmission and dendritic spine morphology. We report that spinophilin is phosphorylated in vitro by protein kinase A (PKA). Phosphorylation of spinophilin was stimulated by treatment of neostriatal neurons with a dopamine D1 receptor agonist or with forskolin, consistent with spinophilin being a substrate for PKA in intact cells. Using tryptic phosphopeptide mapping, site-directed mutagenesis, and microsequencing analysis, we identified two major sites of phosphorylation, Ser-94 and Ser-177, that are located within the actin-binding domain of spinophilin. Phosphorylation of spinophilin by PKA modulated the association between spinophilin and the actin cytoskeleton. Following subcellular fractionation, unphosphorylated spinophilin was enriched in the postsynaptic density, whereas a pool of phosphorylated spinophilin was found in the cytosol. F-actin co-sedimentation and overlay analysis revealed that phosphorylation of spinophilin reduced the stoichiometry of the spinophilin-actin interaction. In contrast, the ability of spinophilin to bind to PP1 remained unchanged. Taken together, our studies suggest that phosphorylation of spinophilin by PKA modulates the anchoring of the spinophilin-PP1 complex within dendritic spines, thereby likely contributing to the efficacy and plasticity of synaptic transmission.

The medium spiny neurons of the nucleus accumbens receive both an excitatory glutamatergic input from forebrain and a dopaminergic input from the ventral tegmental area. This integration point may constitute a locus whereby the N-methyl-D-aspartate (NMDA)-subtype of glutamate receptors promotes drug reinforcement. Here we investigate how dopaminergic inputs alter the ethanol sensitivity of NMDA receptors in rats and mice and report that previous dopamine receptor-1 (D1) activation, culminating in dopamine and cAMP-regulated phosphoprotein-32 kD (DARPP-32) and NMDA receptor subunit-1 (NR1)-NMDA receptor phosphorylation, strongly decreases ethanol inhibition of NMDA responses. The regulation of ethanol sensitivity of NMDA receptors by D1 receptors was absent in DARPP-32 knockout mice. We propose that DARPP-32 mediated blunting of the response to ethanol subsequent to activation of ventral tegmental area dopaminergic neurons initiates molecular alterations that influence synaptic plasticity in this circuit, thereby promoting the development of ethanol reinforcement.

Using homologous recombination, we generated mice lacking phosphodiesterase-mediated (PDE1B) cyclic nucleotide-hydrolyzing activity. PDE1B(-/-) mice showed exaggerated hyperactivity after acute D-methamphetamine administration. Striatal slices from PDE1B(-/-) mice exhibited increased levels of phospho-Thr34 DARPP-32 and phospho-Ser845 GluR1 after dopamine D1 receptor agonist or forskolin stimulation. PDE1B(-/-) and PDE1B(+/-) mice demonstrated Morris maze spatial-learning deficits. These results indicate that enhancement of cyclic nucleotide signaling by inactivation of PDE1B-mediated cyclic nucleotide hydrolysis plays a significant role in dopaminergic function through the DARPP-32 and related transduction pathways.

Recent studies suggest that oestrogen and progestin receptors may be activated by the neurotransmitter dopamine, as well as by their respective ligands. Because intracerebroventricular infusion of D(1), but not D(2), dopaminergic receptor agonists increases oestrous behaviour in oestradiol-primed rats, we wanted to determine if treatment with oestradiol alters the activity of D(1) receptor-associated processes in steroid receptor-containing areas in female rat brain. One D(1) receptor-associated phosphoprotein that may be influenced by oestradiol is a dopamine- and cyclic AMP-regulated phosphoprotein, Mr = 32,000 (DARPP-32). Because DARPP-32 is phosphorylated in response to dopamine acting via a cAMP-dependent protein kinase, it provides a useful marker to examine where in the brain a particular stimulus might be altering the activity of D(1) receptor-containing neurones. To determine if oestradiol alters the phosphorylation of DARPP-32, we stained immunocytochemically brain sections of female rats treated with behaviourally relevant doses of oestradiol or oil vehicle with an antibody that detects only the threonine 34-phosphorylated form of DARPP-32. Behaviourally effective doses of oestradiol increase the phosphorylation of DARPP-32 within the medial preoptic nucleus, bed nucleus of the stria terminalis, paraventricular nucleus of the hypothalamus and the ventromedial nucleus of the hypothalamus, 48 h after treatment. These data suggest that oestradiol increases the activity of D(1) dopamine receptor-associated processes in oestrogen receptor-containing areas of female rat forebrain.

Protein phosphatase inhibitor-1 is a prototypical mediator of cross-talk between protein kinases and protein phosphatases. Activation of cAMP-dependent protein kinase results in phosphorylation of inhibitor-1 at Thr-35, converting it into a potent inhibitor of protein phosphatase-1. Here we report that inhibitor-1 is phosphorylated in vitro at Ser-67 by the proline-directed kinases, Cdk1, Cdk5, and mitogen-activated protein kinase. By using phosphorylation state-specific antibodies and selective protein kinase inhibitors, Cdk5 was found to be the only kinase that phosphorylates inhibitor-1 at Ser-67 in intact striatal brain tissue. In vitro and in vivo studies indicated that phospho-Ser-67 inhibitor-1 was dephosphorylated by protein phosphatases-2A and -2B. The state of phosphorylation of inhibitor-1 at Ser-67 was dynamically regulated in striatal tissue by glutamate-dependent regulation of N-methyl-d-aspartic acid-type channels. Phosphorylation of Ser-67 did not convert inhibitor-1 into an inhibitor of protein phosphatase-1. However, inhibitor-1 phosphorylated at Ser-67 was a less efficient substrate for cAMP-dependent protein kinase. These results demonstrate regulation of a Cdk5-dependent phosphorylation site in inhibitor-1 and suggest a role for this site in modulating the amplitude of signal transduction events that involve cAMP-dependent protein kinase activation.

ARPP-16 and ARPP-19 are closely related cAMP-regulated phosphoproteins that were initially discovered in mammalian brain as in vitro substrates for protein kinase A (PKA). ARPP-16 is enriched in dopamine-responsive medium spiny neurons in the striatum, while ARPP-19 is ubiquitously expressed. ARPP-19 is highly homologous to alpha-endosulfine and database searches allowed the identification of novel related proteins in D. melanogaster, C. elegans, S. mansoni and yeast genomes. Using isoform-specific antibodies, we now show that ARPP-19 is composed of at least two differentially expressed isoforms (termed ARPP-19 and ARPP-19e/endosulfine). All ARPP-16/19 family members contain a conserved consensus site for phosphorylation by PKA (RKPSLVA in mammalian ARPP-16 and ARPP-19), and this site was shown to be efficiently phosphorylated in vitro by PKA. An antibody that specifically recognized the phosphorylated form of ARPP-16/19/19e was used to examine the phosphorylation of ARPP-16/19 family members in intact cells. In striatal slices, the phosphorylation of ARPP-16 was increased in response to activation of D(1)-type dopamine receptors, and decreased in response to activation of D(2)-type dopamine receptors. In non-neuronal cells, ARPP-19 was highly phosphorylated in response to activation of PKA. These results establish that ARPP-16/19 proteins constitute a family of PKA-dependent intracellular messengers that function in all cells. The high levels of ARPP-16 in striatal neurons and its bi-directional regulation by dopamine suggest a specific role in dopamine-dependent signal transduction. The conservation of this protein family through evolution suggests that it subserves an important cellular function that is regulated by PKA.

Cocaine enhances dopamine-mediated neurotransmission by blocking dopamine re-uptake at axon terminals. Most dopamine-containing nerve terminals innervate medium spiny neurons in the striatum of the brain. Cocaine addiction is thought to stem, in part, from neural adaptations that act to maintain equilibrium by countering the effects of repeated drug administration. Chronic exposure to cocaine upregulates several transcription factors that alter gene expression and which could mediate such compensatory neural and behavioural changes. One such transcription factor is DeltaFosB, a protein that persists in striatum long after the end of cocaine exposure. Here we identify cyclin-dependent kinase 5 (Cdk5) as a downstream target gene of DeltaFosB by use of DNA array analysis of striatal material from inducible transgenic mice. Overexpression of DeltaFosB, or chronic cocaine administration, raised levels of Cdk5 messenger RNA, protein, and activity in the striatum. Moreover, injection of Cdk5 inhibitors into the striatum potentiated behavioural effects of repeated cocaine administration. Our results suggest that changes in Cdk5 levels mediated by DeltaFosB, and resulting alterations in signalling involving D1 dopamine receptors, contribute to adaptive changes in the brain related to cocaine addiction.

The bis-indole indirubin is an active ingredient of Danggui Longhui Wan, a traditional Chinese medicine recipe used in the treatment of chronic diseases such as leukemias. The antitumoral properties of indirubin appear to correlate with their antimitotic effects. Indirubins were recently described as potent (IC(50): 50-100 nm) inhibitors of cyclin-dependent kinases (CDKs). We report here that indirubins are also powerful inhibitors (IC(50): 5-50 nm) of an evolutionarily related kinase, glycogen synthase kinase-3beta (GSK-3 beta). Testing of a series of indoles and bis-indoles against GSK-3 beta, CDK1/cyclin B, and CDK5/p25 shows that only indirubins inhibit these kinases. The structure-activity relationship study also suggests that indirubins bind to GSK-3 beta's ATP binding pocket in a way similar to their binding to CDKs, the details of which were recently revealed by crystallographic analysis. GSK-3 beta, along with CDK5, is responsible for most of the abnormal hyperphosphorylation of the microtubule-binding protein tau observed in Alzheimer's disease. Indirubin-3'-monoxime inhibits tau phosphorylation in vitro and in vivo at Alzheimer's disease-specific sites. Indirubins may thus have important implications in the study and treatment of neurodegenerative disorders. Indirubin-3'-monoxime also inhibits the in vivo phosphorylation of DARPP-32 by CDK5 on Thr-75, thereby mimicking one of the effects of dopamine in the striatum. Finally, we show that many, but not all, reported CDK inhibitors are powerful inhibitors of GSK-3 beta. To which extent these GSK-3 beta effects of CDK inhibitors actually contribute to their antimitotic and antitumoral properties remains to be determined. Indirubins constitute the first family of low nanomolar inhibitors of GSK-3 beta to be described.

Dopamine and cAMP-regulated phosphoprotein of M(r) 32,000 (DARPP-32) plays an obligatory role in most of the actions of dopamine. In resting neostriatal slices, cyclin-dependent kinase 5 (Cdk5) phosphorylates DARPP-32 at Thr-75, thereby reducing the efficacy of dopaminergic signaling. We report here that dopamine, in slices, and acute cocaine, in whole animals, decreases the state of phosphorylation of striatal DARPP-32 at Thr-75 and thereby removes this inhibitory constraint. This effect of dopamine is achieved through dopamine D1 receptor-mediated activation of cAMP-dependent protein kinase (PKA). The activated PKA, by decreasing the state of phosphorylation of DARPP-32-Thr-75, de-inhibits itself. Dopamine D2 receptor stimulation has the opposite effect. The ability of activated PKA to reduce the state of phosphorylation of DARPP-32-Thr-75 is apparently attributable to increased protein phosphatase-2A activity, with Cdk5 being unaffected. Together, these results indicate that via positive feedback mechanisms, Cdk5 signaling and PKA signaling are mutually antagonistic.

Paullones constitute a new family of benzazepinones with promising antitumoral properties. They were recently described as potent, ATP-competitive, inhibitors of the cell cycle regulating cyclin-dependent kinases (CDKs). We here report that paullones also act as very potent inhibitors of glycogen synthase kinase-3beta (GSK-3beta) (IC50: 4-80 nM) and the neuronal CDK5/p25 (IC50: 20-200 nM). These two enzymes are responsible for most of the hyperphosphorylation of the microtubule-binding protein tau, a feature observed in the brains of patients with Alzheimer's disease and other neurodegenerative 'taupathies'. Alsterpaullone, the most active paullone, was demonstrated to act by competing with ATP for binding to GSK-3beta. Alsterpaullone inhibits the phosphorylation of tau in vivo at sites which are typically phosphorylated by GSK-3beta in Alzheimer's disease. Alsterpaullone also inhibits the CDK5/p25-dependent phosphorylation of DARPP-32 in mouse striatum slices in vitro. This dual specificity of paullones may turn these compounds into very useful tools for the study and possibly treatment of neurodegenerative and proliferative disorders.

The striatal-enriched protein tyrosine phosphatase (STEP) family is expressed within dopaminoceptive neurons of the CNS and is particularly enriched within the basal ganglia and related structures. Alternative splicing produces several isoforms that are found in a number of subcellular compartments, including postsynaptic densities of medium spiny neurons. The variants include STEP(61), a membrane-associated protein, and STEP(46), a cytosolic protein. The C terminals of these two isoforms are identical, whereas the N-terminal domain of STEP(61) contains a novel 172 amino acid sequence that includes several structural motifs not present in STEP(46). Amino acid sequencing revealed a number of potential phosphorylation sites in both STEP isoforms. Therefore, we investigated the role of phosphorylation in regulating STEP activity. Both STEP(61) and STEP(46) are phosphorylated on seryl residues by a cAMP-dependent protein kinase (PKA)-mediated pathway in striatal homogenates. The specific residues phosphorylated in STEP(61) were identified by site-directed mutagenesis and tryptic phosphopeptide mapping as Ser160 and Ser221, whereas the major site of phosphorylation in STEP(46) was shown to be Ser49. Ser160 is located within the unique N terminal of STEP(61). Ser221 and Ser49 are equivalent residues present in STEP(61) and STEP(46), respectively, and are located at the center of the kinase-interacting motif that has been implicated in protein-protein interactions. Phosphorylation at this site decreases the activity of STEP in vitro by reducing its affinity for its substrate. In vivo studies using striatal slices demonstrated that the neurotransmitter dopamine leads to the phosphorylation of STEP via activation of D1 receptors and PKA.

ARPP-21 is a cyclic AMP-regulated phosphoprotein of M(r) 21 kDa that is enriched in the cell bodies and terminals of medium-sized spiny neurons in the basal ganglia. Using a new phosphorylation state-specific antibody selective for the detection of ARPP-21 phosphorylated on Ser(55), we have demonstrated that activation of dopamine D1 receptors increased the level of ARPP-21 phosphorylation in mouse striatal slices. Conversely, activation of D2 receptors caused a large decrease in ARPP-21 phosphorylation. Treatment of mice with either methamphetamine or cocaine resulted in increased ARPP-21 phosphorylation in vivo. Studies using specific inhibitors of protein phosphatases and experiments in mice bearing a targeted deletion of the gene for DARPP-32, a dopamine-activated inhibitor of protein phosphatase-1, indicated that protein phosphatase-2A is primarily responsible for dephosphorylation of ARPP-21 in mouse striatum. These results demonstrate that phosphorylation and dephosphorylation of ARPP-21 are tightly regulated in the striatum. We speculate that ARPP-21 might mediate some of the physiologic effects of dopamine and certain drugs of abuse in the basal ganglia.

The activation of cAMP-dependent protein kinase regulates the physiological activity of AMPA-type glutamate receptors. In this study, phosphorylation of the AMPA receptor subunit GluR1 at Ser(845) was increased in neostriatal slices by activation of D1-type dopamine receptors and by inhibitors of protein phosphatase 1/protein phosphatase 2A. In contrast, Ser(831), a residue which, when phosphorylated by protein kinase C or calcium/calmodulin-dependent kinase II, increases AMPA receptor channel conductance, was unaffected by either D1 or D2 receptor agonists in neostriatal slices. The phosphorylation of Ser(845), but not Ser(831), was strongly increased in neostriatum in vivo in response to the psychostimulants cocaine and methamphetamine. The effects of dopamine and psychostimulants on the phosphorylation of GluR1 were attenuated in dopamine and cAMP-regulated phosphoprotein M(r) 32 kDa (DARPP-32) knock-out mice. These results identify DARPP-32 and AMPA-type glutamate receptors as likely essential cellular effectors for psychostimulant actions.

In Huntington's disease (HD), mutation of huntingtin causes selective neurodegeneration of dopaminoceptive striatal medium spiny neurons. Transgenic HD model mice that express a portion of the disease-causing form of human huntingtin develop a behavioral phenotype that suggests dysfunction of dopaminergic neurotransmission. Here we show that presymtomatic mice have severe deficiencies in dopamine signaling in the striatum. These include selective reductions in total levels of dopamine- and cAMP-regulated phosphoprotein, M(r) 32 kDA (DARPP-32) and other dopamine-regulated phosphoprotein markers of medium spiny neurons. HD mice also show defects in dopamine-regulated ion channels and in the D(1) dopamine/DARPP-32 signaling cascade. These presymptomatic defects may contribute to HD pathology.

Dopamine is a critical determinant of neostriatal function, but its impact on intrastriatal GABAergic signaling is poorly understood. The role of D(1) dopamine receptors in the regulation of postsynaptic GABA(A) receptors was characterized using whole cell voltage-clamp recordings in acutely isolated, rat neostriatal medium spiny neurons. Exogenous application of GABA evoked a rapidly desensitizing current that was blocked by bicuculline. Application of the D(1) dopamine receptor agonist SKF 81297 reduced GABA-evoked currents in most medium spiny neurons. The D(1) dopamine receptor antagonist SCH 23390 blocked the effect of SKF 81297. Membrane-permeant cAMP analogues mimicked the effect of D(1) dopamine receptor stimulation, whereas an inhibitor of protein kinase A (PKA; Rp-8-chloroadenosine 3',5' cyclic monophosphothioate) attenuated the response to D(1) dopamine receptor stimulation or cAMP analogues. Inhibitors of protein phosphatase 1/2A potentiated the modulation by cAMP analogues. Single-cell RT-PCR profiling revealed consistent expression of mRNA for the beta1 subunit of the GABA(A) receptor-a known substrate of PKA-in medium spiny neurons. Immunoprecipitation assays of radiolabeled proteins revealed that D(1) dopamine receptor stimulation increased phosphorylation of GABA(A) receptor beta1/beta3 subunits. The D(1) dopamine receptor-induced phosphorylation of beta1/beta3 subunits was attenuated significantly in neostriata from DARPP-32 mutants. Voltage-clamp recordings corroborated these results, revealing that the efficacy of the D(1) dopamine receptor modulation of GABA(A) currents was reduced in DARPP-32-deficient medium spiny neurons. These results argue that D(1) dopamine receptor stimulation in neostriatal medium spiny neurons reduces postsynaptic GABA(A) receptor currents by activating a PKA/DARPP-32/protein phosphatase 1 signaling cascade targeting GABA(A) receptor beta1 subunits.