Routine CT evaluation of central vascular ligation in patients undergoing complete mesocolic excision for sigmoid colon cancer.

AIM: Objective and reproducible quality measures of complete mesocolic excision (CME) for colon cancer are not currently available. This study aimed to measure the inferior mesenteric stump length following CME for sigmoid colon cancer and explore surgical, pathological and oncological outcomes in patients with a stump length of <10 mm vs. ≥10 mm. METHOD: This was a single-centre, retrospective cohort study including patients undergoing minimally invasive surgery for sigmoid colon cancer between May 2013 and May 2015. Follow-up CT scans were reviewed, and a vascular stump cut-off of <10 mm for adequate central ligation of the inferior mesenteric artery was applied. Differences in perioperative, histopathological and oncological outcome parameters (overall, disease-free and recurrence-free survival) were explored between <10 mm vs. ≥10 mm groups. RESULTS: A total of 127 patients (43% female) with a median age of 68 years were included. The median follow-up time was 68 months. CT measurements showed good interrater agreement (90% absolute agreement) and reliability among raters (kappa = 0.77, 95% CI 0.53-1.00, p < 0.001). A stump length ≥10 mm was associated with longer operating time (150 vs. 180 min, p = 0.021), intramesocolic resection (p = 0.008), and a shorter distance from the bowel wall to vascular tie (120 vs. 102 mm, p = 0.005). CONCLUSION: An arterial stump length ≥10 mm in sigmoid resection for colon cancer was associated with key clinical quality measures. Measurement of arterial stump length using routine follow-up CT may serve as a quality indicator of vascular ligation in CME surgery.

Ketogenic Diet Suppresses Alcohol Withdrawal Syndrome in Rats.

BACKGROUND: Alcohol use disorder is underdiagnosed and undertreated, and up to 50% of alcohol-abstinent patients diagnosed with alcohol dependence relapse within the first year of treatment. Current treatments for the maintenance of alcohol abstinence in patients with alcohol use disorder have limited efficacy, and there is an urgent need for novel treatment strategies. Decreased cerebral glucose metabolism and increased brain uptake of acetate were recently reported in heavy drinkers, relative to controls. Given the switch of metabolic fuel from glucose to acetate in the alcohol-dependent brain, we investigated the potential therapeutic benefit of a ketogenic diet in managing alcohol withdrawal symptoms during detoxification. METHODS: Male Sprague Dawley rats fed either ketogenic or regular diet were administered ethanol or water orally, twice daily for 6 days while the diet conditions were maintained. Abstinence symptoms were rated 6, 24, 48, and 72 hours after the last alcohol administration. RESULTS: Maintenance on a ketogenic diet caused a significant decrease in the alcohol withdrawal symptoms' "rigidity" and "irritability." CONCLUSIONS: Our preclinical pilot study suggests that a ketogenic diet may be a novel approach for treating alcohol withdrawal symptoms in humans.

Preserved dopaminergic homeostasis and dopamine-related behaviour in hemizygous TH-Cre mice.

Cre-driver mouse lines have been extensively used as genetic tools to target and manipulate genetically defined neuronal populations by expression of Cre recombinase under selected gene promoters. This approach has greatly advanced neuroscience but interpretations are hampered by the fact that most Cre-driver lines have not been thoroughly characterized. Thus, a phenotypic characterization is of major importance to reveal potential aberrant phenotypes prior to implementation and usage to selectively inactivate or induce transgene expression. Here, we present a biochemical and behavioural assessment of the dopaminergic system in hemizygous tyrosine hydroxylase (TH)-Cre mice in comparison to wild-type (WT) controls. Our data show that TH-Cre mice display preserved dopaminergic homeostasis with unaltered levels of TH and dopamine as well as unaffected dopamine turnover in striatum. TH-Cre mice also show preserved dopamine transporter expression and function supporting sustained dopaminergic transmission. In addition, TH-Cre mice demonstrate normal responses in basic behavioural paradigms related to dopaminergic signalling including locomotor activity, reward preference and anxiolytic behaviour. Our results suggest that TH-Cre mice represent a valid tool to study the dopamine system, though careful characterization must always be performed to prevent false interpretations following Cre-dependent transgene expression and manipulation of selected neuronal pathways.

Impact of tumour necrosis factor inhibitor treatment on radiographic progression in rheumatoid arthritis patients in clinical practice: results from the nationwide Danish DANBIO registry.

OBJECTIVES: To compare radiographic progression during treatment with disease-modifying antirheumatic drugs (DMARD) and subsequent treatment with tumour necrosis factor α inhibitors (TNF-I) in rheumatoid arthritis (RA) patients in clinical practice. METHODS: Conventional radiographs (x-rays) of hands and wrists were obtained ∼2 years before start (prebaseline), at baseline and ∼2 years after start (follow-up) of TNF-I. Clinical data were obtained from the DANBIO registry and the patient files. x-Rays were scored blinded to chronology according to the Sharp/van der Heijde method. Annual radiographic progression rates during the DMARD (prebaseline to baseline x-ray) and TNF-I (baseline to follow-up x-ray) periods were calculated. RESULTS: 517 RA patients (76% women, 80% IgM rheumatoid factor positive, 65% anticyclic citrullinated peptide positive, 40% current smokers, age 54 years (range 21-86), median disease duration 5 years (range 0-57)) were included. Patients were treated with infliximab (61%), etanercept (15%) or adalimumab (24%). During the DMARD period 85% of patients received methotrexate, 51% sulphasalazine and 78% prednisolone. The median DMARD period was 733 days (IQR 484-1002) and the median TNF-I period was 562 days (IQR 405-766). The median radiographic progression rate decreased from 0.7 (IQR 0-2.9) total Sharp score units/year (dTSS) in the DMARD period to 0 (0-0.9) units/year in the TNF-I period (p<0.0001, Wilcoxon). Corresponding mean dTSS values were 2.1 (SD 3.7) versus 0.7 (SD 2.3) units/year (p<0.0001, paired t test). 305 patients progressed (dTSS >0) in the DMARD period compared with 158 patients in the TNF-I period (p<0.0001, χ(2)). CONCLUSION: This nationwide observational study of RA patients documented significantly reduced radiographic progression during TNF-I treatment compared with the previous period of DMARD treatment.

Multi-site pre-therapeutic biopsies demonstrate genetic heterogeneity in patients with newly diagnosed diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease, both regarding clinical presentation, response to treatment and outcome. Recently, subclassification of DLBCL based on mutational profile has been suggested, and next generation sequencing (NGS) analysis may be relevant as part of the diagnostic workflow. This will, however, often be based on analysis of one tumor biopsy. Here, we present a prospective study where multi-site sampling was performed prior to treatment in patients with newly diagnosed DLBCL. Two spatially different biopsies from 16 patients were analyzed using NGS with an in-house 59-gene lymphoma panel. In 8/16 (50%) patients, mutational differences were found between the two biopsy sites, including differences in TP53 mutational status. Our data indicate that a biopsy from the extra-nodal site may represent the most advanced clone, and an extra-nodal biopsy should be preferred for analysis, if safely accessible. This will help ensure a standardized stratification and treatment decision.

Involvement of a subpopulation of neuronal M4 muscarinic acetylcholine receptors in the antipsychotic-like effects of the M1/M4 preferring muscarinic receptor agonist xanomeline.

Disturbances in central dopaminergic neurotransmission are believed to be centrally involved in the pathogenesis of schizophrenia. Central dopaminergic and cholinergic systems interact and the cholinergic muscarinic agonist xanomeline has shown antipsychotic effects in clinical studies. Preclinical studies indicate that the M(4) muscarinic cholinergic receptor subtype (mAChR) modulates the activity of the dopaminergic system and that this specific mAChR subtype is involved in mediating the antipsychotic-like effects of xanomeline. A specific neuronal subpopulation that expresses M(4) mAChRs together with D(1) dopamine receptors seems to be especially important in modulating dopamine-dependent behaviors. Using mutant mice that lack the M(4) mAChR only in D(1) dopamine receptor-expressing cells (D1-M4-KO), we investigated the role of this neuronal population in the antipsychotic-like effects of xanomeline in amphetamine-induced hyperactivity and apomorphine-induced climbing. Interestingly, the antipsychotic-like effects of xanomeline in the two models were almost completely abolished in D1-M4-KO mice, suggesting that M(4) mAChRs colocalized with D(1) dopamine receptors are centrally involved in mediating the antipsychotic-like effects of xanomeline. This is consistent with the hypothesis that activation of the M(4) mAChR represents a potential target for the future medical treatment of psychosis.

A subpopulation of neuronal M4 muscarinic acetylcholine receptors plays a critical role in modulating dopamine-dependent behaviors.

Acetylcholine (ACh) regulates many key functions of the CNS by activating cell surface receptors referred to as muscarinic ACh receptors (M(1)-M(5) mAChRs). Like other mAChR subtypes, the M(4) mAChR is widely expressed in different regions of the forebrain. Interestingly, M(4) mAChRs are coexpressed with D(1) dopamine receptors in a specific subset of striatal projection neurons. To investigate the physiological relevance of this M(4) mAChR subpopulation in modulating dopamine-dependent behaviors, we used Cre/loxP technology to generate mutant mice that lack M(4) mAChRs only in D(1) dopamine receptor-expressing cells. The newly generated mutant mice displayed several striking behavioral phenotypes, including enhanced hyperlocomotor activity and increased behavioral sensitization following treatment with psychostimulants. These behavioral changes were accompanied by a lack of muscarinic inhibition of D(1) dopamine receptor-mediated cAMP stimulation in the striatum and an increase in dopamine efflux in the nucleus accumbens. These novel findings demonstrate that a distinct subpopulation of neuronal M(4) mAChRs plays a critical role in modulating several important dopamine-dependent behaviors. Since enhanced central dopaminergic neurotransmission is a hallmark of several severe disorders of the CNS, including schizophrenia and drug addiction, our findings have substantial clinical relevance.

Revealing a compulsive phenotype in cholinergic M4-/- mice depends on the inter-trial interval initiation settings in a five choice serial reaction time task.

BACKGROUND: Muscarinic acetylcholine receptor 4 (M4) modulates dopaminergic neurotransmission and is a target for novel treatments of schizophrenia, cognitive deficits, and addiction. Impulsive and compulsive behaviors are key traits of addiction, yet the importance of M4 receptor signaling to these traits is poorly understood. We investigated impulsive action and compulsivity by measuring premature and perseverative responses in the five choice serial reaction time task (5CSRTT). Furthermore, we hypothesized that inter-trial interval (ITI) initiation settings affected training durations and test performances in these experiments. METHODS: M4-/- and wildtype mice were trained and tested on two versions of the 5CSRTT with different ITI initiation settings. One setting, the head-in condition, allowed the ITI to start while the mouse's head remained in the reward receptacle (magazine). The other setting, the head-out condition, required the mouse to remove its head from the magazine to initiate the ITI. RESULTS AND DISCUSSION: We did not observe differences in premature or perseverative responses in M4-/- mice in either condition, but found evidence of reward-related compulsive behavior in M4-/- mice. In the head-in condition, M4-/- mice were slower to acquire the 5CSRTT, had more omissions, and had longer correct response latencies than wildtype mice. In the head-out condition, genotypes did not differ in training, but M4-/- mice showed small decreases in accuracy. Our findings demonstrate that ITI initiation settings contribute to different training durations and tested behaviors in M4-/- mice, suggesting ITI initiation settings are an important consideration for the general use of the 5CSRTT.

G protein-coupled receptor signaling in VTA dopaminergic neurons bidirectionally regulates the acute locomotor response to amphetamine but does not affect behavioral sensitization.

Amphetamine (AMPH) acts as a substrate of the dopamine transporter (DAT) and causes a dramatic increase in extracellular dopamine (DA). Upon entering DA neurons, AMPH promotes DA efflux via DAT through a mechanism implicating depletion of DA from vesicular stores, activation of kinase pathways and transporter phosphorylation. Despite the role of intracellular signaling for AMPH action, it remains elusive how the response to AMPH is affected in vivo by metabotropic regulation via G protein coupled receptor signaling pathways. Here, we show by employment of Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) that the acute hyperlocomotor response to AMPH is bidirectionally regulated by metabotropic input to VTA DA neurons with a markedly enhanced response upon activation of a Gs-coupled pathway and a markedly decreased locomotor response upon activation of a Gi-coupled pathway. The unique mechanism of action for AMPH was underlined by the absence of an effect of Gs activation on the locomotor response to the DAT inhibitor cocaine. Regardless of the profound effect on the acute AMPH response, repeated Gs activation or Gi activation did not affect development of AMPH sensitization. Furthermore, activation of a Gs-pathway or activation of a Gi-pathway in DA neurons did not have any effect on the AMPH-induced locomotor response in the AMPH sensitized mice. This suggests induction of alterations in DA neuronal functions that overrule the stimulatory or inhibitory effect of metabotropic input seen in drug-naïve mice. The data thereby underline the remarkable strength of maladaptive changes that occur upon intake of strong psychostimulants. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.

Physiological roles of CNS muscarinic receptors gained from knockout mice.

Because the five muscarinic acetylcholine receptor subtypes have overlapping distributions in many CNS tissues, and because ligands with a high degree of selectivity for a given subtype long remained elusive, it has been difficult to determine the physiological functions of each receptor. Genetically engineered knockout mice, in which one or more muscarinic acetylcholine receptor subtype has been inactivated, have been instrumental in identifying muscarinic receptor functions in the CNS, at the neuronal, circuit, and behavioral level. These studies revealed important functions of muscarinic receptors modulating neuronal activity and neurotransmitter release in many brain regions, shaping neuronal plasticity, and affecting functions ranging from motor and sensory function to cognitive processes. As gene targeting technology evolves including the use of conditional, cell type specific strains, knockout mice are likely to continue to provide valuable insights into brain physiology and pathophysiology, and advance the development of new medications for a range of conditions such as Alzheimer's disease, Parkinson's disease, schizophrenia, and addictions, as well as non-opioid analgesics. This article is part of the Special Issue entitled 'Neuropharmacology on Muscarinic Receptors'.

PICK1-Deficient Mice Exhibit Impaired Response to Cocaine and Dysregulated Dopamine Homeostasis.

Protein interacting with C-kinase 1 (PICK1) is a widely expressed scaffold protein known to interact via its PSD-95/discs-large/ZO-1 (PDZ)-domain with several membrane proteins including the dopamine (DA) transporter (DAT), the primary target for cocaine's reinforcing actions. Here, we establish the importance of PICK1 for behavioral effects observed after both acute and repeated administration of cocaine. In PICK1 knock-out (KO) mice, the acute locomotor response to a single injection of cocaine was markedly attenuated. Moreover, in support of a role for PICK1 in neuroadaptive changes induced by cocaine, we observed diminished cocaine intake in a self-administration paradigm. Reduced behavioral effects of cocaine were not associated with decreased striatal DAT distribution and most likely not caused by the ∼30% reduction in synaptosomal DA uptake observed in PICK1 KO mice. The PICK1 KO mice demonstrated preserved behavioral responses to DA receptor agonists supporting intact downstream DA receptor signaling. Unexpectedly, we found a prominent increase in striatal DA content and levels of striatal tyrosine hydroxylase (TH) in PICK1 KO mice. Chronoamperometric recordings showed enhanced DA release in PICK1 KO mice, consistent with increased striatal DA pools. Viral-mediated knock-down (KD) of PICK1 in cultured dopaminergic neurons increased TH expression, supporting a direct cellular effect of PICK1. In summary, in addition to demonstrating a key role of PICK1 in mediating behavioral effects of cocaine, our data reveal a so far unappreciated role of PICK1 in DA homeostasis that possibly involves negative regulation of striatal TH levels.

Subjective perception of cocaine reward in mice assessed by a single exposure place preference (sePP) paradigm.

BACKGROUND: The potential of abused drugs to induce addiction and compulsive drug-related behavior is associated with their ability to alter dopamine signaling. Dopamine plays a key role in reward signaling and it has been of great interest to investigate how various drugs of abuse alter reward-related behavior. COMPARISON WITH EXISTING METHODS: In rodents, the rewarding effects of drugs have often been assessed in self-administration or place preference paradigms; both involving repeated drug exposure and weeks of training and testing. NEW METHOD: Our investigation describes a valid approach to assess the initial rewarding effects of cocaine in mice with a single exposure place preference (sePP) paradigm, avoiding repeated drug injections. RESULTS: We present the sePP paradigm with a 3-day protocol to assess the initial rewarding effects of cocaine. Interestingly, only male mice exhibit sePP to cocaine. To assess subsequent drug-related behavior, the protocol was extended by 3days of extinction followed by reinstatement on day 10. CONCLUSION: The sePP paradigm provides a reliable and convenient approach to assess the initial rewarding effects of cocaine, circumventing the need for repeated drug injections. The sePP protocol allows further dissection of the mechanism and influence of initial cocaine exposure on subsequent drug-related behaviors by including extinction and reinstatement. The lack of sePP in female mice may reflect a biologically relevant sex difference in the initial subjective perception of cocaine-induced reward. This could relate to and explain why males and females have been reported to respond differently to cocaine and cocaine-associated cues.

The glucagon-like peptide 1 receptor agonist Exendin-4 decreases relapse-like drinking in socially housed mice.

Glucagon-like peptide-1 (GLP-1) is a gut peptide that regulates food intake and glucose metabolism. GLP-1 is also produced and released in the brain, and GLP-1 receptors are expressed in brain regions important for alcohol and drug reward, and for the development of addiction. GLP-1 receptor agonists can decrease alcohol intake acutely in rodents. However, alcohol use disorder is a chronic condition that requires treatments to be effective in promoting abstinence from excessive alcohol consumption over time. Here, we assessed the effect of daily treatment with the GLP-1 receptor agonist Exendin-4 in an assay of relapse-like drinking in socially housed mice. Male C57BL/6NTac mice were allowed continuous access to alcohol without tastant in the home cage for 37days. Then, alcohol bottles were removed and Exendin-4 (1.5µg/kg/day) or saline was administered subcutaneously for 8days during alcohol deprivation. Treatment continued for 8 additional days after reintroducing access to alcohol. A high-precision automated fluid consumption system was used to monitor intake of alcohol and water, drinking kinetics, and locomotor activity. Exendin-4 prevented the deprivation-induced increase in alcohol intake observed in control mice, without significantly affecting total fluid intake, body weight, or locomotor activity. The reduced alcohol intake was caused by a protracted latency to the first drink of alcohol and a reduced number of drinking bouts, while bout size and duration were not affected. The effect was maintained undiminished throughout the treatment period. These findings support the possible use of GLP-1 receptor agonists in the treatment of alcohol use disorder.

Muscarinic receptor M4 positive allosteric modulators attenuate central effects of cocaine.

BACKGROUND: Cocaine addiction is a chronic brain disease affecting neurotransmission. Muscarinic cholinergic receptors modulate dopaminergic signaling in the reward system, and muscarinic receptor stimulation can block direct reinforcing effects of cocaine. Here, we tested the hypothesis that specific muscarinic M4 receptor stimulation can attenuate the discriminative stimulus effects and conditioned rewarding effects of cocaine, measures believed to predict the ability of cocaine and cocaine-associated cues to elicit relapse to drug taking. METHODS: We tested the M4-selective positive allosteric modulators VU0152100 and VU0467154 in a drug discrimination assay and a conditioned place preference assay, including extinction and reinstatement of place preference. Specificity of the cocaine discrimination effect was verified using knockout mice lacking either M1 or M4 receptors (M1-/-, M4-/-). We also replicated previous findings in cocaine-induced locomotor hyperactivity and striatal dopamine microdialysis assays. RESULTS: VU0152100 attenuated the discriminative stimulus effect of cocaine in wild-type mice and M1-/- mice, but not in M4-/- mice, without affecting rates of responding. As previously shown with VU0152100, VU0467154 almost eliminated cocaine-induced hyperactivity and striatal dopamine efflux. VU0467154 failed to attenuate acquisition of cocaine-conditioned place preference, but facilitated extinction and prevented reinstatement of the conditioned place preference. CONCLUSIONS: These findings further support the notion that M4 receptors are promising targets for the treatment of cocaine addiction, by showing that results can be replicated using distinct ligands, and that in addition to blocking reinforcing effects of cocaine relevant to ongoing drug taking, M4 positive allosteric modulators can also attenuate subjective and conditioned effects relevant to relapse.

Major femoral vascular access complications after coronary diagnostic and interventional procedures: A Danish register study.

BACKGROUND: Vascular access complications after coronary angiography (CAG) and percutaneous coronary intervention (PCI) are known to increase morbidity, prolong hospitalization and raise hospital costs. Therefore, risk factor identification and improvement of safety strategies for vascular management are important. We aimed to assess the incidence of major vascular complications related to femoral access, and to identify potential risk factors. METHODS: Over a period of six years, 23,870 index procedures (CAG) were performed in two centres, prospectively entered in the database and retrospectively analysed. Data was obtained from the Eastern Danish Heart Registry and cross-matched with data from the Danish Vascular Registry. Index procedures were defined as the first trans-femoral procedure. Demographic, procedural and mortality data, as well as information on access complications requiring surgery within 30 days were collected. Mortality data were collected for minimum 12 months. RESULTS: We identified 130 (0.54%) access complications requiring surgery; 65 pseudoaneurysms (0.28%), 46 arterial occlusions (0.19%), 15 hematomas (nine groin and six retroperitoneal hematomas) (0.06%), and 4 arterial dissections (0.02%). Risk factors for complications were left sided femoral access (OR 4.11 [2.29-7.37] p<0.001), peripheral arterial disease (PAD) (OR 2.42 [1.48-3.94] p<0.0001) and female sex (OR 2.22 [1.51-3.24] p<0.0001). CONCLUSION: Vascular complications related to femoral access in coronary diagnostic and interventional procedures are low (0.54%). Risk factors were left sided access, PAD, and female sex.

Frequency and Effect of Access-Related Vascular Injury and Subsequent Vascular Intervention After Transcatheter Aortic Valve Replacement.

Vascular access and closure remain a challenge in transcatheter aortic valve replacement (TAVR). This single-center study aimed to report the incidence, predictive factors, and clinical outcomes of access-related vascular injury and subsequent vascular intervention. During a 30-month period, 365 patients underwent TAVR and 333 patients (94%) were treated by true percutaneous transfemoral approach. Of this latter group, 83 patients (25%) had an access-related vascular injury that was managed by the use of a covered self-expanding stent (n = 49), balloon angioplasty (n = 33), or by surgical intervention (n = 1). In 16 patients (5%), the vascular injury was classified as a major vascular complication. Absence of a preprocedural computed tomography angiography (CTA) of the iliofemoral arteries (OR 2.04, p = 0.007) and female gender (OR 2.18, p = 0.004) were independent predictors of the need for access-related vascular intervention. In addition, a high sheath/common femoral artery ratio as measured on preoperative CTA was associated with a higher rate of post-TAVR vascular intervention. The radiation dose, iodine contrast volume, transfusion need, length of hospitalization, and 30-day mortality were not significantly different between patients with versus without access-related vascular intervention. In conclusion, access-related vascular intervention in patients who underwent transfemoral-TAVR is not uncommon. Female gender and a high sheath/common femoral artery ratio are risk factors for access-related vascular injury, whereas preprocedural planning with CTA of the access vessels may reduce the risk of vascular injury. Importantly, most access-related vascular injuries may be treated by percutaneous techniques with similar clinical outcomes to patients without vascular injuries.

Antipsychotic-like effect of the muscarinic acetylcholine receptor agonist BuTAC in non-human primates.

Cholinergic, muscarinic receptor agonists exhibit functional dopamine antagonism and muscarinic receptors have been suggested as possible future targets for the treatment of schizophrenia and drug abuse. The muscarinic ligand (5R,6R)-6-(3-butylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[3.2.1]octane (BuTAC) exhibits high affinity for muscarinic receptors with no or substantially less affinity for a large number of other receptors and binding sites, including the dopamine receptors and the dopamine transporter. In the present study, we wanted to examine the possible antipsychotic-like effects of BuTAC in primates. To this end, we investigated the effects of BuTAC on d-amphetamine-induced behaviour in antipsychotic-naive Cebus paella monkeys. Possible adverse events of BuTAC, were evaluated in the same monkeys as well as in monkeys sensitized to antipsychotic-induced extrapyramidal side effects. The present data suggests that, the muscarinic receptor ligand BuTAC exhibits antipsychotic-like behaviour in primates. The behavioural data of BuTAC as well as the new biochemical data further substantiate the rationale for the use of muscarinic M1/M2/M4-preferring receptor agonists as novel pharmacological tools in the treatment of schizophrenia.

Enhanced self-administration of alcohol in muscarinic acetylcholine M4 receptor knockout mice.

Modulation of cholinergic neurotransmission via nicotinic acetylcholine receptors is known to alter alcohol-drinking behavior. It is not known if muscarinic acetylcholine receptor subtypes have similar effects. The muscarinic M4 receptor is highly expressed in the brain reinforcement system and involved in regulation of cholinergic and dopaminergic transmission. Here we investigate, for the first time, the role of the M4 receptor in alcohol consumption using M4 knockout (M4(-/-)) and wild-type (M4(+/+)) mice. Experimentally naïve M4(-/-) and M4(+/+) mice were trained to orally self-administer 5%, 8% and 10% alcohol in 60min sessions, 6 days/week, after having undergone a standard sucrose fading training procedure on a fixed ratio schedule. The mice were further subjected to an extinction period followed by a 1 day reinstatement trial. M4(-/-) mice consumed more alcohol at 5% and 8% compared to their M4(+/+) littermates. The highest alcohol concentration used (10%) did not immediately result in divergent drinking patterns, but after 4 weeks of 10% alcohol self-administration, baseline levels as well as a pattern of M4(-/-) mice consuming more alcohol than their M4(+/+) controls were re-established. Moreover, the M4(-/-) mice displayed a reduced capacity to extinguish their alcohol-seeking behavior. Taken together, alcohol consumption is elevated in M4(-/-) mice, indicating that the M4 receptor is involved in mediating the reinforcing effects of alcohol. The M4 receptor should be further explored as a potential target for pharmacological (positive allosteric modulators or future agonists) treatment of alcohol use disorders.

Selective activation of M4 muscarinic acetylcholine receptors reverses MK-801-induced behavioral impairments and enhances associative learning in rodents.

Positive allosteric modulators (PAMs) of the M4 muscarinic acetylcholine receptor (mAChR) represent a novel approach for the treatment of psychotic symptoms associated with schizophrenia and other neuropsychiatric disorders. We recently reported that the selective M4 PAM VU0152100 produced an antipsychotic drug-like profile in rodents after amphetamine challenge. Previous studies suggest that enhanced cholinergic activity may also improve cognitive function and reverse deficits observed with reduced signaling through the N-methyl-d-aspartate subtype of the glutamate receptor (NMDAR) in the central nervous system. Prior to this study, the M1 mAChR subtype was viewed as the primary candidate for these actions relative to the other mAChR subtypes. Here we describe the discovery of a novel M4 PAM, VU0467154, with enhanced in vitro potency and improved pharmacokinetic properties relative to other M4 PAMs, enabling a more extensive characterization of M4 actions in rodent models. We used VU0467154 to test the hypothesis that selective potentiation of M4 receptor signaling could ameliorate the behavioral, cognitive, and neurochemical impairments induced by the noncompetitive NMDAR antagonist MK-801. VU0467154 produced a robust dose-dependent reversal of MK-801-induced hyperlocomotion and deficits in preclinical models of associative learning and memory functions, including the touchscreen pairwise visual discrimination task in wild-type mice, but failed to reverse these stimulant-induced deficits in M4 KO mice. VU0467154 also enhanced the acquisition of both contextual and cue-mediated fear conditioning when administered alone in wild-type mice. These novel findings suggest that M4 PAMs may provide a strategy for addressing the more complex affective and cognitive disruptions associated with schizophrenia and other neuropsychiatric disorders.