Alpha7 Nicotinic Acetylcholine Receptor Agonists Research Articles

The novel α7 nicotinic acetylcholine receptor agonist EVP-6124 enhances dopamine, acetylcholine, and glutamate efflux in rat cortex and nucleus accumbens.

Alpha7 and α4β2 nicotinic acetylcholine receptor (nAChR) agonists have been shown to improve cognition in various animal models of cognitive impairment and are of interest as treatments for schizophrenia, Alzheimer's disease, and other cognitive disorders. Increased release of dopamine (DA), acetylcholine (ACh), glutamate (Glu), and γ-aminobutyric acid (GABA) in cerebral cortex, hippocampus, and nucleus accumbens (NAC) has been suggested to contribute to their beneficial effects on cognition. Using in vivo microdialysis, we found that EVP-6124 [(R)-7-chloro-N-quinuclidin-3-yl)benzo[b]thiophene-2-carboxamide], a high-affinity α7 nAChR partial agonist, at 0.1mg/kg, s.c., increased DA efflux in the medial prefrontal cortex (mPFC) and NAC. EVP-6124, 0.1 and 0.3mg/kg, also increased efflux of ACh in the mPFC but not in the NAC. Similarly, EVP-6124, 0.1mg/kg, but not 0.03 and 0.3mg/kg, significantly increased mPFC Glu efflux. Thus, EVP-6124 produced an inverted U-shaped curve for DA and Glu release, as previously reported for other α7 nAChR agonists. The three doses of EVP-6124 did not produce a significant effect on GABA efflux in either region. Pretreatment with the selective α7 nAChR antagonist, methyllycaconitine (MLA, 1.0mg/kg), significantly blocked cortical DA and Glu efflux induced by EVP-6124 (0.1mg/kg), suggesting that the effects of EVP-6124 on these neurotransmitters were due to α7 nAChR agonism. MLA only partially blocked the effects of EVP-6124 on ACh efflux in the mPFC. These results suggest increased cortical DA, ACh, and Glu release, which may contribute to the ability of the α7 nAChR agonist, EVP-6124, to treat cognitive impairment and possibly other dimensions of psychopathology.

Effects of splenectomy and GTS-21, a selective α7 nicotinic acetylcholine receptor agonist, on the development of septic ileus in mice

Sepsis remains a leading cause of mortality in our ICUs. Ileus, defined as the inhibition of the propulsive motility in the gastrointestinal (GI) tract, together with mucosal barrier dysfunction will maintain sepsis by the translocation of intestinal bacteria. Preliminary data in our group showed that the administration of GTS-21, a selective alpha7 nicotinic acetylcholine receptor (α7nAChR) agonist, ameliorates inflammation and GI motility disturbances during sepsis [1]. Activation of the α7nAChR is the final step in the vagal anti-inflammatory pathway, a spleen-dependent and macrophage-dependent pathway that dampens inflammation. We aimed to study the effects of splenectomy (SPLX) combined with GTS-21 on GI motility and on local colonic and systemic inflammation, as the role of the spleen in the vagal anti-inflammatory pathway is currently under debate.

The alpha-7 nicotinic receptor partial agonist/5-HT3 antagonist RG3487 enhances cortical and hippocampal dopamine and acetylcholine release

Alpha-7 nicotinic acetylcholine receptor (nAChR) agonists may ameliorate cognitive deficits in schizophrenia, in part, because of their ability to enhance dopaminergic and cholinergic neurotransmission. In the current study, the effects of partial nAChR agonist and 5-HT3 receptor antagonist RG3487 (previously R3487/MEM3454) on dopamine (DA) and acetylcholine (ACh) effluxes in rat prefrontal cortex (mPFC) and hippocampus (HIP) were investigated in awake, freely moving rats. R3487/MEM3454, at doses of 0.1-10mg/kg, s.c., enhanced DA and ACh effluxes in rat mPFC and (HIP), with a peak effect at 0.3- to 0.6-mg/kg doses, producing a bell-shaped dose-response curve. Pretreatment with the selective nAChR antagonist, methyllycaconitine (1.0mg/kg), completely blocked RG3487-induced (0.45mg/kg) DA but not ACh efflux, while the selective 5-HT3 receptor agonist 1-(m-chlorophenyl)-biguanide (1.0mg/kg) partially inhibited cortical ACh but not DA efflux. RG3487 (0.45mg/kg) combined with atypical antipsychotic drug (APD) risperidone (0.1mg/kg), but not typical APD haloperidol (0.1mg/kg), induced a significantly greater increase in HIP ACh efflux. Their combined effect on DA efflux was additive. RG3487, combined with other atypical APDs, namely aripiprazole (0.3mg/kg), olanzapine (1.0mg/kg), and quetiapine (30mg/kg), also produced additive effects on DA efflux. These results suggest that RG3487 enhances DA efflux by nAChR stimulation, whereas ACh efflux is primarily mediated via 5-HT3 receptor antagonism, and that RG3487 alone or as augmentation may improve cognitive impairment in schizophrenia.

Effect of alpha7 nicotinic acetylcholine receptor agonists on attentional set-shifting impairment in rats

Attentional set shifting, a measure of executive function, is impaired in schizophrenia patients. Current standard of care has little therapeutic benefit for treating cognitive dysfunction in schizophrenia; therefore, novel drugs and animal models for testing novel therapies are needed. The NMDA receptor antagonist, MK-801, produces deficits in a rat maze-based set-shifting paradigm, an effect which parallels deficits observed on tests of executive function in schizophrenia patients. Alpha7 nicotinic acetylcholine receptor (nAChR) agonists, currently under clinical development by several companies, show promise in treating cognitive symptoms in schizophrenia patients and can improve cognition in various animal models. The objectives of the present study were to determine whether the MK-801 deficit in set shifting could be reproduced in a drug discovery setting and to determine whether cognitive improvement could be detected for the first time in this task with alpha7 nAChR agonists. The data presented here replicate findings that a systemic injection of the NMDA receptor antagonist MK-801 can induce a deficit in set shifting in rats. Furthermore, the deficit could be reversed by the atypical antipsychotic clozapine as well as by several alpha7 nAch receptor agonists (SSR-180711, PNU-282987, GTS-21) with varying in vitro properties. Results indicate that the MK-801 set-shift assay is a useful preclinical tool for measuring prefrontal cortical function in rodents and can be used to identify novel mechanisms for the potential treatment of cognitive deficits in schizophrenia.

Targeting alpha-7 nicotinic neurotransmission in schizophrenia: A novel agonist strategy

Alpha7 nicotinic acetylcholine receptor (α7 nAChR) agonists may be valuable treatments for negative symptoms and cognitive impairment in schizophrenia. Unfortunately, chronic exposure to an agonist may reduce the receptor's sensitivity. Therefore, we combined CDP-choline, a dietary source of the direct agonist choline, with galantamine, a positive allosteric modulator (PAM) of nicotinic acetylcholine receptors, to improve the efficiency of transducing the choline signal and, possibly, preserve the receptor in a sensitive state. We conducted a single-site, double-blind randomized clinical trial comparing galantamine/CDP-choline to placebos in schizophrenia patients with negative symptoms who were receiving second generation antipsychotics. Forty-three subjects received galantamine and CDP-choline or matching placebos for 16weeks. The primary outcome measure was the 5-item Marder negative-symptoms factor of the Positive and Negative Syndrome Scale (PANSS). Cognition and functioning were also assessed. Trial completion was high; 79%. There was no significant treatment effect on negative symptoms, other PANSS symptom factors, or the MATRICS Cognitive Consensus Battery. There were significant treatment effects in overall functioning and a test of free verbal recall. Three subjects discontinued treatment in the active treatment group for gastro-intestinal adverse events (AE). The most common AE for galantamine/CDP-choline was abdominal pain; for placebo it was headache and sweating. Although there was no significant treatment effect on negative symptoms, the direction of effect mirrored the effects on a cognitive measure and overall functioning. Further study of α7 nAChR agonist/PAMs is warranted in larger studies that will have greater power.

Choline, an alpha7 nicotinic acetylcholine receptor agonist, alleviates hyperalgesia in a rat osteoarthritis model

It has been suggested that activation of alpha7 nicotinic acetylcholine receptors (α7nAChR) could alleviate acute and chronic pain in various abnormal pain models. However, it is unclear whether the stimulation of α7nAChRs has anti-hyperalgesic effects on osteoarthritis. Therefore, we tested whether choline, an α7nAChR agonist, could alleviate chronic inflammatory pain in an osteoarthritis model. Osteoarthritis was induced by injection of monoiodoacetic acid (MIA) into the synovial cavity of the knee joints in rats. Pain was assessed by responses to stimuli on the plantar surface: paw withdrawal threshold (PWT) by up-down methods using a series of von Frey filaments, and paw withdrawal latency (PWL) using radiation heat. Both PWT and PWL decreased after MIA injection, indicating development of mechanical and thermal hyperalgesia. Subsequent intraperitoneal choline injection increased both PWT and PWL. PWT increased in response to choline injections (5–50mg/Kg) in a dose dependent manner. PWL increased significantly in a similar fashion in response to choline (20 and 50mg/Kg). However, intraarticular injection of choline did not result in any change in PWT or PWL. Intrathecal choline increased PWT and PWL. The anti-hyperalgesic effect of intraperitoneal choline was completely blocked by methyllycaconitine when it was injected intrathecally 10min before the choline treatment. These results show that choline could alleviate mechanical and heat hyperalgesia via spinal α7nAChR in the MIA-induced inflammation pain model.

Alpha-7 nicotinic acetylcholine receptor agonists in intracerebral hemorrhage: an evaluation of the current evidence for a novel therapeutic agent

Intracerebral hemorrhage (ICH) is the most deadly and least treatable subtype of stroke, and at the present time there are no evidence-based therapeutic interventions for patients with this disease. Secondary injury mechanisms are known to cause substantial rates of morbidity and mortality following ICH, and the inflammatory cascade is a major contributor to this post-ICH secondary injury. The alpha-7 nicotinic acetylcholine receptor (α7-nAChR) agonists have a well-established antiinflammatory effect and have been shown to attenuate perihematomal edema volume and to improve functional outcome in experimental ICH. The authors evaluate the current evidence for the use of an α7-nAChR agonist as a novel therapeutic agent in patients with ICH.

Alternative pharmacologic targets for the treatment of schizophrenia

The current article provides a brief review of the clinical efficacy and safety outcomes from selected phase I and II clinical trials of compounds in development acting on targets beyond the dopamine D2 receptor in patients with schizophrenia. A number of experimental pharmacological targets have been studied in clinical trials. Among those, glutamatergic and nicotinergic pathways have received most attention. Glycine transporter 1 inhibitors used adjunctively with antipsychotics suggest efficacy for negative symptoms of schizophrenia. Adjunctive alpha7 nicotinic acetylcholine receptor agonists and minocycline may improve negative symptoms and cognitive deficits. Adjunctive oxytocin may benefit psychotic symptoms and social cognitive deficits. Adjunctive erythropoietin may improve cognitive function. Experimental therapeutic research for schizophrenia is rapidly expanding and a number of compounds with novel mechanisms of action are demonstrating encouraging evidence for efficacy across a range of symptoms. However, much work still needs to be conducted before these new agents can be considered for routine clinical treatment. In particular, further assessment of efficacy and longer term safety and tolerability monitoring are required.

The Microglial α7-Acetylcholine Nicotinic Receptor Is a Key Element in Promoting Neuroprotection by Inducing Heme Oxygenase-1 via Nuclear Factor Erythroid-2-Related Factor 2

We asked whether the neuroprotective effect of cholinergic microglial stimulation during an ischemic event acts via a mechanism involving the activation of nuclear factor erythroid-2-related factor 2 (Nrf2) and/or the expression of its target cytoprotective gene, heme oxygenase-1 (HO-1). Specifically, the protective effect of the pharmacologic alpha-7 nicotinic acetylcholine receptor (α7 nAChR) agonist PNU282987 was analyzed in organotypic hippocampal cultures (OHCs) subjected to oxygen and glucose deprivation (OGD) in vitro as well as in photothrombotic stroke in vivo. OHCs exposed to OGD followed by reoxygenation elicited cell death, measured by propidium iodide and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide staining. Activation of α7 nAChR by PNU282987, after OGD, reduced cell death, reactive oxygen species production, and tumor necrosis factor release. This was associated with induction of HO-1 expression, an effect reversed by α-bungarotoxin and by tin-protoporphyrin IX. The protective effect of PNU282987 was lost in microglial-depleted OHCs as well as in OHCs from Nrf2-deficient-versus-wild-type mice, an effect associated with suppression of HO-1 expression in microglia. Administration of PNU282987 1 h after induction of photothrombotic stroke in vivo reduced the infarct size and improved motor skills in Hmox1(lox/lox) mice that express normal levels of HO-1, but not in LysM(Cre)Hmox1(Δ/Δ) in which HO-1 expression is inhibited in myeloid cells, including the microglia. This study suggests the participation of the microglial α7 nAChR in the brain cholinergic anti-inflammatory pathway. Activation of the α7 nAChR/Nrf2/HO-1 axis in microglia regulates neuroinflammation and oxidative stress, affording neuroprotection under brain ischemic conditions.

Systemic Administration of an Alpha-7 Nicotinic Acetylcholine Agonist Reverses Neuropathic Pain in Male Sprague Dawley Rats

Alpha-7 nicotinic acetylcholine receptor (α7 nAChR) agonists attenuate pain and inflammation in preclinical models. This study tested whether systemic delivery of an α7 nAChR agonist attenuates neuropathic pain and associated immune-mediated pro-inflammation. Hind paw response thresholds to mechanical stimuli in male Sprague Dawley rats were assessed before and after sciatic chronic constriction injury (CCI) or sham surgery. Osmotic mini-pumps containing TC-7020, an α7 nAChR selective agonist, were implanted 10 to 14 days after surgery. TC-7020 (1, 3, and 10 mg/kg/d; s.c.) significantly attenuated CCI-induced allodynia, which lasted through 2 weeks of test compound administration. Spinal cords were collected after 2 weeks and processed for microglial and astrocyte activation markers within the ipsilateral L4-L6 dorsal horn. In addition, ipsilateral L4-5 dorsal root ganglia (DRGs) were processed for neuronal injury and satellite cell activation markers. CCI-induced central glial cell activation markers were not suppressed by TC-7020, even though TC-7020 is mildly blood-brain barrier permeable. However, TC-7020 downregulated the integrated density of activation transcription factor 3 (ATF3) but not the number of ATF positive cells. TC-7020 also downregulated phosphorylated extracellular signal kinase (p-ERK) and satellite cell activation in the CCI-affected DRGs. Therefore, systemic α7 nAChR agonist may be effective in treating neuropathic pain via reducing neuronal injury and immune cells activation occurring in the periphery. PerspectiveThese studies demonstrated that TC-7020, an alpha7 nicotinic acetylcholine receptor agonist with partial blood-brain barrier permeability, reversed neuropathic pain in rats, likely via attenuation of inflammation in the DRG and/or the site of sciatic injury.

Spontaneous object recognition and its relevance to schizophrenia: a review of findings from pharmacological, genetic, lesion and developmental rodent models

Spontaneous (novel) object recognition (SOR) is one of the most widely used rodent behavioural tests. The opportunity for rapid data collection has made SOR a popular choice in studies that explore cognitive impairment in rodent models of schizophrenia, and that test the efficacy of drugs intended to reverse these deficits. We provide an overview of the many recent studies that have used SOR to explore the mnemonic effects of manipulation of the key transmitter systems relevant to schizophrenia-the dopamine, glutamate, GABA, acetylcholine, serotonin and cannabinoid systems-alone or in combination. We also review the use of SOR in studying memory in genetically modified mouse models of schizophrenia, as well as in neurodevelopmental and lesion models. We end by discussing the construct and predictive validity, and translational relevance, of SOR with respect to cognitive impairment in schizophrenia. Perturbation of the dopamine or glutamate systems can generate robust and reliable impairment in SOR. Impaired performance is also seen following antagonism of the muscarinic acetylcholine system, or exposure to cannabinoid agonists. Cognitive enhancement has been reported using alpha7-nicotinic acetylcholine receptor agonists and 5-HT(6) antagonists. Among non-pharmacological models, neonatal ventral hippocampal lesions and maternal immune activation can impair SOR, while mixed results have been obtained with mice carrying mutations in schizophrenia risk-associated genes, including neuregulin and COMT. While SOR is not without its limitations, the task represents a useful method for studying manipulations with relevance to cognitive impairment in schizophrenia, as well as the interactions between them.

Preclinical assessment of an adjunctive treatment approach for cognitive impairment associated with schizophrenia using the alpha7 nicotinic acetylcholine receptor agonist WYE-103914/SEN34625

α7 nicotinic acetylcholine receptor (nAChR) agonists are proposed as candidate agents for the adjunctive treatment of cognitive deficits associated with schizophrenia. Despite the pursuit of such an approach clinically, it is surprising that the preclinical profile of pro-cognitive agents in conjunction with antipsychotic drugs is currently unexplored. We determined if the memory-enhancing effects of the selective α7 nAChR agonist WYE-103914 were preserved in the presence of the atypical antipsychotic drug risperidone, and if the antipsychotic-like profile of risperidone was preserved in the presence of WYE-103914. Using the rat novel object recognition (NOR) paradigm, the maintenance of memory-enhancing activity of the α7 nAChR agonist WYE-103914 in the presence of risperidone was examined. Similarly, in the standard tests of antipsychotic-like activity, apomorphine-induced climbing (AIC) in mice and conditioned avoidance responding (CAR) in rats, the preservation of antipsychotic-like activity of risperidone was evaluated in the presence of WYE-103914. WYE-103914 exhibited memory-enhancing activity in rat NOR, and this effect of WYE-103914 was retained in the presence of risperidone. In AIC, the atypical antipsychotic profile of risperidone was not significantly altered by WYE-103914. In contrast, WYE-103914 moderately potentiated the efficacy profile of risperidone in CAR, an effect that did not appear to be convincingly linked to a pharmacokinetic interaction. These data underscore the value of a preclinical evaluation of the adjunctive profile of a memory-enhancing agent in combination with antipsychotics and provide further support to augmentation with α7 nAChR agonists to address the cognitive deficits associated with schizophrenia.

Application of Alpha7 Nicotinic Acetylcholine Receptor Agonists in Inflammatory Diseases: An Overview

Inflammatory disorders are characterized by the influx of immune cells into the vascular wall of veins and/or arteries in response to stimuli such as oxidized-LDL and various pathogens. These factors stimulate the local production of pro-inflammatory cytokines by macrophages and other cells that promote various inflammatory diseases such as atherosclerosis, Crohn's, Alzheimer's and diabetes. Numerous cytokines play a significant role in this process, though tumor necrosis factor (TNF) and various interleukins are thought to be among the most important regulators. These proinflammatory cytokines promote the above-described diseases by inducing endothelial cell dysfunction. In this brief commentary we will discuss some of the latest advances and discoveries in the treatment of these inflammatory diseases, making use of alpha7 nicotinic acetylcholine receptor (alpha7 nAChR) agonists.

Fat and the gut: More than empty calories*

Fat and the gut: More than empty calories*

Novel Alpha-7 Nicotinic Acetylcholine Receptor Agonists Containing a Urea Moiety: Identification and Characterization of the Potent, Selective, and Orally Efficacious Agonist 1-[6-(4-Fluorophenyl)pyridin-3-yl]-3-(4-piperidin-1-ylbutyl) Urea (SEN34625/WYE-103914)

Alpha-7 nicotinic acetylcholine receptor (alpha7 nAChR) agonists are promising therapeutic candidates for the treatment of cognitive impairment. We report a series of novel, potent small molecule agonists (4-18) of the alpha7 nAChR deriving from our continuing efforts in the areas of Alzheimer's disease and schizophrenia. One of the compounds of the series containing a urea moiety (16) was further shown to be a selective agonist of the alpha7 nAChR with excellent in vitro and in vivo profiles, brain penetration, and oral bioavailability and demonstrated in vivo efficacy in multiple behavioral cognition models. Structural modifications leading to the improved selectivity profile and the biological evaluation of this series of compounds are discussed.

HMGB1-Directed Drug Discovery Targeting Cutaneous Inflammatory Dysregulation

Extracellular cytokine function of the non-histone nuclear protein high-mobility group box 1 (HMGB1) has recently been recognized as an important drug target for novel anti-inflammatory therapeutics. Accumulating evidence supports the mechanistic involvement of the alarmin HMGB1 in skin response to microbial infection and ultraviolet-induced solar damage. Moreover, HMGB1 modulation of inflammatory signaling and tissue remodeling is now emerging as a causative factor in wound repair, autoimmune dysregulation, and skin carcinogenesis, representing cutaneous pathologies that affect large patient populations with unmet therapeutic needs. Recent structure-based drug discovery efforts have aimed at increasing the number of small molecule- and biologics-based prototype therapeutics targeting HMGB1. Small molecule drugs that may provide therapeutic benefit through HMGB1-directed mechanisms involve HMGB1 inhibitory ligands, Toll-like receptor antagonists, RAGE antagonists, alpha7 nicotinic acetylcholine receptor agonists, G2A antagonists, serine protease inhibitors, and alpha-dicarbonyl-based soft electrophiles. Using some of these agents, pharmacological modulation of HMGB1-associated cutaneous pathology has been achieved with an acceptable toxicity profile, and preclinical proof-of-concept experimentation has demonstrated feasibility of developing HMGB1-modulators into novel systemic and topical therapeutics that target cutaneous inflammatory dysregulation.

Novel Insights for Systemic Inflammation in Sepsis and Hemorrhage

The inflammatory responses in sepsis and hemorrhage remain a major cause of death. Clinically, it is generally accepted that shock in sepsis or hemorrhage differs in its mechanisms. However, the recognition of inflammatory cytokines as a common lethal pathway has become consent. Proinflammatory cytokines such as tumor necrosis factor (TNF) or high-mobility group box1 (HMGB1) are fanatically released and cause lethal multiorgan dysfunction. Inhibition of these cytokines can prevent the inflammatory responses and organ damage. In seeking potential anti-inflammatory strategies, we reported that ethyl pyruvate and alpha7 nicotinic acetylcholine receptor (alpha7nAChR) agonists effectively restrained cytokine production to provide therapeutic benefits in both experimental sepsis and hemorrhage. Here, we review the inflammatory responses and the anti-inflammatory strategies in experimental models of sepsis and hemorrhage, as they may have a consistent inflammatory pathway in spite of their different pathophysiological processes.

Alpha7 nicotinic acetylcholine receptor agonists: Prediction of their binding affinity through a molecular mechanics Poisson–Boltzmann surface area approach

A group of agonists for the alpha7 neuronal nicotinic acetylcholine receptors (nAChRs) was investigated, and their free energies of binding DeltaG(bind) were calculated by applying the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) approach. This method, based on molecular dynamics simulations of fully solvated protein-ligand complexes, allowed us to estimate the contribution of both polar and nonpolar terms as well as the entropy to the overall free energy of binding. The calculated results were in a good agreement with the experimentally determined DeltaG(bind) values, thereby pointing to the MM-PBSA protocol as a valuable computational tool for the rational design of specific agents targeting the neuronal alpha7 nAChR subtypes.

Neuropeptide Modulators of High Mobility Group Box 1 Secretion as Potential Therapeutic Agents for Severe Sepsis

This Commentary describes a study suggesting that the endogenous neuropeptides vasoactive intestinal peptide (VIP) and urocortin can improve survival in an animal model of lethal sepsis, possibly through their ability to decrease circulating levels of the cytokine-like protein high mobility group box 1 (HMGB1).

The selective α7 nicotinic acetylcholine receptor agonist A-582941 activates immediate early genes in limbic regions of the forebrain: Differential effects in the juvenile and adult rat

Due to the cognitive-enhancing properties of alpha7 nicotinic acetylcholine receptor (alpha7 nAChR) agonists, they have attracted interest for the treatment of cognitive disturbances in schizophrenia. Schizophrenia typically presents in late adolescence or early adulthood. It is therefore important to study whether alpha7 nAChR stimulation activates brain regions involved in cognition in juvenile as well as adult individuals. Here, we compared the effects of the novel and selective alpha7 nAChR agonist 2-methyl-5-(6-phenyl-pyridazin-3-yl)-octahydro-pyrrolo[3,4-c]pyrrole (A-582941) in the juvenile and adult rat forebrain using two markers, activity-regulated cytoskeleton-associated protein (Arc) and c-Fos, to map neuronal activity. Acute administration of A-582941 (1, 3, 10 mg/kg) induced a dose-dependent increase in Arc mRNA expression in the medial prefrontal cortex (mPFC) and the ventral/lateral orbitofrontal (VO/LO) cortex of juvenile, but not adult rats. This effect was mitigated by the alpha7 nAChR antagonist methyllycaconitine. A-582941 also increased c-Fos mRNA expression in the mPFC of juvenile, but not adult rats. Furthermore, A-582941 increased the number of Arc and c-Fos immunopositive cells in the mPFC, VO/LO, and shell of the nucleus accumbens, in both juvenile and adult rats. The A-582941-induced c-Fos protein expression was significantly greater in the mPFC and VO/LO of juvenile compared with adult rats. These data indicate that A-582941-induced alpha7 nAChR stimulation activates brain regions critically involved in working memory and attention. Furthermore, this effect is more pronounced in juvenile than adult rats, indicating that the juvenile forebrain is more responsive to alpha7 nAChR stimulation. This observation may be relevant in the treatment of juvenile-onset schizophrenia.