Tonic engagement of nicotinic receptors bidirectionally controls striatal spiny projection neuron spike timing

Striatal spiny projection neurons (SPNs) transform convergent excitatory corticostriatal inputs into an inhibitory signal that shapes basal ganglia output. This process is fine-tuned by striatal GABAergic interneurons (GINs), which receive overlapping cortical inputs and mediate rapid corticostriatal feedforward inhibition of SPNs. Adding another level of control, cholinergic interneurons (CINs), which are also vigorously activated by corticostriatal excitation, can 1) disynaptically inhibit SPNs by activating α4β2 nicotinic acetylcholine receptors (nAChRs) on various GINs and 2) directly modulate corticostriatal synaptic strength via pre-synaptic α7 nAChR receptors. Measurements of the disynaptic inhibitory pathway, however, indicate that it is too slow to compete with direct GIN-mediated feed-forward inhibition. Moreover, functional nAChRs are also present on populations of GINs that do not respond to phasic activation of CINs, such as parvalbumin-positive fast-spiking interneurons (PV-FSIs), making the overall role of nAChRs in shaping striatal synaptic integration unclear. Using acute striatal slices we show that upon synchronous optogenetic activation of corticostriatal projections, blockade of α7 nAChRs delayed SPN spikes, whereas blockade of α4β2 nAChRs advanced SPN spikes and increased postsynaptic depolarizations. The nAChR-dependent inhibition was mediated by downstream GABA release, and data suggest that the GABA source was not limited to GINs that respond to phasic CIN activation. In particular, the observed spike-advancement caused by nAChR blockade was associated with a diminished frequency of spontaneous inhibitory postsynaptic currents in SPNs, and a parallel hyperpolarization of PV-FSIs. Taken together, we describe opposing roles for tonic (as opposed to phasic) engagement of nAChRs in striatal function. We conclude that tonic activation of nAChRs by CINs both sharpens the temporal fidelity of corticostriatal signaling via pre-synaptic α7 nAChRs and maintains a GABAergic brake on cortically-driven striatal output, processes that may shape SPN spike timing, striatal processing and synaptic plasticity.

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Procognitive effects of varenicline in the animal model of schizophrenia depend on α4β2- and α7-nicotinic acetylcholine receptors

Journal of Psychopharmacology ◽

10.1177/0269881118812097 ◽

2018 ◽

Vol 33 (1) ◽

pp. 62-73 ◽

Cited By ~ 7

Author(s):

Agnieszka Potasiewicz ◽

Joanna Golebiowska ◽

Piotr Popik ◽

Agnieszka Nikiforuk

Keyword(s):

Acetylcholine Receptor ◽

Nicotinic Acetylcholine Receptor ◽

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

Partial Agonist ◽

Set Shifting ◽

Nicotinic Acetylcholine ◽

Α7 Nachr ◽

Α7 Nicotinic Acetylcholine Receptors ◽

Α7 Nachrs

Background: Varenicline, a partial agonist of the α4β2 nicotinic acetylcholine receptor (α4β2-nAChR), is currently used to facilitate smoking cessation. Preclinical and clinical studies have suggested that this compound may also be effective in treating cognitive impairments in schizophrenia. However, it is unclear which nicotinic acetylcholine receptor subtypes may be involved because varenicline is not only a partial agonist for α4β2-nAChRs but also a full agonist for α7 nicotinic acetylcholine receptors (α7-nAChRs). Aim: We investigated the effects of varenicline, compared to the α4β2-nAChR partial agonist TC-2403 and the α7-nAChR full agonist PNU-282987, in a ketamine-based model of schizophrenia-like cognitive deficits on the attentional set-shifting task in rats. The second goal was to elucidate whether the procognitive efficacy of varenicline was due to the compound’s action on α4β2-nAChRs or α7-nAChRs. Methods: Ketamine was administered to rats for 10 consecutive days and the test was performed 14 days following the last injection. The tested compounds were administered 30 min prior to the attentional set-shifting task. Results: Varenicline, TC-2403 and PNU-282987 ameliorated ketamine-evoked set-shifting deficits. While the α4β2-nAChR antagonist dihydro-β-erythroidine and the α7-nAChR antagonist methyllycaconitine completely prevented the procognitive actions of TC-2403 and PNU-282987, respectively, varenicline’s effect was only partially blocked by any given antagonist. Moreover, the combined treatment with TC-2403 and PNU-282987 more effectively facilitated rats’ set-shifting ability than activation of either type of nicotinic acetylcholine receptor alone. Conclusion: The present findings demonstrated that varenicline’s actions on both α7-nAChRs and α4β2-nAChRs may be necessary to produce its full procognitive effect in the present experimental setting.

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Evaluating Commercially Available Antibodies for Rat α7 Nicotinic Acetylcholine Receptors

Journal of Histochemistry & Cytochemistry ◽

10.1369/0022155417725304 ◽

2017 ◽

Vol 65 (9) ◽

pp. 499-512 ◽

Cited By ~ 9

Author(s):

Brijesh K. Garg ◽

Ralph H. Loring

Keyword(s):

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

Drug Targets ◽

Fluorescent Protein ◽

Western Blots ◽

Nicotinic Acetylcholine ◽

Α7 Nachr ◽

Gel Shift Assay ◽

Gel Shift ◽

Α7 Nachrs

Alpha7 nicotinic acetylcholine receptors (α7 nAChRs) are important drug targets in neurological disorders and inflammation, making their detection and localization by validated antibodies highly desirable. However, tests in knockout animals raised questions about specificity of antibodies to mouse α7 nAChRs. To date, methods for validating antibodies for rat or human α7 nAChR have not been reported. We developed a gel-shift assay for western blots using GH4C1 cells expressing either native rat receptors or α7 nAChR-green fluorescent protein (GFP) chimeras to evaluate seven commercially available α7 nAChR antibodies. Blots with anti-GFP antibody detected GFP or α7 nAChR-GFP expressed in GH4C1 cells, and 125I-α-bungarotoxin binding and RNA analysis demonstrated α7 nAChR expression. Validated samples were used to evaluate α7 nAChR antibodies by western blot and immunofluorescence studies. These methods confirmed that two of seven α7 nAChR antibodies identify gel-shifts for α7 nAChR/nAChR-GFP but only one antibody demonstrated low background and significant immunofluorescence differences between wild-type and α7 nAChR expressing GH4C1 cells. However, that polyclonal antibody displayed lot-to-lot variability. Our findings suggest that careful validation methods are required for all α7 nAChR receptor species and antibody lots and that the gel-shift assay may allow for relatively rapid antibody screening.

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APS8 Delays Tumor Growth in Mice by Inducing Apoptosis of Lung Adenocarcinoma Cells Expressing High Number of α7 Nicotinic Receptors

Marine Drugs ◽

10.3390/md16100367 ◽

2018 ◽

Vol 16 (10) ◽

pp. 367

Author(s):

Sabina Berne ◽

Maja Čemažar ◽

Robert Frangež ◽

Polona Juntes ◽

Simona Kranjc ◽

...

Keyword(s):

Lung Cancer ◽

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

A549 Cells ◽

Lung Fibroblasts ◽

Normal Lung ◽

Dependent Manner ◽

Α7 Nachr ◽

Α7 Nachrs

The alkylpyridinium polymer APS8, a potent antagonist of α7 nicotinic acetylcholine receptors (nAChRs), selectively induces apoptosis in non-small cell lung cancer cells but not in normal lung fibroblasts. To explore the potential therapeutic value of APS8 for at least certain types of lung cancer, we determined its systemic and organ-specific toxicity in mice, evaluated its antitumor activity against adenocarcinoma xenograft models, and examined the in-vitro mechanisms of APS8 in terms of apoptosis, cytotoxicity, and viability. We also measured Ca2+ influx into cells, and evaluated the effects of APS8 on Ca2+ uptake while siRNA silencing of the gene for α7 nAChRs, CHRNA7. APS8 was not toxic to mice up to 5 mg/kg i.v., and no significant histological changes were observed in mice that survived APS8 treatment. Repetitive intratumoral injections of APS8 (4 mg/kg) significantly delayed growth of A549 cell tumors, and generally prevented regrowth of tumors, but were less effective in reducing growth of HT29 cell tumors. APS8 impaired the viability of A549 cells in a dose-dependent manner and induced apoptosis at micro molar concentrations. Nano molar APS8 caused minor cytotoxic effects, while cell lysis occurred at APS8 >3 µM. Furthermore, Ca2+ uptake was significantly reduced in APS8-treated A549 cells. Observed differences in response to APS8 can be attributed to the number of α7 nAChRs expressed in these cells, with those with more AChRs (i.e., A549 cells) being more sensitive to nAChR antagonists like APS8. We conclude that α7 nAChR antagonists like APS8 have potential to be used as therapeutics for tumors expressing large numbers of α7 nAChRs.

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Nicotinic acetylcholine receptor expression by directionally selective ganglion cells

Visual Neuroscience ◽

10.1017/s0952523807070435 ◽

2007 ◽

Vol 24 (4) ◽

pp. 523-533 ◽

Cited By ~ 11

Author(s):

CHRISTIANNE E. STRANG ◽

JORDAN M. RENNA ◽

FRANKLIN R. AMTHOR ◽

KENT T. KEYSER

Keyword(s):

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

Ganglion Cells ◽

Partial Agonist ◽

Receptor Expression ◽

Nicotinic Acetylcholine ◽

Preferred Direction ◽

Α7 Nachr ◽

Bath Application ◽

Α7 Nachrs

Acetylcholine (ACh) enhances the preferred direction responses of directionally selective ganglion cells (DS GCs; Ariel & Daw, 1982; Ariel & Adolph, 1985) through the activation of nicotinic acetylcholine receptors (nAChRs; Ariel & Daw, 1982; Massey et al., 1997; Kittila & Massey, 1997). DS GCs appear to express at least two types of nAChRs, those that are sensitive to the partially subtype-specific antagonist methyllycaconitine (MLA), and those that are MLA-insensitive (Reed et al., 2002). Our purpose was to confirm the expression of α7 nAChRs by DS GCs and to assess the contributions of other nAChR subtypes to DS GC responses. Using choline as a nAChR partially subtype-specific agonist, we found that the majority of DS GCs demonstrated responses to choline while under synaptic blockade. The blockade or reduction of choline-induced responses by bath application of nanomolar (nM) concentrations of MLA provided direct evidence that the choline responses were mediated by α7 nAChRs. Because choline is a partial agonist for α3β4 nAChRs (Alkondon et al., 1997), the residual choline responses are consistent with mediation by α3β4 nAChRs. Additionally, a subset of DS GCs responded to nicotine but not to choline, indicating the expression of a third nAChR subtype. The pharmacological results were supported by single cell reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry experiments. The expression of α7 and specific non-α7 nAChR subtypes was correlated with the preferred direction. This indicates the possibility of differential responses to ACh depending on the direction of movement. This is the first description of differential expression of multiple nAChR subtypes by DS GCs.

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Nicotinic Acetylcholine Receptor α7 Subunit Is an Essential Regulator of Seizure Susceptibility

Frontiers in Neurology ◽

10.3389/fneur.2021.656752 ◽

2021 ◽

Vol 12 ◽

Author(s):

Peng Sun ◽

Da-Gang Liu ◽

Xiang-Ming Ye

Keyword(s):

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

Large Body ◽

Onset Time ◽

Control Group ◽

Seizure Susceptibility ◽

Nicotinic Acetylcholine ◽

Α7 Nachr ◽

Neuropsychiatric Diseases ◽

Α7 Nachrs

A large body of data has confirmed that α7 nicotinic acetylcholine receptors (nAChRs) play a pivotal role in cognition, memory, and other neuropsychiatric diseases, but their effect on seizure susceptibility in C57BL/6 wild-type mice is not fully understood. Here, we showed that decreased activity of α7 nAChRs could increase the excitability of CA1 pyramidal neurons and shorten the onset time of epilepsy in pilocarpine-induced mouse models. However, compared with the control group, there was no apparent effect of increasing the activity of α7 nAChRs. Moreover, the expression of α7 nAChRs is downregulated in human epileptogenic tissues. Taken together, our findings indicate that α7 nAChR is an essential regulator of seizure susceptibility.

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Curcumin Potentiates α7 Nicotinic Acetylcholine Receptors and Alleviates Autistic-Like Social Deficits and Brain Oxidative Stress Status in Mice

International Journal of Molecular Sciences ◽

10.3390/ijms22147251 ◽

2021 ◽

Vol 22 (14) ◽

pp. 7251

Author(s):

Petrilla Jayaprakash ◽

Dmytro Isaev ◽

Waheed Shabbir ◽

Dietrich E. Lorke ◽

Bassem Sadek ◽

...

Keyword(s):

Oxidative Stress ◽

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

Pathological Condition ◽

Repetitive Behaviors ◽

Social Deficits ◽

Nicotinic Acetylcholine ◽

Oxidative Stress Status ◽

Inward Currents ◽

Α7 Nachrs

Autistic spectrum disorder (ASD) refers to a group of neurodevelopmental disorders characterized by impaired social interaction and cognitive deficit, restricted repetitive behaviors, altered immune responses, and imbalanced oxidative stress status. In recent years, there has been a growing interest in studying the role of nicotinic acetylcholine receptors (nAChRs), specifically α7-nAChRs, in the CNS. Influence of agonists for α7-nAChRs on the cognitive behavior, learning, and memory formation has been demonstrated in neuro-pathological condition such as ASD and attention-deficit hyperactivity disorder (ADHD). Curcumin (CUR), the active compound of the spice turmeric, has been shown to act as a positive allosteric modulator of α7-nAChRs. Here we hypothesize that CUR, acting through α7-nAChRs, influences the neuropathology of ASD. In patch clamp studies, fast inward currents activated by choline, a selective agonist of α7-nAChRs, were significantly potentiated by CUR. Moreover, choline induced enhancement of spontaneous inhibitory postsynaptic currents was markedly increased in the presence of CUR. Furthermore, CUR (25, 50, and 100 mg/kg, i.p.) ameliorated dose-dependent social deficits without affecting locomotor activity or anxiety-like behaviors of tested male Black and Tan BRachyury (BTBR) mice. In addition, CUR (50 and 100 mg/kg, i.p.) mitigated oxidative stress status by restoring the decreased levels of superoxide dismutase (SOD) and catalase (CAT) in the hippocampus and the cerebellum of treated mice. Collectively, the observed results indicate that CUR potentiates α7-nAChRs in native central nervous system neurons, mitigates disturbed oxidative stress, and alleviates ASD-like features in BTBR mice used as an idiopathic rodent model of ASD, and may represent a promising novel pharmacological strategy for ASD treatment.

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Novel Three-Finger Neurotoxins from Naja melanoleuca Cobra Venom Interact with GABAA and Nicotinic Acetylcholine Receptors

Toxins ◽

10.3390/toxins13020164 ◽

2021 ◽

Vol 13 (2) ◽

pp. 164

Author(s):

Lina Son ◽

Elena Kryukova ◽

Rustam Ziganshin ◽

Tatyana Andreeva ◽

Denis Kudryavtsev ◽

...

Keyword(s):

Nicotinic Acetylcholine Receptors ◽

Gabaa Receptors ◽

Binding Sites ◽

Acetylcholine Receptors ◽

Nicotinic Acetylcholine ◽

High Affinity ◽

Central Loop ◽

Acetylcholine Binding Proteins ◽

Α7 Nachrs

Cobra venoms contain three-finger toxins (TFT) including α-neurotoxins efficiently binding nicotinic acetylcholine receptors (nAChRs). As shown recently, several TFTs block GABAA receptors (GABAARs) with different efficacy, an important role of the TFTs central loop in binding to these receptors being demonstrated. We supposed that the positive charge (Arg36) in this loop of α-cobratoxin may explain its high affinity to GABAAR and here studied α-neurotoxins from African cobra N. melanoleuca venom for their ability to interact with GABAARs and nAChRs. Three α-neurotoxins, close homologues of the known N. melanoleuca long neurotoxins 1 and 2, were isolated and sequenced. Their analysis on Torpedocalifornica and α7 nAChRs, as well as on acetylcholine binding proteins and on several subtypes of GABAARs, showed that all toxins interacted with the GABAAR much weaker than with the nAChR: one neurotoxin was almost as active as α-cobratoxin, while others manifested lower activity. The earlier hypothesis about the essential role of Arg36 as the determinant of high affinity to GABAAR was not confirmed, but the results obtained suggest that the toxin loop III may contribute to the efficient interaction of some long-chain neurotoxins with GABAAR. One of isolated toxins manifested different affinity to two binding sites on Torpedo nAChR.

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α-Conotoxin as Potential to α7-nAChR Recombinant Expressed in Escherichia coli

Marine Drugs ◽

10.3390/md18080422 ◽

2020 ◽

Vol 18 (8) ◽

pp. 422

Author(s):

Yanli Liu ◽

Yifeng Yin ◽

Yunyang Song ◽

Kang Wang ◽

Fanghui Wu ◽

...

Keyword(s):

Escherichia Coli ◽

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

High Performance ◽

Cognitive Disorders ◽

Coli Strain ◽

Xenopus Laevis Oocytes ◽

Obvious Effect ◽

Nicotinic Acetylcholine ◽

Α7 Nachr

α7 nicotinic acetylcholine receptors (nAChR) is an important nicotinic acetylcholine receptors subtype and closely associated with cognitive disorders, such as Alzheimer’s and schizophrenia disease. The mutant ArIB (V11L, V16A) of α-conotoxin ArIB with 17-amino acid residues specifically targets α7 nAChR with no obvious effect on other nAChR subtypes. In the study, the synthetic gene encoding mature peptide of ArIB and mutant ArIB (V11L, V16A) carried a fusion protein Trx and 6 × His-tag was separately inserted in pET-32a (+) vector and transformed into Escherichia coli strain BL21(DE3) pLysS for expression. The expressions of Trx-ArIB-His6 and Trx-ArIB (V11L, V16A)-His6 were soluble in Escherichia coli, which were purified by Ni-NTA affinity chromatography column and cleaved by enterokinase to release rArIB and rArIB (V11L, V16A). Then, rArIB and rArIB (V11L, V16A) were purified by high-performance liquid chromatography (HPLC) and identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Bioactivity of rArIB and rArIB (V11L, V16A) was assessed by two-electrode voltage-clamp electrophysiology in Xenopus laevis oocytes expressing human nAChR subtypes. The results indicated that the yield of the fusion proteins was approximately 50 mg/L and rArIB (V11L, V16A) antagonized the α7 nAChR subtype selectively with 8-nM IC50. In summary, this study provides an efficient method to biosynthesize α-conotoxin ArIB and rArIB (V11L, V16A) in Escherichia coli, which could be economical to obtain massively bioactive disulfide-rich polypeptides at fast speed.

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Statins Prevent β-Amyloid Inhibition of Sympathetic α7-nAChR-Mediated Nitrergic Neurogenic Dilation in Porcine Basilar Arteries

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/sj.jcbfm.9600232 ◽

2005 ◽

Vol 25 (12) ◽

pp. 1573-1585 ◽

Cited By ~ 18

Author(s):

Min-Liang Si ◽

Chen Long ◽

Ding-I Yang ◽

Mei-Fang Chen ◽

Tony Jer-Fu Lee

Keyword(s):

Nicotinic Acetylcholine Receptors ◽

Early Phase ◽

Calcium Influx ◽

Cerebral Hypoperfusion ◽

Α7 Nachr ◽

Inward Currents ◽

Basilar Arteries ◽

Β Amyloid ◽

Α7 Nachrs

The exact mechanism underlying regional cerebral hypoperfusion in the early phase of Alzheimer's disease (AD) is not understood. We have shown in isolated porcine cerebral arteries that stimulation of sympathetic α7-nicotinic acetylcholine receptors (α7-nAChRs) causes release of nitric oxide in parasympathetic nitrergic nerves and vasodilation. We therefore examined if β-amyloid peptides (Aβs), which play a key role in pathogenesis of AD, blocked sympathetic α7-nAChRs leading to reduced neurogenic nitrergic dilation in isolated porcine basilar arteries, using in vitro tissue bath, calcium image, and patch clamping techniques. The results indicated that Aβ1–40, but not Aβ40–1, blocked relaxation of endothelium-denuded basilar arterial rings induced by nicotine (100μ;mol/L) and choline (1 mmol/L) without affecting that induced by sodium nitroprusside or isoproterenol. In cultured superior cervical ganglion (SCG) cells, Aβ1–40, but not Aβ40–1, blocked choline- and nicotine-induced calcium influx and inward currents. The Aβ blockade of the nitrergic vasodilation and inward currents, but not that of calcium influx, was prevented by acute pretreatment with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors mevastatin and lovastatin. These results suggest that Aβ1–40 blocks cerebral perivascular sympathetic α7-nAChRs, resulting in the attenuation of cerebral nitrergic neurogenic vasodilation. This effect of Aβ may be responsible in part for cerebral hypoperfusion occurred in the early phase of the AD, which may be prevented by statins most likely because of their effects independent of cholesterol lowering. Statins may offer an alternative strategy in the prevention and treatment of AD.

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Nicotinic Acetylcholine Receptors Contribute to Learning-induced Metaplasticity in the Hippocampus

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_00383 ◽

2013 ◽

Vol 25 (7) ◽

pp. 986-997 ◽

Cited By ~ 7

Author(s):

Benjamin Becker ◽

Eva M. Klein ◽

Nadine Striepens ◽

Yoan Mihov ◽

Thomas E. Schlaepfer ◽

...

Keyword(s):

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

Low Dose ◽

Controlled Trial ◽

Treated Group ◽

Nicotinic Acetylcholine ◽

Behavioral Learning ◽

Subsequent Learning ◽

Per Se ◽

Α7 Nachrs

Hippocampal learning is thought to induce metaplasticity, which can facilitate subsequent learning. Administered at single low doses, the N-methyl-d-aspartate-type glutamate receptor antagonist memantine predominantly blocks α7 nicotinic acetylcholine receptors (α7 nAChRs). Placebo-controlled administration of a single low dose of memantine in a pharmaco-fMRI experiment may thus help characterize the role of α7 nAChRs in hippocampal metaplasticity. We hypothesized that if α7 nAChRs contribute to learning-induced metaplasticity in the hippocampus, blockade of these receptors with low-dose memantine would selectively interfere with a facilitation of subsequent learning without impairing hippocampal learning per se. To specifically test this hypothesis, we devised a randomized controlled trial in which healthy volunteers were administered a 20-mg single oral dose of memantine or placebo and scanned on three subsequent runs of a hippocampal learning task. Our results indicate no discrepancies in behavioral learning between low-dose memantine- and placebo-treated participants in the first and second run of this task. In the third run, however, only the placebo-treated group showed facilitated behavioral learning, an effect paralleled by decreased neural responses in the hippocampal cornu ammonis region. Our findings suggest that blockade of α7 nAChRs selectively interfered with a learning-induced facilitation of subsequent learning while leaving unimpaired hippocampal learning per se. Taken together, our results provide support for a relevant contribution of α7 nAChRs to learning-associated metaplasticity in the hippocampus.

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