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  • 1
    Electronic Resource
    Electronic Resource
    .alpha.-Conotoxin EI, A New Nicotinic Acetylcholine Receptor Antagonist with Novel Selectivity (1995)
    s.l. : American Chemical Society
    Biochemistry 34 (1995), S. 14519-14526 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00044a030
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  • 2
    Electronic Resource
    Electronic Resource
    Neuronal calcium channel antagonists. Discrimination between calcium channel subtypes using .omega.-conotoxin from Conus magus venom (1987)
    s.l. : American Chemical Society
    Biochemistry 26 (1987), S. 2086-2090 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00382a004
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  • 3
    Electronic Resource
    Electronic Resource
    Purification and sequence of a presynaptic peptide toxin from Conus geographus venom (1984)
    s.l. : American Chemical Society
    Biochemistry 23 (1984), S. 5087-5090 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00317a001
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  • 4
    Electronic Resource
    Electronic Resource
    5-Iodo-A-85380 binds to α-conotoxin MII-sensitive nicotinic acetylcholine receptors (nAChRs) as well as α4β2* subtypes (2002)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 81 (2002), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Recent work suggests that 5-iodo-A-85380, a radioiodinated analog of the 3-pyridyl ether A-85380, represents a promising imaging agent for non-invasive, in vivo studies of α4β2* nicotinic acetylcholine receptors (nAChRs; *denotes receptors containing the indicated subunits), because of its low non-specific binding, low in vivo toxicity and high selectivity for α4β2* nAChRs. As an approach to elucidate nAChR subtypes expressed in striatum, we carried out competitive autoradiography in monkey and rat brain using 5-[125I]iodo-A-85380 ([125I]A-85380) and [125I]α-conotoxin MII, a ligand that binds with high affinity to α6* and α3* nAChRs, but not to α4β2* nAChRs. Although A-85380 is reported to be selective for α4β2* nAChRs, we observed that A-85380 completely inhibited [125I]α-conotoxin MII binding in rat striatum and that A-85380 blocked 〉 90% of [125I]α-conotoxin MII sites in monkey caudate and putamen. These results suggest that A-85380 binds to non-α4β2* nAChRs, including putative α6* nAChRs. Experiments to determine the percentage of [125I]A-85380 sites that contain α-conotoxin MII-sensitive (α6β2*) nAChRs indicate that they represent about 10% of [125I]A-85380 sites in rodent striatum and about 30% of sites in monkey caudate and putamen. These data are important for identifying alterations in nicotinic receptor subtypes in Parkinson's disease and other basal ganglia disorders both in in vitro and in in vivo imaging studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2002.00868.x
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  • 5
    Electronic Resource
    Electronic Resource
    Nicotine-evoked transmitter release from synaptosomes: functional association of specific presynaptic acetylcholine receptors and voltage-gated calcium channels (2001)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 77 (2001), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: It has previously been shown that nicotine-evoked dopamine release from rat striatal synaptosomes and nicotine-evoked norepinephrine release from hippocampal synaptosomes are mediated by distinct nicotinic acetylcholine receptor (nAChR) subtypes. In the present study, the functional association of these nicotinic receptors with specific subtypes of voltage-gated calcium channels was examined. Cd2+ (200 µm), as well as ω-conotoxin MVIIC (5 µm), blocks ∼85% of nicotine-evoked dopamine release from striatal synaptosomes, indicating a major involvement of calcium channels. Furthermore, the toxin-susceptibility suggests that these calcium channels contain α1A and/or α1B subunits. Inhibition of nicotine-evoked dopamine release by conotoxins α-MII and ω-GVIA is additive and indicates that presynaptic α3β2 nAChRs are functionally coupled to α1A, but not α1B, calcium channel subtypes. Conversely, insensitivity to α-AuIB and sensitivity to ω-MVIIC indicate that non-α3β2/α3β4-containing nAChRs are functionally coupled to α1B-containing calcium channels. In contrast, Cd2+ blocks only 65% of nicotine-evoked norepinephrine release from hippocampal synaptosomes, indicating that a substantial fraction of this release occurs through mechanisms not involving calcium channels. This Cd2+-insensitive component of release is blocked by α-AuIB and therefore appears to be triggered by Ca2+ flowing directly through the channels of presynaptic α3β4 nAChRs. Thus, these data indicate that different presynaptic termini can have distinctive functional associations of specific nAChRs and voltage-gated calcium channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2001.00357.x
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  • 6
    Electronic Resource
    Electronic Resource
    Ca2+ changes induced by different presynaptic nicotinic receptors in separate populations of individual striatal nerve terminals (2001)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 76 (2001), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Presynaptic nicotinic acetylcholine receptors likely play a modulatory role in the nerve terminal. Using laser-scanning confocal microscopy, we have characterized physiological responses obtained on activation of presynaptic nicotinic receptors by measuring calcium changes in individual nerve terminals (synaptosomes) isolated from the rat corpus striatum. Nicotine (500 nm) induced Ca2+ changes in a subset (10–25%) of synaptosomes. The Ca2+ responses were dependent on extracellular Ca2+ and desensitized very slowly (several minutes) on prolonged exposure to agonist. The nicotine-induced Ca2+ responses were dose-dependent and were completely blocked by dihydro-β-erythroidine (5 µm), differentially affected by mecamylamine (10 µm) and α-conotoxin MII (100 nm), and not affected by α-bungarotoxin (500 nm). Immunocytochemical studies using well-characterized monoclonal antibodies revealed the presence of the α4 and α3/α5 nicotinic subunits. The nicotine-induced responses were unaffected by prior depolarization or by a mixture of Ca2+ channel toxins including ω-conotoxin MVIIC (500 nm), ω-conotoxin GVIA (500 nm) and agatoxin TK (200 nm). Our results indicate that nicotinic receptors present on striatal nerve terminals induce Ca2+ entry largely without involving voltage-gated Ca2+ channels, most likely by direct permeation via the receptor channel itself. In addition, at least two subpopulations of presynaptic nicotinic receptors reside on separate terminals in the striatum, suggesting distinct modulatory roles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2001.00197.x
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of [125I]epibatidine binding and nicotinic agonist-mediated 86Rb+ efflux in interpeduncular nucleus and inferior colliculus of β2 null mutant mice (2002)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 81 (2002), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The β2 nicotinic acetylcholine receptor subunit null mutation eliminated most high affinity [3H]epibatidine binding in mouse brain, but significant binding remained in accessory olfactory nucleus, medial habenula, inferior colliculus and interpeduncular nucleus. Residual [125I]epibatidine binding sites in the inferior colliculus and interpeduncular nucleus were subsequently characterized. Inhibition of [125I]epibatidine binding by 12 agonists and six antagonists was very similar in these regions. Most acetylcholine-stimulated 86Rb+ efflux is eliminated in thalamus and superior colliculus of β2 null mutants, but significant activity remained in inferior colliculus and interpeduncular nucleus. This residual activity was subsequently characterized. The 12 nicotinic agonists tested elicited concentration-dependent 86Rb+ efflux. Epibatidine was the most potent agonist. Cytisine was also potent and efficacious. EC50 values for quaternary agonists were relatively high. Cytisine-stimulated 86Rb+ efflux was inhibited by six classical nicotinic antagonists. Mecamylamine and d-tubocurarine were most potent, while decamethonium was the least potent. Agonists and antagonists exhibited similar potency in both brain regions. α-Bungarotoxin (100 nm) did not significantly inhibit cytisine-stimulated 86Rb+ efflux, while the α3β4 selective antagonist, αConotoxinAuIB, inhibited a significant fraction of the response in both brain regions. Thus, β2 null mutant mice express residual nicotinic activity with properties resembling those of α3β4*-nAChR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2002.00910.x
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  • 8
    Electronic Resource
    Electronic Resource
    Nicotinic agonists stimulate acetylcholine release from mouse interpeduncular nucleus: a function mediated by a different nAChR than dopamine release from striatum (2001)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 76 (2001), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Acetylcholine release stimulated by nicotinic agonists was measured as radioactivity released from perfused synaptosomes prepared from mouse interpeduncular nucleus (IPN) that had been loaded with [3H]choline. Agonist-stimulated release was dependent upon external calcium and over 90% of released radioactivity was acetylcholine. The release process was characterized by dose response curves for 13 agonists and inhibition curves for six antagonists. α-Conotoxin MII did not inhibit this release, while α-conotoxin AuIB inhibited 50% of agonist-stimulated release. Comparison of this process with [3H]dopamine release from mouse striatal synaptosomes indicated that different forms of nicotinic acetylcholine receptors (nAChRs) may mediate these processes. This was confirmed by assays using mice homozygous for the β2 subunit null mutation. The deletion of the β2 subunit had no effect on agonist-stimulated acetylcholine release, but abolished agonist-stimulated release of dopamine from striatal synaptosomes. Mice heterozygous for the β2 subunit null mutation showed decreased dopamine release evoked by l-nicotine with no apparent change in EC50 value, as well as similar decreases in both transient and persistent phases of release with no changes in desensitization rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2001.00019.x
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  • 9
    Electronic Resource
    Electronic Resource
    Functional properties of neuronal nicotinic acetylcholine receptors in the chick retina during development (2005)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 21 (2005), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Acetylcholine (ACh) has been recognized for a long time as a major neurotransmitter in the retina, however, little is known about the contribution of acetylcholine receptors in synaptic processing. Moreover, even less information is available concerning their role during development. To address this question further, we examined the physiological and pharmacological properties of neuronal nicotinic acetylcholine receptors (nAChRs) in retinal ganglion cells from embryonic (E) 12–18-day-old Leghorn chicks. Patch-clamp recordings in whole-cell configuration revealed that at E12 approximately 21% of the ganglion cells responded to acetylcholine pulses with inward currents. The number of responsive cells progressively increased to 57% at E15 to reach up to 15 positive cells out of 15 cells tested at E18. Acetylcholine-evoked responses could be subdivided, according to their time course, into fast and slowly desensitizing. Taking advantage of the selectivity of the frog toxin epibatidine (Epi), that preferentially activates heteromeric neuronal nicotinic acetylcholine receptors, we compared the currents evoked by this toxin vs. the effects of acetylcholine. A further characterization of the receptor diversity during development was to assess their sensitivity to the α-conotoxin MII (α-CTX-MII), which has been shown to preferentially block α6- and α3β2-containing receptors. These data demonstrate that ganglion cells of the chick retina express multiple receptor subtypes that progressively develop as a function of retina maturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2005.04150.x
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  • 10
    Electronic Resource
    Electronic Resource
    CONUS PEPTIDES TARGETED TO SPECIFIC NICOTINIC ACETYLCHOLINE RECEPTOR SUBTYPES (1999)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biochemistry 68 (1999), S. 59-88 
    Details
    ISSN: 0066-4154
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Biology
    Notes: Abstract The venoms of predatory cone snails represent a rich combinatorial-like library of evolutionarily selected, neuropharmacologically active peptides. A major fraction of the venom components are conotoxins-small, disulfide-rich peptides that potently and specifically target components of the neuromuscular system, particularly ligand- and voltage-gated ion channels. This review focuses on Conus peptides, which act at nicotinic acetylcholine receptors. These nicotinic antagonist peptides from Conus are broadly divided into two groups: those that act at the neuromuscular junction and those that act at subtypes of neuronal nicotinic acetylcholine receptors. The latter include peptides specific for the alpha7, alpha3beta2, and alpha3beta4 nicotinic receptor subtypes. The degree of specificity exhibited by these peptides is remarkable, particularly given their relatively small size. As a group the nicotinic acetylcholine receptor-targeted Conus peptides represent an increasingly well-defined set of tools for probing the structure, function, and physiological role of nicotinic acetylcholine receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.biochem.68.1.59
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