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Taha M, Houchat JN, Taillebois E, Thany SH. The calcium-calmodulin-dependent protein kinase kinase inhibitor, STO-609, inhibits nicotine-induced currents and intracellular calcium increase in insect neurosecretory cells. J Neurochem 2024; 168:1281-1296. [PMID: 38339787 DOI: 10.1111/jnc.16077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 01/24/2024] [Accepted: 01/25/2024] [Indexed: 02/12/2024]
Abstract
Insect neuronal nicotinic acetylcholine receptors (nAChRs) are transmembrane receptors that play a key role in the development and synaptic plasticity of both vertebrates and invertebrates and are considered to be major targets of neonicotinoid insecticides. We used dorsal unpaired median (DUM) neurons, which are insect neurosecretory cells, in order to explore the intracellular mechanisms leading to the regulation of insect neuronal nAChRs in more detail. Using whole-cell patch-clamp and fura-2AM calcium imaging techniques, we found that a novel CaMKK/AMPK pathway could be involved in the intracellular regulation of DUM neuron nAChRs. The CaMKK selective inhibitor, STO, reduced nicotinic current amplitudes, and strongly when co-applied with α-Bgt. Interestingly, intracellular application of the AMPK activator, A-76, prevented the reduction in nicotine-induced currents observed in the presence of the AMPK inhibitor, dorsomorphin. STO prevented the increase in intracellular calcium induced by nicotine, which was not dependent on α-Bgt. Currents induced by 1 mM LMA, a selective activator of nAChR2, were reduced under bath application of STO, and mecamylamine, which blocked nAChR2 subtype, inhibited the increase in intracellular calcium induced by LMA. These findings provide insight into potential complex mechanisms linked to the modulation of the DUM neuron nAChRs and CaMKK pathway.
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Affiliation(s)
- Maria Taha
- Laboratoire Physiologie, Ecologie et Environnement (P2E), USC-INRAE 1328, Université d'Orléans, Orléans, France
| | - Jean-Noël Houchat
- Laboratoire Physiologie, Ecologie et Environnement (P2E), USC-INRAE 1328, Université d'Orléans, Orléans, France
| | - Emiliane Taillebois
- Laboratoire Physiologie, Ecologie et Environnement (P2E), USC-INRAE 1328, Université d'Orléans, Orléans, France
| | - Steeve H Thany
- Laboratoire Physiologie, Ecologie et Environnement (P2E), USC-INRAE 1328, Université d'Orléans, Orléans, France
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2
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Houchat JN, Cartereau A, Taillebois E, Thany SH. Calmidazolium induces a decrease in nicotine-induced currents and intracellular calcium levels after pulse application of nicotine onto insect neurosecretory cells. JOURNAL OF INSECT PHYSIOLOGY 2022; 139:104385. [PMID: 35315336 DOI: 10.1016/j.jinsphys.2022.104385] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 03/01/2022] [Accepted: 03/16/2022] [Indexed: 06/14/2023]
Abstract
Dorsal unpaired median (DUM) neurons, are a class of insect neurosecretory cells, which are involved in the control of several functions, such as excretion and reproduction, or the release of neurohormones. Previous studies demonstrated that they express different nicotinic acetylcholine receptor subtypes, in particular α-bungarotoxin-insensitive receptors, with nAChR1 and nAChR2 subtypes. Here, we demonstrated that pulse application of 1 mM nicotine (300 ms pulse duration) induced inward currents which were reduced under bath application of 15 µM calmidazolium, a calmodulin inhibitor. Bath application of 0.5 µM α-bungarotoxin had no effect on calmidazolium action, suggesting that it could have an indirect effect through α-bungarotoxin-insensitive receptors. Indeed, nicotine-evoked currents were reduced by 10 µM d-tubocurarine, and completely blocked by 5 µM mecamylamine, which affected nAChR1 and nAChR2 subtypes, respectively. Our results demonstrated that nAChR2 subtypes are involved in the indirect effect of calmidazolium. Moreover, we found that this calmidazolium effect was associated to a strong reduction in intracellular calcium levels after pulse application of 1 mM nicotine. Thus, compared to previous studies on mammalian cells, calmidazolium did not cause an increase in intracellular calcium levels in DUM neurons, suggesting that different calcium mechanisms are involved in the calmidazolium effect.
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Affiliation(s)
- Jean-Noël Houchat
- Université d'Orléans, LBLGC USC-INRAE 1328, 1 rue de Chartres, Orléans 45067, France
| | - Alison Cartereau
- Université d'Orléans, LBLGC USC-INRAE 1328, 1 rue de Chartres, Orléans 45067, France
| | - Emiliane Taillebois
- Université d'Orléans, LBLGC USC-INRAE 1328, 1 rue de Chartres, Orléans 45067, France
| | - Steeve H Thany
- Université d'Orléans, LBLGC USC-INRAE 1328, 1 rue de Chartres, Orléans 45067, France.
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3
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Cartereau A, Taillebois E, Le Questel JY, Thany SH. Mode of Action of Neonicotinoid Insecticides Imidacloprid and Thiacloprid to the Cockroach Pameα7 Nicotinic Acetylcholine Receptor. Int J Mol Sci 2021; 22:9880. [PMID: 34576043 PMCID: PMC8471617 DOI: 10.3390/ijms22189880] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 09/01/2021] [Accepted: 09/08/2021] [Indexed: 12/28/2022] Open
Abstract
The functional expression of the cockroach Pameα7 nicotinic acetylcholine receptor subunit has been previously studied, and was found to be able to form a homomeric receptor when expressed in Xenopus laevis oocytes. In this study, we found that the neonicotinoid insecticide imidacloprid is unable to activate the cockroach Pameα7 receptor, although thiacloprid induces low inward currents, suggesting that it is a partial agonist. In addition, the co-application or 5 min pretreatment with 10 µM imidacloprid increased nicotine current amplitudes, while the co-application or 5 min pretreatment with 10 µM thiacloprid decreased nicotine-evoked current amplitudes by 54% and 28%, respectively. This suggesting that these two representatives of neonicotinoid insecticides bind differently to the cockroach Pameα7 receptor. Interestingly, the docking models demonstrate that the orientation and interactions of the two insecticides in the cockroach Pameα7 nAChR binding pocket are very similar. Electrophysiological results have provided evidence to suggest that imidacloprid and thiacloprid could act as modulators of the cockroach Pameα7 receptors.
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Affiliation(s)
- Alison Cartereau
- Université d’Orléans, LBLGC USC INRAE 1328, 45067 Orléans, France; (A.C.); (E.T.)
| | - Emiliane Taillebois
- Université d’Orléans, LBLGC USC INRAE 1328, 45067 Orléans, France; (A.C.); (E.T.)
| | | | - Steeve H. Thany
- Université d’Orléans, LBLGC USC INRAE 1328, 45067 Orléans, France; (A.C.); (E.T.)
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4
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Le Mauff A, Chouikh H, Cartereau A, Charvet CL, Neveu C, Rispe C, Plantard O, Taillebois E, Thany SH. Nicotinic acetylcholine receptors in the synganglion of the tick Ixodes ricinus: Functional characterization using membrane microtransplantation. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2020; 14:144-151. [PMID: 33120248 PMCID: PMC7591337 DOI: 10.1016/j.ijpddr.2020.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 10/04/2020] [Accepted: 10/07/2020] [Indexed: 11/28/2022]
Abstract
Nicotinic acetylcholine receptors are an important class of excitatory receptors in the central nervous system of arthropods. In the ticks Ixodes ricinus, the functional and pharmacological properties of nicotinic receptors located in their neurons are still unknown. The objective of this study was to characterize the pharmacological properties of tick nicotinic receptors using membrane microtransplantation in Xenopus laevis oocytes and two-electrodes voltage clamp method. The membranes microtransplanted were extracted from the tick synganglion. We found that oocytes microtransplanted with tick synganglion membranes expressed nicotinic acetylcholine receptor subtypes which were activated by acetylcholine (1 mM) and nicotine (1 mM). Currents induced by pressure application of acetylcholine and nicotine were diminished by 10 nM α-bungarotoxin and methyllycaconitine, suggesting that they expressed two subtypes of nicotinic receptors, α-bungarotoxin-sensitive and -insensitive, respectively. In addition, we found that nicotine receptors expressed in the synganglion membranes were poorly sensitive to the neonicotinoid insecticides clothianidin (CLT), imidacloprid (IMI), acetamiprid (ACE) and thiamethoxam (TMX), in agreement with their lack of activity as acaricides. Interestingly, current amplitudes were strongly potentialized in the presence of 1 μM PNU-120596. CLT was more active as an agonist than IMI, TMX and ACE. Finally, we demonstrated that microtransplantation of purified membrane from the tick synganglion can be a valuable tool for the development and screening of compounds targeting tick nicotinic acetylcholine receptor subtypes.
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Affiliation(s)
- Anaïs Le Mauff
- LBLGC USC INRAE 1328, Université d'Orléans, 1 rue de Chartres, 45067, Orléans, France
| | - Hamza Chouikh
- LBLGC USC INRAE 1328, Université d'Orléans, 1 rue de Chartres, 45067, Orléans, France
| | - Alison Cartereau
- LBLGC USC INRAE 1328, Université d'Orléans, 1 rue de Chartres, 45067, Orléans, France
| | | | | | | | | | - Emiliane Taillebois
- LBLGC USC INRAE 1328, Université d'Orléans, 1 rue de Chartres, 45067, Orléans, France
| | - Steeve H Thany
- LBLGC USC INRAE 1328, Université d'Orléans, 1 rue de Chartres, 45067, Orléans, France.
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Cartereau A, Taillebois E, Selvam B, Martin C, Graton J, Le Questel JY, Thany SH. Cloning and Expression of Cockroach α7 Nicotinic Acetylcholine Receptor Subunit. Front Physiol 2020; 11:418. [PMID: 32457646 PMCID: PMC7221154 DOI: 10.3389/fphys.2020.00418] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 04/07/2020] [Indexed: 11/13/2022] Open
Abstract
Understanding insect nicotinic acetylcholine receptor (nAChR) subtypes is of major interest because they are the main target of several insecticides. In this study, we have cloned a cockroach Pameα7 subunit that encodes a 518 amino acid protein with futures typical of nAChR subunit, and sequence homology to α7 subunit. Pameα7 is differently expressed in the cockroach nervous system, in particular in the antennal lobes, optical lobes and the mushroom bodies where specific expression was found in the non-compact Kenyon cells. In addition, we found that cockroach Pameα7 subunits expressed in Xenopus laevis oocytes can assemble to form homomeric receptors. Electrophysiological recordings using the two-electrode voltage clamp method demonstrated that nicotine induced an I max current of -92 ± 27 nA at 1 mM. Despite that currents are low with the endogenous ligand, ACh, this study provides information on the first expression of cockroach α7 homomeric receptor.
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Affiliation(s)
- Alison Cartereau
- LBLGC, UPRES EA 1207-USC INRA 1328, Université d’Orléans, Orléans, France
| | | | - Balaji Selvam
- Roger Adams Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Carine Martin
- LBLGC, UPRES EA 1207-USC INRA 1328, Université d’Orléans, Orléans, France
| | - Jérôme Graton
- CEISAM-UMR CNRS 6230, Faculté des Sciences et des Techniques, Université de Nantes, Nantes, France
| | - Jean-Yves Le Questel
- CEISAM-UMR CNRS 6230, Faculté des Sciences et des Techniques, Université de Nantes, Nantes, France
| | - Steeve H. Thany
- LBLGC, UPRES EA 1207-USC INRA 1328, Université d’Orléans, Orléans, France
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Heneberg P, Bogusch P, Astapenková A, Řezáč M. Neonicotinoid insecticides hinder the pupation and metamorphosis into adults in a crabronid wasp. Sci Rep 2020; 10:7077. [PMID: 32341495 PMCID: PMC7184726 DOI: 10.1038/s41598-020-63958-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 04/03/2020] [Indexed: 12/21/2022] Open
Abstract
Neonicotinoid insecticides are associated with a decline in the diversity and distribution of bees and wasps (Hymenoptera: Aculeata). The effects of neonicotinoids on the metamorphosis of aculeates have never been addressed in detail; however, recent evidence suggests that neonicotinoids induce wing abnormalities. We hypothesized that the metamorphosis success of bees and wasps differs in response to contact exposure to field-realistic concentrations of neonicotinoid insecticides or in response to combined exposure to neonicotinoid insecticides and benzimidazole fungicides. We treated prepupae of the model crabronid wasp Pemphredon fabricii with field-realistic concentrations of four neonicotinoids, acetamiprid, imidacloprid, thiacloprid and thiamethoxam, and/or with the benzimidazole fungicide thiabendazole. Treatment with acetamiprid or imidacloprid decreased the pupation rates to only 39% and 32%, respectively. Treatment with thiacloprid or thiamethoxam did not affect the pupation rate when applied alone, but the subsequent treatment of thiacloprid- or thiamethoxam-treated prepupae with thiabendazole led to significant decreases in pupation rates. A high concentration of acetamiprid, which severely affected the pupation rates, had moderate effects on metamorphosis into adults, resulting in 53% metamorphosis success (as opposed to 95% metamorphosis success in the water-treated group). However, imidacloprid or thiamethoxam treatment resulted in only 5%-10% metamorphosis success into adults. Overall survival decreased in response to treatment with any of the neonicotinoids or benzimidazoles or their combinations, with extremely low survival (<2%) following combined treatment with imidacloprid and thiabendazole or thiamethoxam and thiabendazole. In conclusion, neonicotinoids alter insect metamorphosis success, which can be further potentiated by their combination with other agrochemicals, such as benzimidazoles.
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Affiliation(s)
- Petr Heneberg
- Charles University, Third Faculty of Medicine, Prague, Czech Republic.
| | - Petr Bogusch
- University of Hradec Králové, Faculty of Science, Hradec Králové, Czech Republic
| | - Alena Astapenková
- University of Hradec Králové, Faculty of Science, Hradec Králové, Czech Republic
| | - Milan Řezáč
- Crop Research Institute, Functional Biodiversity Group, Prague, Czech Republic
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7
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Moreau E, Mikulska-Ruminska K, Goulu M, Perrier S, Deshayes C, Stankiewicz M, Apaire-Marchais V, Nowak W, Lapied B. Orthosteric muscarinic receptor activation by the insect repellent IR3535 opens new prospects in insecticide-based vector control. Sci Rep 2020; 10:6842. [PMID: 32321987 PMCID: PMC7176678 DOI: 10.1038/s41598-020-63957-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 04/08/2020] [Indexed: 01/14/2023] Open
Abstract
The insect repellent IR3535 is one of the important alternative in the fight against mosquito-borne disease such as malaria, dengue, chikungunya, yellow fever and Zika. Using a multidisciplinary approach, we propose the development of an innovative insecticide-based vector control strategy using an unexplored property of IR3535. We have demonstrated that in insect neurosecretory cells, very low concentration of IR3535 induces intracellular calcium rise through cellular mechanisms involving orthosteric/allosteric sites of the M1-muscarinic receptor subtype, G protein βγ subunits, background potassium channel inhibition generating depolarization, which induces voltage-gated calcium channel activation. The resulting internal calcium concentration elevation increases nicotinic receptor sensitivity to the neonicotinoid insecticide thiacloprid. The synergistic interaction between IR3535 and thiacloprid contributes to significantly increase the efficacy of the treatment while reducing concentrations. In this context, IR3535, used as a synergistic agent, seems to promise a new approach in the optimization of the integrated vector management for vector control.
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Affiliation(s)
- Eléonore Moreau
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France
| | - Karolina Mikulska-Ruminska
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, N. Copernicus University, Torun, Poland
| | - Mathilde Goulu
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France
| | - Stéphane Perrier
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France
| | - Caroline Deshayes
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France
| | - Maria Stankiewicz
- Faculty of Biological and Veternary Sciences, N. Copernicus University, Torun, Poland
| | - Véronique Apaire-Marchais
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France
| | - Wieslaw Nowak
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, N. Copernicus University, Torun, Poland
| | - Bruno Lapied
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France.
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Houchat JN, Taillebois E, Thany SH. Effects of the DAG analogue 1,2-dioctanoyl-sn-glycerol (DiC8) on nicotine- and clothianidin-evoked currents through α-bungarotoxin-insensitive nicotinic acetylcholine receptors expressed on cockroach neurosecretory cells. Neurotoxicology 2020; 78:143-151. [PMID: 32169464 DOI: 10.1016/j.neuro.2020.03.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 03/08/2020] [Accepted: 03/09/2020] [Indexed: 11/18/2022]
Abstract
We previously demonstrated that the cockroach α-bungarotoxin-sensitive nicotinic acetylcholine receptors, nAChR1 and nAChR2 subtypes, are differently sensitive to intracellular calcium pathways. Here, using whole cell patch-clamp recordings, we studied the effects of the diacylglycerol (DAG) analogue 1,2-dioctanoyl-sn-glycerol (DiC8) on nicotine- and clothianidin-evoked currents under an α-bungarotoxin treatment. Our results demonstrated that DiC8 reduced nicotine and clothianidin evoked currents. 10 μM DiC8 suppressed the increase in nicotine-induced currents which was brought about by application of 5 mM caffeine or 9 mM Ca2+, whereas DiC8 did not affect the decrease in nicotine-induced currents induced by BAPTA. Similarly, bath application of caffeine or 9 mM Ca2+ did not change the clothianidin effects, and the amplitude of clothianidin-induced currents was not affected. However, co-application of both 10 μM DiC8 with 9 mM Ca2+, caffeine or BAPTA reduced clothianidin current amplitudes. We conclude that nicotine and clothianidin differently modulate nAChR1 and nAChR2 subtypes under DiC8 treatment, and that nicotine activates nAChR1, whereas clothianidin activates both nAChR1 and nAChR2 subtypes.
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Affiliation(s)
- Jean-Noël Houchat
- Université d'Orléans, LBLGC USC INRA 1328, 1 rue de Chartres, 45067 Orléans, France
| | - Emiliane Taillebois
- Université d'Orléans, LBLGC USC INRA 1328, 1 rue de Chartres, 45067 Orléans, France
| | - Steeve H Thany
- Université d'Orléans, LBLGC USC INRA 1328, 1 rue de Chartres, 45067 Orléans, France.
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9
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Houchat JN, Dissanamossi BM, Landagaray E, Mathé-Allainmat M, Cartereau A, Graton J, Lebreton J, Le Questel JY, Thany SH. Mode of action of sulfoxaflor on α-bungarotoxin-insensitive nAChR1 and nAChR2 subtypes: Inhibitory effect of imidacloprid. Neurotoxicology 2019; 74:132-138. [DOI: 10.1016/j.neuro.2019.06.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 05/29/2019] [Accepted: 06/10/2019] [Indexed: 11/17/2022]
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Yu N, Wang X, Bao H, Liu Z. Identification and functional study of three nAChR regulators, ubiquilin-1, PICK1, and CRELD2, in Locusta migratoria manilensis dorsal unpaired median neurons. J Neurochem 2018; 149:331-345. [PMID: 30485436 DOI: 10.1111/jnc.14636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Revised: 10/06/2018] [Accepted: 11/21/2018] [Indexed: 11/29/2022]
Abstract
Insect nicotinic acetylcholine receptors (nAChRs) are not only important neurotransmitter receptors but also effective insecticide targets. The regulation of nAChRs has been mainly studied in vertebrates, especially in mammals. Here, two types of nAChRs were found present in the locust Locusta migratoria manilensis dorsal unpaired median (DUM) neurons, α-bungarotoxin (α-Bgt)-sensitive nAChRs and α-Bgt-resistant nAChRs, responding to acetylcholine (ACh) at different concentrations. The homologs to three mammalian nAChR regulators, ubiquilin-1, CRELD2 (cysteine-rich with EFG-like domain 2), and PICK1 (protein interacting with PRKCA 1), were characterized in L. migratoria, and their functions on regulating native nAChRs were investigated via RNAi followed by membrane potential measurement with DiBAC4 (3) and agonist-evoked macroscopic current recording in cultured L. migratoria DUM neurons. Ubiquilin-1 and PICK1 negatively regulated nAChRs because silencing of ubiquilin-1 and PICK1 both resulted in increased membrane potential and increased inward currents in DUM neurons, while CRELD2 positively regulated nAChRs as decreased membrane potential and inward currents were observed in DUM neurons. In addition, ubiquilin-1 regulated both α-Bgt-sensitive and α-Bgt-resistant types of nAChRs whereas PICK1 and CRELD2 regulated only the α-Bgt-resistant nAChRs. The present study broadened our understanding on the regulation of insect nAChRs and will benefit pest management given the important role of nAChRs in insect neurons and insecticide science. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.
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Affiliation(s)
- Na Yu
- Key laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Xin Wang
- Chongqing Jiulongpo District Agricultural Commission, Jiulongpo, Chongqing, China
| | - Haibo Bao
- Key laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Zewen Liu
- Key laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
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11
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Taillebois E, Cartereau A, Jones AK, Thany SH. Neonicotinoid insecticides mode of action on insect nicotinic acetylcholine receptors using binding studies. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2018; 151:59-66. [PMID: 30704714 DOI: 10.1016/j.pestbp.2018.04.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2017] [Revised: 04/14/2018] [Accepted: 04/17/2018] [Indexed: 06/09/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are the main target of neonicotinoid insecticides, which are widely used in crop protection against insect pests. Electrophysiological and molecular approaches have demonstrated the presence of several nAChR subtypes with different affinities for neonicotinoid insecticides. However, the precise mode of action of neonicotinoids on insect nAChRs remains to be elucidated. Radioligand binding studies with [3H]-α-bungarotoxin and [3H]-imidacloprid have proved instructive in understanding ligand binding interactions between insect nAChRs and neonicotinoid insecticides. The precise binding site interactions have been established using membranes from whole body and specific tissues. In this review, we discuss findings concerning the number of nAChR binding sites against neonicotinoid insecticides from radioligand binding studies on native tissues. We summarize the data available in the literature and compare the binding properties of the most commonly used neonicotinoid insecticides in several insect species. Finally, we demonstrate that neonicotinoid-nAChR binding sites are also linked to biological samples used and insect species.
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Affiliation(s)
- Emiliane Taillebois
- Université François Rabelais de Tours, Laboratoire Nutrition, Croissance et Cancer, INSERM 1069, 37032 Tours, France
| | - Alison Cartereau
- Université d'Orléans, LBLGC USC INRA 1328, 1 rue de Chartres, 45067 Orléans, France
| | - Andrew K Jones
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
| | - Steeve H Thany
- Université d'Orléans, LBLGC USC INRA 1328, 1 rue de Chartres, 45067 Orléans, France.
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12
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Ashraf J, Ahmad J, Ali A, Ul-Haq Z. Analyzing the Behavior of Neuronal Pathways in Alzheimer's Disease Using Petri Net Modeling Approach. Front Neuroinform 2018; 12:26. [PMID: 29875647 PMCID: PMC5974338 DOI: 10.3389/fninf.2018.00026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 04/30/2018] [Indexed: 11/13/2022] Open
Abstract
Alzheimer's Disease (AD) is the most common neuro-degenerative disorder in the elderly that leads to dementia. The hallmark of AD is senile lesions made by abnormal aggregation of amyloid beta in extracellular space of brain. One of the challenges in AD treatment is to better understand the mechanism of action of key proteins and their related pathways involved in neuronal cell death in order to identify adequate therapeutic targets. This study focuses on the phenomenon of aggregation of amyloid beta into plaques by considering the signal transduction pathways of Calpain-Calpastatin (CAST) regulation system and Amyloid Precursor Protein (APP) processing pathways along with Ca2+ channels. These pathways are modeled and analyzed individually as well as collectively through Stochastic Petri Nets for comprehensive analysis and thorough understating of AD. The model predicts that the deregulation of Calpain activity, disruption of Calcium homeostasis, inhibition of CAST and elevation of abnormal APP processing are key cytotoxic events resulting in an early AD onset and progression. Interestingly, the model also reveals that plaques accumulation start early (at the age of 40) in life but symptoms appear late. These results suggest that the process of neuro-degeneration can be slowed down or paused by slowing down the degradation rate of Calpain-CAST Complex. In the light of this study, the suggestive therapeutic strategy might be the prevention of the degradation of Calpain-CAST complexes and the inhibition of Calpain for the treatment of neurodegenerative diseases such as AD.
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Affiliation(s)
- Javaria Ashraf
- Research Center for Modeling and Simulation, National University of Sciences and Technology, Islamabad, Pakistan
| | - Jamil Ahmad
- Research Center for Modeling and Simulation, National University of Sciences and Technology, Islamabad, Pakistan
| | - Amjad Ali
- Atta-Ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, Pakistan
| | - Zaheer Ul-Haq
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical Sciences, University of Karachi, Karachi, Pakistan
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Benzidane Y, Goven D, Abd-Ella AA, Deshayes C, Lapied B, Raymond V. Subchronic exposure to sublethal dose of imidacloprid changes electrophysiological properties and expression pattern of nicotinic acetylcholine receptor subtypes in insect neurosecretory cells. Neurotoxicology 2017; 62:239-247. [DOI: 10.1016/j.neuro.2017.08.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 07/21/2017] [Accepted: 08/05/2017] [Indexed: 10/19/2022]
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Windley MJ, Vetter I, Lewis RJ, Nicholson GM. Lethal effects of an insecticidal spider venom peptide involve positive allosteric modulation of insect nicotinic acetylcholine receptors. Neuropharmacology 2017; 127:224-242. [PMID: 28396143 DOI: 10.1016/j.neuropharm.2017.04.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/28/2017] [Accepted: 04/06/2017] [Indexed: 01/17/2023]
Abstract
κ-Hexatoxins (κ-HXTXs) are a family of excitotoxic insect-selective neurotoxins from Australian funnel-web spiders that are lethal to a wide range of insects, but display no toxicity towards vertebrates. The prototypic κ-HXTX-Hv1c selectively blocks native and expressed cockroach large-conductance calcium-activated potassium (BKCa or KCa1.1) channels, but not their mammalian orthologs. Despite this potent and selective action on insect KCa1.1 channels, we found that the classical KCa1.1 blockers paxilline, charybdotoxin and iberiotoxin, which all block insect KCa1.1 channels, are not lethal in crickets. We therefore used whole-cell patch-clamp analysis of cockroach dorsal unpaired median (DUM) neurons to study the effects of κ-HXTX-Hv1c on sodium-activated (KNa), delayed-rectifier (KDR) and 'A-type' transient (KA) K+ channels. 1 μM κ-HXTX-Hv1c failed to significantly inhibit cockroach KNa and KDR channels, but did cause a 30 ± 7% saturating inhibition of KA channel currents, possibly via a Kv4 (Shal-like) action. However, this modest action at such a high concentration of κ-HXTX-Hv1c would indicate a different lethal target. Accordingly, we assessed the actions of κ-HXTX-Hv1c on neurotransmitter-gated ion channels in cockroach DUM neurons. We found that κ-HXTX-Hv1c failed to produce any major effects on GABAA or glutamate-Cl receptors but dramatically slowed nicotine-evoked ACh receptor (nAChR) current decay and reversed nAChR desensitization. These actions occurred without any alterations to nAChR current amplitude or the nicotine concentration-response curve, and are consistent with a positive allosteric modulation of nAChRs. κ-HXTX-Hv1c therefore represents the first venom peptide that selectively modulates insect nAChRs with a mode of action similar to the excitotoxic insecticide spinosyn A. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- Monique J Windley
- School of Life Sciences, University of Technology Sydney, Broadway, NSW 2007, Australia
| | - Irina Vetter
- Institute for Molecular Bioscience, University of Queensland, Brisbane St. Lucia, QLD 4072, Australia; School of Pharmacy, University of Queensland, Brisbane St. Lucia, QLD 4072, Australia
| | - Richard J Lewis
- Institute for Molecular Bioscience, University of Queensland, Brisbane St. Lucia, QLD 4072, Australia
| | - Graham M Nicholson
- School of Life Sciences, University of Technology Sydney, Broadway, NSW 2007, Australia.
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Taillebois E, Thany SH. CHARACTERIZATION OF NICOTINE ACETYLCHOLINE RECEPTOR SUBUNITS IN THE COCKROACH Periplaneta americana MUSHROOM BODIES REVEALS A STRONG EXPRESSION OF β1 SUBUNIT: INVOLVEMENT IN NICOTINE-INDUCED CURRENTS. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2016; 93:40-54. [PMID: 27357353 DOI: 10.1002/arch.21340] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Nicotinic acetylcholine receptors are ligand-gated ion channels expressed in many insect structures, such as mushroom bodies, in which they play a central role. We have recently demonstrated using electrophysiological recordings that different native nicotinic receptors are expressed in cockroach mushroom bodies Kenyon cells. In the present study, we demonstrated that eight genes coding for cockroach nicotinic acetylcholine receptor subunits are expressed in the mushroom bodies. Quantitative real-time polymerase chain reaction (PCR) experiments demonstrated that β1 subunit was the most expressed in the mushroom bodies. Moreover, antisense oligonucleotides performed against β1 subunit revealed that inhibition of β1 expression strongly decreases nicotine-induced currents amplitudes. Moreover, co-application with 0.5 μM α-bungarotoxin completely inhibited nicotine currents whereas 10 μM d-tubocurarine had a partial effect demonstrating that β1-containing neuronal nicotinic acetylcholine receptor subtypes could be sensitive to the nicotinic acetylcholine receptor antagonist α-bungarotoxin.
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Affiliation(s)
- Emiliane Taillebois
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM), Université d'Angers, Angers, France
| | - Steeve H Thany
- Laboratoire de Biologie des Ligneux et des Grandes Cultures (LBLGC), Université d'Orléans, Orléans, France
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16
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Mannai S, Bitri L, Thany SH. cGMP/cGMP-dependent protein kinase pathway modulates nicotine-induced currents through the activation of α-bungarotoxin-insensitive nicotinic acetylcholine receptors from insect neurosecretory cells. J Neurochem 2016; 137:931-8. [PMID: 27059649 DOI: 10.1111/jnc.13633] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 03/24/2016] [Accepted: 03/24/2016] [Indexed: 11/28/2022]
Abstract
Insect neurosecretory cells, called dorsal unpaired median neurons, are known to express two α-bungarotoxin-insensitive nicotinic acetylcholine receptor (nAChR) subtypes, nAChR1 and nAChR2. It was demonstrated that nAChR1 was sensitive to cAMP/cAMP-dependent protein kinase (PKA) regulation, resulting in a modulation of nicotine currents. In this study, we show that cyclic guanosine monophosphate (cGMP)/cGMP-dependent protein kinase (PKG) pathway modulates nicotine-induced currents, as increased cGMP affects the second compound of the biphasic current-voltage curve, corresponding to the nAChR2 receptors. Indeed, maintaining the guanosine triphosphate level with 100 μM guanosine triphosphate-γ-S increased nicotine currents through nAChR2. We also demonstrated that inhibition of PKG activity with 0.2 μM (8R,9S,11S)-(-)-9-methoxy-carbamyl-8-methyl-2,3,9,10-tetrahydro-8,11-epoxy-1H,8H,11H-2,7b,11a-trizadibenzo-(a,g)-cycloocta-(c,d,e)-trinden-1-one (KT5823), a PKG specific inhibitor, reduced nicotine-induced current amplitudes. KT5823 effect on nicotine currents is associated with calcium (Ca(2+) ) activity because inhibition of Ca(2+) concentration with cadmium chloride (CdCl2 ) abolished KT5823-induced inhibition mediated by nAChR2. However, specific inhibition of nitric oxide-guanylyl cyclase (GC) complex by 10 μM 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) significantly increased nicotine-induced current amplitudes on both nAChR1 and nAChR2. These results suggest that nicotine-induced currents mediated by both α-bungarotoxin-insensitive nAChR1 and nAChR2 are coupled to the cGMP/PKG pathway. We propose that nicotinic acetylcholine receptor activation induces an increase in intracellular calcium (Ca(2+) ) concentration. Elevation of intracellular Ca(2+) results in the formation of Ca(2+) -calmodulin (CaM) complex, which activates guanylyl cyclase (GC) and/or adenylyl cyclase (AC). Ca(2+) -CaM complex could activate Ca(2+) calmodulin kinase II which could directly or indirectly modulate the nicotinic response. The mechanisms by which cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) interact remain unclear. We demonstrate that nicotine-induced currents are coupled to the cGMP/PKG pathway.
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Affiliation(s)
- Safa Mannai
- Université d'Orléans, Laboratoire de Biologie des Ligneux et des Grandes Cultures (LBLGC), UPRES EA, Rue de Chartres, Orléans, France.,Université de Tunis El Manar, Faculté des Sciences, Campus Universitaire Farhat Hached, Rommana Tunis, Tunisie
| | - Lofti Bitri
- Université de Tunis El Manar, Faculté des Sciences, Campus Universitaire Farhat Hached, Rommana Tunis, Tunisie
| | - Steeve H Thany
- Université d'Orléans, Laboratoire de Biologie des Ligneux et des Grandes Cultures (LBLGC), UPRES EA, Rue de Chartres, Orléans, France
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Abd-Ella A, Stankiewicz M, Mikulska K, Nowak W, Pennetier C, Goulu M, Fruchart-Gaillard C, Licznar P, Apaire-Marchais V, List O, Corbel V, Servent D, Lapied B. The Repellent DEET Potentiates Carbamate Effects via Insect Muscarinic Receptor Interactions: An Alternative Strategy to Control Insect Vector-Borne Diseases. PLoS One 2015; 10:e0126406. [PMID: 25961834 PMCID: PMC4427492 DOI: 10.1371/journal.pone.0126406] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 04/01/2015] [Indexed: 11/25/2022] Open
Abstract
Insect vector-borne diseases remain one of the principal causes of human mortality. In addition to conventional measures of insect control, repellents continue to be the mainstay for personal protection. Because of the increasing pyrethroid-resistant mosquito populations, alternative strategies to reconstitute pyrethroid repellency and knock-down effects have been proposed by mixing the repellent DEET (N,N-Diethyl-3-methylbenzamide) with non-pyrethroid insecticide to better control resistant insect vector-borne diseases. By using electrophysiological, biochemichal, in vivo toxicological techniques together with calcium imaging, binding studies and in silico docking, we have shown that DEET, at low concentrations, interacts with high affinity with insect M1/M3 mAChR allosteric site potentiating agonist effects on mAChRs coupled to phospholipase C second messenger pathway. This increases the anticholinesterase activity of the carbamate propoxur through calcium-dependent regulation of acetylcholinesterase. At high concentrations, DEET interacts with low affinity on distinct M1/M3 mAChR site, counteracting the potentiation. Similar dose-dependent dual effects of DEET have also been observed at synaptic mAChR level. Additionally, binding and in silico docking studies performed on human M1 and M3 mAChR subtypes indicate that DEET only displays a low affinity antagonist profile on these M1/M3 mAChRs. These results reveal a selective high affinity positive allosteric site for DEET in insect mAChRs. Finally, bioassays conducted on Aedes aegypti confirm the synergistic interaction between DEET and propoxur observed in vitro, resulting in a higher mortality of mosquitoes. Our findings reveal an unusual allosterically potentiating action of the repellent DEET, which involves a selective site in insect. These results open exciting research areas in public health particularly in the control of the pyrethroid-resistant insect-vector borne diseases. Mixing low doses of DEET and a non-pyrethroid insecticide will lead to improvement in the efficiency treatments thus reducing both the concentration of active ingredients and side effects for non-target organisms. The discovery of this insect specific site may pave the way for the development of new strategies essential in the management of chemical use against resistant mosquitoes.
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Affiliation(s)
- Aly Abd-Ella
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
- Plant Protection Department, Faculty of Agriculture, Assiut University, Assiut, Egypt
| | - Maria Stankiewicz
- Faculty of Biology and Environment Protection, N. Copernicus University, Torun, Poland
| | - Karolina Mikulska
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, N. Copernicus University, Torun, Poland
| | - Wieslaw Nowak
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, N. Copernicus University, Torun, Poland
| | - Cédric Pennetier
- Institut de Recherche pour le Développement, UMR 224 Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MiVEGEC), Montpellier, France
| | - Mathilde Goulu
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
| | - Carole Fruchart-Gaillard
- CEA, iBiTecS, Service d’Ingénierie Moléculaire des Protéines (SIMOPRO), Laboratoire de Toxinologie Moléculaire et Biotechnologie, Gif sur Yvette, France
| | - Patricia Licznar
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
| | - Véronique Apaire-Marchais
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
| | - Olivier List
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
| | - Vincent Corbel
- Institut de Recherche pour le Développement, UMR 224 Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MiVEGEC), Montpellier, France
- Department of Entomology, Faculty of Agriculture at Kamphaeng Saen, Kamphaeng Saen Campus, Kasetsart University, Nakhon Pathom, Thailand
| | - Denis Servent
- CEA, iBiTecS, Service d’Ingénierie Moléculaire des Protéines (SIMOPRO), Laboratoire de Toxinologie Moléculaire et Biotechnologie, Gif sur Yvette, France
| | - Bruno Lapied
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
- * E-mail:
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Zheng C, Deng QQ, Liu LL, Wang MY, Zhang G, Sheng WL, Weng SJ, Yang XL, Zhong YM. Orexin-A differentially modulates AMPA-preferring responses of ganglion cells and amacrine cells in rat retina. Neuropharmacology 2015; 93:80-93. [PMID: 25656479 DOI: 10.1016/j.neuropharm.2015.01.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Revised: 12/22/2014] [Accepted: 01/20/2015] [Indexed: 01/18/2023]
Abstract
By activating their receptors (OX1R and OX2R) orexin-A/B regulate wake/sleeping states, feeding behaviors, but the function of these peptides in the retina remains unknown. Using patch-clamp recordings and calcium imaging in rat isolated retinal cells, we demonstrated that orexin-A suppressed α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA)-preferring receptor-mediated currents (AMPA-preferring currents) in ganglion cells (GCs) through OX1R, but potentiated those in amacrine cells (ACs) through OX2R. Consistently, in rat retinal slices orexin-A suppressed light-evoked AMPA-preferring receptor-mediated excitatory postsynaptic currents in GCs, but potentiated those in ACs. Intracellular dialysis of GDP-β-S or preincubation with the Gi/o inhibitor pertussis toxin (PTX) abolished both the effects. Either cAMP/the protein kinase A (PKA) inhibitor Rp-cAMP or cGMP/the PKG blocker KT5823 failed to alter the orexin-A effects. Whilst both of them involved activation of protein kinase C (PKC), the effects on GCs and ACs were respectively eliminated by the phosphatidylinositol (PI)-phospholipase C (PLC) inhibitor and phosphatidylcholine (PC)-PLC inhibitor. Moreover, in GCs orexin-A increased [Ca(2+)]i and the orexin-A effect was blocked by intracellular Ca(2+)-free solution and by inositol 1,4,5-trisphosphate (IP3) receptor antagonists. In contrast, orexin-A did not change [Ca(2+)]i in ACs and the orexin-A effect remained in intracellular or extracellular Ca(2+)-free solution. We conclude that a distinct Gi/o/PI-PLC/IP3/Ca(2+)-dependent PKC signaling pathway, following the activation of OX1R, is likely responsible for the orexin-A effect on GCs, whereas a Gi/o/PC-PLC/Ca(2+)-independent PKC signaling pathway, following the activation of OX2R, mediates the orexin-A effect on ACs. These two actions of orexin-A, while working in concert, provide a characteristic way for modulating information processing in the inner retina.
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Affiliation(s)
- Chao Zheng
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China; Cell Electrophysiology Laboratory, Wannan Medical College, 22 West Wenchang Road, Wuhu, Anhui 241002, China
| | - Qin-Qin Deng
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
| | - Lei-Lei Liu
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
| | - Meng-Ya Wang
- Cell Electrophysiology Laboratory, Wannan Medical College, 22 West Wenchang Road, Wuhu, Anhui 241002, China
| | - Gong Zhang
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
| | - Wen-Long Sheng
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
| | - Shi-Jun Weng
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
| | - Xiong-Li Yang
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China.
| | - Yong-Mei Zhong
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China.
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Simon-Delso N, Amaral-Rogers V, Belzunces LP, Bonmatin JM, Chagnon M, Downs C, Furlan L, Gibbons DW, Giorio C, Girolami V, Goulson D, Kreutzweiser DP, Krupke CH, Liess M, Long E, McField M, Mineau P, Mitchell EAD, Morrissey CA, Noome DA, Pisa L, Settele J, Stark JD, Tapparo A, Van Dyck H, Van Praagh J, Van der Sluijs JP, Whitehorn PR, Wiemers M. Systemic insecticides (neonicotinoids and fipronil): trends, uses, mode of action and metabolites. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2015; 22:5-34. [PMID: 25233913 PMCID: PMC4284386 DOI: 10.1007/s11356-014-3470-y] [Citation(s) in RCA: 930] [Impact Index Per Article: 103.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Accepted: 08/15/2014] [Indexed: 04/15/2023]
Abstract
Since their discovery in the late 1980s, neonicotinoid pesticides have become the most widely used class of insecticides worldwide, with large-scale applications ranging from plant protection (crops, vegetables, fruits), veterinary products, and biocides to invertebrate pest control in fish farming. In this review, we address the phenyl-pyrazole fipronil together with neonicotinoids because of similarities in their toxicity, physicochemical profiles, and presence in the environment. Neonicotinoids and fipronil currently account for approximately one third of the world insecticide market; the annual world production of the archetype neonicotinoid, imidacloprid, was estimated to be ca. 20,000 tonnes active substance in 2010. There were several reasons for the initial success of neonicotinoids and fipronil: (1) there was no known pesticide resistance in target pests, mainly because of their recent development, (2) their physicochemical properties included many advantages over previous generations of insecticides (i.e., organophosphates, carbamates, pyrethroids, etc.), and (3) they shared an assumed reduced operator and consumer risk. Due to their systemic nature, they are taken up by the roots or leaves and translocated to all parts of the plant, which, in turn, makes them effectively toxic to herbivorous insects. The toxicity persists for a variable period of time-depending on the plant, its growth stage, and the amount of pesticide applied. A wide variety of applications are available, including the most common prophylactic non-Good Agricultural Practices (GAP) application by seed coating. As a result of their extensive use and physicochemical properties, these substances can be found in all environmental compartments including soil, water, and air. Neonicotinoids and fipronil operate by disrupting neural transmission in the central nervous system of invertebrates. Neonicotinoids mimic the action of neurotransmitters, while fipronil inhibits neuronal receptors. In doing so, they continuously stimulate neurons leading ultimately to death of target invertebrates. Like virtually all insecticides, they can also have lethal and sublethal impacts on non-target organisms, including insect predators and vertebrates. Furthermore, a range of synergistic effects with other stressors have been documented. Here, we review extensively their metabolic pathways, showing how they form both compound-specific and common metabolites which can themselves be toxic. These may result in prolonged toxicity. Considering their wide commercial expansion, mode of action, the systemic properties in plants, persistence and environmental fate, coupled with limited information about the toxicity profiles of these compounds and their metabolites, neonicotinoids and fipronil may entail significant risks to the environment. A global evaluation of the potential collateral effects of their use is therefore timely. The present paper and subsequent chapters in this review of the global literature explore these risks and show a growing body of evidence that persistent, low concentrations of these insecticides pose serious risks of undesirable environmental impacts.
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Affiliation(s)
- N Simon-Delso
- Environmental Sciences, Copernicus Institute, Utrecht University, Heidelberglaan 2, 3584 CS, Utrecht, The Netherlands,
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List O, Calas-List D, Taillebois E, Juchaux M, Heuland E, Thany SH. Inhibition of PaCaMKII-E isoform in the dorsal unpaired median neurosecretory cells of cockroach reduces nicotine- and clothianidin-induced currents. J Neurochem 2014; 130:507-13. [DOI: 10.1111/jnc.12752] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2014] [Revised: 04/08/2014] [Accepted: 04/25/2014] [Indexed: 12/28/2022]
Affiliation(s)
- Olivier List
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM); UPRES EA 2647/USC INRA 1330/SFR 4207 QUASAV; Université d'Angers; UFR Sciences; Angers France
| | - Delphine Calas-List
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM); UPRES EA 2647/USC INRA 1330/SFR 4207 QUASAV; Université d'Angers; UFR Sciences; Angers France
| | - Emiliane Taillebois
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM); UPRES EA 2647/USC INRA 1330/SFR 4207 QUASAV; Université d'Angers; UFR Sciences; Angers France
| | | | - Emilie Heuland
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM); UPRES EA 2647/USC INRA 1330/SFR 4207 QUASAV; Université d'Angers; UFR Sciences; Angers France
| | - Steeve H. Thany
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM); UPRES EA 2647/USC INRA 1330/SFR 4207 QUASAV; Université d'Angers; UFR Sciences; Angers France
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21
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Mathé-Allainmat M, Swale D, Leray X, Benzidane Y, Lebreton J, Bloomquist JR, Thany SH. Quinuclidine compounds differently act as agonists of Kenyon cell nicotinic acetylcholine receptors and induced distinct effect on insect ganglionic depolarizations. INVERTEBRATE NEUROSCIENCE 2013; 13:167-77. [DOI: 10.1007/s10158-013-0160-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2013] [Accepted: 07/08/2013] [Indexed: 12/21/2022]
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Calas-List D, List O, Quinchard S, Thany SH. Calcium pathways such as cAMP modulate clothianidin action through activation of α-bungarotoxin-sensitive and -insensitive nicotinic acetylcholine receptors. Neurotoxicology 2013; 37:127-33. [PMID: 23632304 DOI: 10.1016/j.neuro.2013.04.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 04/20/2013] [Accepted: 04/22/2013] [Indexed: 10/26/2022]
Abstract
Clothianidin is a neonicotinoid insecticide developed in the early 2000s. We have recently demonstrated that it was a full agonist of α-bungarotoxin-sensitive and -insensitive nicotinic acetylcholine receptors expressed in the cockroach dorsal unpaired median neurons. Clothianidin was able to act as an agonist of imidacloprid-insensitive nAChR2 receptor and internal regulation of cAMP concentration modulated nAChR2 sensitivity to clothianidin. In the present study, we demonstrated that cAMP modulated the agonist action of clothianidin via α-bungarotoxin-sensitive and insensitive receptors. Clothianidin-induced current-voltage curves were dependent to clothianidin concentrations. At 10 μM clothianidin, increasing cAMP concentration induced a linear current-voltage curve. Clothianidin effects were blocked by 0.5 μM α-bungarotoxin suggesting that cAMP modulation occurred through α-bungarotoxin-sensitive receptors. At 1 mM clothianidin, cAMP effects were associated to α-bungarotoxin-insensitive receptors because clothianidin-induced currents were blocked by 5 μM mecamylamine and 20 μM d-tubocurarine. In addition, we found that application of 1mM clothianidin induced a strong increase of intracellular calcium concentration. These data reinforced the finding that calcium pathways including cAMP modulated clothianidin action on insect nicotinic acetylcholine receptors. We proposed that intracellular calcium pathways such as cAMP could be a target to modulate the mode of action of neonicotinoid insecticides.
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Affiliation(s)
- Delphine Calas-List
- Université d'Angers, Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM), UPRES EA 2647/USC INRA 1330, UFR de Sciences, 2 Bd. Lavoisier, 49045 Angers, France
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Mathé-Allainmat M, Bodereau-Dubois B, Lapied B, Lebreton J, Thany SH. A fluorinated quinuclidine benzamide named LMA 10203 acts as an agonist of insect nicotinic acetylcholine receptors. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2012; 42:417-425. [PMID: 22421703 DOI: 10.1016/j.ibmb.2012.02.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 02/25/2012] [Accepted: 02/28/2012] [Indexed: 05/31/2023]
Abstract
In the present study, we take advantage of the fact that cockroach dorsal unpaired median neurons express different nicotinic acetylcholine receptor subtypes to demonstrate that simple quinuclidine benzamides such as the 2-fluorinated benzamide LMA 10203, could act as an agonist of cockroach α-bungarotoxin-insensitive nicotinic acetylcholine receptor subtype, called nAChR2. Indeed, 1 mM LMA 10203 induced ionic currents which were partially blocked by 0.5 μM α-bungarotoxin and methyllycaconitine and completely blocked by 5 μM mecamylamine. Moreover, the current-voltage curve revealed that the ionic current induced by LMA 10203 increased from -30 mV to +20 mV confirming that it acted as an agonist of α-bungarotoxin-insensitive nAChR2. In addition, 1 mM LMA 10203 induced a depolarization of the sixth abdominal ganglion and this neuroexcitatory activity was completely blocked by 5 μM mecamylamine. These data suggest that nAChR2 was also expressed at the postsynaptic level on the synapse between the cercal afferent nerve and the giant interneurons. Interestingly, despite LMA 10203 being an agonist of cockroach nicotinic receptors, it had a poor insecticidal activity. We conclude that LMA 10203 could be used as an interesting compound to identify specific insect nAChR subtypes.
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Affiliation(s)
- Monique Mathé-Allainmat
- Université de Nantes, CEISAM UMR 6230, UFR des Sciences et des Techniques, 2 rue de la Houssinière BP 92208, Nantes F-44000, France
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Calas-List D, List O, Thany SH. Nornicotine application on cockroach dorsal unpaired median neurons induces two distinct ionic currents: Implications of different nicotinic acetylcholine receptors. Neurosci Lett 2012; 518:64-8. [DOI: 10.1016/j.neulet.2012.04.058] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 03/27/2012] [Accepted: 04/24/2012] [Indexed: 11/25/2022]
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Nervous System of Periplaneta americana Cockroach as a Model in Toxinological Studies: A Short Historical and Actual View. J Toxicol 2012; 2012:143740. [PMID: 22666245 PMCID: PMC3361271 DOI: 10.1155/2012/143740] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Accepted: 03/01/2012] [Indexed: 11/17/2022] Open
Abstract
Nervous system of Periplaneta americana cockroach is used in a wide range of pharmacological studies, including electrophysiological techniques. This paper presents its role as a preparation in the development of toxinological studies in the following electrophysiological methods: double-oil-gap technique on isolated giant axon, patch-clamp on DUM (dorsal unpaired median) neurons, microelectrode technique in situ conditions on axon in connective and DUM neurons in ganglion, and single-fiber oil-gap technique on last abdominal ganglion synapse. At the end the application of cockroach synaptosomal preparation is mentioned.
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Dupuis J, Louis T, Gauthier M, Raymond V. Insights from honeybee (Apis mellifera) and fly (Drosophila melanogaster) nicotinic acetylcholine receptors: from genes to behavioral functions. Neurosci Biobehav Rev 2012; 36:1553-64. [PMID: 22525891 DOI: 10.1016/j.neubiorev.2012.04.003] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 03/26/2012] [Accepted: 04/04/2012] [Indexed: 11/25/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are widely expressed throughout the central nervous system of insects where they supply fast synaptic excitatory transmission and represent a major target for several insecticides. The unbalance is striking between the abundant literature on nAChR sensitivity to insecticides and the rarity of information regarding their molecular properties and cognitive functions. The recent advent of genome sequencing disclosed that nAChR gene families of insects are rather small-sized compared to vertebrates. Behavioral experiments performed in the honeybee demonstrated that a subpopulation of nAChRs sensitive to the venom α-bungarotoxin and permeant to calcium is necessary for the formation of long-term memory. Concomitant data in Drosophila reported that repetitive exposure to nicotine results in a calcium-dependent plasticity of the nAChR-mediated response involving cAMP signaling cascades and indicated that ACh-induced Ca++ currents are modulated by monoamines involved in aversive and appetitive learning. As in vertebrates, in which glutamate and NMDA-type glutamate receptors are involved in experience-associated synaptic plasticity and memory formation, insects could display a comparable system based on ACh and α-Bgt-sensitive nAChRs.
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Affiliation(s)
- Julien Dupuis
- Université de Toulouse, UPS, Centre de Recherches sur la Cognition Animale (CRCA), 118 route de Narbonne, F-31062 Toulouse Cedex 9, France
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Bodereau-Dubois B, List O, Calas-List D, Marques O, Communal PY, Thany SH, Lapied B. Transmembrane potential polarization, calcium influx, and receptor conformational state modulate the sensitivity of the imidacloprid-insensitive neuronal insect nicotinic acetylcholine receptor to neonicotinoid insecticides. J Pharmacol Exp Ther 2012; 341:326-39. [PMID: 22286500 DOI: 10.1124/jpet.111.188060] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neonicotinoid insecticides act selectively on insect nicotinic acetylcholine receptors (nAChRs). Recent studies revealed that their efficiency was altered by the phosphorylation/dephosphorylation process and the intracellular signaling pathway involved in the regulation of nAChRs. Using whole-cell patch-clamp electrophysiology adapted for dissociated cockroach dorsal unpaired median (DUM) neurons, we demonstrated that intracellular factors involved in the regulation of nAChR function modulated neonicotinoid sensitivity. DUM neurons were known to express two α-bungarotoxin-insensitive nAChR subtypes: nAChR1 and nAChR2. Whereas nAChR1 was sensitive to imidacloprid, nAChR2 was insensitive to this insecticide. Here, we demonstrated that, like nicotine, acetamiprid and clothianidin, other types of neonicotinoid insecticides, acted as agonists on the nAChR2 subtype. Using acetamiprid, we revealed that both steady-state depolarization and hyperpolarization affected nAChR2 sensitivity. The measurement of the input membrane resistance indicated that change in the acetamiprid-induced agonist activity was related to the receptor conformational state. Using cadmium chloride, ω-conotoxin GVIA, and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-acetamide (LOE 908), we found that inhibition of calcium influx through high voltage-activated calcium channels and transient receptor potential γ (TRPγ) activated by both depolarization and hyperpolarization increased nAChR2 sensitivity to acetamiprid. Finally, using N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W7), forskolin, and cAMP, we demonstrated that adenylyl cyclase sensitive to the calcium/calmodulin complex regulated internal cAMP concentration, which in turn modulated TRPγ function and nAChR2 sensitivity to acetamiprid. Similar TRPγ-induced modulatory effects were also obtained when clothianidin was tested. These findings bring insights into the signaling pathway modulating neonicotinoid efficiency and open novel strategies for optimizing insect pest control.
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Affiliation(s)
- Béatrice Bodereau-Dubois
- Laboratoire Récepteurs et Canaux Ioniques Membranaires, Faculté des Sciences, Université d'Angers, Angers, France
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Inhibition of protein kinase C decreases sensitivity of GABA receptor subtype to fipronil insecticide in insect neurosecretory cells. Neurotoxicology 2011; 32:828-35. [DOI: 10.1016/j.neuro.2011.05.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 05/31/2011] [Accepted: 05/31/2011] [Indexed: 01/03/2023]
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Thany SH, Tricoire-Leignel H. Emerging Pharmacological Properties of Cholinergic Synaptic Transmission: Comparison between Mammalian and Insect Synaptic and Extrasynaptic Nicotinic Receptors. Curr Neuropharmacol 2011; 9:706-14. [PMID: 22654728 PMCID: PMC3263464 DOI: 10.2174/157015911798376343] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 06/02/2010] [Accepted: 07/21/2010] [Indexed: 12/03/2022] Open
Abstract
Acetylcholine (ACh) is probably the oldest signalling neurotransmitter which appeared in evolution before the nervous system. It is present in bacteria, algae, protozoa and plants. In insects and mammals it is involved in cell-to-cell communications in various neuronal and non-neuronal tissues. The discovery of nicotinic acetylcholine receptors (nAChRs) as the main receptors involved in rapid cholinergic neurotransmission has helped to understand the role of ACh at synaptic level. Recently, several lines of evidence have indicated that extrasynaptically expressed nAChRs display distinct pharmacological properties from the ones expressed at synaptic level. The role of both nAChRs at insect extrasynaptic and/or synaptic levels has been underestimated due to the lack of pharmacological tools to identify different nicotinic receptor subtypes. In the present review, we summarize recent electrophysiological and pharmacological studies on the extrasynaptic and synaptic differences between insect and mammalian nAChR subtypes and we discuss on the pharmacological impact of several drugs such as neonicotinoid insecticides targeting these receptors. In fact, nAChRs are involved in a wide range of pathophysiological processes such as epilepsy, pain and a wide range of neurodegenerative and psychiatric disorders. In addition, they are the target sites of neonicotinoid insecticides which are known to act as nicotinic agonists causing severe poisoning in insects and mammals.
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Affiliation(s)
- Steeve H Thany
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM), UPRES EA 2647/USC INRA 2023, Université d’Angers, UFR Sciences. 2 Bd Lavoisier, 49045 Angers cedex, France
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Watanabe H, Matsumoto CS, Nishino H, Mizunami M. Critical roles of mecamylamine-sensitive mushroom body neurons in insect olfactory learning. Neurobiol Learn Mem 2010; 95:1-13. [PMID: 20951220 DOI: 10.1016/j.nlm.2010.10.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 09/04/2010] [Accepted: 10/07/2010] [Indexed: 11/27/2022]
Abstract
In insects, cholinergic neurons are thought to transmit olfactory conditioned stimulus (CS) to the sites for associating the CS with unconditioned stimulus (US), but the types of acetylcholine (ACh) receptor used by neurons participating in the association have not been determined. In cockroaches, a type of nicotinic ACh receptor specifically antagonized by mecamylamine (MEC) has been characterized. Here we investigated the roles of neurons possessing MEC-sensitive ACh receptors (MEC-sensitive neurons) in olfactory conditioning of salivation, monitored by changes in activities of salivary neurons, in cockroaches. Local and bilateral microinjection of MEC into each of the three olfactory centers, antennal lobes, calyces of the mushroom bodies and lateral protocerebra, impaired olfactory responses of salivary neurons, indicating that MEC-sensitive neurons in all olfactory centers participate in pathways mediating olfactory responses of salivary neurons. Conditioning of olfactory CS with sucrose US was impaired by injection of MEC into the antennal lobes or calyces, i.e., conditioned responses were absent even after recovery from MEC injection, suggesting that the CS-US association occurs in MEC-sensitive neurons in calyces (most probably Kenyon cells) or in neurons in downstream pathways. In contrast, conditioned responses appeared after recovery from MEC injection into the lateral protocerebra, suggesting that MEC-sensitive neurons in the lateral protocerebra are downstream of the association sites. Since lateral protocerebra are major termination areas of mushroom body efferent neurons, we suggest that input synapses of MEC-sensitive Kenyon cells, or their output synapses upon mushroom body efferent neurons, are the sites for CS-US association for conditioning of salivation.
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Affiliation(s)
- Hidehiro Watanabe
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
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Oliveira EE, Pippow A, Salgado VL, Büschges A, Schmidt J, Kloppenburg P. Cholinergic Currents in Leg Motoneurons of Carausius morosus. J Neurophysiol 2010; 103:2770-82. [DOI: 10.1152/jn.00963.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We used patch-clamp recordings and fast optical Ca2+ imaging to characterize an acetylcholine-induced current ( IACh) in leg motoneurons of the stick insect Carausius morosus. Our long-term goal is to better understand the synaptic and integrative properties of the leg sensory-motor system, which has served extremely successfully as a model to study basic principles of walking and locomotion on the network level. The experiments were performed under biophysically controlled conditions on freshly dissociated leg motoneurons to avoid secondary effects from the network. To allow for unequivocal identification, the leg motoneurons were backfilled with a fluorescent label through the main leg nerve prior to cell dissociation. In 87% of the motoneurons, IACh consisted of a fast-desensitizing ( IACh1) and a slow-desensitizing component ( IACh2), both of which were concentration dependent, with EC50 values of 3.7 × 10−5 and 2.0 × 10−5 M, respectively. Ca2+ imaging revealed that a considerable portion of IACh (∼18%) is carried by Ca2+, suggesting that IACh, besides mediating fast synaptic transmission, could also induce Ca2+-dependent processes. Using specific nicotinic and muscarinic acetylcholine receptor ligands, we showed that IACh was exclusively mediated by nicotinic acetylcholine receptors. Distinct concentration–response relations of IACh1 and IACh2 for these ligands indicated that they are mediated by different types of nicotinic acetylcholine receptors.
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Affiliation(s)
- Eugênio E. Oliveira
- Institute for Zoology, Biocenter, and
- Center for Molecular Medicine Cologne (CMMC) and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; and
| | - Andreas Pippow
- Institute for Zoology, Biocenter, and
- Center for Molecular Medicine Cologne (CMMC) and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; and
| | - Vincent L. Salgado
- BASF Agricultural Products, BASF Corporation, Research Triangle Park, North Carolina
| | | | | | - Peter Kloppenburg
- Institute for Zoology, Biocenter, and
- Center for Molecular Medicine Cologne (CMMC) and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; and
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Lavialle-Defaix C, Moignot B, Legros C, Lapied B. How Does Calcium-Dependent Intracellular Regulation of Voltage-Dependent Sodium Current Increase the Sensitivity to the Oxadiazine Insecticide Indoxacarb Metabolite Decarbomethoxylated JW062 (DCJW) in Insect Pacemaker Neurons? J Pharmacol Exp Ther 2010; 333:264-72. [DOI: 10.1124/jpet.109.163519] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Thany SH. Electrophysiological Studies and Pharmacological Properties of Insect Native Nicotinic Acetylcholine Receptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 683:53-63. [DOI: 10.1007/978-1-4419-6445-8_5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Westmark S, Oliveira EE, Schmidt J. Pharmacological analysis of tonic activity in motoneurons during stick insect walking. J Neurophysiol 2009; 102:1049-61. [PMID: 19515945 DOI: 10.1152/jn.91360.2008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Stick insect middle leg (mesothoracic) motoneurons receive tonic excitatory input during front leg stepping on a treadmill. We studied the pharmacology of this excitatory input to the motoneurons during single-legged treadmill walking (in situ). During bath application of drugs restricted to the mesothoracic ganglion, activity in motoneurons contralateral to the stepping front leg was recorded from neuropilar processes. Application of the cholinergic antagonist atropine reduced the tonic depolarization amplitude. These results were compared with findings in acutely dissociated motoneuron cell bodies (in vitro) under whole cell voltage-clamp conditions. The presence of an acetylcholine-induced current in situ was supported by the finding of an acetylcholine evoked biphasic inward current with a sustained component that could be blocked by atropine. In situ the tonic depolarization was generally increased by application of the neuro-modulator octopamine and decreased by its antagonist mianserin. In vitro, however, octopamine reduced the inward current evoked by acetylcholine application to motoneurons. Intracellular application of bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA) into motoneurons in situ revealed a dependence of the tonic depolarization on Ca(2+) and application of the membrane-permeable cAMP analogue 8-bromo-cAMP increased the tonic depolarization. In contrast, 8-bromo-cAMP reduced the inward current evoked by acetylcholine application to motoneurons in vitro. We conclude that during walking, acetylcholine contributes to mediating the tonic depolarization possibly by acting on atropine-sensitive receptors on motoneurons. Octopamine that is released during walking increases the tonic depolarization. This increase, however, is not based on modulation of cholinergic action on motoneurons but rather on effects on premotor neurons. Both, Ca(2+) and cAMP are likely second messengers involved in mediating the tonic depolarization, but whereas Ca(2+) acts in motoneurons, cAMP does not appear to mediate a cholinergic depolarization in motoneurons.
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Affiliation(s)
- Sandra Westmark
- Zoologisches Institut, Universität zu Köln, 50923 Köln, Germany
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Shen JX, Tu B, Yakel JL. Inhibition of alpha 7-containing nicotinic ACh receptors by muscarinic M1 ACh receptors in rat hippocampal CA1 interneurones in slices. J Physiol 2009; 587:1033-42. [PMID: 19124535 DOI: 10.1113/jphysiol.2008.167593] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cys-loop ligand-gated nicotinic ACh receptors (nAChRs) and G protein-coupled muscarinic ACh receptors (mAChRs) are expressed on rat hippocampal interneurones where they can regulate excitability, synaptic communication and cognitive function. Even though both nAChRs and mAChRs appear to co-localize to the same interneurones, it is not clear whether there is crosstalk between them. We utilized patch-clamp techniques to investigate this issue in rat hippocampal CA1 interneurones in slices under conditions where synaptic transmission was blocked. The alpha7 nAChR-mediated currents were activated by choline, and when the activation of this receptor was preceded by the activation of the M(1) mAChR subtype, the amplitude of alpha7 responses was significantly reduced in a rapidly reversible and voltage-independent manner, without any change in the kinetics of responses. This M(1) mAChR-mediated inhibition of alpha7 nAChRs was through a PLC-, calcium- and PKC-dependent signal transduction cascade. These data show that M(1) mAChRs and alpha7 nAChRs are functionally co-localized on individual rat hippocampal interneurones where the activation of these particular mAChRs inhibits alpha7 nAChR function. This information will help to understand how these cholinergic receptor systems might be regulating neuronal excitability in the hippocampus in a manner that has relevance for synaptic plasticity and cognition.
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Affiliation(s)
- Jian-xin Shen
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, PO Box 12233, Research Triangle Park, NC 27709, USA
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Thany SH, Courjaret R, Lapied B. Effect of calcium on nicotine-induced current expressed by an atypical alpha-bungarotoxin-insensitive nAChR2. Neurosci Lett 2008; 438:317-21. [PMID: 18485593 DOI: 10.1016/j.neulet.2008.04.065] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2007] [Revised: 04/18/2008] [Accepted: 04/20/2008] [Indexed: 11/28/2022]
Abstract
Two distinct native alpha-bungarotoxin (alpha-Bgt)-insensitive nicotinic acetylcholine receptors (nAChRs), named nAChR1 and nAChR2, were identified in the cockroach Periplaneta americana dorsal unpaired median (DUM) neurons. They differed in their electrophysiological, pharmacological properties and intracellular regulation pathways. nAChR2 being an atypical nicotinic receptor closed upon agonist application and its current-voltage relationship resulted from a reduction in potassium conductance. In this study, using whole-cell patch-clamp technique, we demonstrated that calcium modulated nAChR2-mediated nicotine response. Under 0.5 microM alpha-Bgt and 20 mM d-tubocurarine, the nicotine-induced inward current amplitude was strongly reduced in the presence of intracellularly applied BAPTA or bath application of calcium-free solution. In addition, using cadmium chloride, we showed that nicotine response was modulated by extracellular calcium through plasma membrane calcium channels. Moreover, extracellular application of caffeine and thapsigargin reduced nAChR2-mediated response. Together these experiments revealed a complex calcium-dependent regulation of nAChR2.
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Affiliation(s)
- Steeve H Thany
- Laboratoire Récepteurs et Canaux Ioniques Membranaires, UPRES EA 2647/USC INRA, IFR 149 QUASAV, Université d'Angers, UFR de sciences, 2 Boulevard Lavoisier, 49045 Angers, France.
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Tan J, Salgado VL, Hollingworth RM. Neural actions of imidacloprid and their involvement in resistance in the Colorado potato beetle, Leptinotarsa decemlineata (Say). PEST MANAGEMENT SCIENCE 2008; 64:37-47. [PMID: 18022827 DOI: 10.1002/ps.1464] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
BACKGROUND The development of resistance to imidacloprid in eastern US populations of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), threatens this critical use for neonicotinoid insecticides. Previous pharmacokinetic studies with resistant adult CPBs provided no explanation for the high resistance level (over 200-fold) to topically applied imidacloprid. The authors assessed the neural activity of imidacloprid by recording spontaneous activity from a motor nerve leaving the isolated central nervous system to compare the sensitivity of the latter to imidacloprid between susceptible and resistant CPBs. RESULTS On the isolated central nervous system, imidacloprid was initially neuroexcitatory, and neuroinhibitory at higher concentrations. The neuroexcitatory action of imidacloprid was blocked by coapplication of a specific nAChR antagonist, methyllycaconitine, indicating that it is a result of action on nAChRs. The sensitivity to the neuroexcitatory and inhibitory activities of imidacloprid varied independently among individuals in each population. The sensitivity of the central nervous system of resistant CPBs to excitation by imidacloprid did not differ from that of susceptible insects, but the sensitivity to inhibition by imidacloprid was reduced 52- to 58-fold, indicating a possible change in the sensitivity of at least one subgroup of nAChRs. CONCLUSION This study provides evidence that reduced nerve sensitivity to the blocking action of imidacloprid is associated with imidacloprid resistance in the CPB.
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Affiliation(s)
- Jianguo Tan
- Department of Entomology, Michigan State University, East Lansing, MI 48824, USA
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Barbara GS, Grünewald B, Paute S, Gauthier M, Raymond-Delpech V. Study of nicotinic acetylcholine receptors on cultured antennal lobe neurones from adult honeybee brains. INVERTEBRATE NEUROSCIENCE 2007; 8:19-29. [PMID: 18004599 DOI: 10.1007/s10158-007-0062-2] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Accepted: 10/25/2007] [Indexed: 12/21/2022]
Abstract
In insects, acetylcholine (ACh) is the main neurotransmitter, and nicotinic acetylcholine receptors (nAChRs) mediate fast cholinergic synaptic transmission. In the honeybee, nAChRs are expressed in diverse structures including the primary olfactory centres of the brain, the antennal lobes (AL) and the mushroom bodies. Whole-cell, voltage-clamp recordings were used to characterize the nAChRs present on cultured AL cells from adult honeybee, Apis mellifera. In 90% of the cells, applications of ACh induced fast inward currents that desensitized slowly. The classical nicotinic agonists nicotine and imidacloprid elicited respectively 45 and 43% of the maximum ACh-induced currents. The ACh-elicited currents were blocked by nicotinic antagonists methyllycaconitine, dihydroxy-beta-erythroidine and alpha-bungarotoxin. The nAChRs on adult AL cells are cation permeable channels. Our data indicate the existence of functional nAChRs on adult AL cells that differ from nAChRs on pupal Kenyon cells from mushroom bodies by their pharmacological profile and ionic permeability, suggesting that these receptors could be implicated in different functions.
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Affiliation(s)
- Guillaume Stéphane Barbara
- Centre de Recherches sur la Cognition Animale-CNRS, Université Paul Sabatier, 118 rte de Narbonne, 31062, Toulouse, France
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Gao JR, Deacutis JM, Scott JG. The nicotinic acetylcholine receptor subunit Mdalpha6 from Musca domestica is diversified via post-transcriptional modification. INSECT MOLECULAR BIOLOGY 2007; 16:325-34. [PMID: 17439546 DOI: 10.1111/j.1365-2583.2007.00730.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Recent studies showed that deletion of a nicotinic acetylcholine receptor (nAChR) subunit gene, Dalpha6 in Drosophila melanogaster results in a strain that is resistant to spinosad, indicating that Dalpha6 is important for the toxic action of this insecticide. To determine if spinosad resistance in house flies was due to a mutation(s) of Mdalpha6 (the orthologue of Dalpha6 from house flies), cDNAs were cloned and characterized from an insecticide-susceptible and a spinosad-resistant strain of the house fly, Musca domestica. The cDNAs contain a 1470-bp open reading frame encoding 490 amino acid residues, 415-bp 5' untranslated region (UTR) and a polymorphic 3'-UTR of approximately 371 bp. The predicted mature protein possesses 468 amino acid residues, has the typical features of a nAChR alpha subunit and is 97% identical to Dalpha6. Quantitative real-time PCR analysis revealed that Mdalpha6 was expressed in the head and the thorax at 1300- and 26-fold higher levels, respectively, than in the abdomen. There was no difference in the expression level of Mdalpha6 between spinosad-resistant and susceptible strains. Ten isoforms arising from alternative splicing were characterized, with isoform II being most common. A-to-I RNA editing was examined and found at 12 sites: editing at 11 of these sites resulted in an amino acid substitution. Mdalpha6 is linked to autosome 1 (spinosad resistance was previously shown to be linked to autosome 1). Single nucleotide polymorphisms, alternative splicing, mRNA levels and A-to-I RNA editing were compared between head and thorax and between insecticide-susceptible and spinosad-resistant strains. These comparisons indicate that Mdalpha6 is not responsible for spinosad resistance in house flies.
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Affiliation(s)
- J-R Gao
- Department of Entomology, Comstock Hall, Cornell University, Ithaca, NY 14853, USA
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Gao JR, Deacutis JM, Scott JG. Characterization of the nicotinic acetylcholine receptor subunit gene Mdalpha2 from the house fly, Musca domestica. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2007; 64:30-42. [PMID: 17167752 DOI: 10.1002/arch.20158] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
A nicotinic acetylcholine receptor (nAChR) subunit gene, Mdalpha2, was isolated and characterized from the house fly, Musca domestica. This is the first nAChR family member cloned from house flies. Mdalpha2 had a cDNA of 2,607 bp, which included a 696 bp 5'-untranslated region (UTR), an open reading frame of 1,692 bp, and a 219 bp 3'-UTR. Its deduced amino acid sequence possesses the typical characteristics of nAChRs. Mdalpha2 genomic sequence was 11.2 kb in length in the aabys strain and 10.9 kb in the OCR strain, including eight exons and seven introns. Based on the deduced amino acid sequence, Mdalpha2 had the closest phylogenetic relationship to the Drosophila melanogaster Dalpha2 and Anopheles gambiae Agamalpha2, and a similar genomic structure to Dalpha2. Quantitative real-time PCR analysis showed that Mdalpha2 is expressed in the head and the thorax at 150- and 8.5-fold higher levels than in the abdomen. Linkage analysis of a Mdalpha2 polymorphism indicates this gene is on autosome 2. The importance of these results in understanding the diversity and phylogenetic relationships of insect nAChRs, the physiology of nAChRs in the house fly, and the utility of nAChR sequences in resistance detection/monitoring is discussed.
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Affiliation(s)
- Jian-Rong Gao
- Department of Entomology, Comstock Hall, Cornell University, Ithaca, New York 14853, USA
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Thany SH, Lenaers G, Raymond-Delpech V, Sattelle DB, Lapied B. Exploring the pharmacological properties of insect nicotinic acetylcholine receptors. Trends Pharmacol Sci 2006; 28:14-22. [PMID: 17156860 DOI: 10.1016/j.tips.2006.11.006] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2006] [Revised: 10/05/2006] [Accepted: 11/23/2006] [Indexed: 01/07/2023]
Abstract
Insect nicotinic acetylcholine (nACh) receptors are molecular targets of insecticides such as neonicotinoids that are used to control disease-carrying insects and agricultural pests. To date, several insect nACh receptor subunits have been identified, indicating different nACh receptor subtypes and pharmacological profiles. Because of the difficulty in expressing functional insect nACh receptors in heterologous systems, new research tools are needed. Studies on insects resistant to the insecticide imidacloprid and on laboratory-generated hybrid and chimaeric nACh receptors in vitro have provided information about the molecular basis of receptor diversity, neonicotinoid resistance and selectivity. Additionally, recent results indicate that the sensitivity of insect nACh receptors to imidacloprid can be modulated by intracellular phosphorylation mechanisms, which offers a new approach to studying insect nACh receptor pharmacology.
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Affiliation(s)
- Steeve H Thany
- Laboratoire Récepteurs et Canaux Ioniques Membranaires, UPRES EA 2647/USC INRA, Université d'Angers, UFR Sciences, 2 Boulevard Lavoisier, 49045 Angers cedex, France.
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Brulle F, Mitta G, Cocquerelle C, Vieau D, Lemière S, Leprêtre A, Vandenbulcke F. Cloning and real-time PCR testing of 14 potential biomarkers in Eisenia fetida following cadmium exposure. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2006; 40:2844-50. [PMID: 16683633 DOI: 10.1021/es052299x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Important biological activities could be affected in metal exposed species, and amongthe main physiological functions, immunity may provide one (or more) effector(s) which expression can be directly affected by a metal exposure in various macroinvertebrates. As many proteinic effectors showed a high degree of homology between species, we have developed a PCR approach to characterize partial mRNA sequences of selected effectors in the laboratory model, Eisenia fetida. After cloning, levels of expression of each gene were analyzed following exposures (80 and 800 mg/kg) to cadmium spiked soils using real-time PCR. An implemented approach was allowed to test quickly potential biomarkers in Eisenia fetida. Selected effectors were calmodulin, heat shock proteins, superoxide dismutase, catalase, metallothionein, beta-adrenergic receptor kinase, pyruvate carboxylase, trancriptionally controlled tumor protein, protein kinase C, and ubiquitin. Most of the selected effectors did not show variations of expression level after exposure. Others expressed weak changes of expression as heat shock proteins. At lastfor catalase and metallothionein, early suitable variations of expression were observed.
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Affiliation(s)
- F Brulle
- Laboratoire d'Ecologie Numérique et d'Ecotoxicologie, EA 3570, Université de Lille 1, Cité scientifique, Batiment SN3, 59655 Villeneuve d'Ascq Cedex, France
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Defaix A, Lapied B. Role of a novel maintained low-voltage-activated inward current permeable to sodium and calcium in pacemaking of insect neurosecretory neurons. INVERTEBRATE NEUROSCIENCE 2005; 5:135-46. [PMID: 16177888 DOI: 10.1007/s10158-005-0003-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2005] [Accepted: 07/24/2005] [Indexed: 10/25/2022]
Abstract
Among ionic currents underlying neuronal pacemaker activity, low-threshold-activated calcium currents contribute to setting the threshold for spike firing. In the insect central nervous system, dorsal unpaired median (DUM) neurons are capable of generating spontaneous electrical activity. It has previously been shown that two distinct (transient and maintained) low-voltage-activated (LVA) calcium currents are responsible for the generation of the pacemaker potential. Whole-cell recordings in voltage- and current-clamp mode were obtained from short-term cultured DUM neurons. Using 100 mM sodium and 2 mM calcium as charge carrier in the external solution as well as conditions that eliminate calcium currents (0.5 mM CdCl2), voltage-clamp experiments showed that a hitherto unanticipated LVA maintained inward current, activated at around -60 mV, was present. The current amplitude was strongly dependent on internal ATP concentration. Sodium-free solution reduced by 80% the current amplitude. Increasing (5 mM) or decreasing (calcium-free) external calcium concentrations enhanced or reduced, respectively, the maximum conductance without any effect on the voltage dependence. This novel ion channel was permeable to barium but manipulating internal or external magnesium concentrations was without effect on current amplitude or reversal potential. Based on IC50 values, the maintained current was 50-fold less sensitive to TTX than the classical transient voltage-dependent sodium current. Furthermore, it was insensitive to ethosuximide and halothane. Voltage-dependent inactivation analysis revealed an unexpected calcium-sensitive process that involved calcineurin. From these results it appears that, besides the two LVA calcium currents previously described, another LVA maintained inward current permeable to both sodium and calcium was also involved in the generation of the predepolarization. Based on these findings, we propose that a novel calcium-dependent mechanism is involved in the regulation of the pacemaker activity.
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Affiliation(s)
- Antoine Defaix
- Laboratoire RCIM UPRES EA 2647, Université d'Angers, UFR Sciences, 2 Bd Lavoisier, 49045, Angers Cedex, France
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Jones AK, Marshall J, Blake AD, Buckingham SD, Darlison MG, Sattelle DB. Sgbeta1, a novel locust (Schistocerca gregaria) non-alpha nicotinic acetylcholine receptor-like subunit with homology to the Drosophila melanogaster Dbeta1 subunit. INVERTEBRATE NEUROSCIENCE 2005; 5:147-55. [PMID: 16177887 DOI: 10.1007/s10158-005-0007-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2005] [Accepted: 08/02/2005] [Indexed: 10/25/2022]
Abstract
The cloning, sequencing and functional expression of Sgbeta1, a novel locust (Schistocerca gregaria) non-alpha nicotinic acetylcholine receptor (nAChR) subunit is described. This subunit shows 80% identity with the Drosophila melanogaster Dbeta1 and 92% identity with the Locusta migratoria beta1, non-alpha subunits but only 38% identity to Sgalpha1 (also referred to as alphaL1), a previously cloned S. gregaria nAChR alpha-subunit. When expressed in Xenopus laevis oocytes, Sgbeta1 does not respond to nicotine. Responses to nicotine are observed, however, in oocytes co-expressing Sgalpha1 and Sgbeta1, but the pharmacology is indistinguishable from that of currents produced by expressing Sgalpha1 alone. We conclude that either Sgbeta1 does not co-assemble with Sgalpha1, or that it is unable to contribute to the functional properties of the receptor, in the Xenopus oocyte expression system.
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Affiliation(s)
- A K Jones
- MRC Functional Genetics Unit, Department of Human Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1, 3QX, UK
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