title: Expression patterns of nicotinic subunits α2, α7, α8, and β1 affect the kinetics and pharmacology of ACh-induced currents in adult bee olfactory neuropiles.
abstract: Acetylcholine (ACh) is the main excitatory neurotransmitter of the insect brain, where nicotinic acetylcholine receptors (nAChRs) mediate fast cholinergic synaptic transmission. In the honeybee Apis mellifera, nAChRs are expressed in diverse structures including the primary olfactory centers of the brain, the antennal lobes (ALs) and the mushroom bodies (MBs), where they participate in olfactory information processing. To understand the nature and properties of the nAChRs involved in these processes, we performed a pharmacological and molecular characterization of nAChRs on cultured Kenyon cells of the MBs, using whole cell patch-clamp recordings combined with single-cell RT-PCR. In all cells, applications of ACh as well as nicotinic agonists such as nicotine and imidacloprid induced inward currents with fast desensitization. These currents were fully blocked by saturating doses of the antagonists α-bungarotoxin (α-BGT), dihydroxy-β-erythroidine (DHE), and methyllycaconitine (MLA) (MLA ≥ α-BGT ≥ DHE). Molecular analysis of ACh-responding cells revealed that of the 11 nicotinic receptor subunits encoded within the honeybee genome, α2, α8, and β1 subunits were expressed in adult Kenyon cells. Comparison with the expression pattern of adult AL cells revealed the supplementary presence of subunit α7, which could be responsible for the kinetic and pharmacological differences observed when comparing ACh-induced currents from AL and Kenyon cells. Together, our data demonstrate the existence of functional nAChRs on adult MB Kenyon cells that differ from nAChRs on AL cells in both their molecular composition and pharmacological properties, suggesting that changing receptor subsets could mediate different processing functions depending on the brain structure within the olfactory pathway.
authors: Université de Toulouse, UPS, Centre de Recherches sur la Cognition Animale (CRCA), CNRS UMR 5169, 118 route de Narbonne, F-31062 Toulouse Cedex 9, France. raymond@cict.fr
authors: Julien Pierre
authors: JP
authors: Dupuis
authors: Monique
authors: M
authors: Gauthier
authors: Valérie
authors: V
authors: Raymond-Delpech
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D057506:Arthropod Antennae; D001516:Bees / Q000235:genetics / Q000502:physiology*; D001921:Brain / Q000166:cytology* / Q000502:physiology; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D002799:Cholinergic Fibers / Q000502:physiology; D059329:Cholinergic Neurons / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005260:Female; D015870:Gene Expression; D007395:Interneurons / Q000187:drug effects / Q000378:metabolism; D024521:Mushroom Bodies / Q000166:cytology* / Q000502:physiology; D019581:Neuropil / Q000187:drug effects* / Q000502:physiology; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D021122:Protein Subunits / Q000096:biosynthesis / Q000235:genetics; D011978:Receptors, Nicotinic / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D012903:Smell / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology
chemical_list: D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D021122:Protein Subunits; D011978:Receptors, Nicotinic; D000109:Acetylcholine