title: Nicotinic acetylcholine receptor subtypes involved in facilitation of GABAergic inhibition in mouse superficial superior colliculus.
abstract: The superficial superior colliculus (sSC) is a key station in the sensory processing related to visual salience. The sSC receives cholinergic projections from the parabigeminal nucleus, and previous studies have revealed the presence of several different nicotinic acetylcholine receptor (nAChR) subunits in the sSC. In this study, to clarify the role of the cholinergic inputs to the sSC, we examined current responses induced by ACh in GABAergic and non-GABAergic sSC neurons using in vitro slice preparations obtained from glutamate decarboxylase 67-green fluorescent protein (GFP) knock-in mice in which GFP is specifically expressed in GABAergic neurons. Brief air pressure application of acetylcholine (ACh) elicited nicotinic inward current responses in both GABAergic and non-GABAergic neurons. The inward current responses in the GABAergic neurons were highly sensitive to a selective antagonist for alpha3beta2- and alpha6beta2-containing receptors, alpha-conotoxin MII (alphaCtxMII). A subset of these neurons exhibited a faster alpha-bungarotoxin-sensitive inward current component, indicating the expression of alpha7-containing nAChRs. We also found that the activation of presynaptic nAChRs induced release of GABA, which elicited a burst of miniature inhibitory postsynaptic currents mediated by GABA(A) receptors in non-GABAergic neurons. This ACh-induced GABA release was mediated mainly by alphaCtxMII-sensitive nAChRs and resulted from the activation of voltage-dependent calcium channels. Morphological analysis revealed that recorded GFP-positive neurons are interneurons and GFP-negative neurons include projection neurons. These findings suggest that nAChRs are involved in the regulation of GABAergic inhibition and modulate visual processing in the sSC.
authors.affiliation: Department of Developmental Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki, Japan. tendo@nips.ac.jp
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Endo
authors.forename: Yuchio
authors.initials: Y
authors.lastname: Yanagawa
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Obata
authors.forename: Tadashi
authors.initials: T
authors.lastname: Isa
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002038:Bungarotoxins / Q000494:pharmacology; D002104:Cadmium / Q000494:pharmacology; D020916:Conotoxins / Q000494:pharmacology; D004079:Dihydro-beta-Erythroidine / Q000494:pharmacology; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004347:Drug Interactions; D004558:Electric Stimulation; D018756:GABA Antagonists / Q000494:pharmacology; D005968:Glutamate Decarboxylase / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000235:genetics; D008464:Mecamylamine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D016571:Neural Networks, Computer; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D018408:Patch-Clamp Techniques / Q000379:methods; D010852:Picrotoxin / Q000494:pharmacology; D021122:Protein Subunits / Q000502:physiology; D011724:Pyridazines / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000145:classification / Q000502:physiology*; D013477:Superior Colliculi / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D000109:Acetylcholine; D001640:Bicuculline; D002038:Bungarotoxins; D002104:Cadmium; D020916:Conotoxins; D004079:Dihydro-beta-Erythroidine; D004246:Dimethylphenylpiperazinium Iodide; D018756:GABA Antagonists; D005968:Glutamate Decarboxylase; D049452:Green Fluorescent Proteins; D007527:Isoenzymes; D008464:Mecamylamine; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D010852:Picrotoxin; D021122:Protein Subunits; D011724:Pyridazines; D011978:Receptors, Nicotinic; D005680:gamma-Aminobutyric Acid; C098872:alpha-conotoxin MII; C049853:gabazine; C402565:glutamate decarboxylase 1