The glutamate receptor agonist, AMPA, induces acetylcholine release in guinea pig cochlea; a microdialysis study.
Acetylcholine (Ach) has been considered a major neurotransmitter in the inner ear efferent nerve endings. A bioassay analysis has shown that the electrical stimulation of the crossed olivocochlear bundle increased the Ach-like activity in the perilymph. Applying in vivo microdialysis techniques and high-performance liquid chromatography to the perilymph, the change of Ach level was thus measured before and after alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA), a glutamate receptor agonist, was added to the perfusate. Ach was only detectable when the perfusate contained an acetylcholinesterase inhibitor. The level of Ach increased 2-3-fold immediately after AMPA was administered. Our data suggest that the afferent stimulation, such as the administration of AMPA, may therefore induce the release of Ach from the efferent nerve endings.
Hoya
N
N
Department of Otolaryngology, School of Medicine Keio University, 35 Shinanomachi, Shinjuku-Ku, Tokyo 160-5258, Japan. hoya-nor@triton.ocn.ne.jp
Ogawa
K
K
Inoue
Y
Y
Takiguchi
Y
Y
Kanzaki
J
J
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003051:Cochlea / Q000187:drug effects* / Q000294:innervation / Q000378:metabolism; D003056:Cochlear Nerve / Q000187:drug effects / Q000378:metabolism; D004525:Efferent Pathways / Q000187:drug effects* / Q000378:metabolism; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D008297:Male; D017551:Microdialysis; D010477:Perfusion / Q000379:methods; D010498:Perilymph / Q000187:drug effects / Q000378:metabolism; D010830:Physostigmine / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects* / Q000378:metabolism; D017470:Receptors, Glutamate / Q000187:drug effects / Q000378:metabolism; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology*
D002800:Cholinesterase Inhibitors; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D010830:Physostigmine; D000109:Acetylcholine