title: Electrical and mechanical properties and mode of innervation in scorpionfish sound-producing muscle fibres.
abstract: To obtain information about the neural mechanism underlying sound production in teleost fish, we studied the electrical and mechanical properties and mode of innervation in the swimbladder muscle (SBM) fibres of scorpionfish Sebastiscus marmoratus. Action potentials of the SBM fibres in response to direct electrical stimulation neither exhibited overshoot nor propagated along the fibre. Stimulation of the motor nerve, however, uniformly evoked action potentials along the fibre. When neuromuscular transmission was blocked by curare, motor nerve stimulation uniformly evoked endplate potentials along the fibre. These results indicate that action potentials propagate along the nerve branches but not along the SBM fibre membrane. In accordance with the above results, histochemical studies showed that motor nerve branches run along the SBM fibres to form many endplates with cholinesterase activity, indicating multiterminal innervation. The SBM consisted of about 600 fibres, while its motor nerve contained about 100 axons, giving an innervation ratio of about 1:6. Like mammalian fast muscle fibres, the SBM fibres exhibited a low succinic dehydrogenase activity and a high ATPase activity. These results are discussed in connection with the function of the SBM fibres in producing sound.
authors.affiliation: Department of Physiology, School of Medicine, Teikyo University, Itabashi-ku, Tokyo 173-8605, Japan.
authors.forename: Takakazu
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Tateo
authors.initials: T
authors.lastname: Daimon
authors.forename: Ibuki
authors.initials: I
authors.lastname: Shirakawa
authors.forename: Shigeru
authors.initials: S
authors.lastname: Chaen
authors.forename: Haruo
authors.initials: H
authors.lastname: Sugi
mesh_terms: D000200:Action Potentials; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000400:Air Sacs / Q000502:physiology*; D000819:Animal Communication; D000818:Animals; D002802:Cholinesterases / Q000378:metabolism; D003472:Curare; D004558:Electric Stimulation; D005399:Fishes / Q000502:physiology*; D006651:Histocytochemistry; D007564:Japan; D012132:Respiratory Muscles / Q000294:innervation* / Q000378:metabolism / Q000502:physiology*; D013385:Succinate Dehydrogenase / Q000378:metabolism
chemical_list: D003472:Curare; D013385:Succinate Dehydrogenase; D002802:Cholinesterases; D000251:Adenosine Triphosphatases