CHOLINERGIC BRADYCARDIA TEMPERATURE INDUCED IN ANTARCTIC FISHES NOTOTHENIA NEGLECTA AND CHAENOCEPHALUS ACERATUS (19th Symposium on Polar Biology)

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概要

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• The cardiac responses of the Antarctic fishes Notothema neglecta and Chaenocephalus aceratus to acute changes of temperature were studied. The fishes were surgically prepared for electrocardiogram (ECG) recording and placed in a three hour experiment in an experimental chamber containing aerated marine water. The temperature was controlled from +2℃ to -1.8℃. Presence of nitrites in the fish bath was monitored. Atropine and epinephrine were administered into the abdominal cavity through a surgically inserted cannula. Blood samples were taken at initial +2.0℃ and final -1.8℃ for cholmesterase assay. Results showed that: 1. A temperature decrease from +2.0°C to〜-1.8℃ significantly depressed cardiac rate, from 26.9±27 to 5.2±1.4 beats min^<-1> in N neglecta and from 19.0 to 3.0 beats min^<-1> in C aceratus. In one specimen of N. neglecta, a reversible cardiac arrest of 3.0mm was observed. ECG waves did not change during the experiments, except the QRS to QRS or the Q-T intervals at lower temperatures. Respiratory rate was not significantly influenced by temperature, 2. Return of temperature to +1.5/2.0℃ immediately ceased bradycardia, 3. Administration of atropme reversed bradycardia within 5 min; 4. Serum cholmesterase activity decreased at the lowest temperature; 5. Epinephrine neither influenced the cardiac rate at any temperature nor altered cardiac waves. Results demonstrate that severe bradycardia at subzero temperatures is not only an intrinsic cardiac response to cold, but an active one, due to the higher cholinergic tone, that was not observed in the resting state at +2.0℃. No adrenergic influence on heart chronotropism has been found.

• 国立極地研究所の論文

著者

• Goncalves Neuza

  Departamento De Medicina Centra De Ciencias Biologicas E Da Saude Pontificia Universidade Catolica D

• Bacila Metry

  Laboratono De Piscicultura Departamento De Zootecnia Umversidade Federal Do Parana

• Bastos-ramos Wilma

  Departamento De Ciencias Fisiologicas Faculdade De Odontologia Umversidade Estadual Pauhsta (unesp)

• Bastos-Ramos Wilma

  Departamento de Ciencias Basicas, Faculdade de Odontologia, Universidade Estadual Paulista (UNESP)

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• CHOLINERGIC BRADYCARDIA TEMPERATURE INDUCED IN ANTARCTIC FISHES NOTOTHENIA NEGLECTA AND CHAENOCEPHALUS ACERATUS (19th Symposium on Polar Biology)

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