Toru Yazawa and Tomoo Katsuyama
J. Comp. Physiol. A 187, p817-824(2001)
The fluctuation of heartbeat interval was investigated to assess cradio-regulatory
nervous function in freely moving spiny lobsters. This was performed by
time series analysis of the heartbeat interval recorded from restrained
animals, freely moving animals, and isolated hearts. The heart rate of
freely moving animals exhibited on/off switching: i.e., an elevated and
maintained rate was repetitively interrupted by periods of a decreased
rate. Each period was initiated by a sudden decrease in rate and was terminated
by an exponential return to normal activity. In order to explain this characteristic
change in heart rate, we have constructed a neurotransmitter release-reuptake
model for such bi-stable activity of cardio-regulatory nerves. The model
was successful in reproducing the characteristic observed fluctuation.
In freely moving animals, the brain seems to regulate the heart through
the inhibitory nerve in an "on/off" manner. In the hearts of
restrained animals and isolated hearts, the heart rate exhibited white-noise
like fluctuation. This implies that stress impairs the normal bi-stable
regulatory mode.
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