Abstract
Mongrel dogs, rabbits, wistar strain rats, guinea pigs, hamsters, and frogs were given centrifugal acceleration load in three directional mode, i. e. +Gz, -Gz, and Gx, and heart rate was recorded before and during the stress. Changes of heart rate by G stress were compared with each species of animals.
In case of +Gz stress, rats and hamsters showed generally no change or slight slowing of heart rate during increasing G, but some animals showed abrupt bradycardia and ended to death. Hamsters had a tendency of recovering from abrupt severe bradycardia.Dogs, rabbits and guinea pigs showed a tendency of slight tachycardia during increasing G, and showed gradual successive slowing followed by death by continuring G stress.
Frogs had a strong tolerance and maintained normal heart rate all along the G stress.
In case of Gx stress, rats, hamsters and guinea pigs showed a tendency of slight slowing or remaining on the constant level, but some animals which were not able to tolerate to stress showed the same course as in case of +Gz stress.
Rabbits showed slowing from the start of G stress, sometimes transient increase, and marked bradycardia followed by death.
In case of -Gz stress, rats, rabbits, and guinea pigs showed successive bradycardia from the start of G stress and finally ended to death. But a few survived animals showed gradual recovery from marked slowing to normal rhythm. Hamsters showed a tendency of slight initial increase of heart rate, later abrupt bradycardia during constant G stress and ended to death.
Above stated results indicate that there are some variation of heart rate pattern during G stress by the directions of G stress and among the species of animals. In general, it may also say that the large animals such as dogs and rabbits have lower tolerance to G than small animals in view of heart rate change as many authors indicated the same results from many other indicaters.
