Severe Hypotension During the Decreasing Phase of G&lt;SUB&gt;z&lt;/SUB&gt; Stress in Anesthetized Rats Wearing an Anti-G Suit

Maruyama, Satoshi; Kemuriyama, Takehito; Manabe, Tomoko; Takahata, Tomofumi; Shoji, Ichiro; Nishida, Yasuhiro

doi:10.3357/asem.2870.2011

Cited by 2 publications

(23 citation statements)

References 5 publications

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“…We designed and constructed a two-armed centrifuge for acceleration load and testing of small animals (Tomy Seiko, Tokyo, Japan; [ 16 , 22 , 31 , 32 ]). Each arm is 115 cm in length.…”

Section: Small-animal Acceleration Systemmentioning

confidence: 99%

“…Any loading can be selected up to a maximum load capacity of +9.0 Gz (at 86 rpm). At a given load setting, the G onset or offset rates are not linear, but rather exponential, with 0.03 G/second (s) at 3.0 G, 0.04 G/s at 5.0 G, and 0.05 G/s at 7.0 G [ 22 , 31 ]. The rotational speed of the flat plate is separately measured with a tachometer and recorded, and then converted to the G-value by calculation.…”

Section: Small-animal Acceleration Systemmentioning

confidence: 99%

“…All instruments for measuring arterial pressure (AP) and other parameters are mounted on the centrifuge, with their signals transmitted from the centrifuge via a slip-ring, converted by an analog-to-digital converter, and then recorded to and saved on a computer [ 16 , 22 , 31 ].…”

Section: Small-animal Acceleration Systemmentioning

confidence: 99%

“…This means that at this near-zero cephalic AP, the blood flow to the brain is also near zero. Under a load of +1.5 Gz, the cephalic AP declined by approximately 20 to 60 ± 8 mmHg ( n = 7; SD), and under a load of +3.0 Gz it declined by approximately 50 to 24 ± 16 mmHg ( n = 7; SD) [ 17 , 22 , 25 ]. Under a load of +7.0 Gz, the high mortality rate precluded the collection of enough data to allow further statistical analysis.…”

Section: Effects Of G Load Without Anti-g Protectionmentioning

confidence: 99%

“…When the rat was exposed to +5.0 Gz (head-to-tail longitudinal G) for 15 s at an on-set rate of 0.004 G/s), brain AP was decreased to around a zero level. The mean values of seven rats were shown in the text [ 22 , 25 , 31 – 34 ] …”

Section: Effects Of G Load Without Anti-g Protectionmentioning

confidence: 99%

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Effects and biological limitations of +Gz acceleration on the autonomic functions-related circulation in rats

Nishida

Maruyama²,

Shouji

et al. 2016

J Physiol Sci

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The effects of gravitational loading (G load) on humans have been studied ever since the early 20th century. After the dangers of G load in the vertical head-to-leg direction (+Gz load) became evident, many animal experiments were performed between 1920 and 1945 in an effort to identify the origins of high G-force-induced loss of consciousness (G-LOC), which led to development of the anti-G suit. The establishment of norms and training for G-LOC prevention resulted in a gradual decline in reports of animal experiments on G load, a decline that steepened with the establishment of anti-G techniques in humans, such as special breathing methods and skeletal muscle contraction, called an anti-G straining maneuver, which are voluntary physiological functions. Because the issue involves humans during flight, the effects on humans themselves are clearly of great importance, but ethical considerations largely preclude any research on the human body that probes to any depth the endogenous physiological states and functions. The decline in reports on animal experiments may therefore signify a general decline in research into the changes seen in the various involuntary, autonomic functions. The declining number of related reports on investigations of physiological autonomic systems other than the circulatory system seems to bear this out. In this review, we therefore describe our findings on the effects of G load on the autonomic nervous system, cardiac function, cerebral blood flow, tissue oxygen level, and other physiological autonomic functions as measured in animal experiments, including denervation or pharmacological blocking, in an effort to present the limits and the mechanisms of G-load response extending physiologically. We demonstrate previously unrecognized risks due to G load, and also describe fundamental research aimed at countering these effects and development of a scientific training measure devised for actively enhancing +Gz tolerance in involuntary, autonomic system functions. The research described here is rough and incomplete, but it is offered as a beginning, in the hope that researchers may find it of reference and carry the effort toward completion. The advances described here include (1) a finding that cerebral arterial perfusion pressure decreases to nearly zero under +5.0 Gz loads, (2) indications that G load may cause myocardial microinjuries, (3) detection of differences between cerebral regions in tissue-oxygen level under +3.0 Gz load, (4) discovery that hypotension is deeper under decreasing +Gz loads than increasing +Gz loads with use of an anti-G system, due in part to suppression of baroreceptor reflex, and (5) revelations and efforts investigating new measures to reduce cerebral hypotension, namely the “teeth-clenching pressor response” and preconditioning with slight but repeated G loads.

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“…We designed and constructed a two-armed centrifuge for acceleration load and testing of small animals (Tomy Seiko, Tokyo, Japan; [ 16 , 22 , 31 , 32 ]). Each arm is 115 cm in length.…”

Section: Small-animal Acceleration Systemmentioning

confidence: 99%

Section: Small-animal Acceleration Systemmentioning

confidence: 99%

Section: Small-animal Acceleration Systemmentioning

confidence: 99%

Section: Effects Of G Load Without Anti-g Protectionmentioning

confidence: 99%

Section: Effects Of G Load Without Anti-g Protectionmentioning

confidence: 99%

See 3 more Smart Citations