scholarly journals Significance of the Cerebrovascular Effects of Immobilization Stress in the Rabbit

1984 ◽  
Vol 4 (3) ◽  
pp. 397-406 ◽  
Author(s):  
Pierre Lacombe ◽  
Jacques Seylaz
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Immobilization Stress ◽  
Sampling Technique ◽  
Stress Reaction ◽  
Acute Hypertension ◽  
Cerebrovascular Autoregulation ◽  
Arterial Blood ◽  
Systemic Factors

The question of the significance of the cerebrovascular effects of stressful situations in animals is still controversial. In the present article, an experimental model of immobilization stress in the rabbit is described, and its specificity in relation to arterial blood pressure and PaCO2 is investigated. CBF was measured with the multiregional tissue sampling technique using [14C]-ethanol as tracer. After dissipation of althesin anesthesia, the stress reaction was elicited by tactile abdominal stimuli. The response was evidenced by an instantaneous acute hypertension (+ 33.8% during the CBF measurement period). Within the first minute of the reaction, the CBF was significantly increased in all nine structures studied by 39% (caudate nucleus) to 82% (parietotemporal cortex). The study of the influence of arterial blood pressure and the PaCO2 on CBF showed that cerebrovascular autoregulation and CO2 sensitivity were differently affected in the various structures during the stress reaction. However, the stress response of the brain circulation could not be entirely ascribed to one or both of these two systemic factors, thus suggesting the contribution of a local intrinsic activation. The model presented here could be useful for long-term studies of cerebrovascular repercussions of repeated acute hypertensions of a stressful nature.

Effects of isoproterenol on the cardiovascular system of fetal sheep exposed to long-term high-altitude hypoxemia

1995 ◽  
Vol 78 (5) ◽  
pp. 1793-1799 ◽  
Author(s):  
M. Kamitomo ◽  
T. Ohtsuka ◽  
R. D. Gilbert
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Right Ventricular ◽  
High Altitude ◽  
Arterial Blood Pressure ◽  
Left Ventricular ◽  
Arterial Blood ◽  
Isoproterenol Infusion

We exposed fetuses to high-altitude (3,820 m) hypoxemia from 30 to 130 days gestation, when we measured fetal heart rate, right and left ventricular outputs with electromagnetic flow probes, and arterial blood pressure during an isoproterenol dose-response infusion. We also measured the distribution of cardiac output with radiolabeled microspheres during the maximal isoproterenol dose. Baseline fetal arterial blood pressure was higher in long-term hypoxemic fetuses (50.1 +/- 1.3 vs. 43.4 +/- 1.0 mmHg) but fell during the isoproterenol infusion to 41.3 +/- 1.4 and 37.5 +/- 1.4 mmHg, respectively, at the highest dose. Heart rate was the same in both groups and did not differ during isoproterenol infusion. Baseline fetal cardiac output was lower in the hypoxemic group (339 +/- 18 vs. 436 +/- 19 ml.min-1.kg-1) due mainly to a reduction in right ventricular output. During the isoproterenol infusion, right ventricular output increased to the same extent in both hypoxemic and normoxic fetuses (approximately 35%); however, left ventricular output increased only approximately 15% in the hypoxemic group compared with approximately 40% in the normoxic group. The percent change in individual organ blood flows during isoproterenol infusion in the hypoxemic groups was not significantly different from the normoxic group. All of the mechanisms that might be responsible for the differential response of the fetal left and right ventricles to long-term hypoxia are not understood and need further exploration.

Long-Term Telemetry of Direct Arterial Blood Pressure in Unrestricted Hypertensives

2015 ◽  
pp. 211-215
Author(s):  
B. Kr�nig ◽  
K. Dufey ◽  
P. Reinhardt ◽  
J. Jahnecke ◽  
H. P. Wolff
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Arterial Blood ◽  
Direct Arterial Blood Pressure

Physiological characteristics of rats and ground squirrels during prolonged lethargic hypothermia

1960 ◽  
Vol 199 (3) ◽  
pp. 467-471 ◽  
Author(s):  
V. Popovic
Keyword(s):  
Blood Pressure ◽  
Body Temperature ◽  
Arterial Blood Pressure ◽  
Cold Water ◽  
Physiological State ◽  
Low Ph ◽  
Ground Squirrels ◽  
Adult Rats ◽  
Arterial Blood

After intensive cooling, rats can be maintained at constant body temperature during several hours in a cylinder surrounded by cold water. The rats live in lethargic hypothermia at a body temperature of 15°C for 8–10 hours but can recover only if the hypothermia has not lasted more than 5.5 hours, average time of ‘biological survival.’ After 6 or more hours at 15°C adult rats showed irreversible hemoconcentration, hypoglycemia, drop in arterial blood pressure and low pH of the blood, but no change in pulse rate. Artificially cooled ground squirrels survived 110 hours at a body temperature of 10°C, ‘biological survival’ time being only 75 hours. Hemoconcentration, low arterial blood pressure and hypoglycemia have also been found in lethargic ground squirrels during the last part of survival. They cannot be rescued by rewarming. The deeply cooled animal with stabilized temperature is in a physiological state that changes with time and ultimately leads to death. A recovery prognosis during long-term hypothermia has been attempted, and the cause of death has been discussed.

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