Influence of acute hypobaric hypoxia on pain sensitivity in pregnant and non-pregnant ratsстатьяТезисы
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 15 августа 2019 г.
Аннотация:The development of stress-induced analgesia depends on the stressor, the experiment conditions and the sex of animals. As part of a large-scale study devoted to the investigation of intrauterine stresses of various etiology on postnatal development this work was carried out to analyze the effect of acute hypobaric hypoxia, performed in the third trimester of pregnancy, on pain sensitivity of experimental animals.Pregnant (n = 12) and non-pregnant (n = 19) female nonlinear white rats weighing 180-240 g at the beginning of the experiment were housed in individual transparent acrylic cages housing six animals each. Rats were maintained in a 12 hours light, 12 hours dark cycle with average temperature of 22-25oC, circulating air and free access to food and water.Acute hypobaric hypoxia was used as a stress factor on the 20th day of pregnancy. The first day of pregnancy was determined by the presence of sperm in the vaginal smear. Modeling of acute hypobaric hypoxia until the first agonal breath was performed in pressure chamber with an oxygen content of 5 %. Pressure reduction was carried out in 1 minute.Tail flick test that causes a reflex reaction of tail escape by applying thermal stimulus to the tail with a beam of light was used to assess animals’ pain sensitivity. The baseline pain sensitivity was calculated as the arithmetic mean of three consequent measurements of tail flick latency with at least 5 minutes intervals. Further, pain sensitivity was recorded every 15 minutes within 1.5 hours after stress exposure. Since body temperature is an important parameter that should be taken into account when conducting tests using thermal stimulus, in addition rectal body temperature was measured using an electric thermometer at the same time points.It was shown that acute hypobaric hypoxia did not affect the threshold of pain sensitivity in either pregnant or non-pregnant rats. At the same time as control or experimental non-pregnant rats demonstrated more pronounced deviations from the baseline pain sensitivity compared to pregnant rats of both groups.Both pregnant and non-pregnant control rats were characterized by non-significant smooth decrease in body temperature throughout the experiment that did not exceed 0.6-0.9°C and always returned to the baseline 24 hours after. At the same time all rats survived acute hypobaric hypoxia showed noticeable decrease in body temperature by 1.7-2.2 oC throughout the whole period of observation. In addition a day after hypoxia exposure body temperature returned to their baseline values in non-pregnant rats while remained significantly below them in pregnant females.Thus, acute hypobaric hypoxia resulted in significant long lasting drop of body temperature without causing noticeable changes in pain sensitivity of experimental animals. It seems that stress-induced body response depends on animals’ physiological state which may be due to the increased resistance of pregnant females to a single stress exposure. Subsequently rat females exposed to hypoxia on the 20th day of pregnancy had unfavorable outcome of pregnancy more frequently and brought the posterity lagging behind in weight and height one day later than control rats.