THERMOREGULATORY CONTROL DURING PREGNANCY AND LACTATION IN RATS

Citation
Hl. Eliason et Je. Fewell, THERMOREGULATORY CONTROL DURING PREGNANCY AND LACTATION IN RATS, Journal of applied physiology, 83(3), 1997, pp. 837-844
Citations number
38
Categorie Soggetti
Physiology,"Sport Sciences
ISSN journal
87507587
Volume
83
Issue
3
Year of publication
1997
Pages
837 - 844
Database
ISI
SICI code
8750-7587(1997)83:3<837:TCDPAL>2.0.ZU;2-6
Abstract
Although the mechanisms remain unknown, maternal core temperature (T-c ) decreases near term of pregnancy and is increased throughout lactati on in rats. The purpose of our present experiments was to determine wh ether pregnancy and lactation shift the thermoneutral zone of rats and to investigate whether the changes in maternal T-c during pregnancy a nd lactation result from ''forced'' or ''regulated'' thermoregulatory responses. Conscious, chronically instrumented nonpregnant and pregnan t and lactating rats were studied both in a thermocline (a chamber wit h a linear temperature gradient from 12 to 36 degrees C) and in a meta bolic chamber to determine the influence of pregnancy and lactation on selected ambient temperature as well as the thermoregulatory response to changes in ambient temperature. We found that selected ambient tem perature, oxygen consumption, and thermal conductance did not change i n rats studied in a thermocline as T-c decreased near term of pregnanc y. There was, however, a downward shift in the thermoneutral zone of r ats studied in a metabolic chamber near term of pregnancy. During lact ation, selected ambient temperature decreased in rats studied in a the rmocline as oxygen consumption and T-c increased. The thermoneutral zo ne of lactating rats was not different from that of nonpregnant animal s. Thus our data provide evidence that the decrease in T-c near term o f pregnancy in rats results from a regulated thermoregulatory response , whereas the increase in T-c during lactation results from a forced t hermoregulatory response.