Adaptive thermoregulatory reactions of the rabbit fetus at the end of the intrauterine development

The data of permanent simultaneous registration of electrocardiogram, rectal & brown adipose tissue temperatures of the rabbit foetus have been obtained in chronic experiments. The haemodynamic shift in intensity of maternal-placental and foeto-placental blood flow (by female trental injection) led to a decrease in the foetus rectal temperature (0.33 +/- 0.09 degree C in intact foetus and 0.58 +/- 0.27 degree C in retarded foetus, p < 0.05). Both foetuses reacted by rectal temperature decrease (0.65 +/- 0.28 & 0.68 +/- 0.31 degree C, respectively) during immobilisation (by foetus arduan injection). Thus in both series of experimental cooling of foetus, brown fat activation was similar in intact foetus (approximately 53%), but did not change in growth retardation foetus--as a result of its tissue functional immaturity, probably.